NTERNATIONAL VENUS WORKSHOP - INAF · Retrieval of temperature and carbon monoxide from the 4.7um...

INTERNATIONAL VENUS WORKSHOP

ABSTRACT LIST

PROGRAM – PAGE A

Monday, 10th June

Schedule Author Title

9:00 - 13:00 SWT

9:00 - 13:00 Science Working Team meeting (only for the Venus Express team members)

14:30 Session Surface/Interior 14:30 - 15:00 Stofan Venus: Earth’s (Neglected) Twin (Invited) 15:00 - 15:15 Mueller Search for active lava flows with VIRTIS on Venus Express

15:15 - 15:30 Shalygin Venus surface geology from near infrared night side Venus Monitoring Camera images

15:30 - 16:00 Smrekar Diverse Geologic Settings of Recent Volcanism on Venus and Implications for the Interior (Invited)

16:00 - 16:30 Coffee

16:30 Session Surface/Interior 16:30 - 17:00 Sotin Are terrestrial exoplanets Earth-like, Venus-like, or different? (Invited) 17:00 - 17:15 Ghail The influence of rheology and volatiles on the geology of Venus

17:15 - 17:45 Russell Venus and Planetary Magnetism (Invited)

17:45 - 18:00 Luhmann Large-scale magnetic flux ropes in low-altitude ionosphere of Venus: planetary origin or solar wind origin

18:00 - 18:15 Discussion of Surface/Interior/Magnetism

18:15 - 19:45 Poster session 1

Tuesday, 11th June


9:00 Session Plasma & Induced Magnetosphere

9:00 - 9:30 Zhang Physics of Induced Magnetosphere (Invited)

9:30 - 10:00 Luhmann Comparative Plasma Interactions and their Effects at Venus, Mars and Titan (Invited)

10:00 - 10:15 Barabash How the near-Venus space affects the planet

10:15 - 10:30 Stenberg Ion escape from Venus

10:30 - 10:45 Masunaga Dependence of O+ escape rate from the Venusian upper atmosphere on IMF directions: ASPERA-4 observations

10:45 - 11:00 McEnulty Comparisons of Venus Express measurements with an MHD model of O+ ion flows: Implications for atmosphere escape measurements

11:00 - 11:30 Coffee

11:30 Session Plasma & Induced Magnetosphere

11:30 - 11:45 Lundin Solar Wind energy and momentum transfer - Effects on the Venus polar thermosphere

11:45 - 12:00 Fedorov The plasma vortex in the Venusian plasma tail. Steady-state reconnection or fluid motion?

12:00 - 12:15 Nordheim Cosmic ray ionization in the Venusian atmosphere from Monte Carlo modelling

12:15 - 12:30 Dubinin Ionospheric magnetic fields and currents at Mars and Venus

12:30 - 12:45 Vasko Fine structure of the Venus current sheet

12:45 - 13:00 Coates Ionospheric photoelectron observations at Venus

13:00 - 13:15 Gray A survey of Hot Flow Anomalies at Venus

13:15 - 13:30 Russell The Implications of the Observed Evolution of the Co-Orbiting Material in 2201

PROGRAM – PAGE B

Oljato’s Orbit Observed by PVO and VEX

13:30 Lunch

15:30 Etna excursion

Wednesday, 12th June


9:00 Session Dynamics & Structure

9:00 - 9:25 Lebonnois Venus GCM modelling: current status and perspectives in the light of Venus Express datasets (Invited)

9:25 - 9:50 Rodin Non-hydrostatic general circulation model of the Venus atmosphere (Invited) 9:50 - 10:05 Takagi Structures and generation mechanisms of the Venus atmospheric superrotation

10:05 - 10:20 Sugimoto Baroclinic modes in the Venus atmosphere simulated by AFES (Atmospheric GCM For the Earth Simulator)

10:20 - 10:35 Limaye Global Vortex Circulation on Venus - an assessment from Venus Express Observations

10:35 - 10:50 Hueso Measurements of Venus winds from ultraviolet, visible and near infrared images with VIRTIS on Venus Express

10:50 - 11:05 Bertaux Atmospheric Oscillation in the atmosphere of Venus: the Cupido effect

11:05 - 11:30 Coffee

11:30 Session Dynamics & Structure

11:30 - 11:45 Lee Variations of the radiative forcing induced by the cloud top structure changes of the Venus mesosphere

11:45 - 12:00 Grassi Thermal Structure of Venus Mesosphere as Observed by VIRTIS - Venus Express

12:00 - 12:15 Zasova Thermal structure of the Venus mesosphere from remote sensing in the infrared spectral range (VIRA II improvement)

12:15 - 12:30 Tellmann The VeRa Radio Occultation Data Base: Atmosphere and Ionosphere (Invited)

12:30 - 12:45 Tellmann Waves in the Venus Atmosphere detected by the Venus Express Radio Science Experiment VeRa (Invited)

12:45 - 13:00 Migliorini Gravity waves in the Venus upper atmosphere, modelled on VIRTIS/Venus Express data

13:00 - 14:30 Lunch

14:30 Session Upper Mesosphere/Lower Thermosphere

14:30 - 14:45 Piccialli Thermal structure of the upper atmosphere of Venus with SPICAV/VEx data

14:45 - 15:00 Mahieux CO2 rotational temperatures compared to hydrostatic temperatures obtained with the SOIR instrument on board VEx

15:00 - 15:15 Zalucha Incorporation of a gravity wave momentum deposition parameterization into the Venus thermosphere general circulation Model (VTGCM)

15:15 - 15:30 Lopez-Valverde Retrieval of temperature and carbon monoxide from the 4.7um limb non-LTE emission of the upper atmosphere measured by VIRTIS/Venus Express

15:30 - 15:45 Sornig Earth based Doppler-wind and temperature measurements in Venus upper atmosphere using the infrared heterodyne spectrometer THIS

15:45 - 16:00 Clancy Doppler Winds Mapped around the Lower Thermospheric Terminator of Venus: JCMT Observations of the 2012 Solar Transit

16:00 - 16:30 Coffee

16:30 Session Upper Mesosphere/Lower Thermosphere

16:30 - 16:45 Bertaux Venus night side measurements of winds at 115 km altitude from NO bright patches tracking

16:45 - 17:00 Stiepen Venus nitric oxide nightglow distribution: a clue to thermospheric dynamics

17:00 - 17:15 Zasova The O2 nightglow from VIRTIS-M VEX measurements

17:15 - 17:30 Gérard Latitudinal variations of the altitude of the Venus O2 airglow observed with VIRTIS-M: a

PROGRAM – PAGE C

signature of dynamical processes in the upper atmosphere

17:30 - 17:45 Jain Modelling of ultraviolet and visible dayglow emissions on Venus

17:45 - 18:00 Clarke Coordinated Sounding Rocket, HST, and SPICAV Observations of Venus in Nov. 2013

18:00 - 18:15 Discussion of airglow and dynamics

18:15 -19:45 Poster session 2

Thursday, 13th June


9:00 Session Chemistry & Composition

9:00 - 9:15 Encrenaz Ground-based observations of minor species on Venus using infrared spectroscopy (Invited)

9:15 - 9:30 Encrenaz Sulfur and water mapping in the mesosphere of Venus

9:30 - 9:45 Marcq Measurements of minor species at cloud top level

9:45 - 10:00 Fedorova Water vapor and the cloud top variations in the Venus’ mesosphere from SPICAV observations

10:00 - 10:15 McGouldrick Re-analysis of Pioneer Venus SO2 measurements

10:15 - 10:30 Grinspoon Assessing An Impact Hypothesis for Upper Atmosphere Abundance Variations on Venus

10:30 - 11:00 Coffee

11:00 Session Chemistry & Composition

11:00 - 11:15 Sandor Positive Correlation of SO, SO2 in the Dayside Venus Mesosphere: Identification of Diurnal SOx Partitioning from JCMT Submm Spectroscopy

11:15 - 11:30 Sandor Temporal, Spatial Variation of HCl in the Venus Mesosphere, based upon Submm Spectroscopic Observations with JCMT

11:30 - 11:45 Vandaele Trace gases in the mesosphere and lower thermosphere of Venus from SOIR/VEX (Invited)

11:45 - 12:00 Vandaele Contribution of the SOIR/VEX instrument to VIRA II (Invited) 12:00 Session Clouds & Hazes

12:00 - 12:30 Wilquet SPICAV-SOIR mesospheric aerosols observations and modeling (Invited) 12:30 - 12:45 Titov/Markiewicz Venus cloud morphology: monitoring by the VMC/ Venus Express camera continued

12:45 - 13:00 Petrova Physical properties of particles in the upper clouds of Venus from the IR and UV images taken by VMC/VEx at small phase angles

13:00 - 14:30 Lunch

14:30 Session Clouds & Hazes

14:30 - 15:00 Hashimoto Temporal variation of UV reflectivity of Venus: VEX/VMC data analysis (Invited)

15:00 - 15:15 Esposito Causes of the bright and dark features at the Venus cloud tops

15:15 - 15:30 Satoh On the origin of the 1-micron contrast features in Venus clouds

15:30 - 15:45 Maattanen Modeling the clouds on Venus: model development and improvement of a nucleation parameterization

15:45 - 16:00 Imamura Latitudinal and local time dependence of Venus's cloud-level convection

16:00 - 16:15 Ignatiev Cloud top variations from Venus Express measurements (Invited)

16:15 - 16:30 Ignatiev Venus Clouds: Input to VIRA II model from Venus Express and Venera 15 measurements (Invited)

16:30 - 16:45 Discussion of chemistry and clouds

16:45 - 17:15 Coffee

17:15 Session Lab-based

17:15 - 17:40 Helbert High temperature spectroscopy at the Planetary Emissivity Laboratory in

PROGRAM – PAGE D

support of present and future Venus missions" (Invited) 17:40 - 18:05 Slanger Long-lived Emitters in the Atmospheres of the Terrestrial Planets (Invited)

18:05 - 18:30 Hartmann Experimental and theoretical studies of CO2 infrared absorption continua (Invited)

18:30 - 18:45 Kohler Experimental Stability of Tellurium: Implications for the Venusian Radar Anomalies

18:45 - 19:00 Stefani Experimental set-up to study optical properties of gases at typically planetary conditions

19:00 - 19:15 Snels Carbon dioxide collision induced absorption in the 1.18 micron atmospheric window of Venus

20:00 Team dinner

Friday, 14th June


9:00 Session Evolution

9:00 - 9:25 Moresi The influence of surface conditions on global mantle evolution (Invited) 9:25 - 9:40 Gillmann Long term evolution of Venus through Mantle/Atmosphere coupling

9:40 - 9:55 Lebrun Thermal evolution of an early magma ocean in interaction with the atmosphere: conditions for the condensation of a water ocean

9:55 - 10:10 Marcq Early evolution of telluric atmospheres in the magma ocean stage

10:10 - 10:25 Taylor Volcanism and Climate on Venus: An Updated Model

10:25 - 10:50 Goldblatt New calculations of the runaway greenhouse limit: bad news for early Venus and future Earth (Invited)

10:50 - 11:05 Baines The origin and early evolution of Venus, Earth and Mars: Clues from bulk properties and the abundances and isotopic ratios of noble and light gases

11:05 - 11:30 Coffee

11:30 Future

11:30 - 11:45 Nakamura Japan/Akatsuki report

11:45 - 12:00 Zasova Russia/Venera-D report

12:00 - 12:15 Limaye/Baines U.S./VEXAG report

12:15 - 12:30 Drossart Future Venus IR observation plans

12:30 - 12:45 All ISSI/EuroVenus/other reports

12:45 - 13:00 Taylor Venus III book discussions

13:00 - 13:15 Zasova VIRA II discussion

13:15 - 13:30 Wilson Future VEx science plan

13:30 - 14:00 All Discussion

14:00 End

PROGRAM – PAGE E

GROUP 1 POSTER – MON‐WED

Author Title

Cochrane Errors and Artifacts in the Magellan Imagery of the Surface of Venus

Nunes Stereo-Derived Topography To Aid Emissivity Estimates at Tesserae on Venus

Peter A global comparison between VeRa radio science observations of the Venus dayside ionosphere and the IonA model

Russell ULF and ELF Electromagnetic Waves in the Venus Ionosphere: Separating Atmospheric and Magnetosheath Sources

Stenberg Solar wind precipitation on Venus

Molaverdikhani A new dawn-dusk asymmetry in the photoelectron flux of Venus’s Ionosphere

Ogohara Limb fitting and cloud tracking for the study of the Venus atmosphere

Widemann Mesospheric Temperature at Terminator using SDO/HMI Aureole Photometry, DST/FIRS CO2 absorption spectroscopy and comparison with Venus Express

Ando Vertical structure of the Venus vortex

Fukuhara Temperature variation of the cloud top of Venus obtained by photometry observation by LIR onboard Akatsuki

Piccialli Gravity waves in Venus mesosphere observed by the Venus Monitoring Camera on board Venus Express

Marinangeli Polar Vortex: a common element of the Earth and Venus

Peralta Towards a general classification of atmospheric waves on Venus

Yamamoto Simulation of Venus’ polar vortex in the presence of diurnal thermal tide

Machado Venus cloud tops winds with ground-based Doppler velocimetry and comparison with cloud tracking method

Soret The time evolution of O2(a1Δ) individual observations acquired by VIRTIS-M on board Venus Express

Svedhem The variable upper atmosphere of Venus - data from drag and torque measurements by Venus Express

López-Valverde Mapping the lower thermosphere of Venus using VIRTIS/VEx Nadir non-LTE observations at 4.3 um

Migliorini Visible and Infrared nightglow investigation in the Venus atmosphere by means of VIRTIS on Venus Express

García-Muñoz Global imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera

Gray The Effect of Coronal Mass Ejections and Solar Flares on the Venusian Nightglow

Anderson Mt. Etna and the Eistla volcanoes: Comparative studies to constrain venusian volcano evolution and flow emplacement

Bougher / Parkinson Temperatures in Venus' Lower Thermosphere: Comparison of VTGCM and SOIR Profiles at the Terminator

PROGRAM – PAGE F

GROUP 2 POSTER – WED‐FRI

Author Title

Fedorova Observations of the near-IR nightside windows of Venus during Maxwell Montes transits by SPICAV IR onboard Venus Express

Iwagami Ground-based IR observation of oxygen isotope ratios in the Venus atmosphere

Oschlisniok Abundance of sulfuric acid vapor in the Venus atmosphere derived from the Venus Express Radio Science Experiment VeRa

Cottini Water vapor near the cloud tops of Venus from VIRTIS Venus Express day side data

Lorenz On the Possibility of Gamma Ray Flashes from Venusian Lightning

Mills Modeling and observations of mesospheric sulfur chemistry

Robert Spectral inventory of the SOIR spectra onboard Venus Express

Stolzenbach Three-dimensional modelling of Venus photochemistry

Jessup Variations in Venus’ cloud top SO2 and SO gas density with latitude and time of day

Politi VIRTIS-VEX data analysis for the study of the Venus

Carlson Progress in a refined calibration of the Venus Express VIRTIS-M instrument with application to Venus’s ultraviolet absorber

Enomoto Venusian upper hazes observed by Imaging-Polarimetry system HOPS

Kuroda Latitudinal cloud structure in the Venusian northern hemisphere evaluated from Venus Express/VIRTIS observations

Rossi Study of Venus cloud layers by polarimetry using SPICAV/VEx

Takagi High-altitude source for the Venus’ upper haze found by SOIR/Venus Express

Takeshi Simulation of the formation, evaporation and transport of sulfuric acid clouds on Venus using a general circulation model

Cimo Planetary Radio Interferometry and Doppler Experiments for current and future Venusian missions

Molera Calves Interplanetary scintillations study retrieved from Venus Express communications signal

Pluchino Using Venus Express to perform sounding experiments on lunar ionosphere

Rafkin A compact, Low Power Tunable Laser Spectrometer for Trace Gas Measurement in the Venus Atmosphere

Rodin A compact, lightweight infrared heterodyne spectrometer for studies of Venus atmosphere

Perez-Hoyos Analysis of MESSENGER/MASCS data during second Venus flyby

INDEX ‐ PAGE I

Index

Authors Title Page Anderson Mt. Etna and the Eistla volcanoes: Comparative studies to constrain venusian volcano

evolution and flow emplacement 48

Ando Vertical structure of the Venus vortex 42 Baines The origin and early evolution of Venus, Earth and Mars: Clues from bulk properties

and the abundances and isotopic ratios of noble and light gases 36

Barabash How the near-Venus space affects the planet 5 Bertaux Atmospheric Oscillation in the atmosphere of Venus: the Cupido effect 12 Bertaux Venus night side measurements of winds at 115 km altitude from NO bright patches

tracking. 19

Bougher / Parkinson Temperatures in Venus' Lower Thermosphere: Comparison of VTGCM and SOIR Profiles at the Terminator 48

Carlson Progress in a refined calibration of the Venus Express VIRTIS-M instrument with application to Venus’s ultraviolet absorber 53

Cimo Planetary Radio Interferometry and Doppler Experiments for current and future Venusian missions 56

Clancy Doppler Winds Mapped around the Lower Thermospheric Terminator of Venus: JCMT Observations of the 2012 Solar Transit 19

Clarke Coordinated Sounding Rocket, HST, and SPICAV Observations of Venus in Nov. 2013 21 Coates Ionospheric photoelectron observations at Venus 8 Cochrane Errors and Artifacts in the Magellan Imagery of the Surface of Venus 39 Collinson A survey of Hot Flow Anomalies at Venus 9 Cottini Water vapor near the cloud tops of Venus from VIRTIS Venus Express day side data 51 Drossart Future Venus IR observation plans 38 Dubinin Ionospheric magnetic fields and currents at Mars and Venus 8 Encrenaz Ground-based observations of minor species on Venus using infrared spectroscopy 23 Encrenaz Sulfur and water mapping in the mesosphere of Venus 23 Enomoto Venusian upper hazes observed by Imaging-Polarimetry system HOPS 54 Esposito Causes of the bright and dark features at the Venus cloud tops 28 Fedorov The plasma vortex in the Venusian plasma tail. Steady-state reconnection or fluid

motion? 7

Fedorova Water vapor and the cloud top variations in the Venus’ mesosphere from SPICAV observations 24

Fedorova Observations of the near-IR nightside windows of Venus during Maxwell Montes transits by SPICAV IR onboard Venus Express 50

Fukuhara Temperature variation of the cloud top of Venus obtained by photometry observation by LIR onboard Akatsuki 42

García-Muñoz Global imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera 47 Gérard Latitudinal variations of the altitude of the Venus O2 airglow observed with VIRTIS-

M: a signature of dynamical processes in the upper atmosphere 21

Ghail The influence of rheology and volatiles on the geology of Venus 3 Gillmann Long term evolution of Venus through Mantle/Atmosphere coupling. 34 Goldblatt New calculations of the runaway greenhouse limit: bad news for early Venus and

future Earth 35

Grassi Thermal Structure of Venus Mesosphere as Observed by VIRTIS - Venus Express 13 Gray The Effect of Coronal Mass Ejections and Solar Flares on the Venusian Nightglow 47 Grinspoon Assessing An Impact Hypothesis for Upper Atmosphere Abundance Variations on

Venus 25

Hartmann Experimental and theoretical studies of CO2 infrared absorption continua 32 Hashimoto Temporal variation of UV reflectivity of Venus: VEX/VMC data analysis 28

INDEX ‐ PAGE II

Helbert High temperature spectroscopy at the Planetary Emissivity Laboratory in support of present and future Venus missions" 31

Hueso Measurements of Venus winds from ultraviolet, visible and near infrared images with VIRTIS on Venus Express 12

Ignatiev Cloud top variations from Venus Express measurements 30 Ignatiev Venus Clouds: Input to VIRA II model from Venus Express and Venera 15

measurements. 30

Imamura Latitudinal and local time dependence of Venus's cloud-level convection 29 Iwagami Ground-based IR observation of oxygen isotope ratios in the Venus atmosphere 50 Jain Modelling of ultraviolet and visible dayglow emissions on Venus 21 Jessup Variations in Venus’ cloud top SO2 and SO gas density with latitude and time of day 53 Kohler Experimental Stability of Tellurium: Implications for the Venusian Radar Anomalies 32 Kuroda Latitudinal cloud structure in the Venusian northern hemisphere evaluated from

Venus Express/VIRTIS observations 54

Lebonnois Venus GCM modelling: current status and perspectives in the light of Venus Express datasets 10

LeBrun Thermal evolution of an early magma ocean in interaction with the atmosphere: conditions for the condensation of a water ocean 34

Lee Variations of the radiative forcing induced by the cloud top structure changes of the Venus mesosphere 13

Limaye Global Vortex Circulation on Venus - an assessment from Venus Express Observations 11

Limaye/Baines U.S. / VEXAG report 37 Lopez-Valverde Retrieval of temperature and carbon monoxide from the 4.7um limb non-LTE

emission of the upper atmosphere measured by VIRTIS/Venus Express 18

López-Valverde Mapping the lower thermosphere of Venus using VIRTIS/VEx Nadir non-LTE observations at 4.3 um 46

Lorenz On the Possibility of Gamma Ray Flashes from Venusian Lightning 51 Luhmann Large-scale magnetic flux ropes in low-altitude ionosphere of Venus: planetary origin

or solar wind origin 3

Luhmann Comparative Plasma Interactions and their Effects at Venus, Mars and Titan 5 Lundin Solar Wind energy and momentum transfer - Effects on the Venus polar

thermosphere 7

Maattanen Modeling the clouds on Venus: model development and improvement of a nucleation parameterization 29

Machado Venus cloud tops winds with ground-based Doppler velocimetry and comparison with cloud tracking method 44

Mahieux CO2 rotational temperatures compared to hydrostatic temperatures obtained with the SOIR instrument on board VEx 17

Marcq Measurements of minor species at cloud top level 24 Marcq Early evolution of telluric atmospheres in the magma ocean stage 35 Marinangeli Polar Vortex: a common element of the Earth and Venus 43 Masunaga Dependence of O+ escape rate from the Venusian upper atmosphere on IMF

directions: ASPERA-4 observations 6

McEnulty Comparisons of Venus Express measurements with an MHD model of O+ ion flows: Implications for atmosphere escape measurements 6

McGouldrick Re-analysis of Pioneer Venus SO2 measurements 25 Migliorini Gravity waves in the Venus upper atmosphere, modelled on VIRTIS/Venus Express

data 16

Migliorini Visible and Infrared nightglow investigation in the Venus atmosphere by means of VIRTIS on Venus Express 46

Mills Modeling and observations of mesospheric sulfur chemistry 52 Molaverdikhani A new dawn-dusk asymmetry in the photoelectron flux of Venus’s Ionosphere 41 Molera Calves Interplanetary scintillations study retrieved from Venus Express communications

signal 56

INDEX ‐ PAGE III

Moresi The influence of surface conditions on global mantle evolution 34 Mueller Search for active lava flows with VIRTIS on Venus Express 1 Nakamura Japan / Akatsuki report 36 Nordheim Cosmic ray ionization in the Venusian atmosphere from Monte Carlo modelling 7 Nunes Stereo-Derived Topography To Aid Emissivity Estimates at Tesserae on Venus 39 Ogohara Limb fitting and cloud tracking for the study of the Venus atmosphere 41 Oschlisniok Abundance of sulfuric acid vapor in the Venus atmosphere derived from the Venus

Express Radio Science Experiment VeRa 50

Peralta Towards a general classification of atmospheric waves on Venus 44 Perez-Hoyos Analysis of MESSENGER/MASCS data during second Venus flyby 58 Peter A global comparison between VeRa radio science observations of the Venus dayside

ionosphere and the IonA model 39

Petrova Physical properties of particles in the upper clouds of Venus from the IR and UV images taken by VMC/VEx at small phase angles 28

Piccialli Thermal structure of the upper atmosphere of Venus with SPICAV/VEx data 16 Piccialli Gravity waves in Venus mesosphere observed by the Venus Monitoring Camera on

board Venus Express 43

Pluchino Using Venus Express to perform sounding experiments on lunar ionosphere 57 Politi VIRTIS-VEX data analysis for the study of the Venus 53 Rafkin A compact, Low Power Tunable Laser Spectrometer for Trace Gas Measurement in

the Venus Atmosphere 57

Robert Spectral inventory of the SOIR spectra onboard Venus Express 52

Rodin Non-hydrostatic general circulation model of the Venus atmosphere 10 Rodin A compact, lightweight infrared heterodyne spectrometer for studies of Venus

atmosphere 57

Rossi Study of Venus cloud layers by polarimetry using SPICAV/VEx 55 Russell Venus and Planetary Magnetism 3 Russell The Implications of the Observed Evolution of the Co-Orbiting Material in 2201

Oljato’s Orbit Observed by PVO and VEX 9

Russell ULF and ELF Electromagnetic Waves in the Venus Ionosphere: Separating Atmospheric and Magnetosheath Sources 40

Sandor Positive Correlation of SO, SO2 in the Dayside Venus Mesosphere: Identification of Diurnal SOx Partitioning from JCMT Submm Spectroscopy 25

Sandor Temporal, Spatial Variation of HCl in the Venus Mesosphere, based upon Submm Spectroscopic Observations with JCMT 26

Satoh On the origin of the 1-micron contrast features in Venus clouds 29 Shalygin Venus surface geology from near infrared night side Venus Monitoring Camera

images 1

Slanger Abstract Nr. O-014, Slanger, Tom, Long-lived Emitters in the Atmospheres of the Terrestrial Planets 31

Smrekar Diverse Geologic Settings of Recent Volcanism on Venus and Implications for the Interior 2

Snels Carbon dioxide collision induced absorption in the 1.18 micron atmospheric window of Venus 33

Soret The time evolution of O2(a1Δ) individual observations acquired by VIRTIS-M on board Venus Express 45

Sornig Earth based Doppler-wind and temperature measurements in Venus upper atmosphere using the infrared heterodyne spectrometer THIS 18

Sotin Are terrestrial exoplanets Earth-like, Venus-like, or different ? 2 Stefani Experimental set-up to study optical properties of gases at typically planetary

conditions 33

Stenberg Ion escape from Venus 6

INDEX ‐ PAGE IV

Stenberg Solar wind precipitation on Venus 40 Stiepen Venus nitric oxide nightglow distribution: a clue to thermospheric dynamics 20

Stofan Venus: Earth’s (Neglected) Twin 1 Stolzenbach Three-dimensional modelling of Venus photochemistry 52 Sugimoto Baroclinic modes in the Venus atmosphere simulated by AFES (Atmospheric GCM For

the Earth Simulator) 11

Svedhem The variable upper atmosphere of Venus - data from drag and torque measurements by Venus Express 45

Takagi Structures and generation mechanisms of the Venus atmospheric superrotation 11 Takagi High-altitude source for the Venus’ upper haze found by SOIR/Venus Express 55 Takeshi Simulation of the formation, evaporation and transport of sulfuric acid clouds on

Venus using a general circulation model 55

Taylor Volcanism and Climate on Venus: An Updated Model 35 Taylor Venus III book discussion 38 Tellmann The VeRa Radio Occultation Data Base: Atmosphere and Ionosphere 14 Tellmann Waves in the Venus Atmosphere detected by the Venus Express Radio Science

Experiment VeRa 15

Titov / Markiewicz Venus cloud morphology: monitoring by the VMC/ Venus Express camera continued 27 Vandaele Trace gases in the mesosphere and lower thermosphere of Venus from SOIR/VEX 26 Vandaele Contribution of the SOIR/VEX instrument to VIRA II 26 Vasko Fine structure of the Venus current sheet 8 Widemann Mesospheric Temperature at Terminator using SDO/HMI Aureole Photometry,

DST/FIRS CO2 absorption spectroscopy and comparison with Venus Express 41

Wilquet SPICAV-SOIR mesospheric aerosols observations and modelling 27

Yamamoto Simulation of Venus’ polar vortex in the presence of diurnal thermal tide 44 Zalucha Incorporation of a gravity wave momentum deposition parameterization into the

Venus thermosphere general circulation Model (VTGCM) 17

Zasova Thermal structure of the Venus mesosphere from remote sensing in the infrared spectral range (VIRA II improvement) 14

Zasova The O2 nightglow from VIRTIS-M VEX measurements 20 Zhang Physics of Induced Magnetosphere 5

ORAL CONTRIBUTION

ORAL CONTRIBUTIONS

MONDAY, 10 JUNE ‐ PAGE 1

Monday, 10 June

Abstract Nr. 26

Venus: Earth’s (Neglected) Twin

Stofan, Ellen, Proxemy Research Venus, so similar in size and composition to Earth, has a diverse and complex surface that has been studied by spacecraft for over half a century, starting with the flyby of Mariner 2 in 1962. The Venera, Vega, Pioneer Venus, Magellan, and now Venus Express missions have led to an increased understanding of the surface and interior that lies under Venus’s clouds, and what this surface implies about the planet’s evolution. From tesserae to coronae to volcanoes to mountain ranges and fracture belts, analysis of the geologic features on the surface of Venus provide clues to its interior evolution. The ~11 hotspot rises on Venus provide a window into interior processes, and indicate that the planet is still active geologically. However, while our knowledge about Venus has greatly increased, the range of theories to explain what we see remains quite large, and likley will remain so until future investigations are conducted at the surface and in orbit around Venus. As we search beyond our own solar system for Earth-like planets, it becomes more critical to understand why Earth’s twin is so different and what it can tell us about Earth’s past and future.

