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  • Characterization of the par...
    McKenna-Lawlor, S.; Gonçalves, P.; Keating, A.; Morgado, B.; Heynderickx, D.; Nieminen, P.; Santin, G.; Truscott, P.; Lei, F.; Foing, B.; Balaz, J.

    Icarus (New York, N.Y. 1962), 03/2012, Letnik: 218, Številka: 1
    Journal Article

    ► First-time use of ESA’s Mars Energetic Radiation Environment Models/MEREM to estimate the radiation hazard at three prospective landing sites. ► These sites display significantly different hydrological conditions/soil compositions. The surface radiation environments predicted are shown to vary with epoch and landing site. ► The Effective Dose (ED) does not depend on location but the Ambient Dose Equivalent (ADE) does. ► MEREM’s dose predictions are in general agreement with those of NASA’s Heavy Ion-Nucleon Transport Code for Space Radiation/HZETRN. ► The Martian atmosphere provides sufficient shielding to maintain dose levels below currently accepted exposure limits over short (30 days) surface stays. The ‘Mars Energetic Radiation Environment Models’ (dMEREM and eMEREM) recently developed for the European Space Agency are herein used to estimate, for the first time, background Galactic Cosmic Ray (GCR) radiation and flare related solar energetic particle (SEP) events at three candidate martian landing sites under conditions where particle arrival occurred at solar minimum (December, 2006) and solar maximum (April, 2002) during Solar Cycle 23. The three landing sites were selected on the basis that they are characterized by significantly different hydrological conditions and soil compositions. Energetic particle data sets recorded on orbit at Mars at the relevant times were incomplete because of gaps in the measurements due to operational constraints. Thus, in the present study, comprehensive near-Earth particle measurements made aboard the GOES spacecraft were used as proxies to estimate the overall particle doses at each perspective landing site, assuming in each case that the fluxes fell off as 1/r2 (where r is the helio-radial distance) and that good magnetic connectivity always prevailed. The results indicate that the particle radiation environment on Mars can vary according to the epoch concerned and the landing site selected. Particle estimations obtained using MEREM are in reasonable agreement, given the inherent differences between the models, with the related NASA Heavy Ion–Nucleon Transport Code for Space Radiation/HZETRN. Both sets of results indicated that, for short (30days) stays, the atmosphere of Mars, in the cases of the SEPs studied and the then prevailing background galactic cosmic radiation, provided sufficient shielding at the planetary surface to maintain annual skin and blood forming organ/BFO dose levels below currently accepted ionizing radiation exposure limits. The threat of occurrence of a hard spectrum SEP during Cruise-Phase transfers to/from Mars over 400days, combined with the associated cumulative effect of prolonged GCR exposure, poses an as yet unsolved hazard to prospective onboard personnel.