ARAMIS: a Martian radiative environment model built from GEANT4 simulations

Abstract

A new model of the Martian surface radiative environment has been built : Atmospheric RAdiation Model for Ionizing spectra on martian Surface (ARAMIS). Based on Monte Carlo calculations, it offers high computational flexibility for surface spectra with several GEANT4 physics lists tested for different exposures and mission scenarios. ARAMIS performs Monte Carlo simulations independently of any exposure scenario to determine a surface response function that can then be convolved to any input spectrum, avoiding simulation repetition while maintaining results accuracy, using a parametric atmosphere geometry. In particular, the adopted approach enables secondary spectra to be discriminated by type and origin, in order to observe the impact of different primary flux components on the surface dose calculation. The ARAMIS model has been validated with experimental measurements from the RAD (Radiation Assessment Detector) instrument on board the Mars Science Laboratory (MSL) Curiosity rover, and benchmarked against other models in the literature. Built using version 11.1.0 of the GEometry ANd Tracking (GEANT4) toolbox and established models of Galactic Cosmic Ray (GCR) or Solar Particle Event (SEP) spectra, the surface neutron and photon spectra provided by ARAMIS shows a better agreement than other models with high-energy experimental data, reducing model uncertainty for radiation protection calculations.