The Martian surface radiation environment; A Comparison of models and MSL/RAD measurements

Matthi, D.*; Ehresmann, B.*; Lohf, H.*; Khler, J.*; Zeitlin, C.*; Appel, J.*; Sato, Tatsuhiko   ; Slaba, T. C.*; Martin, C.*; Berger, T.*; Boehm, E.*; Boettcher, S.*; Brinza, D. E.*; Burmeister, S.*; Guo, J.*; Hassler, D. M.*; Posner, A.*; Rafkin, S. C. R.*; Reitz, G.*; Wilson, J. W.*; Wimmer-Schweingruber, R. F.*

The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) has been measuring the radiation environment on the surface of Mars since August 6th 2012. In this work, several models such as GEANT4, PHITS, and HZETRN/OLTARIS are used to predict the radiation environment caused by galactic cosmic rays on Mars in order to compare and validate them with the experimental results. Although good agreement is found in many cases for GEANT4, PHITS and HZETRN/OLTARIS, some models still show large, sometimes order of magnitude, discrepancies in certain particle spectra. We have found that RAD data is helping make better choices of input parameters and physical models. These results help to predict dose rates for future manned missions as well as to perform shield optimization studies.