Martian sedimentary rocks. True-colour image of Martian sedimentary rock layers exposed on the 'Payson' ledge on the western edge of Erebus Crater. The rocks formed billions of years ago, and are thought to have been formed by both wind and water sedimentation actions. This image was obtained by the Mars Exploration Rover Opportunity. The colours of this image were created by combining camera filters to approximate what a human would see. Opportunity landed in the Meridiani Planum region of Mars in January 2004, and obtained this image on 3 March 2006, the 749th Martian day of the rover's mission.