Abstract Nr. 83

Search for active lava flows with VIRTIS on Venus Express

Mueller, Nils, Institute of Planetary Research, German Aerospace Center (DLR) The VIRTIS instrument on Venus Express observes thermal emission from the surface of Venus at 1 µm wavelength and thus would detect sufficiently bright incandescent lava flows. No eruptions were detected in the observations between April 2006 and October 2008. Models of the cooling of lava flows on Earth are adapted to Venus ambient conditions to predict thermal emission based on effusion rate. Taking into account the blurring of surface thermal emission by the atmosphere, the VIRTIS images would detect eruptions with effusion rates above 500 to 1000 m3/s. Assuming the average eruption volume and effusion rate distribution of Venus' lava flows is similar to that of the Hawaiian volcanoes Mauna Loa and Kilauea, a typical VIRTIS observation would detect 4% to 10% of all lava flows within its field of view and the whole data set is expected to lead to 0.02 detected eruptions per 1 km3 of lava effused per year. Thus the VIRTIS data can constrain the rate of volcanism on Venus to be less than about 100 km3/yr, at least a factor of 10 higher than existing constraints and the terrestrial value of 4 km3/yr. While VIRTIS data does not place new constraints, the analysis shows that dedicated volcano monitoring at Venus is feasible. There remains a large uncertainty because of the unknown style of volcanism and the not well understood role of wind in lava surface cooling, but it could be significantly reduced by analysis of high resolution radar images of flow fields and altimetry resolving the thickness of flows.

Abstract Nr. 57

Venus surface geology from near infrared night side Venus Monitoring Camera images Shalygin Eugene, Max-Planck Institute für Sonnensystemforschung; Basilevsky Alexander, Max-Planck

Institute für Sonnensystemforschung; Markiewicz Wojciech J., Max-Planck Institute für Sonnensystemforschung; Titov Dmitrij, ESA-ESTEC

We analyse night-time near infra-red thermal emission images of the Venus surface obtained with the 1-µm channel of the VMC onboard Venus Express. We consider if SOME terrains have the different emissivity (and thus mineralogic composition) in comparison to the surrounding basaltic plains. Retrieved emissivity of tessera surface material is lower than that of relatively fresh supposedly


basaltic lavas of plains and volcanic edifices. This is consistent with the hypothesis that the tessera material may be felsic. We found a possible decrease of the emissivity at the top of Tuulikki Mons volcano which, if real, may be due to different (more felsic?) composition of volcanic products on the volcano summit comparing to its slopes.

We simulated lava eruptions to access the possibility to detect ongoing volcanic activity. Simulations showed that 1 square km lava flows should be marginally seen by VMC. 2-3 square km lava fields are visible on the plains and 4-5 square km - even in deep rift zones.

Typical individual lava flows on Tuuliki Mons are large enough to produce contrasts of 1000% between them and surroundings in VMC images. But typical lava flows from shield volcanoes on Earth often have been being formed during weeks to months and the instantaneous size of the hot flow surface was usually much smaller. Thus the detection probability is significantly lower, but it is far from being negligible.

Abstract Nr. 120

Diverse Geologic Settings of Recent Volcanism on Venus and Implications for the Interior

Smrekar, Jet Propulsion Laboratory, NASA/Caltech Analysis of VIRTIS data identified four primary areas of high 1-micron surface emissivity, interpreted as evidence of recent volcanism. Prior analysis of gravity and topography of 3 of the 4 areas, as well as interpretation of their surface geology, indicated that they are likely to be supported by a mantle plume, or hotspots. New analysis of the gravity and topography of the Lada Terra shows that it is also likely to be a hotspot. These features represent different geologic settings. Imdr and Dione are similar to classical terrestrial style hotspot, will a broad topographic rise and 1-3 major volcanoes. Themis Regio is a corona-dominated rise. It has a dozen volcanoes and a similar number of coronae, which are thought to be manifestations of small-scale plumes. Many of the volcanoes and coronae appear to have recent volcanism. This signature is interpreted as a plume coming from the core mantle boundary that gets trapped at the upper-lower mantle boundary, giving rise to multiple small-scale thermal diapirs. Lada Terra is in a class of its own, with a broad topographic swell, with a peripheral trough, rift system, and volcanism. The presence of active mantle plumes on Venus indicates that there must be a thermal boundary layer at the core-mantle boundary, giving rise to plumes. Taken together, these features provide a picture of the interior of Venus that includes a hot thermal boundary layer at the core, a phase transition at the base of the upper mantle, a deformable lithosphere, and a mantle that is heating up.

Abstract Nr. 47

Are terrestrial exoplanets Earth-like, Venus-like, or different ?

Christophe Sotin, Jet Propulsion Laboratory - Caltech Since the discovery of the first exoplanet in the nineties, hundreds of candidates have been reported. Among them, about a dozen are reported to have a density that compares with terrestrial planets, which make them preferred targets for spectral determination of their atmospheres. Venus and Earth, although very close in density, have evolved on very different pathways: different atmospheric composition, lack of current plate tectonics on Venus, liquid water on the Earth’s surface. Venus dynamics is in the so-called ‘stagnant lid regime’ whereas the Earth’s surface is fractured into several plates which move relative to each other in relation with mantle convection. Parameters such as surface temperature, size and atmospheric composition may influence the transition from one regime to the other. Most of the exoplanets found so far may be closer to Venus characteristics than to Earth. Searching for Earth-like planets where plate tectonics operates is a major endeavor in the field of exoplanets. However, this study also suggests that some exoplanets may be remnant cores of giant planets that migrated towards their star while losing their atmosphere by escape processes. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology,


under contract to NASA. Government sponsorship acknowledged.

Abstract Nr. 82

The influence of rheology and volatiles on the geology of Venus

Ghail, Richard, Imperial College London Pyroclastic activity is apparently almost absent on Venus, perhaps indicating a lack of volatiles in the interior. However, an unusual feature near Diana Chasma likely originated as a pyroclastic surge deposit. Its radar characteristics are only subtly different to those of the average Venus surface, meaning that similar deposits may exist elsewhere but not be recognised and the interior may be volatile-rich. Volatiles induce an asthenosphere, which together with decoupling of the crust and mantle caused by the elevated surface temperature, enables stagnant lid recycling below the crust. Fits to global hypsography imply a recycling rate of 5·0 ± 0·5 km² a⁻¹ and the loss of ~90% of a scaled Earth-like heat production rate. Lid recycling by both plume activity and convection is consistent with a number of features, particularly the global network of chasmata, by generating major melting at upwelling sites, an adjacent region of minor melting aiding lateral slip, and downwelling above geoid lows. An age of ~15 Ma is inferred for the western Eistla Regio plume and subcrustal slip rates between 13 and 100 mm a⁻¹ are determined from fits to topographic profiles across the principal chasmata. While Venus appears to be in thermal equilibrium now, higher rates of radiogenic heat production in the past imply a greatly enhanced rate of magmatic resurfacing, which 1 Ga ago was capable of resurfacing the whole planet in ~40 Ma, implying a transition from an Io-like volcanic planet to a tectonic dominated Earth-like regime over that time.

Abstract Nr. 05

Venus and Planetary Magnetism

Russell, Christopher T., UCLA; Cao, Hao, UCLA A magnetic dynamo is a heat engine in which convection occurs in an electrically conducting medium. As a planet cools rapidly, the transport of heat from the metallic core across the mantle to the surface of the body does work by the production of a magnetic field. A source of heat from primordial thermal energy (cooling of the core), radioactivity, latent heat release and expulsion of light fluids as a solid inner core freezes all provide the necessary circulation and heat transport. In the case of a core in the center of a planet, inefficient heat transport in the mantle and crust can stifle heat transport and shut off a dynamo. This appears to have occurred on Venus. We review the physics of planetary dynamos and Venus in particular. We also review the observational evidence on the current state of the Venus dynamo.

Abstract Nr. 114

Large-scale magnetic flux ropes in low-altitude ionosphere of Venus: planetary origin or solar wind origin

Luhmann, Janet G., UC Berkeley; Wei, Hanying, UCLA; Russell, Christopher T., UCLA; Zhang,

Tielong, Austrian Academy of Sciences The Venus Express magnetometer observed large-scale magnetic structures of hundreds of kilometers in spatial size near two hundred kilometer altitudes. Although occurring occasionally, these structures strongly magnetize the low ionosphere (up to a hundred nano-tesla) and are quite different from the small-scale magnetic flux ropes which are generated by the Venus-solar wind interaction with much more frequent occurrence. Zhang et al. (2012) analyzed six such events in 2009 and suggest they have different generation mechanism from the small-scale flux ropes, possibly crustal magnetic remanent or magnetic reconnections. To understand the origin of these large-scale flux ropes, we examine the 2009 data and find they occurs in about 10% of all orbits with locations very close to the Venus geographic north pole (within 0.1 Venus radii). The correlation of occurrence with location and


the eastward component always being positive are consistent with the flux ropes having planetary origin. However, the field component radial from the surface changes polarity from orbit to orbit and does not agree with a crustal field picture. Moreover, the polarity and variation of the radial field are controlled by the orientation of the draped solar wind magnetic field in the Venus magnetosheath, suggesting the flux rope having solar wind origin. In this paper, we investigate these large-scale flux ropes to understand their generation mechanism.

TUESDAY, 11 JUNE – PAGE 5

Tuesday, 11 June

Abstract Nr. 49

Physics of Induced Magnetosphere

Tielong Zhang, Space Research Institute, Austrian Academy of Sciences, Graz, Austria The term induced magnetosphere has been widely used by the recent Venus Express publications. For a planet like Venus or Mars, which has no global intrinsic magnetic field but with atmosphere, an induced magnetosphere is created by the solar wind interaction with the highly conducting ionosphere. It consists of regions near the planet and its wake for which the magnetic pressure dominates all other pressure contributions. The induced magnetosphere is therefore analogous to the magnetosphere of an intrinsically magnetized planet, but occupies a smaller volume. In this talk, we review some of the induced magnetosphere observations by Venus Express.

Abstract Nr. 08

Comparative Plasma Interactions and their Effects at Venus, Mars and Titan Luhmann, J.G.; Wang, Y-C.;Ledvina, S.A., SSL, University of California, Berkeley; Ma, Yingjuan; Wei,

Hanying; Russell, C.T.,IGPP UCLA; Zhang, T-L., IWF, Graz; Barabash, S., IRF, Kiruna; Kallio, E.; Jarvinen, R., FMI; Sillanpaa, I., SWRI; Westlake, J.,JHUAPL; Fang, X., LASP, University of Colorado

The 'weakly magnetized planets' Venus, Mars and Titan represent a sequence of increasingly complex plasma interactions-with increasingly complex consequences. Venus is perhaps the best understood because it is a case where the incident flow is supersonic and the relevant scalings allow fluid plus test particle treatments of the system. The Mars case adds not only the complexity of the crustal magnetic fields but also an increasing need to consider finite ion gyroradius effects. Titan presents some other complications including the presence of a permanent external field component from the Saturn dipole and subsonic interaction with a highly nonthermal external particle population. And Titan's atmosphere is also greatly extended compared to its planetary counderparts. We take a look at what we have learned about some of the similarities and contrasts, and consider still open issues of interest for future investigations and comparative studies.

Abstract Nr. 108

How the near-Venus space affects the planet

Stas Barabash, Swedish Institute of Space Physics The solar wind flowing around Venus affects the planet’s atmosphere and ionosphere via energy, matter, and momentum transfer. The energy transfer causes the non-thermal escape of planetary ions. The matter transfer results in the deposition of the solar wind hydrogen and helium into the atmosphere. The momentum transfer causes atmospheric sputtering. There might even occur processes involving the angular momentum transfer to the upper ionosphere. We review the most recent observations of all these processes by the ASPERA-4 instrument onboard Venus Express (Analyzer of Space Plasmas and Energetic Atoms) and compare them with two other terrestrial planets, Mars and Earth. The overall conclusion is at the present time the induced magnetosphere of Venus creates a strong magnetic barrier substantially reducing the influence of the near-Venus environment on the planet.

Abstract Nr. 95

Ion escape from Venus


Stenberg Gabriella, Swedish institute of space physics; Barabash Stas, Swedish institute of space

physics; Futaana Yoshifumi,Swedish institute of space physics We use more than three years of data from the ASPERA-4 instrument onboard Venus Express to estimate the net outflow of protons and heavy ions from Venus. The ion escape appears to exclusively take place in the induced magnetotail region and no heavy ions are present in the magnetosheath. Protons of solar wind origin are travelling around the planet and penetrating the tail, resulting in a mix of planetary and solar wind protons inside the induced magnetosphere boundary. The escape rates of ions inside the tail agree with results from recent published studies, where other analysis methods have been used. We also present average flux patterns in the near Venus space based on computed average distribution functions. We compare our results for Venus with a recent study of ion escape from Mars, where the same analysis method has been applied to data from the ASPERA-3 instrument on Mars Express.

Abstract Nr. 70

Dependence of O+ escape rate from the Venusian upper atmosphere on IMF directions: ASPERA-4 observations

Masunaga Kei, Swedish Institute of Space Physics, Kiruna, Sweden; Futaana Yoshifumi, Swedish

Institute of Space Physics, Kiruna, Sweden; Stenberg Gabriella, Swedish Institute of Space Physics, Kiruna, Sweden; Barabash Stas, Swedish Institute of Space Physics, Kiruna, Sweden; Zhang

Tielong, Space Research Institute, Austrian Academy of Science, Graz, Austria; Fedorov Andrei, Centre d’Etude Spatiale des Rayonnements, Toulouse, France; Okano Shoichi, Institute for

Astronomy, University of Hawaii, Pukalani, HI, USA; Terada Naoki, Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan

We present the dependence of O+ escape flux rate on the upstream interplanetary magnetic field (IMF) direction calculated from the data obtained from the Analyser of Space Plasma and Energetic Atoms (ASPERA-4) instrument and the magnetometer (MAG) onboard Venus Express. The data in the period between June 21, 2006 and May 31, 2010 is classified into two cases: the perpendicular IMF case (167 events) and the parallel IMF case (82 events), where IMF is nearly perpendicular to the solar wind velocity and nearly parallel to it. We average O+ fluxes observed in the nightside region and statistically calculate the escape rate for each IMF case. The O+ escape rates of (5.8 ± 2.9) × 1024 s-

1(perpendicular IMF case) and (4.9 ± 2.2) × 1024 s-1 (parallel IMF case) are obtained. Since these values are not significantly different, we conclude that several acceleration mechanisms must balance each other in order to keep the escape rate constant.

Abstract Nr. 109bis

Comparisons of Venus Express measurements with an MHD model of O+ ion flows: Implications for atmosphere escape measurements

McEnulty, Tess, LASP, University of Colorado, Boulder; Yingjuan Ma, IGPP, University of California, Los

Angeles; Janet G. Luhmann, SSL, University of California, Berkeley; Demet Ulusen, Space Technologies Research Institute, Ankara, Turkey; Imke de Pater, Department of Astronomy, University

of California, Berkeley; Andrei Fedorov, Institut de Recherche en Astrophysique et Planetologie, Toulouse, France; David Brain, LASP, University of Colorado, Boulder

The Venus Express (VEX) Ion Mass Analyzer (IMA) detects low energy (< 100 eV) oxygen ions flowing into the wake. Investigators have suggested that the majority of the O+ escape measured by the IMA is in this low energy population. However, the spacecraft potential and relative velocity complicate interpretation of these ions. Due to these complications, there is still an open question of whether or not all of these low energy ions are actually escaping. Some of the measured ions may actually be gravitationally bound, even out to ~1.5 Venus radii in the wake. To illustrate these complications in interpreting these measured low energy ions, we compare VEX ion measurements in this region to results from a magnetohydrodynamic model. The model simulations highlight how IMA measurements


of O+ can be affected by the spacecraft relative velocity and potential. In addition, we simulate multiple different orbit trajectories in the model and show how the O+ IMA measurements depends on orbit geometry and interplanetary magnetic field direction. We then integrate O+ escape flux in the wake region of the model along the VEX orbit to illustrate how non-escaping (gravitationally bound) ions could affect estimates of total O+ escape.

Abstract Nr. 101

Solar Wind energy and momentum transfer - Effects on the Venus polar thermosphere Lundin Rickard, Swedish Institute of Space Physics; Barabash, S., Swedish Institute of Space Physics; Futaana, S., Swedish Institute of Space Physics; Holmstrom, M., Swedish Institute of Space Physics;

Perez-de-Tejada. H., UNAM, Mexico City, Mexico; Sauvaud, J-A., CESR/CNRS Toulouse, France An analysis of the average ion flow properties in the Venus magnetosphere and plasma tail reveals the existence of a large-scale flow vortex, i.e. solar wind H+ (SW H+) and ionospheric O+ curling right-handed tailward (as viewed from the Sun. The vortex commences at dusk (-Y), driven by a transverse (to the solar wind) aberration flow component. Dusk magnetosheath and ionospheric ions move westward across the nightside into the dawn sector, from where the tailward and lateral flow merges into a tailward-moving vortex. Analyzing the fluid dynamics of the SW H+ energy and momentum (E&M) transfer to O+ at the terminator, we find that E&M balance (efficiency ≈1) is achieved in the altitude range 1200 - 600 km. Below 600 km a combined Westward O+ and energetic neutral atom (ENA) flow completely dominates the momentum flux, the average O+ and ENA flow going in the direction of the Venus atmospheric superrotation. An analysis of the solar wind H+ ionospheric O+ energy and momentum (E&M) transfer to the neutral gas in the Venus thermosphere and upper atmosphere over the polar region, reveals that external/solar wind, and the corresponding ionospheric ion forcing, may drastically affect the short term wind pattern down to 150 km. For instance, we find that the average ionospheric O+ wind is capable, via ion drag, to set a polar cap CO2 air mass at 150-200 km altitude in motion by 200 m/s in less than 5 minutes. Below 150 km, E&M transfer downward to the upper atmosphere is expected due to frictional forcing, although at a much slower pace.

Abstract Nr. 107 The plasma vortex in the Venusian plasma tail. Steady-state reconnection or fluid motion?

Fedorov Andrey, IRAP/UPS/CNRS, Toulouse, France; S. Barabash, IRF, Kiruna, Sweden; T.L.

Zhang, University of science and technology, Hefei, China; J.A. Sauvaud, IRAP/UPS/CNRS, Toulouse, France

The plasma and magnetic field statistics, accumulated since 2006 by Venus Express Aspera-4 and MAG data show: 1. The minimum of the magnetic fileld in the close Venusian wake 2. The planetward averaged ion flow observed in the same region. The case study (Zhang, 2012, Nature) gives at least one evidence of the plasmoid-like event that can be associated with a tail magnetic reconnection. The present paper combines statistical and case studies to answer the question: if the observed plasma vortex is caused by a pseudo-steady state reconnection, or it is a characteristic fluid motion.

Abstract Nr. 74

Cosmic ray ionization in the Venusian atmosphere from Monte Carlo modelling Tom Nordheim, Mullard Space Science Laboratory, University College London; Lewis R. Dartnell, UCL Institute for Origins, University College London; Andrew J. Coates, Mullard Space Science Laboratory,

University College London The atmospheres of the terrestrial planets are constantly exposed to solar and galactic cosmic rays,


the most energetic of which are capable of affecting deep atmospheric layers through nuclear and electromagnetic particle cascades. The energy deposited by these interactions is thought to be an important driver for atmospheric chemistry and may possibly affect cloud microphysics, and in regions beneath the penetration of ultraviolet radiation, cosmic rays are the primary ionization agent. It is therefore crucial to quantify the amount of energy deposited by cosmic rays in the atmosphere by altitude, as this is required to estimate ionization and conductivity profiles. Detailed studies have considered the propogation of cosmic rays in the atmospheres of Earth, Mars, Titan and the Giant Planets. However, to date, only a few studies (Dubach et al, 1974; Borucki et al, 1982) have considered such interactions in the Venusian atmosphere, notably using Boltzmann transport approximations. In this work we will present preliminary results of full Monte Carlo modelling of solar and galactic ray cosmic ray primaries interacting with the Venusian atmosphere during solar minimum and maximum conditions. In addition, the radiation dose during extreme events (e.g Carrington Flare event) will be discussed.

Abstract Nr. 02

Ionospheric magnetic fields and currents at Mars and Venus

Dubinin E., Max-Planck-Institute for Solar System Research, Lindau, Germany Mars Express and Venus Express spacecraft have provided us a wealth of in-situ observations of characteristics of induced magnetospheres of Mars and Venus at low altitudes during solar minimum conditions. At such conditions large-scale magnetic fields are observed deeply in the ionospheres (magnetized ionospheres). The observations again raise a long-standing question about the origin of these fields. The problem is intimately related to the issue of electric current system and their closure. Analysis of ASPERA-3, ASPERA-4, MARSIS and MAG data reveals a lot of features which require a more sophisticated view at the origin and the topology of the ionospheric magnetic fields. Differing perspectives at this problem are widely discussed.

Abstract Nr. 122

Fine structure of the Venus current sheet

Vasko Ivan, Space Research Institute, Moscow; Zelenyi Lev, Space Research Institute, Moscow; Artemyev Anton, Space Research Institute, Moscow; Petrukovich Anatolii, Space Research Institute, Moscow; Zhang Tielong, IWF, Graz; Fedorov Andrei, CNRS, France; Malova Helmi, Space Research Institute, Moscow; Popov Viktor, Space Research Institute, Moscow; Nakamura Rumi, IWF, Graz

One of the gaps in our knowledge of the Venus current sheet (CS) is the CS thickness. The reason is that the CS is in motion during observations (flapping motion) and the velocity of the flapping motion cannot be determined by the single-spacecraft mission. On the other hand one can say something about the CS spatial scale by studying the fine structure of magnetic field profiles. We have used the data of Venus Express mission to study the structure of the Venus CS near the planet based on the statistics of 13 CS crossings observed during steady conditions in the solar wind in years 2006-2010. We have found that observed magnetic field profiles can be separated into single-scale and double-scale. Plasma data have shown that double-scale CSs are oxygen-dominated, while single-scale CSs can be proton-dominated as well as oxygen dominated. The observed profiles can be adequately described in the frame of thin anisotropic CS model. The model predicts that double-scale CSs appear due to the trapped oxygen population, picked up from the ionosphere. In addition the model predicts that the CS thickness is only several particle gyroradii.

Abstract Nr. 93

Ionospheric photoelectron observations at Venus

Coates Andrew, UCL-MSSL; Wellbrock Anne, UCL-MSSL; Frahm Rudy, SwRI; Winningham David, SwRI; Barabash Stas, IRF; Lundin R, IRF


The Venus ionosphere at the top of the planet’s thick atmosphere is sustained by photoionization. The consequent photoelectrons may be identified by specific features in the energy spectrum at 20-30 eV. The ASPERA-4 electron spectrometer has an energy resolution designed to identify the photoelectron peaks. Photoelectrons are seen not only in their production region, the sunlit ionosphere, but also at more distant locations in the Venus environment. Here, we present a summary of the work to date on observations of photoelectrons at Venus, and their comparison with similar processes at Titan and Mars, and we present further data on the distant photoelectrons at Venus.

Abstract Nr. 86

A survey of Hot Flow Anomalies at Venus

G.A. Collinson, Heliophysics Science Division, NASA Goddard Space Flight Center, USA; D.G. Sibeck, Heliophysics Science Division, NASA Goddard Space Flight Center, USA; A. Masters, Institute

of Space and Astronomical Science, JAXA, Japan; N. Shane,Mullard Space Science Laboratory, University College London, UK; T.L. Zhang, Austrian Academy of Sciences, Space Research Institute,

Gratz, Austria; A. Fedorov, Universite de Toulouse, UPS-OMP, IRAP, Toulouse, France; S. Barabash, Swedish Institute of Space Physics, Kiruna, Sweden; A.J. Coates, Mullard Space Science

Laboratory, University College London, UK; T.E. Moore,Mullard Space Science Laboratory, University College London, UK; J.A. Slavin, University of Michigan, Ann Arbor, Michigan, USA

We present the first survey of Hot Flow Anomalies (HFAs) at the bow shock of Venus, expanding on our recent initial case study of a single event [Collinson et al., 2012]. HFAs are an explosive plasma phenomena, through the interaction between an interplanetary current sheet and a planetary bow shock, wherein a pocket of reflected solar wind plasma becomes heated and rapidly expands. We show that the newly discovered Cytherean HFAs are very important at Venus because: (1) they are common, occurring at a rate of ~2 per day; (2) They are very large when compared to the overall size of the system (0.4-1.7 Rv or (~130% of the sub-solar bow shock distance); and (3) unlike at magnetized planets, occur very close (1.5-3Rv) to the surface of the planet. Given that the large fluctuations in pressure associated with an HFA drive large motions in the location of the Earth’s magnetopause, HFAs have the potential to be extremely disruptive to the induced magnetosphere and unprotected ionosphere of Venus. Thus we hypothesize that HFAs have a much more dominant role in the dynamics of the induced magnetosphere of Venus relative to the magnetospheres of magnetized planets.

