I was reading this CNN story forwarded to me from a friend.
CNN.com - Digging for life in the deadest desert - Aug 5, 2004

It is amazing that bacteria can survive in nuclear waste, volcanic vents, and other extremes. Just about any place on Earth you can point your finger down at the ground and be sure there are billions of bacteria where you are pointing. But not in Chile's Atacama Desert!

Scientists are studying Chile's Atacama Desert, the driest part on Earth. Rainfall is measured in millimeters per decade, and some areas have not seen precipitation in hundreds of years. Yup, that's pretty dry. And scientists suspect that's why it is the only place one earth where nothing survives, not even bacteria!

Further, they suspect that when the solar system was younger, the conditions on Mars were much wetter. However, having a 'wetter' Mars is no guarantee of life. Mars gets lots more radiation than Earth due to its thinner atmosphere. So by examining the extremes of how life survives on Earth in extreme conditions, maybe one day we will finally have proof of life on Mars.

Either that or we could just get a better shot of the Face On Mars.