NASA's
Spirit rover has encountered a problem on Mars that is familiar to most drivers
on Earth: it is stuck in dirt and spinning its wheels.
The five
wheels that still rotate on the robot have been slipping severely in soft dirt
during recent driving attempts, sinking the wheels about halfway into the
ground.
The rover
team of engineers and scientists has suspended driving
Spirit temporarily while studying the ground around the rover and planning
simulation tests of driving options with a test rover at NASA's Jet Propulsion
Laboratory in Pasadena, Calif.
"Spirit
is in a very difficult situation," said JPL's John Callas, project manager
for Spirit and its twin rover, Opportunity. "We are proceeding
methodically and cautiously. It may be weeks before we try moving Spirit again.
Meanwhile, we are using Spirit's scientific instruments to learn more about the
physical properties of the soil that is giving us trouble."
Both Spirit
and Opportunity
have been trundling across the Martian surface for more
than 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 to
its next target, Endeavour Crater.
Spirit has
been driving counterclockwise from north to south around a low plateau called
"Home Plate" for two months. The rover progressed 400 feet (122
meters) on that route before reaching its current position.
Spirit's
current sunken situation has raised concerns that the rover's belly pan could
now be low enough to contact rocks underneath the chassis, which would make
getting out of the predicament even more difficult.
Spirit's
right-front wheel stopped working three years ago. Since then the six-wheeled
robot has been driving backward to circumvent the problem. Driving with just
five powered wheels while dragging or pushing an immobile wheel adds to the
challenge of the current situation.
In 2005,
rover controllers had to dig Opportunity out of its own quagmire, when
all six of its wheels were stuck in a deep sand dune.
On a more
positive note, wind has removed some of the dust accumulated on Spirit's solar
panels three times in the last month, increasing the rover's capability for
generating electricity.
"The
improved power situation buys us time," Callas said. "We will use
that time to plan the next steps carefully. We know that dust storms could
return at any time, although the skies are currently clear."
Behavioral
problems that Spirit exhibited in early April — episodes
of amnesia, computer resets and failure to wake for communications sessions
— have not recurred in the past three weeks, though investigations have yet to
diagnose the root causes.
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