Abstract Nr. 09

The Implications of the Observed Evolution of the Co-Orbiting Material in 2201 Oljato’s Orbit Observed by PVO and VEX

Russell, Christopher T., UCLA; Lai, Hairong, UCLA; Delzanno, Gian Luca, LANL; Zhang,

Tielong, Austrian Academy of Sciences The observation with PVO and VEX of the time-varying IFE rate in the “Oljato-sensitive” sector of ecliptic longitudes provides an important window into how “meteor” streams evolve. The fact that there was a broad region of increased IFE occurrence centered around Oljato suggests that material was broken free from Oljato sometime before 1980. These newly produced “bolides” themselves evolved over a period of about 20 years so that they were no longer producing collisions in 2012. This suggests that a warning system for Earth could be developed by launching a set of perhaps a dozen small magnetometer-equipped spacecraft that would have a 1-year orbit period, but would orbit the Sun in a slightly elliptical orbit so the satellites would spend time inside and outside 1 AU, but remain ahead of the Earth in its orbit a fixed offset to provide time for analysis and follow-up. When swarms of IFEs are seen at longitudes of known near-1-AU crossing objects, radar and optical measurements could be made along that body’s orbit when the Earth reached that longitude. When hazardous co-orbiting material was located, a decision could be made as to whether it was necessary to destroy or remove it and how to accomplish this. We note that we already have spacecraft at 1 AU around Earth and displaced from Earth (STEREO A and B). These spacecraft could be used to test this concept before deployment.

WEDNESDAY, 12 JUNE – PAGE 10

Wednesday, 12 June

Abstract Nr. 51

Venus GCM modelling: current status and perspectives in the light of Venus Express datasets

Lebonnois Sebastien, LMD, CNRS

In recent years, the study of Venus atmospheric system has made a step forward, thanks to the combination of new observations from Venus Express and of development of evolved General Circulation Models (GCM). During this talk, I will review the available GCMs developed around the world and their most recent results. The difficulties met when comparing them with each other, potentially related to the tricky question of angular momentum conservation in these tools, will be mentioned. These models benefit from the recent Venus Express datasets: temperatures in the cloud region and above (VIRTIS, VeRa, SPICAV), cloud-tracking wind speeds (VIRTIS, VMC), composition below and above the clouds (VIRTIS, SPICAV), as well as their time variability where wave activity is now put to evidence. The role of the thermal tides in the dynamics and their observations will be discussed. Among these GCMs, I will present in more details the perspectives for the LMD GCM, developed in close collaboration with colleagues from LATMOS. Recently, we have used idealized tracers to study how the circulation may explain the latitudinal profiles of CO and OCS around 35km of altitude (E. Marcq, LATMOS). The implementation of a photochemical module is underway (F. Lefèvre and A. Stolzenbach, LATMOS), and a microphysical model for clouds is also in development (A. Määttänen, LATMOS). At LMD, we are studying the impact of adding a parametrization for gravity waves generated close to the surface, and prepare new parameterizations to extend the model top up to 140 km.

Abstract Nr. 109

Non-hydrostatic general circulation model of the Venus atmosphere

Rodin Alexander, Moscow Institute of Physics and Technology, Space Research Institute; Mingalev Igor, Polar Geophysical Institute; Orlov Konstantin, Polar Geophysical Institute

We present the results of general circulation simulations of the Venus atmosphere based on full set of gas dynamics equations. There are several regions in the Venus atmosphere where breaking hydrostatic balance may influence general circulation, including polar vortices. The model implements the explicit semi-Lagrangian integration technique and allows for transport of passive tracers. Thermal forcing could be simulated optionally either by relaxation to specified temperature field, or by full-scale radiative transfer solver based on consecutive scattering order approximation. The model takes advantage of GPU accelerators using CUDA technology and runs on spatial grids with the resolution 1.4o in horizontal scale and 250 m in the vertical. Simulations reproduce the vertical and latitudinal structure of zonal superrotation, typically splitting into two midlatitude jets. Above 100 km the model reveals complex flow patterns that may be interpreted as a manifestation of the subsolar-antisolar circulation. Simulations also reproduce polar vortices with variable zonal wavenumber, characterized by strong downwelling motion in the central area. The maintenance of vortices suggest extra cooling of the circumpolar atmosphere within the cloud deck and heating above the clouds.

The work has been supported by the Ministry of Education and Science of Russian Federation grant #11.G34.31.0074 and Russian Academy of


Sciences program #22

Abstract Nr. 10

Structures and generation mechanisms of the Venus atmospheric superrotation

Takagi, Masahiro, Kyoto Sangyo University; Matsuda, Yoshihisa, Tokyo Gakugei University The Venus atmospheric superrotation is one of the most remarkable phenomena in the planetary science. Though several mechanisms have been proposed so far, the generation mechanism remains unclear. In the present study, we focus on the Gierasch mechanism (GM) and the thermal tide mechanism (TTM). In order to examine their dynamical interactions, some numerical experiments with different distributions of the solar heating have been carried out. The results show that the superrotation is maintained by GM and TTM, independently. The spatial structures of the mean zonal flow are different for these cases. The midlatitude jets are formed only in the GM case. It is also noted that GM can work with the realistic solar heating, unlike the previous studies (Yamamoto and Takahashi 2003; Hollingsworth et al. 2007). The difference may be due to the initial condition, which is the superrotating flow in the present study. In the case with the diurnal heating (i.e., both GM and TTM are included), the superrotation is maintained by TTM mainly, because the mean meridional circulation is localized in the upper atmosphere above the cloud layer. It is also found that several kinds of waves including the baroclinic instability waves appear. These waves which are excited in the low static stability levels may contribute to the momentum and heat transport.

Abstract Nr. 06

Baroclinic modes in the Venus atmosphere simulated by AFES (Atmospheric GCM For the Earth Simulator)

Sugimoto Norihiko, Keio University; Takagi Masahiro, Kyoto Sangyo University; Matsuda

Yoshihisa, Tokyo Gakugei University An atmospheric general circulation model (AGCM) for Venus is being developed on the basis of AFES (AGCM For the Earth Simulator) in order to study phenomena on Venus atmosphere by the numerical simulation with high resolution. As a first step toward long time high resolution numerical simulation to reproduce super-rotation, we investigate unstable modes on the condition of the idealized super-rotation by T42L60 numerical simulation with realistic static stability. Super-rotation is assumed to exist at initial state and to be maintained by the relaxation forcing due to the meridional temperature gradient. In the time evolution of this setting, baroclinic modes grow in the cloud layer with small static stability. The structures of unstable modes are similar to those obtained in the previous linear stability analysis initially, but changed by the nonlinear interactions in the later stage. Meridional transport of momentum and heat by these unstable modes is discussed. The results of T159L120 high resolution simulation, long time (300 years) numerical simulations with and without solar heating, starting from state of rest and super-rotation, will be shown in the presentation.

Abstract Nr. 46

Global Vortex Circulation on Venus - an assessment from Venus Express Observations Limaye, Sanjay, University of Wisconsin; Markiewicz, Wojciech, Max Planck Institute for Solar System

Research Seven years of observations of Venus Express provide an idea of the range of the basic cloud level zonal circulation of the atmosphere and the accompanying global cloud morphology and some information about the circulation above and below the clouds. The results of these observations and the recent efforts in numerical simulations of the global circulation point to gaps in our knowledge


needed to understand the maintenance of the superrotation of the atmosphere. VMC and VIRTIS observations provide information about the top of clouds and middle cloud level on Venus while the VeRa thermal structure profiles constrain the thermal support for the circulation between about 45 -85 km above the mean surface. Inferences about the circulation above 85 km come from airglow observations from VIRTIS and from the SOIR and SPICAV thermal structure profiles. Of these, VMC provides the most continuous record of the southern hemisphere. These observations show recurring dynamical features in the core region of the vortex while away from the core region considerable asymmetry is seen many times. The relative stability and longevity of global vortex circulation which was first inferred from 1974 Mariner 10 observations and indicated by Pioneer Venus Orbiter (1978 – 1983) and Galileo fly-by (1990) through the Venus Express epoch suggest that the vortex has been a long term feature of the atmosphere for a very long time. In fact, as there is little evidence for the supply of the energy, it is likely that the vortex circulation on Venus is the longest lived vortex and the largest in terms of relative size compareed to the planet. We still lack definitive measurements that can provide the meridional transport of angular momentum at any level as a function of latitude with confidence to assess the relative importance of the proposed mechanisms for the maintenance of the superrotation.

Abstract Nr. 34

Measurements of Venus winds from ultraviolet, visible and near infrared images with VIRTIS on Venus Express

Hueso, Ricardo, Dpto. Física Aplicada I, Escuela Técnica Superior de Ingeniería, UPV/EHU, Bilbao

(Spain); Bandos, Tatyana, Dpto. Máquinas y Motores Térmicos, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco, UPV/EHU, Bilbao (Spain); Garate-Lopez, Itziar, Dpto. Física

Aplicada I, Escuela Técnica Superior de Ingeniería, UPV/EHU, Bilbao (Spain); Peralta, Javier,Instituto de Astrofísica de Andalucía, (CSIC) Granada (Spain); Sánchez-Lavega, Agustín, Dpto. Física Aplicada

I, Escuela Técnica Superior de Ingeniería, UPV/EHU, Bilbao (Spain) After 6 years orbiting Venus the Venus Express mission has provided the largest database of visual and infrared observations of the Venus clouds at different layers with the combination of VMC and VIRTIS instruments. We present further measurements of cloud motions in the South hemisphere of Venus obtained from the VIRTIS-M visible channel observations at different wavelengths sensitive to the upper cloud haze at 65-70 km height (dayside ultraviolet images) and the middle cloud deck (dayside visible wavelengths and near infrared images around 1 mm) about 5 km deeper in the atmosphere. The measurements were obtained with a semi-automatic cloud correlation algorithm that largely avoids spurious measurements and is robust enough to be used in images of very different characteristics in terms of signal to noise ratio, spatial resolution and time separation between images. We focus this study on wind measurements of the South Polar latitudes closing around the South Polar Vortex and on the middle cloud deck whose motions and variability have not been studied in detail before because of low contrast of atmospheric features in these wavelengths. We use a combination of VIRTIS images in nearby wavelengths to increase the signal to noise ratio and apply strong image spatial filters to increase the contrast of the atmospheric details. Both cloud layers are studied simultaneously to infer similarities and differences between vertical levels, cloud morphologies and winds. We summarize the result of the new measurements and compare with our previous studies of winds with VIRTIS data.

Abstract Nr. 20

Atmospheric Oscillation in the atmosphere of Venus: the Cupido effect

Bertaux Jean-Loup, LATMOS/UVSQ/CNRS As observed by SPICAV on Venus Express, the quantity of SO2 above the clouds of Venus has drastically changed in the recent years (Marcq et al., 2012), reaching a maximum around 2007,


followed by a strong decrease (factor 5-10). Assuming that this is not due to volcanic activity, it reveals a major change in the atmospheric circulation pattern, since SO2 is a tracer of upwelling. A similar decrease was observed after 1978 by Pioneer Venus. This suggests that SO2 variations are a sign of a global atmospheric oscillation, periodic or pseudo-periodic, reminiscent of Earth Quasi Biennial Oscillation (QBO), or El Niño-La Niña phenomenon. By analogy, we propose to name this new Venus oscillation “the Cupido effect”, after the name of the son of Venus. We will discuss the possible relation of the Cupido effect with three topics. One Venus general circulation model produces decadal variations (Parish et al., 2011) that could be essentially the Cupido effect. The zonal wind speed at Venus cloud top is observed (with VMC) to increase since 2006 (Khatuntsev et al., 2012). The rotation of the solid body as measured accurately by Magellan radar in 1990-1992 at 243. 0185 ± 0.0001 days is significantly faster than the rotation averaged over 16 years at 243.023±0.002 days as measured by VIRTIS with thermal IR features on the ground of Venus (Mueller et al., 2012). Such a change of the rotation period could be associated to atmospheric changes, as is observed on Earth.

Abstract Nr. 45 Variations of the radiative forcing induced by the cloud top structure changes of the Venus

mesosphere

Lee, Y.J., ISAS/JAXA, Japan; Titov, D., ESA/ESTEC, the Netherlands; Ignatiev, N., IKI, Russia; Tellmann, S., Rheinish Institute for Environmental Research, Germany; Pätzold, M., Rheinish Institute

for Environmental Research, Germany; Piccioni, G., INAF-IAPS, Italy The radiative forcing by the clouds is one of important parameters to understand the radiative energy balance of the Venus mesosphere. The thick clouds (48-70 km) reflect ~76 % of solar radiation back to space. About 70 % of remaining solar flux is absorbed above 60 km altitude by clouds, gases, and unknown UV absorber [Crisp 1986; Crisp and Titov, 1997]. Also, the clouds absorb a large fraction of the outgoing thermal emission from the hot deep atmosphere, making them the second strongest greenhouse agent in the Venus atmosphere [Bullock, 1997]. Then, temperature and cloud top structure determine the outgoing thermal emissions. Venus Express observations revealed significant changes in the cloud top altitude and aerosol scale height [Ignatiev et al., 2009; Lee et al., 2012]. We performed full radiative transfer modeling of the solar and thermal radiation with cloud top structure variations and latitudinal temperature. The sensitivity study shows the solar heating rate at the cloud top level changes from 10 K/day to 95 K/day in the sub-solar region depending on the cloud top structures. We found that around one-third of total solar heating at the cloud tops was the contribution of the unknown UV absorber, in the averaged low latitude condition. The sensitivity study of the thermal cooling rate shows the 5-30 K/day range of variations depending on the cloud top structures. Diurnal averaged net radiative forcing shows an increasing net cooling at the cloud tops from -0.1~-2.5 K/day at low latitudes to -11 K/day in the polar region.

Abstract Nr. 61

Thermal Structure of Venus Mesosphere as Observed by VIRTIS - Venus Express

Grassi Davide, IAPS-INAF; Migliorini Alessandra, IAPS-INAF; Politi Romolo, IAPS-INAF; Ignatiev Nikolay, IKI-RAS; Piccioni Giuseppe, IAPS-INAF; Drossart Pierre, Observatoire de Paris - Meudon

We review here the results achieved by VIRTIS in studying the air temperature fields of Venus mesosphere (65-90km). Measurements are limited to nighttime conditions, since during daytime the 4.3 microns band is prone to non-LTE contamination.

Main features of temperature fields.The 'cold-collar' previously detected by Pioneer Venus Orbiter is the most striking structure in Venus temperature fields. It is observed in both hemispheres and is centered about 70 degrees from the equator; it extends vertically up to 70 km above the mean surface.


Similarly, the 'polar dipole' is also detected in temperature fields, where its signature is confined below 70 km.

Latitude/local time average temperature fields.VIRTISdataset size allows to bin temperature retrievals according different parameters. For their implication on dynamical phenomena occurring in the Venus atmosphere, average air temperature fields in the local time/latitude/pressure space are of special interest. VIRTIS-M maps show the occurrence of a temperature minima in the cold collar around 2-3 LT, while at higher levels (80 km) the morning side is warmer than its evening counterpart. Despite the sparsity of sampling, these features are also suggested by VIRTIS-H observations in the northern hemisphere.

Latitude/longitude average temperature fields. Time series analysis of VIRTIS-M retrieved temperatures indicate a clear periodicity equal to one Venus solar day. This observation lead to an investigation of average latitude/longitude/pressure air temperature fields from VIRTIS-M data. The expected longitudinal uniformity is violated by a particularly cold collar between 180E and 270E and a warm region at 120E, 70S at the 12.6 mbar level (75 km).

Abstract Nr. 124

Thermal structure of the Venus mesosphere from remote sensing in the infrared spectral range (VIRA II improvement)

Zasova Ludmila, (1) IKI RAS, Moscow, (2) MIPT, Dolgoprudny, Russia; Gorinov Dmitry, (1) IKI RAS,

Moscow, (2) MIPT, Dolgoprudny, Russia; Grassi Davide, (3) IASP-INAF, Rome, Italy; Migliorini Alessandra, (3) IASP-INAF, Rome, Italy; Haus Rainer, (4)DLR, Berlin, Germany; Piccioni Giuseppe, (3)

IASP-INAF, Rome, Italy; Pierre Drossart, (5) LESIA, Paris, France We analyze the measurements of two spectrometers: VIRTIS –M on Venus Express and Fourier spectrometer on Venera-15 (FSV15). Both experiments worked on polar orbits. The first one made measurements in 2006 – 2009 and obtained millions spectra in the near IR spectral range. From VIRTIS-M data the temperature profiles were retrieved from 4.3 µm CO2 band on the night side only. It was covered altitude range from 65 to 95 -100km, latitudes 20 -80 °S ( Grassi, Migliorini). FSV15 worked for 2 month in 1983 and it was obtained about 1500 spectra in the thermal IR. Temperature profiles were retrieved from 15 μm CO2 band. At each orbit the measurements were made practically simultaneously (within 1 hour) on the day and night sides symmetrically for latitudes from 20 to 87 N. Coverage in local time was not perfect, observations around noon and around night are absent. In spite of this, four amplitudes of thermal tide vs. latitude and altitude were calculated (Zasova et al. 2007). After comparison of the VIRTIS averaged data and FSV15 it was found many similarities (Grassi et al. 2010). The aim of this work is more detailed comparison of the retrieved thermal structure of the mesosphere from VIRTIS and FSV15. It was studied also temporal variation using brightness temperature (it approximately corresponds to temperature in atmosphere at H(τ =1) from VIRTIS data. It was averaged data over several periods of observations and compare the T(φ, LT) at different altitude levels. It was found significant temporal variation, especially in the upper mesosphere.

Abstract Nr. 66

The VeRa Radio Occultation Data Base: Atmosphere and Ionosphere Tellmann, Silvia, Rheinisches Institut fuer Umweltforschung (RIU), Department of Planetary Research,

Cologne, Germany; Haeusler, Bernd, Institut für Raumfahrttechnik, Universitaet der Bundeswehr


Muenchen, Munich, Germany; Paetzold, Martin,Rheinisches Institut fuer Umweltforschung (RIU), Department of Planetary Research, Cologne, Germany; Bird, Michael K.,Argelander-Institut fuer

Astronomie, University of Bonn, Bonn, Germany; Imamura, Takeshi, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa, Japan; Hinson, David P. , Department of Electrical Engineering, Stanford University, Stanford, California, USA; Tyler,

G. Leonard, Department of Electrical Engineering, Stanford University, Stanford, California, USA; Withers, Paul, Space Science Section, Boston University, Boston, MA, USA; Peter, Kerstin, Rheinisches

Institut fuer Umweltforschung (RIU), Department of Planetary Research, Cologne, Germany; Oschlisniok, Janusz, Rheinisches Institut fuer Umweltforschung (RIU), Department of Planetary

Research, Cologne, Germany The Venus Express Radio Science Experiment VeRa performs routinely radio-sounding measurements of the Venus atmosphere and ionosphere as part of the ESA Venus Express (VEX) mission since 2006. A total of more than 700 vertical scans of the Venus ionosphere and atmosphere were obtained until the end of February 2013. The polar orbit of VEX provides the opportunity to study the troposphere and mesosphere between 40 – 90 km at almost all planetocentric latitudes under varying illumination conditions. The temperature profiles are investigated with regard to latitudinal and local time dependencies. Comparisons will be shown with the VIRA model of the lower atmosphere. The Mesosphere shows a high variability resulting from atmospheric waves and turbulence. The ionosphere consists of a two layer structure between 115 km to 160 km. The main layer V2 is dominantly formed by solar EUV photoionisation, the lower V1 is formed by solar X-ray and dominant secondary ionization. The ionospheric data set covers a period of changing solar activity. The topside is highly variable and the ionopause is located at extremely low altitudes (250 – 330 km) during the declining phase of the solar cycle and at solar minimum . These data are compared with the VIRA ionospheric data which are based on Pioneer Venus occultations observed during solar minimum. The modeling of observed electron density profiles based on the VIRA neutral background atmosphere shows a general agreement with the V2 peak densities but a systematic underestimate of the V2 peak altitude for low solar zenith angles. The modeled V2 layer width is systematically too broad.

Abstract Nr. 68 Waves in the Venus Atmosphere detected by the Venus Express Radio Science Experiment

VeRa Tellmann, Silvia, Rheinisches Institut fuer Umweltforschung (RIU), Department of Planetary Research,

Cologne, Germany; Haeusler, Bernd, Institut für Raumfahrttechnik, Universitaet der Bundeswehr Muenchen, Munich, Germany; Hinson, David P.,Department of Electrical Engineering, Stanford University, Stanford, California, USA; Tyler, G. Leonard, Department of Electrical Engineering,

Stanford University, Stanford, California, USA; Andert, Thomas P., Institut für Raumfahrttechnik, Universitaet der Bundeswehr Muenchen, Munich, Germany; Bird, Michael K., Argelander-Institut für

Astronomie, University of Bonn, Bonn, Germany; Imamura, Takeshi, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa, Japan; Paetzold, Martin, Rheinisches Institut fuer Umweltforschung (RIU), Department of Planetary Research, Cologne,

Germany; Remus, Stefan, ESAC, ESA, Villa Franca, Spain Next to quasi-horizontal waves and eddies on near planetary scales, diurnally – forced eddies and thermal tides, small-scale gravity waves and turbulence play a significant role in developing as well as maintaining the atmospheric superrotation. With the Venus Express Radio Science Experiment VeRa we retrieved more than 700 atmospheric profiles in the mesosphere and troposphere of Venus in the approximate altitude range of 40-90 km. The atmospheric profiles cover a wide range of latitudes and local times, enabling us to study atmospheric waves phenomena at different spatial scales in the mesosphere and troposphere. Small-scale temperature variations with vertical wavelengths of 4 km or less have significant wave amplitudes in the stable atmosphere above the tropopause as compared with the only shallow temperature perturbations in the adjacent middle cloud layer. We found evidence for a local time dependence of gravity wave activity in the low latitude range. Gravity wave amplitudes are at their maximum in the early afternoon, indicating that convection is a


possible wave source. We also found that the gravity wave activity showed a strong latitudinal dependence with an increase of wave activity with increasing latitude in both hemispheres. These results suggest that convection (at low latitudes) as well as topographical forcing (at high northern latitudes), possibly in combination with convection and/or Kelvin-Helmholtz instabilities, are possible key processes for the generation of gravity waves. On the other hand, the upper mesosphere in the low latitudes is strongly influenced by thermal tides. The presence of different wave modes will be investigated.

Abstract Nr. 54

Gravity waves in the Venus upper atmosphere, modelled on VIRTIS/Venus Express data

Migliorini Alessandra, IAPS-INAF, Rome; Altieri Francesca, IAPS-INAF, Rome; Shakun Alexey, IKI, Space Research Institute, Moscow; Zasova Ludmila, IKI, Space Research Institute, Moscow; Piccioni

Giuseppe, IAPS-INAF, Rome; Drossart Pierre, LESIA, Observatory of Paris, Paris Gravity waves play a crucial role in atmospheric circulation because they transport energy and momentum, and influence large scale motions. They can propagate horizontally and vertically, with the amplitude of the oscillation growing upper ward. They are related to the buoyancy force which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Since gravity waves can induce fluctuations on temperature and density fields, they affect the airglow intensities. Double peaked O2 profiles are possible evidences of gravity waves vertically propagating, and they are often observed with VIRTIS instrument in the night side of Venus. In analogy to the Earth’s and Mars cases, we use a well known theory to model the O2 nightglow emissions affected by gravity waves propagation, to investigate the waves properties in the upper atmosphere of Venus. Here we propose a statistical discussion of the gravity waves characteristics, like vertical wavelength and wave amplitude, with respect to local time and latitude.

Abstract Nr. 91

Thermal structure of the upper atmosphere of Venus with SPICAV/VEx data

Piccialli A. , LATMOS-UVSQ, Guyancourt, France Venus upper atmosphere (80-140 km altitude) is one of the most interesting regions on the planet. It is a transition region characterized by a complex dynamic: strong retrograde zonal winds dominate the lower mesosphere while a solar-antisolar circulation can be observed in the upper mesosphere/lower thermosphere. The SPICAV (Spectroscopy for the investigation of the characteristics of the atmosphere of Venus) instrument operates on board the ESA orbiting platform Venus Express since 2006. It is a remote sensing spectrometer covering distinct spectral regions in ultraviolet (118–320 nm) and near-infrared (650–1700 nm). In the stellar occultation mode the UV sensor is particularly well suited to measure the vertical profiles of CO2, temperature, SO2, SO, clouds and aerosols of the middle and upper atmosphere of Venus. We will present a preliminary study of Venus atmospheric structure between 80 and 140 km using SPICAV-UV stellar occultation observations. A very large dataset has been collected by SPICAV-UV that consists of more than 500 stellar occultation profiles performed at all latitudes and seasons during nighttime. The upper atmosphere of Venus shows a very large temporal variability, variations both orbit-to-orbit and with local time are observed. A permanent warm area appears distinctly at the mesopause at about 90-100 km of altitude which was never observed before Venus Express. As first explanation, this feature is interpreted as the result of adiabatic heating in the downwelling branch of the solar-antisolar thermospheric circulation on the night side.

Abstract Nr. 59 CO2 rotational temperatures compared to hydrostatic temperatures obtained with the SOIR

instrument on board VEx


Mahieux Arnaud, Belgian Institute for Space Aeronomy; Wilquet Valérie, Belgian Institute for Space Aeronomy; Vandaele Ann Carine, Belgian Institute for Space Aeronomy; Robert Séverine, Belgian Institute for Space Aeronomy; Drummond Rachel,Belgian Institute for Space Aeronomy; Lopez Valverde Miguel, Instituto de Astrofísica de Andalucía/CSIC; Lopez Puertas Manuel, Instituto de

Astrofísica de Andalucía/CSIC; Funke Bernd, Instituto de Astrofísica de Andalucía/CSIC; Bertaux Jean-Loup,LATMOS/CNRS

The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 µm) at a resolution of 0.12 cm-1, the highest of all instruments on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere at the terminator in the upper mesosphere and lower thermosphere (70 to 170 km) with an emphasis on vertical distribution of the gases. In particular, measurements of CO2 density vertical profiles have been routinely performed. From these density measurements, kinetic temperature profiles are derived using the hydrostatic equilibrium. A permanent cold layer is observed at the mesopause (~ 120 km). A different and independent method is developed here, making use of the information obtained from the rotational structure of the CO2 bands to derive rotational temperature profiles. The rotational temperature profiles are compared to the hydrostatic temperature profiles, and they confirm the presence of the cold layer at the mesopause. At higher altitudes (above 140 km) there are systematic differences between them, although the sensitivity to the rotational structure is smaller. These differences will be discussed in view of the non-LTE theory, and in order to design future observations with SOIR.

