Martian surface. True colour image from the panoramic camera on NASA's Mars exploration rover Opportunity of the Olympia outcrop (centre) in the Erebus Crater. The outcrop exposes sulphate-rich sedimentary rocks that were mostly formed from windblown sediments, although some were formed in the presence of water. Opportunity and its sister rover Spirit were launched in the summer of 2003. Opportunity landed on Mars on 24th January 2004. Its mission is to analyse soil and rocks and search for water.