This image, taken by the microscopic imager on the Mars Exploration Rover Opportunity, shows a geological region of the rock outcrop at Meridiani Planum, Mars dubbed "El Capitan." The region was in a shadow when the image was acquired. Several images, each showing a different part of this region in good focus, were merged to produce this view. The area in this image, taken on Sol 28 of the Opportunity mission, is approximately 3 centimeters (1.2 inches) across.
Image Credit: NASA/JPL/US Geological Survey