Abstract Nr. 25

Incorporation of a gravity wave momentum deposition parameterization into the Venus thermosphere general circulation Model (VTGCM)

Zalucha, Angela, SETI Institute; Brecht, Amanda, NASA Ames Research Center; Rafkin, Scot, Southwest Research Institute; Bougher, Steve, University of Michigan; Alexander,

Joan, NorthWest Research Associates - CoRA The gravity wave drag parameterization of Alexander and Dunkerton [1999] was implemented into a Venus Thermosphere General Circulation Model (VTGCM) to investigate breaking gravity waves as a source of momentum deposition in Venus' thermosphere. Previously, deceleration of zonal jets on the morning and evening terminators in models was accomplished via Rayleigh friction, a linear drag law that is not directly linked to any physical mechanism. The Alexander and Dunkerton [1999] parameterization deposits all of the momentum of a breaking wave at the breaking altitude and features a spectrum of wave phase speeds whose amplitudes are distributed as a Gaussian about a center phase speed. We did not find a combination of wave parameters (namely center phase speed, amplitude at center phase speed, and distribution width) to produce sufficient drag in the jet cores that would bring VTGCM density and nightglow emissions into agreement with Venus Express observations. Gravity waves launched below 100 km either break in the strong shear zones below 115 km or are reflected, and do not propagate into the jet core regions where drag is needed. However, if the condition of total internal reflection of high frequency waves was removed, waves were able to penetrate the jet cores. The results we present demonstrate that the physics of gravity wave schemes developed for the middle atmosphere may not be appropriate for the thermosphere and that damping mechanisms other than nonlinear breaking/saturation dominate and should be accounted for at these heights.

Abstract Nr. 110

Retrieval of temperature and carbon monoxide from the 4.7um limb non-LTE emission of the upper atmosphere measured by VIRTIS/Venus Express

López-Valverde, Miguel A., IAA/CSIC, Granada (Spain); Gilli, Gabriella, IAA/CSIC, Granada (Spain); Peralta, Javier, IAA/CSIC, Granada (Spain); Bougher, Stephen W., Univ. of Michigan, Ann Harbour


(USA); Brecht, Amanda, NASA-Ames Research Center (USA); Drossart, Pierre, LESIA, Observatoire de Paris (France); Piccioni, Giuseppe, IAPS, Rome (Italy)

Solar fluorescence is a form of breakdown of Local Thermodynamic Equilibrium (LTE) which greatly enhances the molecular IR emissions in the upper atmospheres of the planets. An example if the daytime emission by atmospheric CO at 4.7 um in the terrestrial planets, and recently observed by VIRTIS/VEx in the limb of Venus at 100-150 km tangent altitudes. We will present this data set, its analysis and inversion, and a first comparison with the VTGCM predictions. The data was binned in order to improve SNR, which unfortunately is not large and this reduced the latitude and local time resolution of the final dataset. The data was also binned in altitude, in 10-km boxes, although the weighting functions are even broader. The intensity of the emission carries information on the CO abundance while the rotational structure revealed by VIRTIS contains information on the kinetic temperature. We designed a retrieval scheme to obtain CO and temperature simultaneously. The main non-LTE effects (solar illumination, radiative transfer, collisions with CO2 non-LTE populations) were taken into account in the forward model, which includes a detailed non-LTE model for CO2 and CO populations in Venus. Despite the large data averages the resulting spectra are noisy, but this dataset supply a new and valuable insight into the upper mesosphere and lower themosphere of Venus. We will present the Latitude and LocalTime variations of the CO and temperature obtained and analyze them with the help of similarly boxed data from dedicated VTGCM simulations.

Abstract Nr. 113

Earth based Doppler-wind and temperature measurements in Venus upper atmosphere using the infrared heterodyne spectrometer THIS.

Sornig Manuela, RIU-PF at the University of Cologne

Dynamics of the Venusian atmospheric transition zone between the sub-solar to anti-solar (SS-AS) flow dominated region above 120km and the superrotation dominated region below 90 km is not yet fully understood. Temperatures in the same region are not very well constrained and we lack in a comprehensive understanding of this atmospheric region. Therefore measurements of these parameters on various time scales and on different locations on the planet are essential for validation of global circulation models and a comprehensive understanding of the atmosphere. Such observations can be provided by the Cologne infrared heterodyne spectrometer THIS. Operating around 10μm THIS fully resolves CO2 non-LTE emission lines for Doppler-wind and temperature retrievals at an pressure level of 1μbar (~110km). In addition broader CO2 absorption lines can be used to gain information about the temperature profile lower down in the atmosphere (~60-90 km). Doppler-wind velocities and temperature results including a report about wave activities from campaigns between 2007 to 2013 will be presented.

Abstract Nr. 37

Doppler Winds Mapped around the Lower Thermospheric Terminator of Venus: JCMT Observations of the 2012 Solar Transit

R Todd Clancy, Space Science Institute; Brad Sandor, Space Science Institute; James Hoge, National


Research Council of Canada, Joint Astronomy Center Doppler shifts of sub-millimeter 12CO (346 GHz) and 13CO (330 GHz), and millimeter 12CO (230 GHz) line absorptions were mapped around the circumdisk terminator of Venus during the June 5, 2012 solar transit, employing the James Clerk Maxwell Telescope (JCMT). Radiative transfer analysis of these thermal line absorptions yields cross-terminator winds in the Venus lower thermosphere (100-120km) over the local time (LT) and latitude extent of the atmospheric limb presented by the inferior conjunction, nightside apparent disk of Venus. The unique solar transit geometry provides enhanced spatial resolution of the terminator associated with solar illumination of this atmospheric limb region, and so provides the first characterization of the instantaneous distribution of cross terminator flow in the Venus lower thermosphere versus LT and latitude. Furthermore, by mapping Doppler winds over the nightside disk preceding and following the solar transit, we place the highly variable zonal and subsolar-to-antisolar (SSAS) circulation components of the nightside lower thermosphere (Clancy et al, 2012) in the context of the day-to-night cross terminator flow that drives this chaotic nightside dynamical regime. The solar transit observations indicate substantially supersonic (150-290 m/s) day-to-night cross terminator winds that vary by as much as 50% over a one hour timescale and are significantly (by 20-140 m/s) stronger over the evening versus the morning terminator. These behaviors likely contribute to both the variability and the apparent retrograde zonal component of circulation in the Venus nightside upper atmosphere. They also support dynamical arguments for preferential deceleration of the morning sector SSAS circulation due to momemtum deposition associated with gravity waves propogating from the lower atmosphere (Alexander, 1992).

Abstract Nr. 11

Venus night side measurements of winds at 115 km altitude from NO bright patches tracking.

Bertaux Jean-Loup, LATMOS,UVSQ,CNRS; Gérard Jean-Claude, LPAP, Université de Liège; Stiepen,

Arnaud, LPAP, Université de Liège; Marcq, Emmanuel, LATMOS,UVSQ,CNRS; Montmessin, Franck, LATMOS,UVSQ,CNRS; Dalaudier, Francis,LATMOS,UVSQ,CNRS; Hauchecorne,

Alain, LATMOS,UVSQ,CNRS; Segret, Boris, LATMOS,UVSQ,CNRS The UV NO emission on the night side is due to air transported from day to night in the thermospheric circulation and recombination of N+O atoms. Both Pioneer Venus (1978) and SPICAV/VEX show that the statistical center of the emission is off towards morning from the anti-solar point, as if it were pushed by super-rotation. However, the emission takes place at 115 km, while VIRTIS/VEX, with maps of O2 emission (peak altitude 95 km) in the night side of Venus (recombination of O+O), has shown that the maximum of emission is statistically centered on the antisolar point. Therefore, there is no influence of super-rotation at 95 km. One way to explain this paradox is that the cause of the super rotation is different at 115 km and in the lower atmosphere. Alternately, some gravity waves could propagate from below, crossing the altitude 95 km with minimal interaction, and breaking around 115 km, depositing their momentum. Also, the altitude of N2 photo-dissociation is higher in the thermosphere than CO2, therefore the thermospheric circulation pattern may be different for the transport of N atoms, and O atoms. We have started building maps of the NO emission with VEX. The idea is that NO emission is concentrated generally in rather well defined patches of light. Therefore, by comparing maps taken at 1 hour or 24 hr interval, we can make a “bright patch tracking”, and derive directly the velocity of the moving air parcel containing N and O, or


the wave velocity if relevant to the emission.

Abstract Nr. 29

Venus nitric oxide nightglow distribution: a clue to thermospheric dynamics

Stiepen Arnaud, Université de Liège - Laboratoire de Physique Atmosphérique et Planétaire; Gérard Jean-Claude, Université de Liège - LPAP; Dumont Maïté, Université de Liège - LPAP; Cox Cédric, Université de Liège - LPAP; Bertaux Jean-Loup, Laboratoire Atmosphères, Milieux,

Observations Spatiales (LATMOS) Nitric oxide δ and γ emissions on the nightside of Venus have been extensively observed by SPICAV on board Venus Express. They arise from radiative recombination of O(3P) and N(4S) atoms produced on the dayside of the planet through photodissociation of CO2 and N2. These atoms are carried to the nightside by the global subsolar to antisolar circulation. We analyze a wide dataset of nadir observations obtained during low to medium solar conditions to determine the statistical distribution of the NO nightglow. This global map is the first one since the Pioneer Venus era 35 years ago. It is fully compatible with it in spite of the different solar activity level. The NO airglow emission shows a statistical bright region extending from 01:00 to 03:30 local time and -25° to 10° latitude. The mean intensity within this region is 3.9kR, and the hemispheric intensity is 1.9 kR. Intensities as high as ~20 kR have been observed on some occasions. The location of the statistical brightest region of the NO emission raises key questions about the dynamics in the thermosphere. Superrotation is observed at cloud top level (~70 km) but disappears at the altitude of the O2(a

1Δ) emission (~95 km). It is present again in the lower thermosphere with the NO emission at 115 km and at high altitude with the He bulge at ~250 km. This statistical view is completed by individual latitudinal cuts that occasionally show multiple emission peaks within the bright region.

Abstract Nr. 125

The O2 nightglow from VIRTIS-M VEX measurements

Zasova Ludmila, IKI RAS, Moscow, MIPT, Dolgoprudny, Russia; Gorinov Dmitry, IKI RAS, Moscow, MIPT, Dolgoprudny, Russia; Khatuntsev Igor, IKI RAS, Moscow, MIPT, Dolgoprudny, Russia; Ignatiev

Nikilay, IKI RAS, Moscow, MIPT, Dolgoprudny, Russia; Altieri Francesca, IASP-INAF, Rome, Italy; Migliorini Alessandra, IASP-INAF, Rome, Italy; Piccioni Guseppe, IASP-INAF, Rome, Italy; Drossart

Pierre, LESIA, Paris, France We continue a study of the O2 night glow from VIRTIS-M spectra. The main topic is vertical and horizontal distribution of the emission. It was found that horizontal distribution of global intensity of the O2 emission correlates with measured from movement of the O2 features wind speed. Areas of high positive values of horizontal divergence of the flow correspond to the minimum intensity of the airglow and vice versa, negative values (meaning a convergence) coincide with the maxima intensity of airglow. Maximal wind speed, observed at the morning side, corresponds to the minimum intensity in the global map. Temperature global map, retrieved from the 4.3 μm CO2 band of VIRTIS spectra (Grassi&Migliorini), T(φ,LT), also reveal a temperature minimum at 90-100 km, coinciding in position with minimum intensity of O2 and maximum of horizontal wind speed. In spite of this intrinsically not contradictory picture, horizontal distribution of the O2 nightglow cannot be explained within well known modes of circulation of Venus atmosphere: zonal retrograde superrotation and SS-AS flow.

Abstract Nr. 22

Latitudinal variations of the altitude of the Venus O2 airglow observed with VIRTIS-M: a signature of dynamical processes in the upper atmosphere


Jean-Claude Gérard, LPAP - Université de Liège; Lauriane Soret, LPAP - Université de Liège; Giuseppe

Piccioni, IAPS-INAF Roma; Pierre Drossart, Observatoire de Paris - Meudon The VIRTIS-M multispectral imager measured the characteristics of the nightside airglow at 1.27 μm between 15 May 2006 and 14 October 2008. This emission layer is associated with the recombination of oxygen atoms formed by dissociation of CO2 molecules on the dayside. The O atoms are subsequently carried to the nightside by the subsolar to antisolar global circulation where they recombine to form O2 singlet delta metastable molecules. Images of the Venus limb at 1.27 μm have been assembled to analyze the two-dimensional (latitude-altitude) distribution in quasi-meridional cuts through the atmosphere. It is therefore possible to visualize latitudinal changes in the altitude of the emission. We find that this altitude generally increases toward the north pole. Occasionally, an abrupt increase of several kilometers is observed in the 60° N region. We use a photochemical-dynamical model to investigate how changes in the vertical transport efficiency can possibly explain these observations.

Abstract Nr. 52

Modelling of ultraviolet and visible dayglow emissions on Venus Jain, Sonal Kumar, Space Physics Laboratory, Vikram Sarabhai Space Center, Indian Space Research Organisation Trivandrum, India; Bhardwaj, Anil, Space Physics Laboratory, Vikram Sarabhai Space

Center, Indian Space Research Organisation Trivandrum, India We have developed a model to study CO Cameron and N2 triplet bands, CO2

+ ultraviolet doublet, and atomic oxygen ultraviolet (2972 Å) and visible (5577 and 6300 Å) line emissions on Venus for low, moderate, and high solar activity conditions. Our calculation suggests that CO Cameron band in Venusian dayglow is mainly produced by electron impact excitation of CO (e-CO) followed by electron and photon impact dissociative excitation of CO2. For solar moderate (F10.7 = 130) condition, CO Cameron band and CO2

+ UV doublet emissions maximize at 135 km with intensities of 2300 kR and 330 kR, respectively. The calculated intensities are in agreement with the recent SPICAV/Venus Express observation . The overhead intensity of N2 Vegard-Kaplan (VK) bands in wavelength ranges 4000-8000, 3000-1900, 2000-3000, and 1500-2000 Å are 22%, 39%, 35%, and 4% of the total VK band emission. Emissions between 6000 and 8000 Å wavelength consist of about 50% of the total First Positive band system, while 90% of Second Positive band system is due to the emissions lie in wavelengths between 3000 and 4000 Å. The calculated intensity of N2 VK band on Venus is about an order of magnitude higher than that on Mars due to higher abundance of N2 on Venus and small heliocentric distance of Venus. Densities of O(1S) and O(1D), and height-integrated overhead and line of sight (limb) intensities of OI 2972, 5577, and 6300 Å emissions are calculated on Venus. The results will be presented and discussed.

Abstract Nr. 121

Coordinated Sounding Rocket, HST, and SPICAV Observations of Venus in Nov. 2013

Clarke, John T , Boston University; Bertaux, Jean-Loup, LATMOS and BU; Carveth, Carol, Boston University; Chaufray, Jean-Yves, LATMOS; Gladstone, Randy, SwRI; Darling, Nathan, Boston

University A coordinated set of observations of Venus in Nov. 2013 will address the escape of water from the upper atmosphere as related to measurements of the ratio of deuterium to hydrogen at various altitude levels. The observations will be performed by the Venus Spectral Rocket (VeSpR) sounding rocket experiment, the HST Space Telescope Imaging Spectrograph (STIS), and the SPICAV/SOIR instruments on Venus Express. The VeSpR experiment is a high spectral resolution system designed specifically to resolve the D and H Ly alpha emissions from planetary atmospheres. The present version of this payload will measure the D/H ratio at the level above CO2 photo-absorption, or above roughly 110 km altitude. Similar observations are now permitted using the HST/STIS in echelle mode, where previously HST observations of Venus were not allowed. The SOIR instrument has previously measured the ratio of HDO/H2O in the middle atmosphere between 70-110 km, and found a variation


with altitude in the D/H ratio. New observations will be made for comparison with the other instruments. The goal is to understand the path that both D and H atoms take as water is photodissociated, and the atoms move to the top of the atmosphere where they can escape into space. The detailed physical processes must be understood to know how to relate the measured tow order of magnitude enhancement in the Venusian D/H ratio to the historic escape of a volume of water from the early atmosphere.

THURSDAY, 13 JUNE – PAGE 23

Thursday, 13 June

Abstract Nr. 03

Ground-based observations of minor species on Venus using infrared spectroscopy

T. Encrenaz, LESIA, Paris Observatory, France; T. Greathouse, SwRI, San Antonio, TX, USA; M. Richter, Physics Department, UC Davis, CA, USA; J. Lacy, Dept. of Astronomy, University of Texas,

Austin, TX, USA; B. Bézard, LESIA, Paris Observatory, France; T. Fouchet, LESIA, Paris Observatory, France; T. Widemann, LESIA, Paris Observatory, France

Sulfur dioxide and water vapor on Venus have been monitored using Venus Express and results suggest significant spatial and temporal variations. Ground-based imaging spectroscopy at high spectral resolution provides a complementary method to study minor species over and within the clouds. This method is well suited for studying latitudinal or day/night variations because, unlike in-orbit observations, global instantaneous maps of minor species can be recorded. In this talk, we review recent results on minor species from ground-based infrared spectroscopy. In particular, we present SO2 and H2O maps obtained with the TEXES high-resolution imaging spectrometer at the NASA Infrared Telescope Facility (IRTF). Two observing runs took place in January and October 2012, respectively, at 7 microns and 19 microns, with a resolving power of about 70000 and a spatial resolution of about 1.5 arcsec. The 7-microns radiation probes the cloud top, while the 20-microns radiation probes a few kilometers below. Both HDO and SO2 were identified in our spectra. Water maps show that H2O is globally uniform over the disk, with a mean mixing ratio of 1.5 ppm, and no significant temporal change on a timescale of two days. In contrast, SO2 maps show strong local and temporal variations over a timescale of a day, with maximum values of about 100 ppb (Encrenaz et al. A&A 543, A153, 2012). There is a significant decrease of the SO2content between the cloud and the lower mesosphere. These results will be presented and discussed.

Abstract Nr. 04

Sulfur and water mapping in the mesosphere of Venus

T. Encrenaz, LESIA, Paris Observatory, France; R. Moreno, LESIA, Paris Observatory, France; T. Fouchet, LESIA, Paris Observatory, France; E. Lellouch, LESIA, Paris Observatory, France; A.

Moullet, NRAO, Charlottesville, VA, USA Both sulfur dioxide and water vapor play a major role in the aeronomy and dynamics of Venus’ atmosphere. In the lower troposphere, their mixing ratios are about 30-50 ppm and 130 ppm, respectively. At an altitude of about 70 km, they are drastically reduced by photochemistry and by the formation of H2SO4 clouds. Venus Express UV and IR data, as well as ground-based infrared observations, have shown evidence for strong local and temporal variations of SO2 at the cloud top and above. At high altitude (80-90 km), SO2 and SO have been detected by ground-based submillimeter observations. They show evidence for a drastic increase of the sulfur abundance, implying the probable presence of an upper mesospheric sulfur-bearing aerosol source. ALMA offers an unprecedented possibility to map H2O and SO2 with a high spatial resolution (about 1 arcsec) in the 70 – 100 km range, over the disk of Venus. During Cycle 0, using the compact configuration of ALMA, we have observed Venus in 4 sequences, each of 30 minutes integration time, on November 14, 15, 26 and 27, 2011. Transitions of CO, SO2, SO and HDO have been observed simultaneously in the 335-346 GHz frequency range. The diameter of


Venus was 12 arcsec. In addition to sulfur and water maps, the CO maps will be used for a retrieval of mesospheric winds. The observations will be presented and discussed.

Abstract Nr. 71

Measurements of minor species at cloud top level Marcq, Emmanuel, LATMOS / Univ. de Versailles Saint-Quentin; Bertaux, Jean-Loup, LATMOS / CNRS;

Montmessin, Franck,LATMOS / CNRS; Belyaev, Denis, LATMOS / IKI; Encrenaz, Thérèse, LESIA / CNRS

The top of the clouds is a transitional region between the troposphere and the mesosphere of Venus. Thus, minor species originating from both domains and very different chemical pathways are able to reach this region and interact with each other, effectively coupling the lower and upper atmopshere. These complex chemical interactions are, ultimately, responsible for creating and maintaining the thick and ubiquitous H2SO4-H2O cloud cover, with far reaching consequences on the chemistry of the whole atmosphere of course, but also on virtually all the other aspects of this atmopshere (radiative budget, circulation, surface-atmosphere interactions). Accurate and frequent measurements of key minor species involved in the major chemical cycles (suflur and carbon, mainly) are therefore crucial for a better understanding of the Venusian atmosphere. In this talk, I shall review measurements of two species that our team have conducted recently:

SO2 measurements using SPICAV-UV/Venus Expressin nadir mode [Marcq et al., 2011, 2013], for which consistent latitudinal variations and temporal variability on a large range of timescales have been evidenced. We should also provide some simple modeling able to account for these variations using the LMD-GCM [Lebonnois et al., 2009], at least from a qualitative point of view.

CO measurements using C-SHELL/IRTF. This work is still in progress at the time, but preliminary results point that CO and CO2 column densities could be measured near 4.5 µm on both day and night sides of Venus.

Abstract Nr. 50

Water vapor and the cloud top variations in the Venus’ mesosphere from SPICAV observations

Fedorova Anna, Space Research Institute (IKI); Moscow Institute of Physics and Technology (MIPT); Bertaux Jean-Loup,LATMOS; Marcq Emmanuel, LATMOS; Korablev Oleg, Space Research Institute

(IKI); Moscow Institute of Physics and Technology (MIPT); Montmessin Franck, LATMOS SPICAV VIS is an AOTF (acousto-optical tunable filter) spectrometer working in the spectral range of 0.65-1.7 µm onboard the Venus-Express mission. It provides measurements of the H2O abundance above Venus’ clouds based on the 1.38-µm band and the cloud top altitude based on the CO2 bands in the range of 1.4-1.6 μm. The new calibrations of the instrument in 2010-2012 allowed updating of results reported earlier. The cloud top altitude has been routinely retrieved for dataset from 2006 to 2013 (VEx orbits 23-2500) taking into account multiple-scattering in the cloudy atmosphere. The τ=1 level at 1.48 μm varies from 69 to 73 kmat lower latitudes and from 64 to 68 kmat high latitudes near the Poles. The possible long-term and year-to-year variations were studied. The H2O mixing ratio from the 1.38 μm band varies from 4 to 12 ppm with larger variations in the lower latitudes which was not observed by VIRTIS-H from the 2.56 μm H2O band at altitudes of 68-70 km. The 1.38 μm H2O band is sensitivity to altitudes of 55-70 km and a vertical gradient of water within the upper clouds can be responsible for the water behavior. The spot pointing observations for wide variations of viewing angle in the near-IR spectral range are useful to determine the vertical gradient of water within the clouds.

Abstract Nr. 116

Re-analysis of Pioneer Venus SO2 measurements


McGouldrick, Kevin, University of Colorado Boulder; Esposito, Larry, University of Colorado Boulder A previous analysis of Pioneer Venus Orbiter Ultraviolet Spectrometer (PVOUVS) data at wavelengths of 207nm and 237nm by Esposito et al. (1988) suggested a significant decline in SO2 concentration at 40mb occurred over the course of a decade between 1979 and 1988. More recent observations of Venus made by ultraviolet spectrometers on Venus Express and ground based heterodyne spectroscopy suggest that SO2 concentrations at 40mb in the Venus atmosphere of today is closer to the values obtained near the start of the Pioneer Venus mission, and/or suggest the existence of an increase in SO2 concentration at higher altitudes (above about 1mb). The Pioneer Venus Ultraviolet Spectrometer exhibited a spectral range from about 110nm to about 330nm. We have been attempting to incorporate the data from these additional wavelenghts to further constrain the SO2 measurements that can be derived from observations carried out by Pioneer Venus during its lifetime. We present results of a re-analysis of the PVOUVS data from the first 500 orbits of the Pioneer Venus mission that take into account the new knowledge of the Venus upper atmosphere that has been gained in the last twenty years, including the advances driven by the observations made by ESA's Venus Express spacecraft, in orbit since 2006.

Abstract Nr. 98

Assessing An Impact Hypothesis for Upper Atmosphere Abundance Variations on Venus

Grinspoon David, NASA/Library of Congress; Glaze Lori, NASA/GSFC Observed sulfur dioxide variations in the upper atmosphere of Venus have been attributed to either volcanic injection or dynamical overturn. In theory the impact of small comets could also produce such a signature. Because the below-cloud atmosphere is much richer in SO2, a rising impact fireball could temporarily inject substantial SO2 above the clouds. In the case of the SL-9 impact on Jupiter such an effect was observed, post-impact. We will present estimates of the cometary mass required and the expectation frequency for an impact of the appropriate magnitude, in order to assess the likelihood of this explanation for any observed variations in upper atmosphere composition.

Abstract Nr. 75 Positive Correlation of SO, SO2 in the Dayside Venus Mesosphere: Identification of Diurnal

SOx Partitioning from JCMT Submm Spectroscopy

Sandor, Brad, Space Science Institute; Clancy, Todd, Space Science Institute; Mills, Franklin, Australian National University and Space Science Institute

Sub-mm spectroscopic observations of the Venus upper mesospheric indicate SO and SO2 abundances have comparable magnitude in the dayside atmosphere,with correlation coefficient 0.9. On the nightside, SO abundances are always small,such that the SO/SO2 ratio is near zero. Since 2004, submm spectroscopy with the James Clerk Maxwell Telescope (JCMT) has been used to measure abundances of SO2 (346.652 GHz) and SO (346.528 GHz) in the Venus mesosphere. The two molecules are observed simultaneously (same bandpass). Altitude resolution (70-100 km sensitivity) is retrieved from shape of the pressure-broadened absorption lines, indicating an inversion with far more SOx above 85 km than below. Total abundance (SO + SO2) exhibits strong, unexplained time variability both day and night. However, the SO/SO2 ratio varies diurnally, with value roughly 1.0 on dayside, and near zero at night. Maximum total abundances (SO + SO2) are similar (70 ppb) on day and night sides, with no evidence this sum has diurnal dependence. We suggest SO2 photolysis, balanced by unknown recombination reactions is responsible for dayside partitioning of SOx into SO and SO2, while the total SOx exhibits secular, but not diurnal variation. Empirically, diurnal SOx partitioning in the Venus mesosphere has many terrestrial atmospheric analogs which are photochemically well understood. Details of Venus SOx partitioning are undoubtedly much different from those of any terrestrial case. However, discovery and characterization of this pattern in Venus SOx provides a critical constraint to photochemical modeling of the Venus mesosphere.

