Coating on a Rock standing beside Concepción Crater - Sol 2150 (Sx credits: NASA/JPL/Caltech-Cornell Univ. - Dx credits: Dr Paolo C. Fienga - Lunexit Team)

Caption NASA:"This image from the Microscopic Imager (MI) 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 named Concepción.

The Rover took this image during the 2150th 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 cm (1,2") across. The color comes from imaging the same area with the PanCam and it is in false color, so to highlight differences in materials.
The Coating includes a Layer in which peppercorn-size Spherules, nicknamed "blueberries", are packed densely".