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Mars Radiation Environment Characterization

MarsREC + Ongoing activities. Mars Radiation Environment Characterization. Results, previous and ongoing activities Ana Keating Ali Mohammadzadeh Petteri Nieminen Mario Pimenta Eamonn Daly. Mars images courtesy of ESA Portal Multimedia Gallery. Outline. MarsREC model description

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Mars Radiation Environment Characterization

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  1. MarsREC + Ongoing activities Mars Radiation Environment Characterization Results, previous and ongoing activities Ana Keating Ali Mohammadzadeh Petteri Nieminen Mario Pimenta Eamonn Daly Mars images courtesy of ESA Portal Multimedia Gallery

  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 3rd Space weather Week

  3. MarsREC LIP & ESA ESA 18121/04/NL/CH Ana Keating keating@lip.pt 5º longitude

  4. Abstract MarsREC : • 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. 3rd Space weather Week

  5. 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) 3rd Space weather Week

  6. MACLIDIG4 Updated version MACLIDIG4

  7. 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. 3rd Space weather Week

  8. 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). 3rd Space weather Week

  9. 5º 5º Simulation Setup The 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 3rd Space weather Week

  10. 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. 3rd Space weather Week

  11. Analysed Locations • 6 different Locations • North and South, East& West • Solar Longitude 180º-210º G, H, I, J Different times of the Martian day at Long. 0º: • 02h, 12h, 22h Tyrrena Paterae A,B,C,D,E,F 3rd Space weather Week

  12. Fluxes of Particles Olympus Mons cliff (I), 1.3 km of elevation • At low energies:n, g, e- • At high energies : p GCR: • The Ions mainly:Deuteron, Triton, Alpha SEP: • No significant signature of Ions due to GCR Backscattering GCR • 60% All particles • 96% Neutrons Backscattering SEP • 19% All particles • 51% Neutrons due to SEP 3rd Space weather Week

  13. Fluences and Doses Fluences Doses due to GCR Fluence Maps *Considered event duration of 338 hours 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 3rd Space weather Week

  14. 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 3rd Space weather Week

  15. Backscattered neutronsdecrease Primaries decrease Secondaries increase Transfer Functions Fluence at the surface varies with the atmospheric pressure at the surface These resultsaredue to : • Denser air column that primary particles travel through, higher probability of interaction, absorption and spallation • Backscattered neutrons mostly due to Primary protons 3rd Space weather Week

  16. Dependence with Solar Longitude Total integrated fluence of all detected particles at the surface of Mars 3rd Space weather Week

  17. Day and Night Variations 3rd Space weather Week

  18. Low Energy Neutrons Variation • Neutrons E< 30MeV • Mars Univarsal Time Martian Longitude 0º: • 22h : 191K • 02h : 208K • 12h : 248K • Fluences Per year ~ 5x108n/cm2 • Temperature changes -> 1% 3rd Space weather Week

  19. Dependence on landing site • Maximum Differences in fluence expected => 35% Surface pressure = 189,4 Pa Surface pressure = 1004 Pa • In particular: • N =57% • P = 12% • E = 37% • g= 26% 3rd Space weather Week

  20. MarsREM MarsREM Preliminar results, ongoing A. Keating M. Pimenta L. Desorgher F. Lei P. Truscott B. Quaghebeur P.Nieminen 19770/06/NL/JD Mars images courtesy of ESA Portal Multimedia Gallery

  21. MarsREM Aim • 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 3rd Space weather Week

  22. MarsREM Dependence on soil: r & Composition 3rd Space weather Week

  23. MarsREM Conclusions MarsREC 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 ... 3rd Space weather Week

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