  The notion of liquid water beneath the ice layer at the south polar layered
deposits of Mars is an interesting possibility given the implications for
astrobiology, and possible human habitation. A body of liquid water located at
a depth of 1.5 km has been inferred from radar data in the South Polar Cap.
However, the high temperatures that would facilitate the existence of liquid
water or brine at that depth are not consistent with estimations of heat flow
that are based on the lithosphere's flexure. Attempts to reconcile both issues
have been inconclusive or otherwise unsuccessful. Here, we analyse the possible
role of subsurface ammonia and methanol in maintaining water in a liquid state
at subsurface temperatures that are compatible with the lithosphere strength.
Our results indicate that the presence of these compounds at the base of the
south polar layered deposits can reconcile the existence of liquid water with
previous estimations of surface heat flow.
