NASA's Mars Exploration Rover Opportunity used its navigation camera to take this picture showing a light-toned rock, "Tisdale 2," during the 2,690th Martian day, or sol, of the rover's work on Mars (Aug. 18, 2011). The rock is about 12 inches (30 centimeters) tall.

In subsequent sols, the rover used tools on its robotic arm to examine Tisdale 2. That rock and others on the ground beyond it were apparently ejected by the impact that excavated a 66-foot-wide (20-meter-wide) crater, called "Odyssey," which is nearby to the left (north) of this scene. Odyssey and these rocks are on a low ridge called "Cape York," which is a segment of the western rim of Endeavour crater. Part of Opportunity's array of photovoltaic cells is visible in the foreground.