Mars images courtesy of ESA Portal Multimedia Gallery Mars Radiation Environment Characterization...

Mars images courtesy of ESA Portal Multimedia Gallery

Mars Radiation Environment Characterization

Results, previous and ongoing activities

Ana KeatingAli MohammadzadehPetteri NieminenMario PimentaEamonn Daly

MarsREC+

Ongoing activities

16/11/06 3rd Space weather Week 2

Outline

MarsREC model description

Radiation Environment at the surface– Fluences– Doses– Dose Equivalents

Variability of the Radiation Environment– Dependence on Time of the day– Dependence on Solar Longitude– Dependence on Landing Location

MarsREM ongoing activities – Dependence on soil density– Dependence on subsoil composition

Conclusions

LIP & ESAESA 18121/04/NL/CH

Ana [email protected]

MarsREC

5º longitude


AbstractMarsREC : Integrated simulation tool for Mars Radiation Environment and

Radiation induced Effect in EEE Components. – landing locations, time and season of the Martian year.

MarsREC consists of two Modules: – Radiation Environment Characterization Module – Radiation Effects Module.

Models features include

– input solar cycle modulated GCR and SEP spectra, both based on CREME-96,

– transport thru the Martian atmosphere and regolith,– creation of secondary radiation, using the Geant4 Monte-Carlo toolkit – atmosphere MCD – Seasonal and diurnal variations are considered for different location.– Surface topology (MOLA)

Outputs:– Energetic particle transport histories, maps of radiation fluxes, doses

dose equivalents and SEU rate predictions.


Atmospheric Database European Martian Climate Database (MCD)

– Temperature, wind, density, pressure, radiative fluxes, etc

– Stored on a 5ºx5 º, longitude-latitude grid from the surface to 120km

– Height of each atmospheric layer

– Fields (wind, temperature, pressure...) are averaged and stored 12 times a day (Mars Universal Time at longitude 0o),

– for 12 Martian “seasons”

– Each season covers 30º in solar longitude (Ls)

t

bbt p

p

g

RTzz ln

MACLIDIG4MACLIDIG4 Updated version


Topology

Radiation Environment mapping

Mars Orbiter Laser Altimeter (MOLA) on board NASA's Mars Global Surveyor (MGS) spacecraft. Data converted into a 5ºx5º Grid

highly dependent on the topology.


Atmosphere and Geology The Martian atmospheric density being very low (in the

order of magnitude of 10-2 Kg m-3), works as a soft attenuator for incoming radiation.

Important contribution from secondary particles generated and backscattered at the surface of Mars.

Mars soil is about 3.75 g cm-3 and the mantle and crust bulk composition consist mainly of SiO2 and FexOy.

The impact of different dust scenarios is not expected to be very significant!

Dust density is typically less than 10-3 g/cm2 (= 0.5x10-3% of the atmospheric density).


Simulation SetupThe geometry implemented in Geant4 program takes into

account: The pixel size given by the 5ºx5º accuracy of MCD, for each (long, latitude)

location

Average composition of the soil of 30% Fe2O3 and 70% of SiO2, and density of 3.75 g/cm3;

The thickness of the 32 atmospheric layers given by the sigma levels of MCD;

A fix atmospheric composition consisting of:

– 95% CO2

– 2.5% N2

– 1.25% Ar

– 1.15% O2

– 0.07% CO

– 0.03% H2O

The atmospheric density, temperature and pressure are given by the 32 layers of the atmospheric table computed from MCD.

Different times of the Martian Day correspond to different geometry set-ups

5º

5º


Radiation inputs CREME96 for near-Earth interplanetary.

Galactic cosmic rays (GCR) – Solar-quiet proton flux in the solar maximum

– Simulated as isotropic momentum distribution: 105protons

Particle events (SPE)– Energetic protons : “worst week” model

– Simulated perpendicularly to the surface : 105protons

Models are based on measurements at Earth (1AU)

The phasing in the solar cycle : foreseen for ExoMars.


Analysed Locations 6 different Locations North and South, East& West Solar Longitude 180º-210º

Tyrrena Paterae

G, H, I, J

A,B,C,D,E,F

Different times of the Martian day at Long. 0º:

02h, 12h, 22h


Olympus Mons cliff (I), 1.3 km of elevation

Fluxes of Particles

At low energies: n,, e-

At high energies : p

GCR:The Ions mainly: Deuteron,

Triton, Alpha

SEP:No significant signature of Ions

Backscattering GCR60% All particles

96% Neutrons

Backscattering SEP19% All particles

51% Neutrons

due to GCR

due to SEP


Fluences and Doses

Tyrrhena Paterae.

Total fluence (one year GCR) of neutrons with energy higher than

30MeV at the surface of Mars for due to GCR protons, at A, B, D, F

Fluence Maps

Fluences

*Considered event duration of 338 hours

Doses due to GCR


Ambient Dose Equivalent

MarsREC post-processing module

Uses the FLUKA fluence-to-ambient dose equivalent

conversion coefficients,

For each kind of particles

Convoluted by the MarsREC fluence as function of particle energy

E

iEHi EfH i*

EHif *


Transfer FunctionsFluence at the surface varies with the atmospheric pressure at the

surface

These results are due to :

Denser air column that primary particles travel through, higher probability of interaction, absorption and spallation

Backscattered neutrons mostly due to Primary protons

Secondaries increasePrimaries decrease Backscattered neutrons decrease


Dependence with Solar Longitude

Total integrated fluence of all

detected particles at the surface of Mars


Day and Night Variations


Low Energy Neutrons Variation Neutrons E< 30MeV

Mars Univarsal TimeMartian Longitude 0º:

– 22h : 191K– 02h : 208K– 12h : 248K

Fluences Per year ~ 5x108n/cm2

Temperature changes-> 1%


Dependence on landing site

Surface pressure = 189,4 Pa Surface pressure

= 1004 Pa

*Maximum Differences in fluence expected => 35%

In particular:

N =57%

P = 12%

E = 37%

= 26%

Mars images courtesy of ESA Portal Multimedia Gallery

Preliminar results, ongoing

A. KeatingM. PimentaL. DesorgherF. LeiP. TruscottB. QuaghebeurP.Nieminen 19770/06/NL/JD

MarsREM

MarsREM


Merge and extending MarsREC & Mars-Planetocosmic models for the Mars, Phobos and Deimos, including treatment of surface topology and composition, subsurface, atmospheric composition and density (including diurnal and annual variations), and local magnetic fields.

Create a user-friendly engineering tool (QARM)

Interface with SPENVIS

New ion physics

MarsREM

Aim


Dependence on soil: & Composition

MarsREM


MarsREM

ConclusionsMarsREC framework is capable of: Predicting RE at the surface (locations, solar longitudes, Time) Tracking all primary and secondary particles (backscattering) Predicting RE variation with climate changes along the Martian year. Evaluating Dose Equivalents and Dose depositions at the surface of Mars Calculating the energy spectra and particle species, radiation fluxes at component

level, energy depositions and doses Computing SEU rates in specific components.

Results show: TID at the surface of Mars is of lesser concern to EEE components,

Dose Equivalents are of major concern for manned missions

Relative abundance of protons and neutrons may result in important DD and SEE effects.

Results show good agreement with experimental data and other software predictions.

MarsREM - Activities will improve and merge de existent models for Mars and Moons

- Results expected to improve with description of new ion physics, soil information ...

Mars images courtesy of ESA Portal Multimedia Gallery Mars Radiation Environment Characterization...

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