Scroll right to see the inside of Endurance Crater, the large impact feature now being investigated by the Opportunity rover rolling across Mars. The crater's walls show areas of light rock that might hold clues about the ancient watery past of this Martian region. Inspection of this true-color image shows, however, that much of this interesting rock type is confined to crater walls that might be hard for even this wily robot to access. Both of the Mars rovers have now successfully completed their original mission and are now exploring topical opportunities.