Aquifer (Mars)

Definition

It is widely accepted that liquid water was present on the surface of Mars during its early history. Although parts of this water have vanished into space or were consumed in chemical reactions, substantial amounts are still present today. The current physical conditions on Mars’ surface usually do not allow liquid water to be stable, and therefore, it occurs as water ice within the pore space of the permafrost soil or as few km-thick polar ice caps. It can be assumed that at a certain depth below the surface, usually estimated to be a few kilometers, the cryosphere transitions into an aquifer (Lasue et al. 2013). The depth at which the water ice turns into groundwater depends on for Mars not well known factors, such as the water salinity, the soil porosity and permeability, or the geothermal gradient and thermal conductivity of the subsurface. The presence of groundwater on Mars is insofar of interest to astrobiologists as aquifers on Earth are populated by microbial life...