This mosaic of five images taken by the microscopic imager on the Mars Exploration Rover Opportunity on sol 87 shows the hole drilled by the rover's rock abrasion tool into the rock dubbed "Pilbara." A sliced "blueberry," or spherule, which is darker and harder than the rest of the rock, can be seen near the center of the hole. The rock abrasion process left a pile of rock powder around the side of the hole, and to a lesser degree, inside the hole. The grinding penetrated an area of rock about 7.2 millimeters (about 0.28 inches) deep and 4.5 centimeters (about 1.8 inches) in diameter.