Wheel Stalls Hinder Stuck Mars Rover Again

One of the wheels on the stuck Mars rover Spirit has stalled again, once more causing a snag in NASA?s attempts to free the rover.

Spirit's right-rear wheel stalled again on Nov. 28 during the first step of a two-step extrication maneuver. The wheel first stalled a week prior during another drive attempt, though engineers couldn't replicate the stall during diagnostic tests last week. Those tests showed a fully functioning wheel.

This most recent stall had some different characteristics than the new stall, a NASA report said. It occurred more quickly and had a different signature to it.

Engineers think this new stall could be caused not by the Martian terrain, but might be internal to the plucky rover?s right-rear wheel actuator.

Rover project engineers are developing a series of diagnostics to explore the actuator health and to isolate potential terrain interactions. These diagnostics won't be run before Wednesday and any future driving attempts will depend on the results of those tests.

Before the Nov. 28 drive ended, Spirit completed 4.5 feet (1.4 meters) of wheel spin and the rover's center moved 0.02 inch (0.5 mm) forward, 0.01 inch (0.25 mm) to the left and 0.02 inch (0.5 mm) downward. Since the effort to free Spirit began, the rover has performed 31 feet (9.5 meters) of wheel spin and the rover's center, in total, has moved 0.63 inches (16 mm) forward, 0.39 inches (10 mm) to the left and 0.20 inches (5 mm) downward.

The rover, and its sister robot Opportunity, have been exploring different parts of Mars since January 2004.

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