Mars Exploration Rovers (MER) (U.S.)
Destination: Mars. Launched: June 10, 2003 (Spirit) and July 7 (Opportunity). Arrival: Jan. 2004. Mission: To deploy, in two different locations, Spirit and Opportunity, two identical long-range rovers that can trek up to 300 yards (100 m) across the surface in a Martian day. The rovers' sophisticated instruments enable them to act as mobile field geologists, taking color pictures, analyzing soil and rocks, and searching for past and present evidence of water. The rovers were designed to operate for 90 days but were performing so well the mission was extended. Spirit made a successful landing on Jan. 3, 2004, and started beaming 3-D images of the planet the next day. On Jan. 6, Spirit began to send sharp color pictures of the planet back to Earth. Opportunity landed on Jan. 24, 2004, on the opposite side of Mars from Spirit and began sending images the next day. Both rovers, on opposite sides of the planet, found evidence that water was present, and even flowed, in the planet's past. As of July 21, 2006, Spirit had racked up 2.91 mi (4,685 m) on its odometer and Opportunity has traveled 3.45 mi (5,555 m).