Science magazine has chosen the discoveries of NASA’s Mars Exploration Rover (MER) mission as Breakthrough of the Year in its Dec. 17 edition, published today. The principal scientific investigator for the mission’s twin-rover science program is Steve Squyres, professor of astronomy at Cornell University, assisted by a large team of researchers, 28 of them at Cornell, including 15 students. The mission is managed by the Jet Propulsion Laboratory in Pasadena, Calif. The journal, published by the American Association for the Advancement of Science, says that its annual top honor is awarded for the mission’s discovery of evidence for the prolonged presence of potentially life-supporting, salty, acidic water on the planet’s surface.