Opportunity Rover at Mars. This is how Opportunity, one of NASA MER mission's rovers, is looking like after one year at Mars. This picture was taken by the mast panoramic camera, along with an identical picture taken at Spirit, Opportunity's twin, to assess how the rovers have been affected by dust after one year on the Red Planet. It appears that Opportunity is much less dust-coated than its twin. This is clearly seen here, as the rover is mostsly looking as just unpacked. Opportunity and Spirit are two identical rovers which shared the same journey to Mars and which landed at two different locations there, looking for evidence of a watery, life-hospitable past. Due to their success -and to the capability of both rovers to continue their work, the mission has been extended and both Opportunity and Spirit are still working at Mars. Spirit is working inside a vast Martian crater named Gusev Crater, thought to have been once a lakebed, as Opportunity is working at Meridiani Planum plains which might have been an ancient ocean or sea. Despite obvious evidence that water once existed at Mars, it's still unclear whether it existed beyond simple "playas", kinds of shallow, salty, diminutive swamps, and whether the sedimentary rocks which formed at Mars were due to water only or where mostly volcanic rocky particles cemented back through water and wind. picture NASA/JPL/Cornell