In explaining extensive evidence for past liquid water, the debate on whether Mars was primarily warm and wet or cold and arid 4-Ga ago has continued for decades. The Sun’s luminosity was ~30% lower 4-Ga ago; thus, most Martian climate models struggle to elevate the mean annual surface temperature past the melting point of water. Geothermal basal melting of thick ice sheets may help resolve that paradox. In this work, we model the thermophysical evolution of ice and estimate the geothermal heat flux required to produce meltwater on a cold, arid Mars. We then analyze geophysical and geochemical data, showing that basal melting would have been feasible on Mars 4-Ga ago. Alternatively, if Mars were warm and wet 4-Ga ago, the geothermal flux would have even sustained hydrothermal activity. Accordingly, regardless of the actual nature of the ancient Martian climate, the deep subsurface could have been the most habitable region on Mars.
Speaker: Lujendra Ojha, Rutgers University
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