"Alex writes:
One should note that the preliminary GRS suite data reported today are relatively unconstrained at this point. Bill Boynton, the GRS PI, was very careful to say, in response to a reporter's question, that quantities will take much longer analysis, though the strength of the hydrogen signal, especially over the residual south polar cap was certainly surprising.
That said, given the cryogenic temperatures no one (including the most optimistic Blue Mars types) is claiming that any of this putative H2O is in anything other than ice (or ice matrix) form."

I'll take up the cudgel! TES readings show temperatures can get up to +20 C as far south as 60S latitude:

South Polar Cap Recession
http://wwwflag.wr.usgs.gov/USGSFlag/Space/MGS_TES/spole99.html

This is during the daytime. Nighttime temperatures do drop precipitously. Since the resolution of the GRS is at the hundreds of km scale, you very well could have thin layers of water that become liquid over a range of this size. Also, you could have a frozen over lake with the sunlight penetrating the ice keeping the water liquid below the ice. Somewhat paradoxically the ice covering has the property of keeping the heat in even during the very cold nighttime.

Bob Clark