Abstract Nr. 103


Temporal, Spatial Variation of HCl in the Venus Mesosphere, based upon Submm

Spectroscopic Observations with JCMT

Sandor, Brad, Space Science Institute; Clancy, Todd, Space Science Institute Submm spectroscopic observations of Venus mesospheric (70-100 km) HCl (625.9 GHz) were conducted with the James Clerk Maxwell Telescope (JCMT). Nightside equatorial measurements (2010) indicate abundances below (but not above) 80 km are consistent with model prediction (eg. Yung and DeMore, 1982), and with prior low to mid-latitude measurements (eg. Krasnopolsky, 2010; at 74 km). However, observed submm abundances above 80 km are much smaller than model values, and reveal strong secular (1 month) time variation at local midnight. Retrieved submm equatorial profiles are consistent with SOIR polar HCl above 85 km (Vandaele et al., 2008), but show larger abundances in the lower mesosphere. Agreement between submm and SOIR HCl in the upper mesosphere provides cross-validation of the two methods, while disagreement in the lower mesosphere may indicate latitude variation at that altitude. We have suggested (Sandor and Clancy, 2012) downward transport of HCl-poor thermospheric air as a possible mechanism for depleting HCl in both the polar (SOIR) and nightside equatorial (submm) atmosphere. However, early analysis of the first (March, 2013) submm dayside observations finds consistency with nightside HCl, indicating the simple downward transport hypothesis is not sufficient. Further, comparison of day/night profiles indicates any diurnal dependence is significantly weaker than the observed secular nightside variation. Modest latitude resolution of dayside observations shows no variation of the HCl altitude profile between equatorial and mid-latitudes.

Abstract Nr. 33

Trace gases in the mesosphere and lower thermosphere of Venus from SOIR/VEX observations

Vandaele Ann C., IASB-BIRA; Drummond, R., IASB-BIRA; Mahieux, A., IASB-BIRA; Robert, S., IASB-

BIRA; Wilquet, V., IASB-BIRA; Bertaux, J.-L., LATMOS The wavelength range probed by SOIR/VEX allows a detailed chemical inventory of the Venus atmosphere. Several trace gases, such as H2O/HDO, HF, HCl, CO, or SO2, are observed together with CO2, leading to the derivation of their vertical density profiles. Temperature and total density profiles are deduced from the CO2 density profiles and VMR are obtained for all trace gases. The measurements all occur at the Venus terminator, morning and evening sides, covering all latitudes from the North Pole to the South Pole. The vertical resolution is between 100 and 500 m in the Northern hemisphere, and is poorer at southern latitudes (between 1 and 2.5 km). The typical vertical extent of the profiles ranges from 70 to 120 km (for CO2 : from 70 to 170 km), encompassing thus the mesosphere and the lower thermosphere of the planet. The Venus atmospheric region probed by SOIR is very special as it acts as a transition region between two distinct dynamical regimes characterized by different flow patterns: the zonal retrograde flow below 70 km and the subsolar to antisolar circulation above 100 km. Some of the detected trace gases play important roles in the chemistry of the atmosphere. The study of CO, being mainly produced through the photodissociation of CO2 at high altitudes by solar ultraviolet radiation, can lead to significant information on the dynamics taking place in this region. Results from SOIR observations of trace gases will be presented and discussed. We will report and analyze short and long term time variations. The latitudinal dependency will also be investigated.

Abstract Nr. 32

Contribution of the SOIR/VEX instrument to VIRA II Vandaele Ann C., IASB-BIRA; Drummond, R., IASB-BIRA; Mahieux, IASB-BIRA; Robert, IASB-BIRA;

Wilquet, IASB-BIRA; Belyaev, IKI; Fedorova, IKI; Montmessin, LATMOS; Bertaux, LATMOS The SOIR instrument on-board Venus Express performs solar occultation measurements in the IR


region (2.2 - 4.4 mm) at a resolution of 0.12 cm-1. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the selection of the wavelength range. Several trace gases, such as H2O and its isotopologue HDO, HF, HCl, CO, or SO2, are measured together with CO2 in the SOIR wavelength range. Vertical density profiles (from 70 to 170 km) together with the temperature and total density profiles, allow the determination of VMR vertical profiles. The measurements all occur at the Venus terminator, both the morning and evening side, covering all latitudes from the North Pole to the South Pole. The vertical resolution is very good from the North Pole to 40° North (resolution between 100m to 500 m), and is poorer in the Southern hemisphere (resolution between 1 and 2.5 km). Aerosol extinction vertical profiles are also routinely monitored, leading to some information on the characteristics of the aerosols present. We will present some results concerning the observations of CO2, temperature, trace gases and aerosols as well as data available to build information on the structure and dynamics of the Venus atmosphere. The possible contribution to VIRA II will be discussed.

Abstract Nr. 36

SPICAV-SOIR mesospheric aerosols observations and modelling

Wilquet Valérie, IASB-BIRA; Daerden Frank, IASB-BIRA; Drummond Rachel, IASB-BIRA; Mahieux Arnaud, IASB-BIRA; Robert Séverine, IASB-BIRA; Vandaele Ann Carine, IASB-BIRA; Montmessin

Franck, LATMOS-IPSL; Bertaux Jean-Loup, LATMOS-IPSL The SPICAV-SOIR instrument on-board VEX performs coordinated solar occultation measurements with SPICAV-UV (118–320 nm), SPICAV-IR (0.65–1.7 µm,) and SOIR (2.2 - 4.4 µm) and is able to target the layer of aerosols above the clouds at the terminator. From independent retrievals for each channel, it has been postulated that the upper haze on Venus includes, in some instances, a bimodal population, one type of particles with a radius comprised between ~0.1 and 0.3 µm and the second type, detected in the IR, with a radius varying between ~0.4 and 1 µm. In addition, a high temporal variability in the aerosol loading was inferred from SOIR observations over 4 years, as well as a latitudinal dependency. We propose to refine the size distribution retrieval of aerosols based on the Mie theory and on the observed spectral dependence of light extinction in the spectra through a unique retrieval procedure combining the data from the 3 channels of the instrument. We will also search for a dependence on altitude of the aerosol particles size distribution and of aerosol composition and compare the variations in aerosol loading to other key parameters retrieved such as water and SO2composition or temperature. We also aim at developing a microphysical model to calculate the time dependent haze particle size distributions assuming an initial size distribution of background aerosols. The model would simulate the formation, growth, evaporation, and sedimentation of particles. Results of this on-going research will be presented and discussed.

Abstract Nr. 129

Venus cloud morphology: monitoring by the VMC/ Venus Express camera continued

Dmitrij Titov, ESA/ ESTEC Venus Monitoring Camera (VMC) onboard the ESA Venus Express spacecraft continues investigations of the cloud morphology in ultraviolet, visible, and near-IR spectral bands with spatial resolution from 50 km at apocentre to a few hundred of meters at pericentre. The imaging shows strong spatial and latitudinal variations of the cloud pattern and significant temporal changes on all scales. The camera discovered new cloud features like bright “lace clouds” and cloud columns at the low latitudes, dark polar oval and narrow circular and spiral “grooves” in the polar regions, different types of waves at the high latitudes. The VMC observations revealed detailed structure of the sub-solar region and the afternoon convective wake, the bow-shape features and convective cells, the mid-latitude transition region and the “polar cap”. Besides the cloud morphology the VMC observations have important implications for the problems of the unknown UV absorber, microphysical processes, dynamics and


radiative energy balance at the cloud tops. We will present an overview of the recent VMC observations and compare them to the earlier results.

Abstract Nr. 24

Physical properties of particles in the upper clouds of Venus from the IR and UV images taken by VMC/VEx at small phase angles

Petrova Elena, Space Research Institute, Moscow, Russia ; Shalygina Oksana, Max-Planck-Institut für

Sonnensystemforschung, Katlenburg-Lindau, Germany; Markiewicz , Wojciech The cause of the difference in brightness of the UV features in the upper clouds of Venus still remains unknown. The glory feature observed by VMC/VEx at small phase angles allows us to determine the size of cloud particles and their refractive index. The analysis of the limited information available for the cases, when the UV contrasts are seen near the glory features allowed for further constraints of the cloud properties. First, it was found that some UV contrasts observed near the equator at the local noon are caused by variations (less than 10%) in the amount of submicron absorbing particles (or in their absorbing properties). Second, from variations of the angular position of the glory maximum in the UV phase profiles observed before the local noon, the decrease of the effective radii of sulfuric acid droplets (from 1.05 to 0.9 micron) in the upper cloud layer with increasing latitude (from 40S to 60S) was revealed. The increase in the amount of 0.9-micron particles may also cause the UV-bright features often observed at about 50S.

Abstract Nr. 96

Temporal variation of UV reflectivity of Venus: VEX/VMC data analysis George L. Hashimoto, Okayama University; Manabu Yamada, Chiba Institute of Technology; Takehiko

Satoh, ISAS/JAXA We examined a temporal variability in ultraviolet reflectivity of Venus using images obtained by the Venus Monitoring Camera (VMC) on board the Venus Express spacecraft. It is a well known fact that there is a spatial variation in the uv reflectivity of Venus. However, temporal variability has not been well understood. We use a long-term continuous observation of Venus Express which enables us to examine a temporal variation in the uv reflectivity. VMC observed a reflection of sunlight at 365 nm wavelength. Since the intensity of reflected light depends on the solar incidence angle and emission angle, it is necessary to investigate the dependences on these parameters. We calculated a solar incidence angle and emission angle for each pixel of the images, and determined the dependencies on the solar incidence angle and emission angle. Our analysis revealed that there is a tempral variation in the uv reflectivity on the Venus' southern hemisphere.

Abstract Nr. 118

Causes of the bright and dark features at the Venus cloud tops

LW Esposito, LASP, University of Colorado The Venus clouds show dark UV features and occasional brightenings. I review the physical and chemical processes proposed to create these features: convection, advection, nucleation, photochemistry, aerosol growth and fallout. Titov (2008) and others have shown that cloud top height variations cannot explain the features. I conclude that a volcanic eruption is unlikely to create a bright spot like that reported by Limaye (2009). The VMC UV channel (Titov etal 2012) has observed many of these features, and provides an excellent data set. I will compare explanations from Esposito and Travis (1982), Titov etal, Marcq etal (2013) and Encrenaz etal (2013). The best hope for resolving these questions is simultaneous remote sensing andin situmeasurements of the cloud regions.

Abstract Nr. 130


On the origin of the 1-micron contrast features in Venus clouds

Takehiko Satoh, ISAS/JAXA

Though week, contrast features in Venus clouds at a wavelength of 1 um have been known since they were imaged with Galileo/SSI during its flyby to Venus. They somewhat resemble more prominent markings seen in the ultraviolet but move with different (slower) speed, indicating the 1-micron contrast features may originate from lower altitudes than the UV markings. We are motivated to carry out correlative study of the UV, visible, and near IR (1 micron) data to quantitatively understand from which level these features originate. Such information will tell us the vertical profile of absorption, the driving force of the atmospheric motion. At this workshop, we report some preliminary results of radiative transfer modeling and cloud-tracking analysis.

Abstract Nr. 48

Modeling the clouds on Venus: model development and improvement of a nucleation parameterization

Määttänen Anni, Centre National de la Recherche Scientifique, Université Versailles Saint Quentin,

Laboratoire Atmosphères, Milieux, Observations Spatiales, Guyancourt, France; Bekki Slimane, Centre National de la Recherche Scientifique, Université Versailles Saint Quentin, Laboratoire Atmosphères,

Milieux, Observations Spatiales, Guyancourt, France; Vehkamäki Hanna,Department of Physics, University of Helsinki, Helsinki, Finland; Julin Jan, Department of Physics, University of Helsinki,

Helsinki, Finland, presently at: Department of Applied Environmental Science and Bert Bolin Centre for Climate Research, SE-10691 Stockholm, Stockholm University, Sweden; Montmessin Franck, Centre National de la Recherche Scientifique, Université Versailles Saint Quentin, Laboratoire Atmosphères,

Milieux, Observations Spatiales, Guyancourt, France; Ortega, Ismael K.,Department of Physics, University of Helsinki, Helsinki, Finland; Lebonnois Sébastien, Laboratoire de météorologie dynamique,

Centre national de la recherche scientifique, Université Pierre et Marie Curie, Paris, France As both the clouds of Venus and aerosols in the Earth's stratosphere are composed of sulfuric acid droplets, we use a model [1,4] developed for stratospheric aerosols and clouds to study the clouds on Venus. The model describes key microphysical processes including a parameterization for two-component nucleation [8] of water and sulfuric acid, condensation/evaporation, and sedimentation. Coagulation and turbulent diffusion are being added in the 1-D version of the model. Since the model describes explicitly the size distribution with tens of size bins (50-500), it can handle multiple particle modes. The existing nucleation parameterization [7] has been improved to cover the very low relative humidity (RH) found in the atmosphere of Venus. We have made several modifications to improve the 2002 model [7], most notably ensuring that the two-component model behaves as predicted by the analytical studies at the one-component limit reached at extremely low RH. We have also chosen to use a self-consistent cluster distribution [9], constrained by scaling it to recent quantum chemistry calculations [3]. First tests of the model have been carried out with temperature profiles from VIRA [2] and from the LMD Venus GCM [5], and with a compilation of water vapor and sulfuric acid profiles, as in [6]. Preliminary results are evaluated against observations. [1] Jumelet et al., JGR, 2009. [2] Kliore et al., 1986. [3] Kurtén et al., BER, 2007 [4] Larsen et al., JGR, 2000. [5] Lebonnois et al. JGR, 2010. [6] McGouldrick and Toon, Icarus 191, 2007. [7] Vehkamäki et al. JGR, 2002 [9] Wilemski and Wyslouzil, J.Chem.Phys. 1995.

Abstract Nr. 81

Latitudinal and local time dependence of Venus's cloud-level convection

Takeshi Imamura, Japan Aerospace Exploration Agency, Japan; Takehito Higuchi, The University of Tokyo, Japan; Yasumitsu Maejima, Meteorological Research Institute, Japan; Masahiro Takagi, Kyoto Sangyo University, Japan; Norihiko Sugimoto, Keio University, Japan; Kohei Ikeda, Japan Agency for

Marine-Earth Science and Technology, Japan On Venus, in a manner analogous to the Earth, the energy fluxes of incoming solar radiation and


outgoing thermal IR radiation do not balance each other out at each latitude: low latitudes are subjected to excessive solar heating, while high latitudes are subjected to excessive IR cooling. Such energy imbalance should affect the structure of the cloud-level convection. Excessive heating and cooling occur also periodically with the period of the atmospheric super-rotation, because irradiation to a certain cloud-level air changes as the air is advected by the super-rotation. We constructed a two-dimensional numerical model of Venus’s cloud-level convection and studied the latitude dependence and the diurnal variation of the convection stucture. IR heating and cooling are taken from a one-dimensional radiative-convective equilibrium calculation for a globally-averaged condition, and solar heating is given as a function of the local time and the latitude. The result shows a remarkable variation of the structure of convection with latitude and local time. The suggested latitudinal variation is qualitatively consistent with observed features of the convection layer depth and the activity of atmospheric waves.

Abstract Nr. 105

Cloud top variations from Venus Express measurements

Ignatiev Nikolay, IKI-RAS; Piccioni Giuseppe, IAPS-INAF; Drossart Pierre, Observatoire de Paris – Meudon; Titov Dmitri, ESA-ESTEC; Markiewicz Wojciech, MPS; Khatuntsev Igor, IKI-RAS

Simultaneous observations on the dayside of Venus with VIRTIS-M and VMC instruments onboard Venus Express have been used to map the cloud top altitude and to search for its possible correlation with the UV absorption (Ignatiev et al., 2009, JGR 114, E00B43). Despite a very non-uniform view of Venus in the UV, the location of the upper boundary of the clouds, derived from the observation of the absorption bands in the reflected IR spectrum, demonstrates a smooth systematic behavior with the latitudinal trends symmetric with respect to equator. A comparison of the first work with the measurements made with the high resolution channel (-H) of VIRTIS (Cottini et al., 2012, Icarus 217, 561) suggested that a correction of -2 km in low latitudes has to be applied to the absolute values of the cloud tops. In low and middle latitudes the cloud top defined as the level of unit optical depth at 1.5 micron is thus located at 72+/-1 km. It decreases poleward of +/-50 degrees and reaches 62–68 km in polar regions. The minimum depression of the cloud tops coincides with the hot eye of the planetary vortex. Cloud top can experience fast variations of about 1 km in tens of hours, while larger long-term variations of several kilometers have been observed only at high latitudes. UV markings sometimes correlate with the cloud top altimetry, however the difference between adjacent UV dark and bright regions never exceeds few hundred meters. Analysis of periodicities in the data similar to that found in the cloud top winds has been performed.

Abstract Nr. 100

Venus Clouds: Input to VIRA II model from Venus Express and Venera 15 measurements.

Ignatiev Nikolay, IKI-RAS; Zasova Ludmila, IKI-RAS The original VIRA model of Venus clouds based on measurements from the Pioneer Venus descent probes and orbiter described mainly cloud particle sizes, properties and their vertical distribution. Later measurements from Venera-15 and Venus Express permitted more detailed studies of horizontal and vertical variations. Imaging of Venus in the UV range shows variety of cloud features that include mottled and streaky clouds in the low latitudes, bright mid-latitude belt and “polar cap” with imbedded oval polar dipole. Despite this non-uniform picture the location of the upper boundary of the clouds demonstrates a smooth systematic behavior with the latitudinal trends symmetric with respect to equator: from 72+/-1 km to 62–68 km in polar regions, with the effective scale height being changed from 4 to 0.5-2 km. The upper haze demonstrates a similar latitudinal behavior. Venera-15 measurements revealed solar-related structures in the position of cloud tops. The effective average particle size radius is equal to (1.3+/-0.5) micron at latitudes of 0–70, and 50% larger in the polar regions. There are evidences that the two modes, micron and submicron, are still both present at altitudes higher than 70.0 km. UV markings correlate with the cloud top altimetry, however the difference between adjacent UV dark and bright regions never exceeds few hundred meters. In contrast to the relatively uniform upper cloud boundary, the total cloud thickness experience strong variations. Similar to the cloud top latitudinal behavior, the altitude of the cloud base seems also to


fall between 50 and 75 degrees from 46 to 42 km.

Abstract Nr. 58 High temperature spectroscopy at the Planetary Emissivity Laboratory in support of present

and future Venus missions"

Jorn Helbert, Institute for Planetary Research, DLR; Alessandro Maturilli, Institute for Planetary Research, DLR; Nils Mueller,Institute for Planetary Research, DLR

The atmosphere of Venus allows observations of the surface only in very narrow spectral windows around 1 micron. These have been successfully used by the VenusExpress, Galileo and Cassini spacecrafts as well as by ground-based observers. For any other planetary body this spectral range would be observed in reflectance. However for Venus we can obtain useful data only during nighttime using the thermal emission of the surface. So far no systematic studies have been done on the emissivity of Venus analog materials at high temperatures in this wavelength range due to the significant technical challenges of such experiments. At the Planetary Emissivity Laboratory (PEL) we started 6 years ago to extend our laboratory capabilities to support specifically missions to Venus and Mercury. Both planets exhibit surface temperatures up to 500°C and this extreme temperature range affects the spectral characteristics of the surface minerals. PEL operates a Bruker Vertex 80V, coupled to a custom build planetary simulation chamber. To obtain measure with a very high signal to noise ratio at 1 micron a liquid nitrogen cooled MCT/InSb detector is used. PEL uses an innovative approach for heating samples to Venus surface temperatures of 500°C. chamber. The samples are placed in a stainless steel sample cup, which is heated by a 1.5kW induction system. This approach minimizes heat loss to the chamber. We have obtained first test measurements of a carbonatite and an ijolite sample clearly indicating changes of the emissivity signature with temperature. We will report on the experiments and future plans for the laboratory.

Abstract Nr. 14

Long-lived Emitters in the Atmospheres of the Terrestrial Planets

Slanger, Tom, SRI International To a large extent, the study of nightglow emissions from the terrestrial planets requires techniques that target optically metastable emitters. For all three planets, oxygen atoms and molecules are particularly important, and their excited states typically exhibit long radiative lifetimes. As a consequence, collisional processes rather than radiation require evaluation. As the principal absorbers - CO2 for Mars and Venus and O2 for Earth - produce O-atoms, it is not surprising that in the three cases, knowledge of O/O2 chemistry is crucial. It is interesting to note that the OH molecule is now known to be important in the three atmospheres [Soret et al., 2012], and that the long history of understanding OH kinetics and pathways at Earth is now extended to the cases of Venus/Mars. Techniques developed at SRI International for metastable collisional processes utilize a variety of techniques, including resonance-enhanced multiphoton ionization (REMPI) [Slanger and Copeland, 2003] and fluorescence [Pejaković et al., 2005], the key being to interrogate the metastable densities over time scales far shorter than their actual radiative lifetimes. Additional kinetic information can be derived from ground-based observations of Venus/Mars, where O/O2 nightglow spectra are discernible, cf. the oxygen green line, the O2 Herzberg II bands, and the 1.27 μ O2 Infrared Atmospheric band. Soret, L., J.-C. Gerard, G. Piccioni, and P. Drossart,Planet. Space Sci. 73, 387-396, 2012. Slanger, T.G. and R.A. Copeland,Chem. Rev. 103, 4731-4765, 2003. Pejaković, D.A., R.A. Copeland, T.G. Slanger, and K.S. Kalogerakis,Chem. Phys. Lett. 405,372-377, 2005.


Abstract Nr. 131

Experimental and theoretical studies of CO2 infrared absorption continua

J.-M. Hartmann, Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS (UMR 7583), Universités Paris Est-Créteil et Paris-Diderot 94010 Créteil Cedex, France

Classical Molecular Dynamics Simulations (CMDS) have been carried for gaseous CO2 starting from the intermolecular potential energy surface. Through classical calculations for a large number of molecules treated as rigid rotors, the Auto-Correlation Functions (ACF) of the molecule intrinsic dipole and of the dipole induced by inter-molecular interactions are calculated. The Laplace-Fourier tranforms of these ACF then directly yield the absorption spectrum, free of any adjustable parameter. Comparisons with spectra measured at LISA and in other groups are then made in the far and mid infrared regions. They show that the proposed approach leads to very satisfactory agreement with experiments, both for collision-induced absorption and for absorption in the far wings of allowed bands. This opens promising perspectives for a difficult theoretical problem which cannot be solved by purely quantum approaches. It also opens the route for the prediction of the "continua" in Venus’ atmosphere whose importance for radiative transfer and remote sensing is well known and will be discussed.

Abstract Nr. 73

Experimental Stability of Tellurium: Implications for the Venusian Radar Anomalies Kohler, Erika, Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville,

AR, 72701, USA; Chevrier, Vince, Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR, 72701, USA; Gavin, Patricia,Arkansas Center for Space and Planetary

Sciences, University of Arkansas, Fayetteville, AR, 72701, USA; Johnson, Natasha,National Aeronautics and Space Administration (NASA) Goddard Space Flight Center, Greenbelt, MD, 20771,

USA Radar mapping of the surface of Venus shows areas of high reflectivity in the Venusian highlands at altitudes between 2.5-4.75 kilometers. While theoretical studies have been beneficial, the origins remain unclear and few experimental investigations have been completed. This research experimentally investigates the stability of tellurium under Venusian conditions with its implications as a possible source of the radar anomalies. Stability and reactive experiments on tellurium and mercury sulfide were conducted in the Venus simulation chamber at NASA Goddard Space Flight Center under average Venusian surface conditions, and highland conditions (460°C and 90 bar, 380°C and 55 bar respectively). The latter conditions are the anticipated temperature and pressure at the anomalies altitude. Both compounds were also heated in a Lindberg tube oven at the University of Arkansas to 460°C and 380°C at ambient pressure. After each experiment, the samples were weighed and then analyzed using X-Ray Diffraction (XRD). Tellurium is unstable under all Venusian conditions and reacts with atmospheric CO2 to form paratellurite (TeO2). Mercury sulfide vaporizes under all Venusian conditions leaving the mercury to react with tellurium forming coloradoite (HgTe). The chamber experiments show the same phase changes for both compounds. However, the Venusian highland conditions are more favorable for the formation of coloradoite with XRD results showing 3% of the sample was coloradoite at 460°C and 30% forming at 380°C. Coloradoite forms primarily under conditions corelating with the anomaly altitudes and is a semiconductor, indicating coloradoite could be the source for the Venusian radar anomalies.

Abstract Nr. 88

Experimental set-up to study optical properties of gases at typically planetary conditions

Stefani Stefania, IAPS-INAF ; Piccioni Giuseppe, IAPS-INAF; Snels Marcel, ISAC-CNR; Adriani Alberto, IAPS-INAF


In this work we present an experimental set-up used to study the optical properties of the CO2, the main constituent of the Venus’s atmosphere, at extreme conditions. This apparatus consists of a Fourier Transform InfraRed (FT-IT) interferometer and a customized gas cell, designed to support pressure up to 350 bar and temperature up to 300 ◦ C. Varying the pressure and temperature of the carbon dioxide according to a real vertical profile, we recreated the same physical conditions of the Venus deep atmosphere. The CO2 absorption coefficients, recorded with a resolution of 2 cm-1, give us information about the behavior from an altitude of 50 km down to 16 km. Experimental data have been compared with synthetic spectra obtained by using a Line Mixing Model (LMM), which take into account the line mixing effect. The comparison between measured and simulated data leads us to conclude that the LMM reproduces the data with an integral deviation better than 6% on the full range explored. The integration of the FT-IR with a multi-pass gas cell, recently acquired, will allow us to study in more details the complex phenomenon of the Collision-Induced-Absorption (CIA), in addition to the line mixing and far wings absorption. All the measurements in the lab will significantly improve the knowledge and the prediction of the radiative transfer calculations, in particular for the Venus deep atmosphere.

Abstract Nr. 55

Carbon dioxide collision induced absorption in the 1.18 micron atmospheric window of Venus

Snels Marcel, ISAC/CNR, via del Fosso del Cavaliere, 100, 00133, Rome, Italy; Stefani Stefania, IAPS-

INAF, via del Fosso del Cavaliere, 100, 00133, Rome, Italy; Piccione Giuseppe, IAPS-INAF, via del Fosso del Cavaliere, 100, 00133, Rome, Italy; Adriani Alberto, IAPS-INAF, via del Fosso del Cavaliere,

100, 00133, Rome, Italy The carbon dioxide absorption in the atmospheric windows of Venus is mainly due to collision induced processes. Whereas absorption close to the band centres of allowed absorption bands is proportional to the number density, collision induced absorption scales with the square of the density, since two-body forces are involved. These processes can be divided in three categories; collision induced bands, far wings of allowed bands and continuum absorption.

Collision induced bands are infrared inactive bands which become active due to an collision induced transition dipole moment. They can be observed as isolated bands or they can be superimposed on allowed bands. Presently no theoretical model is available to predict the collision induced absorption of carbon dioxide. The so-called far wings of allowed bands are described in an empirical way, scaling their intensity with line shape correction factors (chi-factors), which are determined from experimental spectra. The continuum absorption is a spectrally flat contribution which is taking into account extreme far wings and any other contributions.

A dedicated cavity ring down spectrometer with an effective optical path of several km has been developed to measure attenuation of monochromatic light around 1180 nm, through a CO2 atmosphere at room temperature and at pressures ranging from 0- 40 bar. Preliminary results showed that this attenuation had a linear variation with density due to Rayleigh scattering and a quadratic component due to collision induced processes. The wavelength dependence of these collision induced processes has also been measured from 1179.5 to 1182.7 nm.

