Stability of martian water "Liquid water can be stable against
freezing and stable against boiling, but unstable with respect
to evaporation. The situation is analogous to Earth's oceans.
Liquid water on the surface does not freeze because temperatures
are higher than the melting point, and it does not boil because
the vapor pressure corresponding to the temperature of the water
is less than the surface pressure. Yet the water does evaporate
because the atmosphere is not saturated. A similar situation can
occur on Mars, though the odds are much more likely for
boiling." "But whether it boils or evaporates, either way the
water will cool because of the heat loss and thus it will
eventually freeze."