Introduction
On the basis of the prevalence of cold environments in our solar system, the search for extraterrestrial life is focused largely on icy habitats. The McMurdo Dry Valleys (MDV) area is a polar desert with a mean annual temperature below freezing and extremely low humidity (Wharton et al.,1995) and thus offers a suitable earthly analog to our nearest exobiological candidate, Mars. Water is thought to have been abundant on Mars early in its geological history (Solomon et al., 2005; Squyres et al., 2006; Head and Marchant, this volume, Chapter 2) and perhaps may even have flowed across the surface more recently (Hauber et al., 2005; Head et al., 2005; Malin et al., 2006). Life as we know it requires the presence of liquid water to mediate biochemical reactions for energy as well as a reasonably stable environment in which to grow; therefore the search for extraterrestrial life has been largely a search for environments where liquid water can be maintained for some duration (e.g., Carr, 1983).
There is significant geomorphological evidence, and mounting physical evidence supporting the presence of paleolakes on ancient Mars (Squyres et al., 2006). This intrigues exobiologists because paleolakes would provide a suitable habitat for early martian life forms (Carr, 1983; Wharton et al., 1995; Doran et al., 2004). Lakes on the martian surface would have become progressively colder over geological time, developing seasonal and eventually perennial ice covers (Carr, 1983).