This false-color composite image, taken at a region of the rock outcrop dubbed "Shoemaker's Patio" near the Mars Exploration Rover Opportunity's landing site, shows finely layered sediments, which have been accentuated by erosion. The sphere-like grains or "blueberries" distributed throughout the outcrop can be seen lining up with individual layers. This observation indicates that the spherules are geologic features called concretions, which form in pre-existing wet sediments. Other sphere-like grains, such as impact spherules or volcanic lapilli (fragments of material etween 2 and 64 millimeters or .08 and 2.5 inches in maximum dimension that are ejected from a volcano) are thought to be deposited with sediments and thus would form layers distinct from those of the rocks. This image was captured by the rover's panoramic camera on the 50th martian day, or sol, of the mission. Data from the camera's infrared, green and violet filters were used to create this false-color picture.