Burns Cliff on Mars . ... Credit Copyright: Mars Exploration Rover Mission , JPL , NASA Explanation: The majestic walls of Endurance Crater contain layers of clues about the ancient past of Mars . In fact, the deeper the layer, the older the clue. The particular crater wall imaged above was dubbed Burns Cliff and was in front of the robot rover Opportunity last week. ... Today, more practically, Burns Cliff blocks one exit direction for Opportunity to leave Endurance Crater . ...