Despite the fondest desires of science fiction fans, everyone knows Mars isn't inhabited by little green men. In fact, Mars is a desolate, hostile world, with unbearably cold temperatures, no atmosphere to speak of, and violent dust storms. But could there ever have been life there, in some form? And if so, what happened to it? And could life exist there again one day? Maybe even human life? Elaine Scott takes readers on a journey through history and space and then into an exciting future as she explores the growing body of evidence that water---and therefore the potential for life---was present on Mars at one time. Even more titillating, the possibility of human habitation now hovers on the horizon, maybe within the next 30 years---an exciting prospect for young readers, some of whom may be among those first colonists.