Influence of higher atmospheric pressure on the Martian radiation environment: Implications for possible habitability in the Noachian epoch

The Noachian epoch (similar to 4.5-3.5 billion years ago) is a promising era for a possible emergence of life on Mars. The presence of runoff channels in areas formed during the Noachian suggests that liquid water existed at least sporadically during that time, with liquid water being regarded as a prerequisite for life. To have sustained liquid water, the atmospheric pressure on Noachian Mars must have been significantly higher than in the present. When considering the possibility of life on Noachian Mars, one conceivable restriction is given by the ionising radiation environment. Using PLANETOCOSMICS- and Geant4-simulation codes, we calculate the radiation environment on the Martian surface and the resulting radiation exposure for different atmospheric conditions. Here, we present absorbed dose and dose equivalent rates resulting from galactic-cosmic-proton and alpha-particle-induced radiation environments, as well as changes of these rates caused by an increase of atmospheric pressure.