Mars Odyssey

"2001 Mars Odyssey is part of NASA's Mars Exploration Program, a long-term effort of robotic exploration of the red planet...For the first time, the mission globally mapped the amount and distribution of many chemical elements and minerals that make up the martian surface. Maps of hydrogen distribution led scientists to discover vast amounts of water ice in the polar regions buried just beneath the surface." Read more about the mission at the Mars Odyssey homepage.