GEOL3045: Planetary Geology

GEOL3045: Planetary Geology

Lysa ChizmadiaVenus

From Mariner to Venera to Venus Express

Lysa ChizmadiaVenus

From Mariner to Venera to Venus Express

IntroductionIntroduction Second planet from the

Sun Distance = 1.1 x 108 km 0.72 AU

Diameter = 1.2 x 104 km

Mass = 4.9 x 1023 kg Very circular orbit

Eccentricity < 1% Aphelion: 1.09 x 108 km Perihelion: 1.07 x 108 km

Retrograde rotation From east to west Venusian day = 243 days Venusian year = 225

days

Second planet from the Sun Distance = 1.1 x 108 km 0.72 AU

Diameter = 1.2 x 104 km

Mass = 4.9 x 1023 kg Very circular orbit

Eccentricity < 1% Aphelion: 1.09 x 108 km Perihelion: 1.07 x 108 km

Retrograde rotation From east to west Venusian day = 243 days Venusian year = 225

days

Image from: http://www.nineplanets.org/venus.html

Shows phases Supported

Copernicus’ heliocentric theory

Mean surfaces temperature = 462C ~isothermal Hotter than Mercury

Shows phases Supported

Copernicus’ heliocentric theory

Mean surfaces temperature = 462C ~isothermal Hotter than Mercury

Earth’s Twin PlanetEarth’s Twin Planet Similar sizes:

1.2 x 104 km (95% of ) = 1.3 x 104 km

Similar masses: 4.9 x 1023 kg (80% of )

= 6.0 X 1024 kg

Similar densities 5.25 g/cm3 vs. 5.52 g/cm3 vs. Similar bulk compositions

Young surfaces Recent geologic activity Including volcanism & weathering

Similar sizes: 1.2 x 104 km (95% of ) = 1.3 x 104 km

Similar masses: 4.9 x 1023 kg (80% of )

= 6.0 X 1024 kg

Similar densities 5.25 g/cm3 vs. 5.52 g/cm3 vs. Similar bulk compositions

Young surfaces Recent geologic activity Including volcanism & weathering

Rare impact crater on Venus

Images from: http://en.wikipedia.org/wiki/Venus

Relative sizes of the terrestrial planets

Venusian GeographyVenusian Geography Highlands (~ continents)

Ishtar Terra ~ size of Australia Northern hemisphere Interior high plateau: Lakshmi Planum Surrounding by highest mountains

Maxwell Montes Highest mts have high albedo

substance Speculation: Te & PbS

Aphrodite Terra ~ size of S. America Equator

Broad depressions (~ ocean basins) Atalanta Planitia Guinevere Planitia Lavinia Planitia

Highlands (~ continents) Ishtar Terra ~ size of Australia

Northern hemisphere Interior high plateau: Lakshmi Planum Surrounding by highest mountains

Maxwell Montes Highest mts have high albedo

substance Speculation: Te & PbS

Aphrodite Terra ~ size of S. America Equator

Broad depressions (~ ocean basins) Atalanta Planitia Guinevere Planitia Lavinia Planitia Image from:

http://www.nineplanets.org/venus.html

Magellan radar map (false color)

Image from: http://en.wikipedia.org/wiki/Venus

Map of Venus, higher elevations in reds & yellows

Venusian AtmosphereVenusian Atmosphere

Densest of all terrestrial planets 96.5% CO2 & 3.4% N2

90-92 times thicker than Greenhouse effect

Responsible for high Ts Receives 25% of sunlight as Mercury

Clouds of CO2 & H2SO4

Atm contains 0.015% SO2

Has intermittent lightning Indicates weathering

Venus Express 2005-2009 Studying atmosphere

Densest of all terrestrial planets 96.5% CO2 & 3.4% N2

90-92 times thicker than Greenhouse effect

Responsible for high Ts Receives 25% of sunlight as Mercury

Clouds of CO2 & H2SO4

Atm contains 0.015% SO2

Has intermittent lightning Indicates weathering

Venus Express 2005-2009 Studying atmosphereImages from:

http://en.wikipedia.org/wiki/Venus

Venus in visible light

Venus in UV light

Venusian VolcanismVenusian Volcanism Magellan’s radar

showed much of Venus is covered in lava flows Several shield

volcanoes E.g. Sif Mons & Sapas

Mons

>152 volcanic domes Flat-top domes called

pancake domes Consistent w/ viscous

lavas High silica lavas?

