Just saw this mentioned on Bautforum.com:

FOR RELEASE: Thursday, May 21, 2009
Research Demonstrates Potential for Liquid Water on Present-Day Mars.
"The extreme temperatures found on Mars typically lead to either crystallization or evaporation of water, making it difficult to imagine that water could be found in liquid form. However, salts have been shown to lower the freezing point of water – which is why street crews use salt on the roads to melt ice, Hanley said. Some salts, like perchlorates, lower the freezing point substantially. It turns out that the temperature for the liquid phase of magnesium perchlorate – 206 degrees Kelvin – is a temperature found on Mars at the Phoenix landing site. Based on temperature findings from the Phoenix lander, conditions would allow this perchlorate solution to be present in liquid form for a few hours each day during the summer."
http://dailyheadlines.uark.edu/15090.htm

Bob Clark