Soft Ground Puts Spirit in Danger Despite Gain in Daily Energy

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif. May 11, 2009
Guy.Webster@jpl.nasa.gov

MARS EXPLORATION ROVER MISSION STATUS REPORT

Soft Ground Puts Spirit in Danger Despite Gain in Daily Energy

PASADENA, Calif. -- The five wheels that still rotate on NASA's Mars Exploration Rover
Spirit have been slipping severely in soft soil during recent attempts to drive, 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, Pasadena, Calif.

"Spirit is in a very difficult situation," JPL's John Callas, project manager for Spirit and its
twin rover, Opportunity, said Monday. "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 operated more than five years longer than their originally
planned missions of three months on Mars and have driven much farther than designed.
The rover team has so far developed ways to cope with various symptoms of aging on both
rovers.

Spirit has been driving counterclockwise from north to south around a low plateau called
"Home Plate" for two months. The rover progressed 122 meters (400 feet) on that route
before reaching its current position.

In the past week, the digging-in of Spirit's wheels 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 situation more difficult. The right-front wheel on Spirit stopped working
three years ago. Driving with just five powered wheels while dragging or pushing an
immobile wheel adds to the challenge of the situation.

Favorably, three times in the past month, wind has removed some of the dust accumulated
on Spirit's solar panels. This increases 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.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars
Exploration Rover project for NASA's Science Mission Directorate, Washington.

#2009-082
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