FRIDAY, 14 JUNE – PAGE 34

Friday, 14 June

Abstract Nr. 115

The influence of surface conditions on global mantle evolution

Moresi, Louis, Monash University; Lenardic, Adrian, Rice University The ability of the lithosphere to participate in convection is controlled by the mantle stresses and whether they induce failure in the uppermost few kilometres of the thermal boundary layer. These stresses can change markedly with moderate changes in the surface temperature because mantle viscosity is so sensitive to temperature. The effective strength of the lithosphere can also be influenced by the surface properties such as the presence of water which can produce weaker faults, for example. We will summarise the approach to understanding the global effects of changes in the surface conditions.

Abstract Nr. 18

Long term evolution of Venus through Mantle/Atmosphere coupling.

GILLMANN Cedric, ORB (Royal Observatory of Belgium), Bruxelles, Belgium; TACKLEY Paul, ETHZ, Institute für Geophysik, Zürich, Switzerland

We propose to investigate the evolution of the atmosphere and surface conditions on Venus and how they are linked with mantle dynamics. Coupling occurs outward due to mantle degassing, and inward through surface temperature providing boundary conditions for convection processes. Atmospheric escape is taken into account. During early evolution, hydrodynamic escape is dominant. We use a model developed to take into account the linked escape of Hydrogen and Oxygen. A significant portion of the early atmosphere can be removed this way. For later evolution, we focus on non-thermal escape, as observed by the ASPERA. Post 4 Ga escape is low. The atmosphere is replenished by volcanic degassing. We use the advanced StagYY code for mantle dynamics and corresponding volcanic output. We use a gray radiative-convective model for the atmosphere of Venus. By tracking the evolution of greenhouse gasses in the atmosphere (water and CO2) we follow surface conditions and temperature over time. We are able to obtain a Venus-like behavior, with resurfacing events. We are also able to create evolutions leading to present-day conditions. CO2 pressure stays nearly stable but water pressure is strongly sensitive to volcanic activity, leading to variations in surface temperatures of up to 200K. We observe a clear negative feedback of the atmosphere on volcanic activity, as higher surface temperatures lead to a stagnant or episodic lid convection and less melt production. On the other hand, a lower surface temperature seems to favor mobile lid convection.

Abstract Nr. 60 Thermal evolution of an early magma ocean in interaction with the atmosphere: conditions

for the condensation of a water ocean

Lebrun Thomas, Univ. Paris Sud, Lab IDES CNRS; Massol Hélène, Univ. Paris Sud, Lab IDES CNRS; Eric Chassefiere, Univ. Paris Sud, Lab IDES CNRS; Davaille Anne, Univ. Paris Sud, Lab FAST CNRS;

Marcq Emmanuel, LATMOS, CNRS; Sarda Philippe, Univ. Paris Sud, Lab IDES CNRS; Leblanc François, Univ. Paris 6, LATMOS, CNRS; Brandeis Geneviève, IPGP, CNRS

The thermal evolution of magma oceans produced by collision with giant impactors late in accretion is expected to depend on the composition and structure of the atmosphere through the greenhouse effect of CO2 and H2O released from the magma during its crystallization. In order to constrain the various cooling timescales of the system, we developed a 1D parameterized convection model of a magma ocean coupled with a 1D radiative convective model of the atmosphere. We conducted a


parametric study and described the influences of the initial volatile inventories, the initial depth of the magma ocean and the Sun-planet distance. Our results suggest that a steam atmosphere delays the end of the magma ocean phase by typically 1 Myr. Water vapor condenses to an ocean after 0.1 Myr, 1.5 Myr and 10 Myr for, respectively, Mars, Earth and Venus. This time would be virtually infinite for an Earth-sized planet located at less than 0.66 AU from the Sun. Using a more accurate calculation of opacities, we show that Venus is much closer to this threshold distance than in previous models. So there are conditions such as no water ocean is formed on Venus. Moreover, for Mars and Earth, water ocean formation time scales are shorter than typical time gaps between major impacts. This implies that successive water oceans may have developed during accretion, making easier the loss of their atmospheres by impact erosion. On the other hand, Venus could have remained in the magma ocean stage for most of its accretion.

Abstract Nr. 117

Early evolution of telluric atmospheres in the magma ocean stage

Marcq, Emmanuel, LATMOS / Univ. de Versailles Saint-Quentin; Lebrun, Thomas, IDES / Univ. Paris 11; Massol, Hélène, IDES / Univ. Paris 11; Chassefière, Éric, IDES; Leblanc, François, LATMOS

In order to investigate the evolution of telluric planets, we have to understand the possible outcome of the very early stages, when interactions between the primitive atmosphere and the solid planet are much more pervasive than at later stages. A joint work between LATMOS (atmosphere) and IDES (interior) has thus been led by H. Massol, and have already led to two publications (E. Marcq, 2012 ; Lebrun et al., 2013). This talk will focus on the behaviour of the atmosphere, modeled following Kasing et al. (1988) work with minimal adjustement of the thermal profile and calculations of the outgoing IR (0-104 cm-1) flux only using k-correlated and continuum opacities. The main results are :

Above a certain threshold surface temperature dependent on the total amount of CO2 and H2O, the blanketing effect becomes inefficient (i.e., even the upper radiative part of the atmosphere becomes hot enough to cool efficiently) and rapid thermal cooling may occur ;

Below this threshold, the thermal flux becomes nearly constant and independent on the surface temperature. This behavior was already known (Nakajima-Kombayashi-Ingersoll limit), but the value we find for this flux (about 200 W/m2) is much lower than previous estimates.

Future work will imply a redesign of the atmospheric model and a incorporating atmospheric escape processes so that the simulations may be extended far after a few million years at it is presently the case.

Abstract Nr. 38

Volcanism and Climate on Venus: An Updated Model

Taylor, Fred, Oxford University An attempt is made to represent the climate history of Venus by a single time-dependent model. This aims to incorporate all known facts and data, interpolated with simple physical models, analogies with Earth, and considered assumptions. In each epoch, a key factor is the level of volcanic emission of different gases into the atmosphere and this must be estimated from the evidence. The case is presented for the overall activity being similar, or somewhat higher, than Earth at the present time, and 5 to 100 times higher in the fairly recent past. Future Venus will have little or no volcanic emission, like present-day Mars, and the climate may relax to the tropical Earth-like state predicted by Arrhenius and others before the space era.

Abstract Nr. 133

New calculations of the runaway greenhouse limit: bad news for early Venus and future Earth

Goldblatt C., University of Victoria, Canada


We all know that Venus went through a runaway greenhouse in the past, with hydrogen escape from the resultant steam atmosphere giving rise to the observed D/H enrichment. In this talk, I will review the physics of the runaway greenhouse in terms on limits on outgoing thermal radiation and on the absorption of solar radiation, present new calculations of these limits and discuss the implications for Venus and Earth.

Planetary atmospheres must be in long-term radiation balance, with solar radiation absorbed matched by thermal radiation emitted. For hot moist atmospheres, however, there is an upper limit on the thermal emission which is decoupled from the surface temperature. If net absorbed solar radiation exceeds this limit the planet will heat uncontrollably, the so-called ``runaway greenhouse''.

We have calculated the clear-sky radiation limits at line-by-line spectral resolution for the first time. The thermal radiation limit is lower than previously reported (282Wm-2 rather than 310Wm-2) and much more solar radiation would be absorbed (294Wm-2 rather than 222Wm-2, using the Solar constant at Earth as a reference).

For Earth, the implication is that a runaway greenhouse steam atmosphere may be a stable state under the present insolation, contrary to previous results. Avoiding a runaway greenhouse under the present solar constant requires that the atmosphere is subsaturated with water, and that cloud albedo forcing exceeds cloud greenhouse forcing. For Venus, these results make an early habitable period more difficult to justify. Possible saviours for early Venus could be a dense nitrogen atmosphere (more Rayleigh scattering would mean less sunlight woruld be absorbed) or more low cloud.

Abstract Nr. 79 The origin and early evolution of Venus, Earth and Mars: Clues from bulk properties and the

abundances and isotopic ratios of noble and light gases Baines, K. H., SSEC, University of Wisconsin - Madison; Atreya, S. K., University of Michigan; Bullock,

M. A., Southwest Research Institute; Grinspoon, D. H., Denver Museum of Natire and Science; Mahaffy, P. R., NASA Goddard Space Flight Center; Russell, C. T. , University of California, Los

Angeles; Schubert, G. , University of California, Los Angeles; Zahnle, K. J., NASA/Ames Research Center

Based on similar bulk compositions, Venus, Earth and Mars likely formed in the same realm of the solar nebula. However, variations in the noble gas content of each – particularly in the isotopic ratios of xenon, krypton and neon, can distinguish whether the trio of terrestrial planets that bear significant atmospheres had major contributions to their makeup contributed by (1) asteroids, (2) the outer solar system via comets, (3) inner-solar-system objects that were markedly processed by the solar wind, and/or (4) erosional processes, such as the EUV and charged-particle precipitation from the bright, early Sun or from large impacts during the late stages of accretion. While the entire inventory of noble gases is known accurately for Earth and Mars,.our knowledge of the inventory for Venus is severely lacking. Indeed, there are no measurements for the nine isotopes of xenon, the measurements of the krypton abundance range over more than an order of magnitude, and many of the other noble gas isotopic abundances are known to just the ~ 10-20 % level. In this talk, we discuss specific origin and early evolutionary scenarios for the planets of the inner solar system based on their bulk properties (e.g., size, composition, magnetic fields, rotation rate, and satellites) and on what is known and unknown about the inventories of their noble gases and light isotopes, highlighting hypotheses that could be confirmed or rejected through the acquisition of more precise data, especially for Venus.

Abstract Nr. 43

Present status of AKATSUKI

Nakamura Masato, ISAS; AKATSUKI Project team, ISAS Japanese Venus Climate Orbiter 'AKATSUKI' (PLANET-C) was successfully launched at 06:58:22JST on May 21, by H-IIA F17. The malfunction, which happened during the Venus Orbit Insertion (VOI) on 7


Dec, 2010 is as follows. Orbital maneuver engine (OME) was fired 08:49 JST on Dec. 7. 1min. after firing the spacecraft went into the occultation region and we had no telemetry, but we expected to continuous firing for 12min. Recording on the spacecraft told us later that, unfortunately the firing continued just 152sec. and stopped. The reason of the malfunction of the OME was the blocking of check valve on the gas pressure line to push the fuel to the engine. We failed to make the spacecraft the Venus orbiter, and it is rotating the sun with the orbital period of 203 days. Most of the fuel still remains, but the OME was found to be broken. We decided to use only RCS for orbit maneuver and 3 minor maneuvers in November 2012 were successfully done so that AKATSUKI will meet Venus in late 2015. We are considering several scenarios only using RCS for VOI. In the presentation we will show the possible orbits and how we put the spacecraft into those orbits. They have higher apoapsis than we expected in the initial design, but they are still westward and equatorial that is ideal to reveal the mechanism of the super-rotation of the atmosphere, and we think we will be able to achieve the scientific goals which we have been proposing.

Abstract Nr. 123

Future Exploration of Venus

Limaye, University of Wisconsin; International Venus Exploration Working Group, COSPAR By the end 2015, Venus Express will have observed Venus for nearly ten years, just short of one solar cycle, or nearly fifteen Venus days. A number of significant discoveries have been made and a lot of new questions have been raised by these observations. The knowledge gained from these results is helping refine ideas for future exploration of Venus for the questions that have not been addressed by Venus Express, others that can be refined or narrowed and new ones that require new measurements. These will also be helped by the assessment of the Venus atmospheric observations available to date through the efforts of the international teams that are proposing to the International Space Science Institute to discuss the thermal structure, sulfur dioxide abundance and clouds/aerosols. The Comparative Climatology of Terrestrial Planets Conference sponsored by all four Divisions within NASA's Science Mission Directorate considered Venus as a natural laboratory for better understanding of climates of extra-solar planets and also our own in the context of the continuing discussion of solar and cosmic ray influences on the climate that encourage long term monitoring of Venus to refute or confirm such connections. The opportunities for future exploration missions to Venus are available through the competed programs such as ESA's Cosmic Vision Program for M and L class missions and through NASA's Discovery and New Frontiers Programs. the US National Academies Decadal Survey of Planetary Science has recommended the Venus Climate Mission to be carried out during 2013-2022. The constrained budgets predicted in the near future for NASA however make the prospects for launch of this mission unpredictable at present and can improve only through coordinated international efforts. Other agencies appear to have cintinuing interest in exploring Venus, and we await the insertion of JAXA's Akatsuki mission into orbit in Venus in 2015 or 2016. The Venus Exploration Analysis Group (VEXAG) has initiated a Roadmap activity to focus some attention on the future exploration efforts and also provides opportunities for international dialog through the International Venus Exploration Topical Group. At the last COSPAR meeting in July 2012 a Venus International Exploration Working Group was formed. Continuing inter agency dialog is critical to the success of a coordinated strategy to explore Venus as a system as considered by the decadal survey. Small missions can answer focused questions about Venus, while larger, Cooperative, international missions are more able to address a broader range of science.

Abstract Nr. 12

Beyond Venus Express : clues for future infrared remote sensing experiments


Pierre Drossart, LESIA, Observatoire de Paris

Along the Venus Express nominal and extended mission, infrared remote sensing instruments (VIRTIS, SPICAV, and VMC) have provided numerous parameters of the Venus surface and atmosphere, expanding by a large factor our knowledge of the planet. To go beyond, there is no doubt about the necessity for a future mission to access to the atmosphere and surface through in situ sounding by landers or balloon experiments, but there are still many aspects accessible to remote sensing which would provide first rank scientific investigations. Among still almost unexplored domains are the studies of the Venus seismology, on the one hand, and of the upper mesospheric wave activity on the other hand. A comparison with the first clues obtained from VIRTIS on board Venus Express on gravity waves (Garcia et al, JGR, 2010) observed in the upper atmosphere from CO2 non-LTE emissions will give access to science specifications for an instrument devoted to upper atmosphere wave activity measurements. Some of the wave activity can be produced by a coupling between Venus seismic activity and wave propagation in the ionosphere, as exemplified by Earth tsunami detection from ionospheric disturbances (e.g. Makela et al, GRL, 2011), and threshold of detection depending on instrument sensitivity will be discussed.

Abstract Nr. 39

Venus III Book Status

Taylor, Fred, Oxford University As a contribution to the session on 'Venus International Reference Atmosphere, VIRA II', it is proposed to present an update on the status of the proposed 'Venus III' book that has been discussed at several earlier Venus-oriented meetings (eg Madison 2010) or sessions at larger meetings (eg DPS 2010). There has been little forward progress recently,and colleagues are invited to consider whether the idea still has validity, and if so what might be a reasonable schedule, alongside or after VIRA II.

POSTER CONTRIBUTION

POSTER CONTRIBUTIONS Poster Sessions will take place on Monday afternoon (10 June) and Wednesday afternoon (12 April) at the Polifunzionale Hall. Poster Size Each poster board has a dimension of 100 cm (width) x 200 cm (height). Posters, portrait orientation, must not exceed 100 cm on width and 120 cm on height to fit the assigned space and be easily readable. All poster contributions will have a number and an assigned space on poster boards. Mounting the Posters Posters of group 1 can be mounted Monday afternoon and removed on Wednesday afternoon. Posters of group 2 can be mounted on Wednesday afternoon and may be removed on Friday morning, before the end of the workshop. All necessary material for poster display (pins, etc) will be provided on site.

GROUP 1 POSTER – MON‐WED – PAGE 39

Group 1 poster – Mon‐Wed

Abstract Nr. 92

Errors and Artifacts in the Magellan Imagery of the Surface of Venus

C G Cochrane, Imperial College; R C Ghail, Imperial College NASA’s plan for Magellan did not include a ground truth campaign or stereo imaging. After 2 Cycles of imaging covering 98% of the surface of Venus, and following a stereo trial, NASA did approve a third Cycle for stereo mapping. Cycle 3 coverage was limited by Tracking Station availability and radar performance, and ended on radar failure. There are no published papers on the systematic errors in the Magellan stereo data. Here, 62 Digital Elevation Model (DEM)s are used to characterise these horizontal plane ground position errors and show them to be within the range of 118 to 128 m. This range is rather larger than some previous authors have estimated but comparable to the 100 m positioning accuracy required for InSAR imaging during the EnVision Mission. The paper goes on to show how mapping from the Magellan might be used for EnVision navigation, the importance of characterising EnVision’s imaging performance by terrestrial ground truth comparison, and how the Magellan DEMs illustrate the types of artefact to be avoided by EnVision.

Abstract Nr. 65

Stereo-Derived Topography To Aid Emissivity Estimates at Tesserae on Venus

Nunes, Jet Propulsion Lab, NASA/Caltech; Mitchell, Jet Propulsion Lab, NASA/Caltech; Hensley, Jet Propulsion Lab, NASA/Caltech; Mueller, German Space Agency (DLR); Smrekar, Jet Propulsion Lab,

NASA/Caltech Though dominated by plains volcanism and thick-lid lithosphere, earlier periods of the recorded geologic history of Venus display, in the form of tesserae, considerable lateral deformation, thin lithosphere, and thick crust. Tessera formation is not understood; models include mantle-crust coupling above downwellings, volcanic underplating, and even compositionally distinct crust. Surface emissivity for the southern hemisphere was derived from surface brightness acquired at 1.18 µm by the VIRTIS instrument on Venus Express. Large tessera terrains seen by VIRITS (e.g., Alpha Regio) have low emissivity signatures, possibly indicating relatively high silica [Mueller et al., 2008]. Such more evolved composition generally indicates lower solidus, lower mechanical strength, and may hold significant implications for crustal evolution. To obtain emissivity values from VIRTIS data it is necessary to correct for terrain elevation, but Magellan altimetry is neither accurate nor spatially resolved for properly correcting for elevation in tesserae. We seek to lessen this limitation by creating high resolution DEM’s from stereo coverage of Magellan SAR imaging. Our technique [Hensley and Shaffer,1994] uses a hierarchical scheme that applies a 2-D normalized correlation function to determine offsets between two images with formal error calculation, which is of crucial importance in constraining emissivity values. Our preliminary results with lateral resolution of 600 m and vertical resolutions of less than 100 m, similar toHowington-Kraus et al.[2006], are a marked improvement over Magellan altimetry. We are currently processing data for tessera near Alpha Regio and will use the resulting DTM and uncertainties to constrain tessera emissivity.

Abstract Nr. 69

A global comparison between VeRa radio science observations of the Venus dayside ionosphere and the IonA model

Peter, Kerstin, Rheinisches Institut für Umweltforschung, Abt. Planetenforschung, Cologne,

Germany; Pätzold, Martin,Rheinisches Institut für Umweltforschung, Abt. Planetenforschung, Cologne, Germany; Tellmann, Silvia, Rheinisches Institut für Umweltforschung, Abt.


Planetenforschung, Cologne, Germany; Häusler, Bernd, Institut für Raumfahrttechnik, Universität der Bundeswehr München, Munich, Germany; Bird, Michael K., Argelander-Institut für Astronomie,

Bonn, Germany The radio science experiment VeRa on Venus Express has been sounding the atmosphere and ionosphere of Venus since 2006. To date, more than 400 complete vertical electron density profiles have been recorded for a large variety of observational parameters (solar zenith angle, latitude, local time, season, solar activity cycle). IonA (Ionization in Atmospheres), a fast and flexible software package for the 1D photochemical modeling of lower planetary ionospheres, is examined here for the ionosphere of Venus. The background neutral atmosphere for Venus is taken from the VenusGRAM model, which interpolates temperature/density profiles of the most important atmospheric species as a function of planetary latitude, solar local time and zenith angle from the VIRA database. The solar radiation for the IonA model is taken from the Solar2000 program. These underlying databases allow the direct modeling of the Venus ionosphere for the given VeRa observational parameters and therefore a direct comparison between the observation and the IonA model. Although the general structure of the lower Venus ionosphere is reproduced by IonA, the inadequate VIRA neutral atmosphere model induces significant differences between observation and IonA. The actually encountered neutral atmosphere at ionospheric altitudes is either warmer or of higher density (or both) than the VIRA predictions.

Abstract Nr. 07 ULF and ELF Electromagnetic Waves in the Venus Ionosphere: Separating Atmospheric and

Magnetosheath Sources

Russell, Christopher T., UCLA; Hart, Richard A., UCLA; Leinweber, Hannes, UCLA; Wei, Hanying, UCLA; Strangeway, Robert J., UCLA; Zhang, Tielong, Austrian Academy of Sciences

The Venus Express magnetometer has two tri-axial sensors separated by a one-meter boom that allows the separation of spacecraft and ambient contributions to the observed spectrum. In the ionosphere two distinct wave types are seen: circularly-polarized right-handed waves and linearly-polarized largely compressional ULF waves. The first type is detected over the entire spectral band. The latter waves are seen usually at lowest frequencies below about 10 Hz, but when the ambient field strength is high (~50 nT), the linearly polarized waves can be detected over the entire frequency band of the magnetometer. The behavior of these "ULF" linearly polarized waves is consistent with their propagation across the magnetic field from below or above the spacecraft. The behavior of the ELF circularly polarized waves is consistent with their propagation along the magnetic field from a nearby source (~300 to 600 km away). We examine the occurrence of both wave modes at low altitudes and high, and conclude that the circularly polarized waves are produced below the spacecraft in the atmosphere and that the linearly polarized waves are produced in the solar wind interaction region at high altitudes.

Abstract Nr. 94

Solar wind precipitation on Venus

Stenberg Gabriella, Swedish institute of space physics; Futaana Yoshifumi, Swedish institute of space physics; Barabash Stas,

Solar wind ions are known to precipitate onto the atmosphere of Mars. The large gyroradii of hot particles in the magnetosheath compared to the size of the induced magnetosphere/magnetic barrier make it possible for the ions to gyrate through the barrier. Venus interacts with the solar wind in a similar way and an induced magnetosphere is formed around the planet. However, the scale-sizes are different and precipitation of solar ions onto the atmosphere of Venus is less frequently occurring. We use ion data from ASPERA-4 on Venus Express to investigate how often precipitation of protons and alpha-particles occurs on Venus. With a statistical approach we also estimate the net inflow of solar wind ions onto the ionosphere of Venus. We highlight the differences between solar wind ion precipitation at Mars and Venus and suggest possible explanations for the observed differences.


Abstract Nr. 108

A new dawn-dusk asymmetry in the photoelectron flux of Venus’s Ionosphere

Molaverdikhani Karan, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA; Brain David A., Laboratory for Atmospheric and Space Physics, University of

Colorado, Boulder, Colorado, USA; Mcenulty Tess,Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA

Photoelectrons are excellent tracers of ionospheric plasma. Produced via photoionization of atmospheric neutral particles by solar EUV and X-ray radiation, photoelectrons remain tightly bound to magnetic field lines passing through their location of origin. Spacecraft measurements of photoelectrons therefore allow us to infer which regions of space around a planet are magnetically connected to the ionosphere. We have developed and tested an automatic algorithm to detect the presence of photoelectrons in ASPERA-4 ELS measurements. The algorithm identifies ionospheric photoelectron distributions as a localized peak between 20 to 30 eV in electron energy spectrum. We have applied the filter to six years of Venus Express data to determine the distribution and variability of photoelectrons near the planet, with special emphasis on altitudes <1000 km . We present the characteristics of the measured photoelectron energy distributions, and show how they vary temporally and spatially at Venus. We have identified a new dawn-dusk asymmetry in the ionosphere. Photoelectron flux is enhanced on the dawn side at solar minimum below 250 km and enhanced on the dusk side to higher altitudes as solar activity increases. We find no correlation between these flux enhancements and Interplanetary Magnetic Field strength or direction. We present some plausible ideas to explain the newly found asymmetry based on the asymmetry of neutrals near Venus and plasma transport mechanisms.

Abstract Nr. 78

Limb fitting and cloud tracking for the study of the Venus atmosphere

OGOHARA Kazunori, Japan Aerospace Exploration Agency; KASHIMURA Hiroki, Japan Aerospace Exploration Agency; KOUYAMA Toru, National Institute of Advanced Industrial Science and

Technology; SATO Naoki, Tokyo Gakugei University; TAKAGI Masahiro, Faculty of Science, Kyoto Sangyo University; IMAMURA Takeshi, Japan Aerospace Exploration Agency; HORINOUCHI

Takeshi, Hokkaido University We have developed the new image processing system for the study of the planetary atmosphere. We have successfully corrected attitude information of the satellite, which has a serious effect on the accuracy of cloud motion vectors (CMVs). We can transform accurately a Venus image into a longitude-latitude map of brightness using the "limb fitting" technique and can obtain CMVs by tracking cloud features on such longitude-latitude maps of brightness. The attitude correction by limb fitting has so large impacts on CMVs that the direction of the meridional component of CMVs in low latitudes is completely changed. We have already obtained longitude-latitude maps of brightness and CMVs as NetCDF files using our system from all VMC images (UV, NIR1, NIR2 and VIS) that have been released to the public (ftp://psa.esac.esa.int/pub/mirror/VENUS-EXPRESS/VMC/). We will be able to progress the study of the Venus atmospheric dynamics using such brightness and CMV datasets.

Abstract Nr. 119

Mesospheric Temperature at Terminator using SDO/HMI Aureole Photometry, DST/FIRS CO2 absorption spectroscopy and comparison with Venus Express

Widemann Thomas, LESIA - UMR CNRS 8109, Observatoire de Paris-Meudon - Place Jules-Janssen, 92190 Meudon cedex; Tanga Paolo, Laboratoire LAGRANGE – UMR CNRS 7293, Observatoire de la Côte d’Azur, Université de Nice Sophia Antipolis BP4229 – 06304 Nice Cedex 4 – France ; Vandaele


Ann Carine , Belgian Institute for Space Aeronomy, Brussels, Belgium; Wilquet Valérie, Belgian Institute for Space Aeronomy, Brussels, Belgium; Mahieux Arnaud, Belgian Institute for Space

Aeronomy, Brussels, Belgium; Jaeggli Sarah A. , Montana State University, MT; Reardon Kevin, National Solar Observatory, Tucson, AZ; Penn Matthew J., National Solar Observatory,

Tucson, AZ; Pasachoff Jay M., Williams College-Hopkins Observatory, Williamstown, MA We report on Solar Dynamical Observatory/HMI photometric observations and Dunn Solar Telescope/FIRS Adaptative Optics spectropolarimetric observations of CO2 absorption at 1.57 and 1.61um during the June 5-6 transit of Venus. Close to ingress and egress phases, the fraction of Venus disk projected outside the solar photosphere is outlined by an irregular thin arc of light called the “aureole”. We have shown that the the aureole photometry reflects the local density scale height and the altitude of the refracting layer (Tanga et al. 2012). SDO measurements are in agreement with the VEx/SOIR temperatures obtained during orbit 2238 at evening terminator during solar ingress (46.75N - LST = 6.075PM) and solar egress (31.30N - LST = 6.047PM) as seen from the orbiter. The polar aureole, significantly brighter than the mid-latitude aureole due to the larger scale height of the polar mesosphere, appears consistently offset toward morning terminator by about 15 deg. latitude near 75N. This result reflects local latitudinal structure in the polar mesosphere, both in temperature and aerosol altitude distribution. The Facility IR Spectropolarimeter is a multi-slit spectropolarimeter designed for the Dunn Solar Telescope at the National Solar Observatory on Sacramento Peak in New Mexico to study magnetism on the solar surface. Sun-subtracted Venus limb observations show intensity distribution of vibrational CO2 bands 221 2nu + 2nu2 + nu3 at 1.571um and 141 nu1 + 4nu2 + nu3 à 1.606um. Comparison with ESA / Venus Express / SOIR mean profiles (Mahieux et al., 2012) and temperature modeling at terminator will be discussed at the meeting. Mahieux et al., J. Geophys. Res. , VOL. 117, E07001, doi:10.1029/2012JE004058 (2012) Tanga et al., Icarus 218, 207-219 (2012)

Abstract Nr. 27

Vertical structure of the Venus vortex Ando Hiroki, ISAS/JAXA; Imamura Takeshi, ISAS/JAXA; Bernd Häusler, Universität der Bundeswehr

München; Martin Pätzold,Universität zu Köln The existence of the Venus vortex which orbits the polar with the period of ~3 days has been know from the Pioneer Venus mission, and there are some theoretical studies which explain how this phenomena are maintained. However, the definitive dynamical model has not been constructed yet because vertical structure of the Venus vortex is not clearly known. In this study, we used the vertical temperature profiles obtained from January 20th to 26th 2008 and examined the deviations from the mean temperature field within the altitude range of 55-70 km. As a result, we found the quasi-periodic fluctuations with the period of ~3.2 days at each altitude. Then, the phases and amplitudes of these fluctuations are calculated to find that the structure of the vortex seems to be barotropic.

