Using its rock abrasion tool, otherwise known as "Rat," NASA's Mars Exploration Rover Opportunity dotted the slope of "Endurance Crater" with dimples that give scientists a glimpse into its layered geologic history. This image from the rover's navigation camera, taken on sol 169 (July 15, 2004), highlights the prolific work of the robotic "rodent." How many Rat holes can you identify? You will be able to check your answer against an image to be posted soon with all the holes identified.