This image from the microscopic imager on NASA's Mars Exploration Rover Opportunity shows details of the coating on a rock called "Chocolate Hills," which the rover found and examined at the edge of a young crater called "Concepción."
The rover took this image during the 2,150th Martian day, or sol, of its mission on Mars (Feb. 9. 2010). This target patch on Chocolate Hills is called "Aloya."
The view covers an area about 3 centimeters (1.2 inches) across. The color comes from imaging the same area with the panoramic camera and is false color to highlight differences in materials.
The coating includes a layer in which peppercorn-size spheres nicknamed "blueberries" are packed densely.