Life is one of the most persistent phenomena on Earth. It seems that wherever conditions are even remotely favourable, there it is. Organisms can be found in the most arid of deserts: the frozen, inhospitable lands of Antarctica. Here species manage to carve out niches and survive, even flourish in their own unique way. The persistence of life on Earth is part of what drives us to search beyond our planet. Just how constant is this phenomenon we call life? Investigations into the possibility of life on other worlds have no choice but to start on Earth. In order to model extra-terrestrial biological systems scientists must look to Earth-based systems for inspiration. Antarctica provides the exobiologist with a wealth of information. Here can be found some of the hardiest species living under the most extreme physical conditions on Earth. The cold, dry desert regions of Antarctica’s Dry Valleys have been likened to the harsh Martian surface. Ice covered lakes are havens of biological activity. Could the same have been true on Mars as an atmospheric crisis led to increasingly hostile surface conditions? Investigations into the ecological niches occupied by Antarctic micro-organisms provide scientists with ideas of where to begin looking for evidence of life on Mars.