Magellan’s radar showed much of Venus is covered in lava flows Several shield

volcanoes E.g. Sif Mons & Sapas

Mons

>152 volcanic domes Flat-top domes called

pancake domes Consistent w/ viscous

lavas High silica lavas?

Sif Mons

Pancake volcanoes in Alpha Regio regionImages from:

http://www.geology.sdsu.edu/how_volcanoes_work/venus.html

Radial lava flows Sapas Mons

Coronae & ArachnoidsCoronae & Arachnoids Coronae

Circular raised structures surrounded by ridges & grooves & radial lines

Seem to be collapsed domes over large magma chambers E.g. Crater Lake

Arachnoids Ovoid features w/ concentric

rings & complex fracture networks

Similar but smaller than coronae

Possibly precursor to coronae

Coronae Circular raised structures

surrounded by ridges & grooves & radial lines

Seem to be collapsed domes over large magma chambers E.g. Crater Lake

Arachnoids Ovoid features w/ concentric

rings & complex fracture networks

Similar but smaller than coronae

Possibly precursor to coronae

Image from: http://www.nineplanets.org/venus.html

Pandora Coronae

Images from: http://www.geology.sdsu.edu/how_volcanoes_work/venus.html

Ba’het Coronae

Arachnoids

Prominent U.S. SatellitesProminent U.S. Satellites Mariner 2:

First satellite to visit Venus Flyby in December 1962 Discovered Venus is very hot

(~800C) w/ dense CO2-rich atmosphere

Pioneer Venus in 1978 Orbiter & 4 atmospheric probes Made 1st high quality map of Venus

Magellan in 1989 Mapped 98% of surface Gravity field map for 95% of surface

Mariner 2: First satellite to visit Venus Flyby in December 1962 Discovered Venus is very hot

(~800C) w/ dense CO2-rich atmosphere

Pioneer Venus in 1978 Orbiter & 4 atmospheric probes Made 1st high quality map of Venus

Magellan in 1989 Mapped 98% of surface Gravity field map for 95% of surface

Venera 7, 9 & 10Venera 7, 9 & 10 Venera 7 in 1970

1st probe to return surface data from another planet

Venera 9 & 10 in 1975 1st spaceship to land on

another planet Clouds 30-40 km thick Pressure 90 atm Temperature 485C Windspeed 3.5 m/s

Also Venera 11-16 Detected possible seismic

activity Observed strong lightning Discovered pancake volcanoes,

coronae & arachnoids

Venera 7 in 1970 1st probe to return surface data

from another planet

Venera 9 & 10 in 1975 1st spaceship to land on

another planet Clouds 30-40 km thick Pressure 90 atm Temperature 485C Windspeed 3.5 m/s

Also Venera 11-16 Detected possible seismic

activity Observed strong lightning Discovered pancake volcanoes,

coronae & arachnoids

Image from: http://www.nineplanets.org/venus.html

Venusian surface from Venera 9

Image from: http://en.wikipedia.org/wiki/Venera_10

Venusian surface from Venera 9 & 10

Image from: http://www.solarviews.com/eng/venus.htm

Venusian surface from Venera 13

SummarySummary Earth’s twin in size & bulk composition

Also, young surfaces Geologic activity & weathering

Densest atmosphere for terrestrial planets ~90 times higher than Earth Greenhouse effect keeps T high &

constant Lightning & “snow” indicate weather

Prominent features include Volcanoes (shield & pancake) Coronae (magma rising) Arachnoids (collapsed volcanoes)

Earth’s twin in size & bulk composition Also, young surfaces

Geologic activity & weathering

Densest atmosphere for terrestrial planets ~90 times higher than Earth Greenhouse effect keeps T high &

constant Lightning & “snow” indicate weather

Prominent features include Volcanoes (shield & pancake) Coronae (magma rising) Arachnoids (collapsed volcanoes)