Abstract Nr. 30

Temperature variation of the cloud top of Venus obtained by photometry observation by LIR onboard Akatsuki

Fukuhara Tetsuya, Hokkaido Univ.; Kouyama Toru, AIST; Imamura Takeshi, ISAS/JAXA; Futaguchi

Masahiko, Rikkyo Univ.; Shima Yuna, Hokkaido Univ.; Taguchi Makoto, Rikkyo Univ.; LIR team, Although Akatsuki failed to enter the Venus’ orbit, the Longwave Infrared Camera (LIR) successfully acquired 52 photometry data of day-side Venus between February and March 2011 at a distance of 1.2-1.7×107 km. The spatial resolution of LIR and an apparent diameter of Venus being almost equivalent, Venus' disk in the image extends to several pixels that include both Venus and the background radiation. All brightness pixels that included Venus were summarized and background radiations were removed from them to estimate a Venus' original brightness components. They have been converted to the brightness temperatures by using calibration data acquired in the laboratory


before the launch, and variation during the observation has been obtained. These discrete data having heterogenous data gaps, the Lomb-Scargle periodgram, which is better suitable than Fast Fourier Transform, has been applied to obtain a power spectrum density. The result shows spectrum peaks at 5-day and 8-day period. The 5-day period may be caused by the super rotation, and the 8-day period may be a planetary-scale wave that has the phase velocity of ~50 m/s.

Abstract Nr. 84 Gravity waves in Venus mesosphere observed by the Venus Monitoring Camera on board

Venus Express

Piccialli Arianna, LATMOS-UVSQ, Guyancourt,France High resolution images of Venus Northern hemisphere obtained with the Venus Monitoring Camera (VMC/VEx) allow studying small-scale dynamical phenomena at the cloud tops (~66 km altitude) and mesoscale features like wave trains. A systematic visual search of these waves was performed; more than 1500 orbits were analyzed and wave patterns were observed in about 300 images. Four types of waves were identified in VMC images on the base of their morphology: long, medium, short and irregular waves. With the aim to characterize the wave types and their possible source of excitation, we retrieved wave properties such as location (latitude and longitude), local time, solar zenith angle, packet length and width, orientation, and wavelength of each wave. Thelong type wavesappear as long and narrow straight features extending more than a few hundreds kilometers and with wavelengths between 7 and 17 km.Medium type wavesexhibit irregular wavefronts extending more than 100 km and with wavelengths in the range 8 – 21 km.Short wave packetshave a width of several tens of kilometers and extend to few hundreds kilometers and are characterized by smaller wavelengths (3 – 16 km).Irregular wave fieldsappear to be the result of wave breaking or wave interference. The waves are often identified in all VMC filters and are mostly found at high latitudes (60–80ºN) and seem to be concentrated above Ishtar Terra, a continental size highland that includes the highest mountain belts of the planet.

Abstract Nr. 40

Polar Vortex: a common element of the Earth and Venus.

Prof. Lucia Marinangeli, Dr. Arturo Cannito, DISPUTer - Universita' G. d'Annunzio - Chieti Polar vortices are common structures and can be found at the poles of any planet with an atmosphere.Earth and Venus have a persistent, large-scale cyclone located near one or both of a planet's geographical poles, although with different origins. On Earth, the polar vortices are located in the middle and upper troposphere and the stratosphere. They surround the polar highs and lie in the wake of the polar front. These cold-core low-pressure areas strengthen in the winter and weaken in the summer. ]They usually span 1000–2000 kilometers in which the air is circulating in a counter-clockwise manner in the northern hemisphere and clockwise manner in the southern hemisphere. The reason for the rotation is the same as any other cyclone, the Coriolis effect. Instead, on Venus where the Coriolis force is negligible, the polar vortices are due to a complex atmospheric patterns. Images from (VIRTIS) instrument have shown that the Venus’ polar vortex change continuously internal structure and position with a period of 5 to 10 Earth days. This situation could be related to what happens at the Earth’s South Pole over Antarctica to understand climate evolutions and change of planets with atmosphere. On the Earth, synoptic perturbations of the Antarctic polar vortex such as distortion or displacement away from the geographic pole, might influence drought in Australia. We explore possible analogies between the terrestrial and venusian polar vortex which may help to explain why arid climatic conditions are getting worst in Southern Australia and if there is a direct link between polar vortex and weather conditions elsewhere.

Prof. Lucia Marinangeli Dr. Arturo Cannito


Abstract Nr. 01

Towards a general classification of atmospheric waves on Venus

Peralta J., IAA/CSIC (Spain); Luz D., OAL/CAAUL (Portugal); Imamura T., JAXA (Japan); Piccialli A., LATMOS-UVSQ (France)

The atmospheric superrotation of Venus goes on being a puzzling phenomenon in the Solar system and is still considered an open problem in geophysical fluid dynamics. A general agreement exists among numerous works concerning the main role that atmospheric waves should have in the generation and maintenance of the superrotation, although most of them try to study the impact of the waves with complex GCMs or using adapted terrestrial dispersion relations by considering frames fixed to the winds. In this work we derive, for the first time, the dispersion relations for a wide variety of possible atmospheric waves in Venus. These dispersion relations are analytically extracted from the primitive equations under reasonable assumptions valid for the cloud region of Venus and above, and the effect of the meridional shear of the wind and the vertical variation of the static stability are also considered. Noteworthy similarities are found for small-scale and mesoscale waves in comparison with the Earth; the global-scale waves, however, exhibit significant differences. These dispersion relations allow building dispersion graphs for different regions of the atmosphere of Venus and classifying a number of waves identified in Venus Express remote sensing data. Finally, a new type of global-scale wave whose restoration force is the centrifugal force is predicted by our equations, which has been confirmed by observations.

Abstract Nr. 17

Simulation of Venus’ polar vortex in the presence of diurnal thermal tide

Yamamoto, Masaru, RIAM, Kyushu University Dynamical impacts of diurnal thermal tide on Venus' polar vortex have not been fully understood, though polar diurnal tides were observed in the Pioneer Venus IR observation. In this study, polar vortex in the presence of thermal tide is investigated using a Venusian middle atmosphere general circulation model (Yamamoto and Takahashi 2012). At 70 km, warm polar region is formed by the thermal-wind relation associated with a high latitude jet in the cloud layer, and cold collar and hot oval (monopole) near the pole are enhanced by the polar diurnal tide. In such a zonally non-uniform basic field (of zonal mean with slowly traveling diurnal tide), unstable vortices with higher zonal wavenumbers form hot dipole and tripole. A hot dipole appears and breaks up into a tripole, when divergent eddies with zonal wavenumbers 2 and 4 are predominant in the polar hot oval region. Hot (cold) anomalies correspond to convergences (divergences) of horizontal wind, and are by 90 deg out of phase with the eddy vorticity component. Because the vortical eddies transport heat toward the cold region, the polar vortices are mainly formed by baroclinic waves in the presence of polar diurnal tide. The present work suggests that both thermal tide and baroclinic wave are dynamically important in the formation of the Venusian polar vortices.

Abstract Nr. 85

Venus cloud tops winds with ground-based Doppler velocimetry and comparison with cloud tracking method

Machado, Pedro, ) LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon cedex, France.; Widemann, Thomas, ) LESIA, Observatoire de Paris, CNRS,

UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon cedex, France.; Luz, David, CAAUL-Centro de Astronomia e Astrofísica da Universidade de Lisboa, Portugal, ; Peralta,

Javier, Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain. We present new results based on Doppler wind velocimetry obtained with the 3.60 m Canada-France-Hawaii telescope (CFHT) and the Visible Spectrograph ESPaDOnS in 2009 and 2011. These observations consisted of high-resolution spectra of Fraunhofer lines in the visible range (0.37–1.05 mm) to measure the winds at cloud tops using the Doppler shift of solar radiation scattered by cloud


top particles in the observer’s direction (Widemann et al., 2007, 2008). The complete optical spectrum was collected over 40 spectral orders, at a resolution of about 80000. We measured the winds using Doppler shifted solar lines and compare with our measurements with VLT/UVES (Machado et al., 2012) and with synchronized coordinated observations by the Venus Monitoring Camera (VMC) and the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instruments from Venus Express (ESA). The observations included various points of the dayside hemisphere at a phase angle of 67º, between +10° and -60° latitude, in steps of 10°, and from +70° to -12° longitude in steps of 12°. Doppler retrievals are in general good agreement with measurements based on cloud tracking, as was the case in previous investigations. Our analysis technique allows characterizing the latitudinal zonal wind profile and its variability, using repeated acquisitions extending over several days, as well as the effect of large-scale planetary waves in the maintenance of superrotation. To provide the best description of the wind field observed, we compare our results to a series of wind models. New constrains on detection of a meridional circulation will be assessed.

Abstract Nr. 19

The time evolution of O2(a1Δ) individual observations acquired by VIRTIS-M on board Venus Express

Soret Lauriane, ULg - LPAP; Gérard Jean-Claude, ULg - LPAP; Piccioni Giuseppe, IAPS - INAF;

Drossart Pierre, Observatoire de Paris Meudon - LESIA The O2(a1Δ) nightglow emission at 1.27 µm may be used as a tracer of the Venus upper mesosphere dynamics. This emission has been observed with VIRTIS-M-IR on board Venus Express. Previous studies showed that the emission maximum is statistically located close to the antisolar point at ~96 km. This airglow results from the production of oxygen atoms on the Venus dayside by photodissociation and electron impact dissociation of CO2 and CO, which are then transported to the nightside by the subsolar to antisolar general circulation, where they recombine to create metastable O2(a1Δ) molecules. Their radiative deexcitation produces the O2(a1Δ) nightglow with a maximum near the antisolar point. However, VIRTIS individual observations indicate that the O2(a1Δ) nightglow emission is highly variable, both in intensity and location. Individual observations acquired during a short period of time can also be grouped sequentially. Bright emission patches can thus be tracked and both their displacement and intensity variations can be analyzed. The peak intensity can vary from 1 to 6 megaRayleighs. We show that the emission peak moves with a mean value of ~80 m s-1, in good agreement with an earlier study by Hueso et al. (2008). The velocity vector in intensity and direction is evaluated approximately every 60 min. These displacements are highly variable, but some dynamical characteristics can be deduced from the observations. These results will be compared with other results of velocity determination in the upper mesosphere.

Abstract Nr. 132

The variable upper atmosphere of Venus - data from drag and torque measurements by Venus Express

Håkan Svedhem , ESA/ESTEC, Research and Space Science Dep., Noordwijk, Netherlands

([email protected]); Ingo Müller-Wodarg , Imperial College, London, UK; Pascal Rosenblatt , Royal Observatory, Brussels, Belgium

Until recently the only information on the structure of the polar upper atmosphere of Venus available has been based on the reference atmosphere models such as the VTS3 or VIRA models. These models extrarpolate the values from low latitudes to high latitudes by using equivalent solar zenith angles. New measurements by Venus Express show that such extrapolations not always give correct results and that there is a permanent overestimate of the density at high latitudes.

These new results have been reached by using two different but related techniques, both using an atmospheric drag effect on the spacecraft. By reducing the pericentre altitude the total mass density in the altitude range 150-200km can be measured in situ by monitoring the orbital decay caused by the drag on the spacecraft by the atmosphere via direct tracking of the Doppler signal on the


telecommunication link. Such measurements have been performed with Venus Express several times during the last years as part of the Venus Express Atmospheric Drag Experiment (VExADE). The results indicate a large variability within only a few days and have led to questions if these variations are real or within the uncertainty of the measurements. A completely different and independent measurement is given by monitoring the torque asserted by the atmosphere on the spacecraft. This is done by monitoring the momentum accumulated in the reaction wheels during the pericenter pass and at the same time considering all other perturbing forces. This requires the spacecraft to fly in an asymmetric attitude with respect to the center of gravity, center of drag and the velocity vector. This technique has proven very sensitive, in particular if the geometric asymmetry is large, and offers an additional method of measuring atmospheric densities in-situ that previously had not been explored with the Venus Express spacecraft. Similar measurements have been done in the past by Magellan at Venus and by Cassini at Titan. Between 2009 and 2012 several campaigns, with altitudes going as low as 165 km, were held. The highest density measured was 7.7 10-12kg/m3 which is significantly less than earlier models predict. The results largely confirm the density measurements by the VExADE drag measurements and add to the confidence in the results from these measurements. By using these drag and torque results and assuming a hydrostatic diffusive equilibrium atmosphere a new model has been constructed.

Abstract Nr. 111 Mapping the lower thermosphere of Venus using VIRTIS/VEx Nadir non-LTE observations

at 4.3 um López-Valverde, Miguel A. , IAA/CSIC, Granada (Spain); Peralta, Javier, IAA/CSIC, Granada (Spain); Gilli, Gabriella, IAA/CSIC, Granada (Spain); Drossart, Pierre, LESIA, Observatoire de Paris (France);

Piccioni, Giuseppe, IAPS, Rome (Italy) A specific set of measurements by VIRTIS/Venus Express is analyzed, that of the infrared emissions of CO2 during daytime in a nadir geometry at 4.3um, originated under breakdown of local thermodynamic equilibrum (LTE) in the upper atmosphere. The scientific exploitation of this nadir dataset is challenging. Non-LTE observations are normally taken in the limb and their vertical variation is used to sound the atmosphere in detail. Our goal here is not the vertical but the spatial variability on the horizontal at the layer of the emission, which according to our non-LTE model is located in the upper mesosphere/lower thermosphere of Venus, at about 110-135 km. Non-LTE theory predicts such CO2 emissions after direct solar pumping to be observed in nadir, to present large variations with SZA and emission angle and to consist of a mixture of individual contributions from a large number of different ro-vibrational CO2 bands, whose intensities respond to diverse collisional and radiative relaxations. All this is confirmed by the measurements, however, a precise simulation is difficult. In addition to the non-LTE complexities and uncertainties, a careful geometrical ray-tracing at the monochromatic level is needed, as well as a correction for the contamination from solar scattering at the Venus clouds. We will present the peculiarities of these non-LTE emissions, the selection of observations from VIRTIS-H, the best fits to the measurements achieved with our simulations, and the results of the inversion scheme designed to obtain and map the temperatures in the Venus lower thermosphere.

Abstract Nr. 56 Visible and Infrared nightglow investigation in the Venus atmosphere by means of VIRTIS

on Venus Express

Migliorini Alessandra, IAPS-INAF, Rome; Piccioni Giuseppe, IAPS-INAF, Rome; Gérard Jean-Claude, LPAP,ULg, Liége; Soret Lauriane, LPap, ULg, Liége; Slanger Tom G., MPL, SRI International;

Politi Romolo, IAPS-INAF, Rome; Snels Marcel, ISAC-CNR, Rome; Drossart Pierre, LESIA, Observatory of Paris, Paris

The oxygen Venus nightglow emissions in the visible spectral range have been known since the early observations from the Venera spacecraft. The major emissions are attributed to the Herzberg II band system, observed in the 400-700 nm spectral range. Additional transitions, belonging to the


Chamberlain system, have been also identified. Recent limb observations with the VIRTIS instrument on board Venus Express allowed to study the vertical distribution of the Herzberg II system of O2, in particular the 0-v''(with v''= 7 to 13) bands. The integrated intensity of the Herzberg II bands with v''= 7-11 varies in the range 83.8-116.4 kR at peak, for the analyzed data. The peak intensity of the emission is observed at an altitude of 93-98 km for the same dataset. Three bands of the Chamberlain system, centred at 560nm, 605 nm, and 657 nm have been identified as well in the VIRTIS data. The peak position is observed about 4 km higher than the emissions due to the Herzberg II and the IR atmospheric systems. This puzzling issue can be addressed with a 1-dimensional model developed starting from realistic O2 and CO2density profiles. By adjusting the uncertainquenching coefficients, we are able to reproduce the peak intensities and altitudes of the three systems. Finally, a comparison with simultaneous observations in the IR shows that the IR atmospheric bands peak 1-2 km higher than the Herzberg II system bands. This is also in agreement with the simulations of the 1-D model.

Abstract Nr. 99

Global imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera

García-Muñoz Antonio, ESA/RSSD, ESTEC, Noordwijk, Netherlands ; Hueso Ricardo, Dpto. Física Aplicada I, Escuela Técnica Superior de Ingeniería, UPV/EHU, Bilbao (Spain); Sanchez-Lavega

Agustin, Dpto. Física Aplicada I, Escuela Técnica Superior de Ingeniería, UPV/EHU, Bilbao (Spain); Markiewicz Wojciech J. , (6) Max Planck Institute for Solar System Research, Katlenburg-Lindau,

Germany; Titov Dimitri V., ESA/RSSD, ESTEC, Noordwijk, Netherlands ; Witasse Olivier, ESA/RSSD, ESTEC, Noordwijk, Netherlands ; Opitz Andrea, ESA/RSSD, ESTEC, Noordwijk, Netherlands

We have investigated the Venus O2 visible nightglow with imagery from the Venus Monitoring Camera (VMC) on Venus Express. The images show a faint but distinct emitting layer at about 100 km altitude attributed to the so-called Herzberg II system of O2, first detected in the Venus atmosphere by the Venera 9 and 10 missions. The VMC visible filter (passband of 502-568 nm at 1/4 maximum transmission) is most sensitive to the v”=9, 10 bands of the c(0)-X(v”) progression, that occur at 513 and 551 nm, respectively. Drawing from data collected between April 2007 and January 2011, we studied the emission’s global distribution. The inferred limb-viewing intensities are on the order of 150 kR at the lower latitudes and seem to drop somewhat towards the poles. The emission is generally stable, although there are episodes when the intensities rise up to 500 kR. Our mapping complements past in-orbit surveys of the O2 visible nightglow, namely those from the Venera missions and Pioneer Venus Orbiter, and provides simultaneous temporal, latitudinal/longitudinal and vertical resolution of the emission. We compare a set of VMC observations with coincident measurements of the O2nightglow at 1.27 micron made with the Visible and Infrared Thermal Imaging Spectrometer, also on Venus Express. We do not find conclusive evidence for a different behavior between the visible and near-infrared emissions.

Abstract Nr. 41

The Effect of Coronal Mass Ejections and Solar Flares on the Venusian Nightglow

Gray, Candace, New Mexico State University; Chanover, New Mexico State University; Tom Slanger, SRI International

The study of planetary nightglow provides us with ways of determining a planet's upper atmosphere composition, chemistry, transport, and evolution. Venus has several strong nightglow features, including the O(1S-1D) transition at 5577.3 Å (oxygen green line). This feature is known to be highly temporally variable, unlike the Earth's green line. The reason for this variability is unknown. We propose that the variability is due to large amounts of extreme ultraviolet (EUV) light and/or charged particles that interact with Venus' upper atmosphere following solar flare


eruptions, coronal mass ejections (CMEs), and strong solar wind streams (SWS) from the Sun.

To test our hypothesis, we observed Venus on the 3.5m Astrophysical Research Consortium (ARC) telescope at Apache Point Observatory with the ARC high resolution echelle spectrograph. Observations were made between April - July 2012 following large solar events. We detected Venusian green line after two separate events: after a CME impact not preceded by a flare, and after an X-flare eruption and a large CME impact. Less than a day after the large CME impact, we found the Venusian green line emission strength to be comparable to the original detection, which was the strongest emission ever detected. The green line strength decayed over the next two nights. From this we conclude that charged particles from CMEs are a likely source of green line emission. We did not detect emission after solar flares that were not followed by a CME, but there are several reasons this may have occurred, as we will discuss.

Abstract Nr. 134

Mt. Etna and the Eistla volcanoes: Comparative studies to constrain venusian volcano evolution and flow emplacement

S.W. Anderson, ; E.R. Stofan, ; S.E. Smrekar,

The magnitude and change of volumetric flow rates at basaltic volcanoes are known to affect both the morphology of individual lava flows, and the shape of the volcano itself. The episodic nature of most eruptions are a function of how energy is stored, and released in volcanic systems, which in turn affects the surface morphology of the erupted products. Therefore, a careful analysis of basaltic surfaces and vent locations can be used as a means by which to understand the both the volcanic history and eruption dynamics for older volcanoes and those in planetary environments. Previous studies of Mount Etna (Italy), Kilauea (Hawaii) and Krafla (Iceland) volcanoes show effusion rate trends that relate to both surface morphology and eruption dynamics that can be used to assess the formation of venusian volcanoes. Sif Mons shows gross morphological characteristics, such as a central vent complex and flows with varying surface morphologies that are similar to that found at Mount Etna, suggesting that eruptions are fed by overflow of the time-averaged magma supply with individual eruptive events that are characterized by steady effusion and long-term eruption rates. In contrast, Gula shows a well-establish rift system and a less complex surrounding flow field that are typically produced by eruptions that have high intensity peaks early followed by exponentially-decreasing effusion and long-term eruption rates.

Abstract Nr. 135 Temperatures in Venus' Lower Thermosphere: Comparison of VTGCM and SOIR Profiles at

the Terminator

S. Bougher , U. of Michigan; C. Parkinson , U. of Michigan; A. Brecht, NASA ARC, CA, USA ; J. Fischer , GSFC, Greenbelt, MD, USA; A-C. Vandaele , BIRA, Brussels, Belgium; V. Wilquet , BIRA,

Brussels, Belgium; A. Mahieux , BIRA, Brussels, Belgium The thermospheric general circulation model for Venus (VTGCM) produces temperatures, densities, and winds over ~70-200 km that can be compared to Venus Express measurements (Brecht et al. 2012). This study will examine the modeled temperatures and the corresponding CO2 density distributions near the terminators in comparison with observations from the Solar Occultation in the InfraRed (SOIR) instrument. Currently, SOIR terminator profiles of CO2 densities and temperatures


have been compiled for 79-selected orbits obtained between 2006-2011 (Mahieux et al. 2012). These profiles represent a global view of the atmospheric characteristics at the Venusian terminator over an altitude range from ~70 to 170 km. These profiles show a general trend revealing a strong temperature minimum around 125 km and the weaker of two temperature maxima near 100-115 km. The temperature structure is reflected in the CO2 density profiles. These profiles provide detailed constraints for global circulation models of the upper atmosphere of Venus, including their simulated temperatures and underlying thermal balances.

For comparisons, VTGCM temperature profiles are extracted from the terminator that corresponds to five latitude bins (0-30N, 30-60N, 60-70N, 70-80N, 80-90N) presently used in the SOIR data analysis. Sensitivity tests with the VTGCM are conducted to show possible sources of variability in the temperature profiles. Also, the impacts of upward propagating waves (e.g. Kelvin wave) on these temperatures are examined. The study will help characterize Venus’ upper atmosphere near the terminators and provide insight into the physical mechanisms responsible for the mean structure and its variability.

GROUP 2 POSTER – WED‐FRI ‐ PAGE 50

Group 2 poster – Wed‐Fri

Abstract Nr. 97 Observations of the near-IR nightside windows of Venus during Maxwell Montes transits

by SPICAV IR onboard Venus Express Fedorova Anna, Space Research Institute (IKI); Moscow Institute of Physics and Technology (MIPT);

Bézard Bruno, LESIA, Observatoire de Paris, section de Meudon, CNRS; Bertaux Jean-Loup, LATMOS-UVSQ; Korablev Oleg, Space Research Institute (IKI); Moscow Institute of Physics

and Technology (MIPT) One of the difficulties in modeling of Venus’ nightside windows is an additional CO2 continuum opacity due to collision-induced CO2 bands and/or extreme far wings of strong allowed CO2 bands. Characterization of the CO2 continuum absorption at near-IR wavelengths and also search for a possible vertical gradient of minor species near the surface require observations over different surface elevations. The largest change of altitudes occurs during a passage above Maxwell Montes at high northern latitudes. In 2011 and 2012 the SPICAV IR performed two sets of observations over Maxwell Montes during 8 and 6 orbits, respectively, in the 1.10-, 1.18- and 1.28-μm windows with a variation of surface altitude from -2 to 9 km. We will present results on the CO2 continuum absorption for the 1.10- and 1.18-μm windows and an investigation of the H2O mixing ratio gradient from the SPICAV data.

Abstract Nr. 16

Ground-based IR observation of oxygen isotope ratios in the Venus atmosphere

IWAGAMI Naomoto HASHIMOTO George ROBERT Séverine O, University of Tokyo Okayama University Belgian Institute of Space Aeronomy Senshu University University of Tokyo

The oxygen isotope ratios 17O/16O and 18O/16O in the solar system show a clear systematic relation. And the relation differs planet by planet. For example, the 17O/16O ratio as a function of 18O/16O ratio in Mars appears to be larger than that in the Earth-Moon system by 0.05 %. This fact indicates that the proto-Earth-Mars matter was so well mixed but with a systematic localization. In such a way, the isotope ratios may provide information about the origin and evolution of the planets. However, 17O/16O ratio in Venus has never been quantified, and may provide further information about the mixing history of the early solar system if measured. The ratios may be quantified by ground-based CO2 IR spectroscopic measurements. By assuming a use of IRTF CSHELL spectrometer with a nominal resolution of 42000, we looked for suitable wavenumber regions to quantify the17O/18O and 18O/16O ratios. The suitable region for the former is found at 2648 cm-1, and for the latter at 4582 cm-1. Preliminary analysis shows that δ17O=+38±53 ‰ and δ18O=-41±52 ‰ where the uncertainties include random errors only; they coincide with those of the earth-moon system within random errors. However, the systematic error anticipated in the line intensities seems to be larger.

