Posted by tourdemars to Life on Mars at December 1, 2003 12:00 PM

While Mars can claim some unique features - the largest volcano and the deepest canyon in the solar system - its rocky, dusty, cold landscape has yet to yield signs of the ultimate prize: life. Three simple words - follow the water - have become the mantra of astrobiologists studying the Red Planet because the presence of water is believed to be a prerequisite for life, either past or present. But as scientists look for evidence of water on Mars, they are faced with an underlying dilemma: Will they know life when they see it?