NASA's Opportunity rover is continuing to circle the rocky rim of Endurance Crater, searching for the right place to try and go in. At its deepest point, the crater descends 20 metres (66 feet), so operators are looking for a sheet of stable rock that will stop the rover from slipping in the Martian sand. So far, it looks like the slope is 18 to 20 degrees, which is within the rover's ability to climb back out - just barely. In Eagle crater, where Opportunity landed, the rover was unable to get out from a 17-degree slope because of fine dust at the top of the crater's rim.