NASA?sSpirit rover has encountered a problem on Mars that is familiar to most driverson Earth: it is stuck in dirt and spinning its wheels.
The fivewheels that still rotate on the robot have been slipping severely in soft dirtduring recent driving attempts, sinking the wheels about halfway into theground.
The roverteam of engineers and scientists has suspended drivingSpirit temporarily while studying the ground around the rover and planningsimulation tests of driving options with a test rover at NASA's Jet PropulsionLaboratory in Pasadena, Calif.
"Spiritis in a very difficult situation," said JPL's John Callas, project managerfor Spirit and its twin rover, Opportunity. "We are proceedingmethodically and cautiously. It may be weeks before we try moving Spirit again.Meanwhile, we are using Spirit's scientific instruments to learn more about thephysical properties of the soil that is giving us trouble."
Both Spiritand Opportunityhave been trundling across the Martian surface for morethan five years now, far surpassing their original three-month missions. Opportunity is currently on the opposite side of the planet from Spirit, making its way toits next target, Endeavour Crater.
Spirit hasbeen driving counterclockwise from north to south around a low plateau called"Home Plate" for two months. The rover progressed 400 feet (122meters) on that route before reaching its current position.
Spirit'scurrent sunken situation has raised concerns that the rover's belly pan couldnow be low enough to contact rocks underneath the chassis, which would makegetting out of the predicament even more difficult.
Spirit'sright-front wheel stopped working three years ago. Since then the six-wheeledrobot has been driving backward to circumvent the problem. Driving with justfive powered wheels while dragging or pushing an immobile wheel adds to thechallenge of the current situation.
In 2005,rover controllers had to dig Opportunity out of its own quagmire, whenall six of its wheels were stuck in a deep sand dune.
On a morepositive note, wind has removed some of the dust accumulated on Spirit's solarpanels three times in the last month, increasing the rover's capability forgenerating electricity.
"Theimproved power situation buys us time," Callas said. "We will usethat time to plan the next steps carefully. We know that dust storms couldreturn at any time, although the skies are currently clear."
Behavioralproblems that Spirit exhibited in early April ? episodesof amnesia, computer resets and failure to wake for communications sessions? have not recurred in the past three weeks, though investigations have yet todiagnose the root causes.