Abstract Nr. 67 Abundance of sulfuric acid vapor in the Venus atmosphere derived from the Venus Express

Radio Science Experiment VeRa

Oschlisniok Janusz, Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung, Universität zu Köln, Köln, Germany; Pätzold, Martin, Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung, Universität zu Köln, Köln, Germany; Häusler, Bernd, Institut für


Raumfahrttechnik, Universität der Bundeswehr München, Neubiberg, Germany; Tellmann, Silvia, Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung, Universität zu Köln,

Köln, Germany; Bird, Michael K., Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung, Universität zu Köln, Köln, Germany; Andert, Thomas, Institut für

Raumfahrttechnik, Universität der Bundeswehr München, Neubiberg, Germany; Remus, Stefan, European Space Astronomy Centre (ESAC), Villanueva, Spanien

The radio science experiment VeRa probes the Venus atmosphere with radio signals at 3.6 cm (X-Band) and 13 cm (S-Band) wavelengths. The planet Venus is enshrouded by a roughly 20 km thick cloud layer extending from 50 km to 70 km altitude. While the clouds are mostly composed of liquid sulfuric acid droplets, a haze layer of sulfuric acid vapor exists below the clouds. A decrease in the signal intensity caused by gaseous H2SO4 absorption is observed in VeRa radio occultation experiments below the cloud region (Oschlisniok et al., 2012). This radio absorption is used to determine the abundance of H2SO4 in the cloud and sub-cloud region. The VEX orbit enables study of the global distribution of gaseous sulfuric acid abundance. Vertical absorptivity profiles and the resulting sulfuric acid vapor profiles are presented and compared with previous missions. Together with results from other Venus Express experiments, the derived global distribution of gaseous sulfuric acid is used to study Venus atmospheric dynamics.

Abstract Nr. 128

Water vapor near the cloud tops of Venus from VIRTIS Venus Express day side data Cottini Valeria, NASA GSFC, Greenbelt, USA; Ignatiev Nikolay, Space Research Institute or Russian

Academy of Sciences (IKI RAN), Moscow, Russia; Piccioni Giuseppe, INAF IAPS, Roma, Italy; Drossart P. , LESIA, Observatoire de Paris, Meudon, France; Markiewicz W., Max Planck Institute for

Solar System Research, Katlenburg-Lindau, Germany We observe the dayside of Venus with VIRTIS [1] instrument on board Venus Express to measure the cloud top altitude and water vapor abundance near this level. An extended analysis of these measurements by Cottini et al. [2] was limited by a northern hemisphere due to geometry of observations on first 1000 orbits of the mission. Further measurements significantly improve the latitudinal coverage and demonstrated symmetric behavior of clouds and water vapor in both hemispheres. [1] Drossart, P., Piccioni, G., and 29 co-authors: Scientific goals for the observation of Venus by VIRTIS on ESA/Venus Express mission, Planet. Space Sci., Vol. 55, pp. 1653-1672, 2007. [2 Cottini, V., Ignatiev, N. I., Piccioni, G., Drossart, P., Grassi, D., and Markiewicz, W. J.: Water vapor near the cloud tops of Venus from Venus Express/VIRTIS dayside data, Icarus, Vol. 217, pp. 561-569, 2012.

Abstract Nr. 44

On the Possibility of Gamma Ray Flashes from Venusian Lightning

Lorenz, Ralph, JHU Applied Physics Lab Venus lightning remains mysterious, with some electromagnetic indications of discharges but predominantly negative optical searches. In the mid-1990s, earth-orbiting astrophysical observatories surprisingly discovered a new window on lightning - terrestrial gamma ray flashes (TGFs) produced by the bremmstrahlung of relativistic electrons accelerated upwards from the lightning discharge. Could this phenomenon occur on Venus ? In fact, the Pioneer Venus Orbiter (PVO), in orbit at Venus for some 14 years, carried an Orbiter Gamma Ray Detector (OGBD) for astrophysical studies. Since PVO burned up on entry in 1992, before TGFs were discovered, we do not believe the OGBD data has been examined for Venusian flashes. We have correlated the OGBD data from NSSDC with the ephemeris from the PDS Planetary Magnetospheres node to search for variations in count rate that may be associated with altitude, geographic location and time of day. Unfortunately the data are too coarsely binned in time to detect an obvious signal.


Nonetheless, the possibility remains that future gamma ray instrumentation in Venus orbit could search more deeply for Venus Gamma-ray Flashes (VGFs). To inform such proposals, we have set up a gamma-ray propagation model for the Venus atmosphere using full photon and electron physics in the MCNPX code (Monte Carlo Neutral Particle eXtended) to explore at what altitude VGFs must occur to be visible from orbit.

Abstract Nr. 90

Modeling and observations of mesospheric sulfur chemistry

Mills, Australian National University and Space Science Institute; Sandor, Space Science Institute; Clancy, Space Science Institute

Observations of SO2 and SO in Venus' mesosphere have raised a number of interesting questions, including the consistent detection of a layer above 85 km with greater gas-phase mixing ratios than are found below 85 km, substantial temporal and time-of-day variations in mixing ratios, and substantial variations in the SO2/SO ratio. The last is an important observational test for photochemical models of the sulfur oxide chemistry in Venus' mesosphere. Initial comparisons of model simulations and observations found reasonable agreement on the day side (albeit with considerable variability in the observations) and factor of 100 differences on the night side. Further analysis of the observations has identifed distinct and different patterns in the SO2/SO ratio on the day and night sides. This poster will discuss these analyses and their interpretation via time-of-day model simulations.

Abstract Nr. 35

Spectral inventory of the SOIR spectra onboard Venus Express Robert Séverine, IASB-BIRA; Mahieux Arnaud, IASB-BIRA; Wilquet Valérie, IASB-BIRA; Drummond

Rachel, IASB-BIRA; Vandaele Ann Carine, IASB-BIRA The set of spectra recorded by the SOIR instrument on board Venus Express have been carefully studied from a spectroscopic point of view. The SOIR instrument combines an echelle spectrometer and an Acousto-Optical Tunable Filter for order selection. It performs solar occultation measurements in the IR region (2.2 - 4.4 µm) at a resolution of 0.10 - 0.24 cm-1. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer (65 to 180 km) with emphasis on the vertical distribution of gases (CO2, CO, H2O, HCl, HF…). The sensitivity of the SOIR instrument and the high concentration of CO2 on Venus, coupled with the long absorption paths sounded during solar occultation observations, enable us to detect weak absorption bands of rare CO2 isotopologues. Different tools (manual and automatic calibration, automatic assignment with respect to HITRAN 2008) were developed and applied to the SOIR spectra leading to the creation of the wavenumber list of each observed line. The tools used to calibrate the spectra and to produce the line list will be described extensively for a selected number of orbits.

Abstract Nr. 62

Three-dimensional modelling of Venus photochemistry

Stolzenbach Aurelien, LATMOS; Lefevre Franck, LATMOS; Lebonnois Sebastien, LMD; Maattanen Anni, LATMOS

We have developed a new code of the Venus atmospheric chemistry based on our photochemical model already in use for Mars (e.g., Lefèvre et al., J. Geophys. Res., 2004). For Venus, the code also includes a parameterized treatment of cloud microphysics that computes the size distribution and


composition of sulphuric acid droplets. Recently, we coupled this photochemical-microphysical package to the LMD general circulation model (Lebonnois et al., J. Geophys. Res., 2010). We will describe preliminary results obtained with this first three-dimensional model of the Venus photochemistry. The distribution of key chemical species as well as their variations in space and time will be compared to observations performed from Venus Express and from the Earth.

Abstract Nr. 72

Variations in Venus’ cloud top SO2 and SO gas density with latitude and time of day

Jessup, Kandis-Lea, Southwest Research Institute Venus’ H2SO4 clouds are formed from SO2 gas via the sulfur-oxidation cycle, beginning with SO2 photolysis; followed by the formation of SO3 via SO2oxidation, which then reacts with H2O forming H2SO4. In spite of decades of effort, we do not fully understand the way in which the sulfur-oxide cycle proceeds (Sandor et al. 2010, Sandor et al. 2011). In order to establish patterns in the sulfur-oxide photochemical behavior as a function of latitude and time of day 200-300 nm HST/STIS observations were obtained on Dec 28, 2010, Jan 22, 2011 and Jan 27, 2011 that recorded Venus’ cloud top (65-75 km) SO2 and SO gas absorption signatures at 0.3 nm spectral resolution at latitudes ranging from 20N to 60 S at multiple times of day (Jessup et al. 2012). We present an overview of the results, showing that i) an SO2 abundance of ~ 10-350 ppb was retrieved, consistent with previous Venus Express SPICAV observations made at ±25° latitude (Marcq et al. 2011, Marcq et al. 2013); and, ii) similar to the SPICAV observations, the observed SO2 gas density decreased as the latitude increased from 20 S towards 20 N. The observed SO2 gas density also decreased with local time from the morning terminator towards noon, as expected for a gas density controlled by photochemical destruction; while variation in the observed SO gas density per latitude paralleled that of the SO2 gas, indicating that the latitudinal distribution of the SO gas density was NOT solely controlled by SO2 photolysis. Interpretation of the data is on-going.

Abstract Nr. 102

VIRTIS-VEX data analysis for the study of the Venus

Politi Romolo, INAF-IAPS, via del Fosso del Cavaliere, 100, 00133, Rome, Italy; Migliorini Alessandra, INAF-IAPS, via del Fosso del Cavaliere, 100, 00133, Rome, Italy; Piccioni

Giuseppe, INAF-IAPS, via del Fosso del Cavaliere, 100, 00133, Rome, Italy; Drossart Pierre, LESIA, 5, place Jules Janssen, 92195 Meudon, Paris, France

The Venus Express spacecraft has performed more then 2500 orbits around Venus in more than 6 years of mission. In this time VIRTIS was able to acquire more than 1 TB of data using the visible channel. . In this work we analyze the Bright Factor evolution, on short and long time scales, through the available dataset. The Bright Factor is defined as the ratio between the Venus' VIRTIS spectrum, M-Vis channel, and the Solar spectrum, scaled to the Venus distance. The geometric configuration of the observation is taken in account dividing the spectrum acquired from VIRTIS by a factor proportional to the cosine of the incidence angle. The VIRTIS data are filtered on the local time in order to select only the data from the day side, and the emergence angle, by excluding too high angles of observations. The range explored is between 300 and 1000 nm. We start from an analysis of a global averaged map, that cover all the mission period, to arrive to the single orbit maps, through seasonal variations. We also report the temporal evolution at selected locations and specific wavelengths. Finally, we report the profiles of the Bright Factor versus latitude and local time with the help of 3D maps.

Abstract Nr. 42

Progress in a refined calibration of the Venus Express VIRTIS-M instrument with application to Venus’s ultraviolet absorber

Carlson, Robert W., Jet Propulsion Laboratory, California Institute of Technology; Piccioni,


Giuseppe, Istituto di Astrofisica e Planetologia Spaziali The VIRTIS experiment on Venus Express has collected a wealth of spectra that are useful for studying the ultraviolet absorber present in Venus’s clouds and for possibly identifying the species providing this absorption. However the spectrometer, similar to most grating instruments, suffers from the presence of scattered light that has hindered easy interpretation of the spectra. We have developed methods to satisfactorily remove the scattered light and have recalibrated the response using standard star spectra. Analysis of Venus spectra is now proceeding and preliminary scientific results, as well as the description of the refinement methods, will be presented in the poster.

Abstract Nr. 77

Venusian upper hazes observed by Imaging-Polarimetry system HOPS Enomoto Takayuki, The Graduate University for Advanced Studies; Satoh Takehiko, Japan Aerospace

Exploration Agency; Yoshikazu Nakatani, Kyoto University; Nakakushi Takashi, Wakayama University; Sato Takao, NICT; Ohtsuki Shoko, Senshu University; Hosouchi Mayu, University of

Tokyo Physical properties of the aerosols in the Venusian upper atmosphere can be derived by measuring the polarization of light scattered by them. Kawabata et al. [1980] obtained polarization maps of Venus from the data of Orbiter Cloud Photopolarimeter (OCPP) onboard the Pioneer Venus Orbiter, and found numerous haze particles distributed mainly on polar region. The variability of hazes and clouds can change latitudinal balance of solar absorption and atmospheric dynamics. Two dimensional polarization maps are needless to say advantageous as they allow us to selectively pick up the local characteristics. We developed a planetary imaging-polarimetry system HOPS (Hida Optical Polarimetry System), which can take polarization maps. The optical system of HOPS includes a Wollaston prism and a half wave retarder, and the observation channels are 930, 647(650), 548(546), and 438nm. For the purpose of monitoring of Venusian upper hazes, we performed observations at the Hida observatory of Kyoto Univ. in May, Aug., and Oct. 2012. From quick-looks of the data, it may be indicated that the distribution of haze particles at the time of HOPS observations is somewhat similar to that was observed by PVO/OCPP. We are planning to observe at other phase angles and developing the computational code for multiple light scattering including the effect of polarization for the purpose of quantitative evaluations.

Abstract Nr. 76

Latitudinal cloud structure in the Venusian northern hemisphere evaluated from Venus Express/VIRTIS observations

M. Kuroda, Tohoku Univ.; Y. Kasaba, Tohoku Univ.; T. Kuroda, Tohoku Univ.; P. Drossart, Obs. de

Paris; G. Piccioni, INAF-IAPS The averaged latitudinal distributions of Venusian northern cloud, i.e, its opacity, temperature at the top, altitude at the top and the carbon monoxide under the cloud, were evaluated from the Venus Express/VIRTIS nadir observations. There are several characteristics related to the polar region clouds: (1) The cloud optical thickness around the polar region in 65-80° N is 1.5 times larger than that in the mid-latitudes. It suggests that the number of cloud particles is larger or the optical characteristics of cloud particles are different. (2) The averaged cloud top temperature is gradually decreases from 0-40° N (232±2 K) to 70° N (223±5 K), and increases again to the north pole (233±6 K), while the averaged cloud top altitude monotonously decreases from the equator (68.2±1.6 km) to the north pole (58.3±1.0 km). Both suggest that the Venusian cold and hot polar structures are lower cloud top regions. (3) The averaged CO mixing ratio under the cloud increases from the equator (16±3 ppm) to 70o N (24±5 ppm), and decreases to 80o N (19±5 ppm). This profile has a negative correlation to the cloud top temperature. Since CO under the cloud is transported from the upper cloud layer, it suggests that the cold collar is the down-welling region. Those results are used as the baseline of the Venus General Circulation Model (VGCM) [Kuroda et al., in this meeting.]


Abstract Nr. 23

Study of Venus cloud layers by polarimetry using SPICAV/VEx Rossi Loic, LATMOS/UVSQ; Marcq Emmanuel, LATMOS/UVSQ; Montmessin Franck, LATMOS/CNRS;

Fedorova Anna, Space Research Institute (IKI); Bertaux Jean-Loup, LATMOS/CNRS The study of Venus's cloud layers is important in order to understand the structure and dynamics of its atmosphere. The main cloud layers between 50 and 70 km are thought to consist in ~1 um radius droplets of a H2SO4-H2O solution. Nevertheless, the composition and the size distribution of the droplets are difficult to constrain more precisely. In the early 1980s, Kawabata et al.(1980) used the polarization data from Pioneer Venus' OCPP instrument to constrain the properties of the haze. We introduce here the model we developed, based on the BH-MIE scattering model. Taking into account the same size distribution of droplets as Kawabata et al., we obtained the polarization degree after a single Mie scattering given the effective radius and variance of the distribution and the refractive index of the droplets. We also present the first application of our model to the so-far unexploited SPICAV-IR polarization data under the single scattering assumption. We then plan to integrate our model into a radiative transfer model which will take into account the multiple scattering. With polarization and phase function observations in wavelengths ranging from 650 to 1625 nm, we will be able to put better constraints on the properties of cloud and haze particles, with a primary focus on the cloud droplets characterization.

Abstract Nr. 28

High-altitude source for the Venus’ upper haze found by SOIR/Venus Express

TAKAGI Seiko, University of Tokyo The Solar Occultation at InfraRed (SOIR) on board Venus Express is designed to measure the atmospheric transmission at high altitudes (60-220 km) in the IR (2.2-4.3 µm) with high resolution by solar occultation. The SOIR data obtained in 2006-2009 are analyzed to obtain knowledge of the Venus’ upper haze layer. Vertical distributions of upper haze extinction and mixing ratio (defined as extinction divided by the total density) are derived from the SOIR data. Mixing ratio is found to increase at 90 km and above at both high and low latitudes. It means that haze production is present in this altitude region competing with the vertical eddy diffusion. From comparison with the vertical distributions of SO and SO2 mixing ratios reported by Belyaev et al. (2012), it is speculated that sulfide is closely related to the haze chemistry. At high latitude, mixing ratio is found to be constant at 70-90 km. It means that the vertical eddy diffusion is dominant over the chemistry. Whereas at low latitudes, mixing ratio decreases with altitude at 70-90 km. It means that haze production in the cloud-top region is competing with the vertical eddy diffusion.

Abstract Nr. 53

Simulation of the formation, evaporation and transport of sulfuric acid clouds on Venus using a general circulation model

Takeshi Kuroda, Tohoku University; Fumiya Kato, Simulation of the formation, evaporation and

transport of sulfuric acid clouds on Venus using a general circulation model; Akira Nitta, The University of Tokyo; Morihiro Kuroda, Tohoku University; Yasumasa Kasaba, Tohoku University;

Masaaki Takahashi, The University of Tokyo Sulfuric acid clouds, which exist in 50-70 km altitudes of the Venus' atmosphere, are considered to have a strong influence on the thermal balance. We are investigating the formation and movement of the clouds using a Venus general circulation model (VGCM), and showing the preliminary results in this presentation. Our VGCM is based on the CCSR/NIES/FRCGC AGCM [Ikeda, 2011] which extends from the surface up to ~95 km. The model reproduces the consistent zonal wind fields of super-rotation with observations in the cloud layer with the forcing of gravity waves and a new comprehensive radiative transfer model considering the effects of molecules (CO2, H2O, CO, SO2 and OCS), 75% H2SO4 cloud


particles and unknown UV absorber at the cloud top. We have implemented the radiatively-passive tracers of 75% H2SO4 cloud particles with four different size modes into the VGCM. The condensation and evaporation processes between the clouds and H2SO4 vapor are implemented, and the formed clouds are distributed into the four size modes according to the observed abundance ratios at each altitude. The release of latent head during condensation is also implemented. After the calculations for 1 Venusian day (117 terrestrial days) from the horizontally-uniform states, the cloud abundances of all size modes tended to increase in higher latitudes in comparison with the simulations without the condensation/evaporation processes [Kuroda M. et al., 2013]. This may be because the evaporations of clouds enhance the transport of H2SO4 to the polar regions by the Hadley circulation.

Abstract Nr. 21 Planetary Radio Interferometry and Doppler Experiments for current and future Venusian

missions.

Giuseppe Cimo, Joint Institute for VLBI in Europe; Guifre Molera Calves, Joint Institute for VLBI in Europe; Sergei Pogrebenko,Joint Institute for VLBI in Europe; Dmitry Duev, Joint Institute for VLBI

in Europe; Tatiana Bocanegra Bohamon, Joint Institute for VLBI in Europe; Leonid Gurvits, Joint Institute for VLBI in Europe

Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique to track spacecraft using Very Long Baseline Interferometry (VLBI) in order to estimate state-vectors with high accuracy. PRIDE provides a wide range of scientific outcomes, from geodynamics to fundamental physics. The Venus Express (VEX) spacecraft has been the main target for tests and scientific experiments of the PRIDE team at the Joint Institute for VLBI in Europe (JIVE). My contribution will focus on PRIDE measurements of the Venus Express spacecraft. I will talk about our VLBI observations of the VEX signal presenting the scientific outcomes of these experiments. A number of VLBI images of the VEX spacecraft will be presented, including data of the latest Venus atmospheric drag campaign, when the VEX periapsis was lowered in order to study the upper atmosphere of Venus above its North Pole.

Abstract Nr. 31

Interplanetary scintillations study retrieved from Venus Express communications signal

Molera Calves, Guifre, Joint Institute for VLBI in Europe Very Long Baseline Interfererometry (VLBI) and Doppler tracking is one of the most powerful tools for determining accurately the position of a spacecraft. The Planetary Radio Interferometry and Doppler Experiment (PRIDE) has been included as a part of the scientific suite by a number of future planetary science missions. PRIDE provides estimates of spacecraft state vectors based on VLBI phase referencing and radial Doppler measurements. Furthermore, the phase of the transmitted signal can be precisely extracted by using the reference clocks at the ground stations. The fluctuations of the phase of the received signal are associated to propagation along the interplanetary plasma. We present here a new study of the interplanetary scintillations retrieved from the Venus Express spacecraft communication link. The observations at X-band were performed for more than three years. We have used several radio telescopes from the European VLBI Network (EVN) to track and monitor the behaviour of the signal at different distances and solar elongations of VEX with respect to Earth. The results obtained provide a model of the phase scintillation index and the Total Electron Content (TEC) for the orbit of Venus around the Solar System. These results are important for precise orbit determination in future planetary and deep space missions.

Abstract Nr. 89


Using Venus Express to perform sounding experiments on lunar ionosphere

Pluchino Salvatore, INAF-IRA; Schilliro' Francesco, INAF-IRA The Lunar Radio Occultation (LRO) program performed at the INAF-IRA Medicina and Noto radiotelescopes consists in collecting data of the lunar Total Electron Content, at different limb longitudes and time, in order to study long-term variation of the Moon's ionosphere. We analyse the effects on the wave amplitude and phase modifications of VEX signals, that are correlated to the electron density (ED) of the crossed lunar ionosphere. Pioneer-7 in 1966 first proved the existence of a thin lunar ionosphere (ED ~4x107el/m3). Further readings of the ED ~104el/cm3 were provided in situ by the CPLE-Experiment onboard the Apollo14 mission. Few years later, measurements performed with the spacecrafts Luna-19 and Luna-22 revealed a 10 km plasma layer, with an ED ~0.5-1x103el/cm3. Recently the interest in the study of the lunar ionosphere has risen due to the space-agencies programs about lunar radioastronomical stations. New measurements are important to build a long-term map of the ED distribution of the lunar ionosphere. LRO program started at Medicina in September 2006 with the observation of SMART-1 during its impact on the Moon. It proceeded in 2007 and 2008 with the observation of the lunar occultations of Saturn, Venus, and Mars (where Cassini, VEX, MEX, MRO and MO were occulted by the Moon). On Dec 2008 we performed the first Italian-VLBI tracking experiment by detecting the VEX carrier signals with the 3 radiotelescopes (IRA and ASI). We are planning new VEX signals tracking during the next Venus-lunar occultations: on Sep 8, 2013 and on Feb 26, 2014.

Abstract Nr. 13

A Compact, Low Power Tunable Laser Spectrometer for Trace Gas Measurement in the Venus Atmosphere

Rafkin, Scot, Southwest Research Institute; Silver, Joel, Southwest Sciences, Inc.; Stanton,

Alan, Southwest Science, Inc. A newly developed tunable laser spectrometer (TLS) capable of simultaneously measuring many of the key photochemical species in the atmosphere of Venus is presented. The instrument consists of a low-power (<10 mW) and low mass (<50 mg) vertical cavity emitting laser source and photodetector, a multi-pass optical cell to provide a long absorption path in a compact design, and laser driving and digital signal processing electronics. The sensor takes advantage of two key technological developments: 1) a patented multiple-pass optical cell design that uses small mirrors and dense spot patterns to give a long optical path with a small footprint; and 2) a low power and compact electronics system. The design for Venus is robust in the corrosive sulfuric acid environment and is capable of operating at temperatures of up to at least 370 K; the instrument is ideal for an atmospheric balloon investigation at altitudes of 50 km or higher. The major advantage of this system over previously developed TLS instruments is the multichannel gas measuring capability, an increase in path length and sensitivity without an increase in mirror size, a dramatic decrease in mass and power, and the robust nature of the design in a hostile environment. Most of the instrument components and electronics are at TRL-6 with the combined system at TRL-4. Current best estimates of total instrument mass and power are 750 mW and 1 kg, respectively.

Abstract Nr. 127 A compact, lightweight infrared heterodyne spectrometer for studies of Venus atmosphere

Rodin Alexander, Moscow Institute of Physics and Technology, Space Research Institute; Klimchuk Artem, Moscow Institute of Physics and Technology, General Physics Institute; Nadezhdinsky Alexander, General Physics Institute, Moscow Institute of Physics and Technology; Ignatov

Anton, Moscow Institute of Physics and Technology; Benderov Oleg, Moscow Institute of Physics and Technology; Pereslavtseva Anastasia, Moscow Institute of Physics and Technology, General Physics

Institute

A new concept of the near- and mid-heterodyne spectrometer, based on waveguide coupling of the signal and local oscillator radiation channels and


sweeping LO frequency is proposed for spacecraft application. In the near-IR spectral range, radiation of a tunable DFB diode laser, dynamically stabilized on a reference gas cell is used as LO, is combined with the signal channel by a single mode optical fiber. In the mid infrared range, where single mode fiber is not available, tunable QCL laser and integrated waveguide system are employed. This concept allows to build a compact and lightweight instrument for solar occultations, limb and nadir observations, which may be installed onboard future Venus orbiter. Scientific objectives of the proposed experiment include trace gas analysis, independent profiling of temperature and pressure and search for non-hydrostatic regions in the Venus atmosphere, observations of NLTE emissions and high resolution Doppler measurements of wind field. The work has been supported by the Ministry of Education and Science of Russian Federation grant #11.G34.31.0074

Abstract Nr. 87

Analysis of MESSENGER/MASCS data during second Venus flyby

S. Perez-Hoyos, UPV/EHU; A. Garcia-Muñoz, ESTEC; A. Sanchez-Lavega, UPV/EHU; G. Holsclaw, LASP - University of Colorado; W. McClintock, LASP - University of Colorado

In June 2007, the MESSENGER spacecraft performed its second Venus flyby during its travel to Mercury. The spacecraft acquired several spectra of the reflected sunlight from the equatorial region of the planet and covering from the middle ultraviolet (195nm) to the near infrared (1450 nm) using the MASCS instrument (MUV-UVVS and VIRS channels). In this work we present an analysis of the data and their spectral and spatial variability following the mission footprint on the Venus disk. In order to reproduce the observed reflectivity and obtain information on the upper clouds and the unknown UV absorber, we use XtraRT, a radiative transfer code based on DISORT and the HITRAN database, which includes SO, SO2, CO2 and H2O absorption together with absorption and scattering by mode-1 and mode-2 cloud particles. We discuss the sensitivity of our models to key atmospheric parameters and some preliminary results. The MASCS observations of Venus mean a valuable opportunity for cross-calibration with VIRTIS, the spectrometer on board the Venus Express mission.

NTERNATIONAL VENUS WORKSHOP - INAF · Retrieval of temperature and carbon monoxide from the 4.7um...

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