Mars was thought to have been cold, dead and dry for eons, but striking new evidence suggests the planet was relatively warm and wet in geologically recent times, and that even today there are reserves of water frozen beneath the planet's surface. This highly absorbing book relates how NASA and ESA have sought evidence of life on Mars. The author provides a comprehensive account of the recent Spirit and Opportunity Mars Exploration Rover missions, and describes the planning for the tests carried out by the Viking missions in 1976, with an account of the debate over their results.