On the way out of "Endurance Crater," NASA's Mars Exploration Rover Opportunity has been making observations along the crater wall, an intriguing and revealing geological path. One factor that immediately caught the eyes of scientists was a noticeable difference between light rocks and dark rocks along the crater rim. The pictured rock, "Tipuna," lies just under the dividing line, in the dark section. Opportunity's panoramic camera took this image during the rover's 306th martian day, or sol (Dec. 3, 2004). The image gives an up-close view of Tipuna, revealing complex layering that was likely caused by ancient flowing water or wind deposition. Scientists have used the rover's rock abrasion tool to expose interior material for analysis on both dark and light rocks near Tipuna.