These four images were taken by NASA's Mars Exploration Rover Opportunity on sols 632 and sol 633 (Nov. 3 and 4, 2005) before and after using the rock abrasion tool on sol 633 to grind into a rock target dubbed "Kalavrita." The images on the top are mosaics of four frames each from the microscopic imager. The images on the bottom are from the rover's front hazard-avoidance camera. The dotted white circle in the lower-left image shows the approximate location of where the rock abrasion tool would grind into the target. Kalavrita was analyzed to investigate how the rock outcrops near the crater "Erebus" compare with rock outcrops to the north that were analyzed along Opportunity's traverse from "Endurance Crater" to Erebus Crater. The abraded circle is about 4.5 cm (1.8 inches) across.