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Mars OdysseyA US probe, launched Apr. 7 2001, that was part of NASA's Mars Exploration Program, a long-term series of crewless investigations of Mars. It reached Mars in Oct. 2001 and commenced its primary mission to map the chemical makeup of the planet and scout out likely places where water or ice might be found by future probes searching for evidence of past life. Odyssey's primary mission ended on Aug. 24 2004 after well over 10 000 orbits, and it embarked upon an extended mission. During its first 34 months in orbit, Odyssey discovered ice just below the surface at the Martian poles and investigated the radiation environment in low Mars orbit, thereby aiding the assessment of radiation risk to future human spaceflight missions to the planet. In addition to its science activities, Odyssey served as a communications relay for the Mars Exploration Rovers Spirit and Opportunity. It would continue this role during its extended mission.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006