NASA's bogged-down Mars rover Spirit hit another snag in its
attempt to free itself from a sand trap when one of its wheels stalled as it
tried to move forward, NASA reports.
Spirit's wheel stalled during the second step of its third
drive attempt since the effort
to free it from a sandy feature called Troy began in earnest on Nov. 17.
The rover also hit a snag during its first drive attempt last week when it
sensed it was tilting too much and stopped spinning its wheels after just a few
seconds.
The wheel that stalled during the third attempt was the
rover's right-rear wheel; Spirit's
left-middle wheel also stalled back in May, but has since worked normally.
The stall occurred this time because the wheel's progress
fell behind the expected rotation rate. The rover had completed about 13 feet
(4 meters) of commanded wheel spin before the stall stopped the drive.
Though the wheel spun for that distance, the rover did not
actually move that far. The center of the rover moved about 0.2 inch (4
millimeters) forward, 0.1 inch (3 millimeters) to the left and about 0.1 inch (3
millimeters) down, NASA said. During its second drive attempt, the rover also
moved forward slightly.
On Monday, the rover team planned to run a set of
diagnostics to explore the right rear wheel stall. The diagnostics will include
a rotor resistance test, a possible steering test, a small backward rotation of
just the right-rear wheel and a short (about 3 feet, or 1 meter) forward
commanded motion of the rover.
Spirit won't attempt to drive again until Wednesday at the
earliest, according to a NASA statement.
Spirit and its
rover twin, Opportunity, have been on Mars for nearly six years now.
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