Potential Habitability of Present-Day Martian Subsurface for Earth-Like Methanogens

The intense debate about the presence of methane in the martian atmosphere has stimulated the study of methanogenic species that are adapted to terrestrial habitats that resemble martian environments. We examined the environmental conditions, energy sources, and ecology of terrestrial methanogens that thrive in deep crystalline fractures, subsea hypersaline lakes, and subglacial water bodies, considered analogs of a hypothetical habitable martian subsurface. We combined this information with recent data on the distribution of buried water/ice and radiogenic elements on Mars, and with models of the subsurface thermal regime of this planet, we identified a 4.3-8.8 km-deep regolith habitat at the midlatitude location of Acidalia Planitia that might fit the requirements for hosting putative martian methanogens analogous to the methanogenic families, Methanosarcinaceae and Methanomicrobiaceae.