NASA's Mars Rover has Uncertain Future as Sixth Anniversary Nears

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Guy Webster/Veronica McGregor 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov, veronica.mcgregor@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

News release: 2009-207 Dec. 31, 2009

NASA's Mars Rover has Uncertain Future as Sixth Anniversary Nears

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2009-207&cid=release_2009-207

PASADENA, Calif. -- NASA's Mars rover Spirit will mark six years of unprecedented science
exploration and inspiration for the American public on Sunday. However, the upcoming Martian
winter could end the roving career of the beloved, scrappy robot.

Spirit successfully landed on the Red Planet at 8:35 p.m. PST on Jan. 3, 2004, and its twin
Opportunity arrived at 9:05 p.m. Jan. 24, 2004. The rovers began missions intended to last for three
months but which have lasted six Earth years, or 3.2 Mars years. During this time, Spirit has found
evidence of a steamy and violent environment on ancient Mars that was quite different from the wet
and acidic past documented by Opportunity, which has been operating successfully as it explores
halfway around the planet.

A sand trap and balky wheels are challenges to Spirit's mobility that could prevent NASA's rover
team from using a key survival strategy for the rover. The team may not be able to position the robot's
solar panels to tilt toward the sun to collect power for heat to survive the severe Martian winter.

Nine months ago, Spirit's wheels broke through a crusty surface layer into loose sand hidden
underneath. Efforts to escape this sand trap barely have budged the rover. The rover's inability to use
all six wheels for driving has worsened the predicament. Spirit's right-front wheel quit working in
2006, and its right-rear wheel stalled a month ago. Surprisingly, the right-front wheel resumed
working, though intermittently. Drives with four or five operating wheels have produced little
progress toward escaping the sand trap. The latest attempts resulted in the rover sinking deeper in the
soil.

"The highest priority for this mission right now is to stay mobile, if that's possible," said Steve Squyres
of Cornell University in Ithaca, N.Y. He is principal investigator for the rovers.

If mobility is not possible, the next priority is to improve the rover's tilt, while Spirit is able to generate
enough electricity to turn its wheels. Spirit is in the southern hemisphere of Mars, where it is autumn,
and the amount of daily sunshine available for the solar-powered rover is declining. This could result
in ceasing extraction activities as early as January, depending on the amount of remaining power.
Spirit's tilt, nearly five degrees toward the south, is unfavorable because the winter sun crosses low in
the northern sky.

Unless the tilt can be improved or luck with winds affects the gradual buildup of dust on the solar
panels, the amount of sunshine available will continue to decline until May 2010. During May, or
perhaps earlier, Spirit may not have enough power to remain in operation.

"At the current rate of dust accumulation, solar arrays at zero tilt would provide barely enough energy
to run the survival heaters through the Mars winter solstice," said Jennifer Herman, a rover power
engineer at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The team is evaluating strategies for improving the tilt even if Spirit cannot escape the sand trap, such
as trying to dig in deeper with the wheels on the north side. In February, NASA will assess Mars
missions, including Spirit, for their potential science versus costs to determine how to distribute
limited resources. Meanwhile, the team is planning additional research about what a stationary Spirit
could accomplish as power wanes.

"Spirit could continue significant research right where it is," said Ray Arvidson of Washington
University in St. Louis, deputy principal investigator for the rovers. "We can study the interior of
Mars, monitor the weather and continue examining the interesting deposits uncovered by Spirit's
wheels."

A study of the planet's interior would use radio transmissions to measure wobble of the planet's axis
of rotation, which is not feasible with a mobile rover. That experiment and others might provide more
and different findings from a mission that has already far exceeded expectations.

"Long-term change in the spin direction could tell us about the diameter and density of the planet's
core," said William Folkner of JPL. He has been developing plans for conducting this experiment with
a future, stationary Mars lander. "Short-period changes could tell us whether the core is liquid or
solid," he said.

In 2004, Opportunity discovered the first mineralogical evidence that Mars had liquid water. The
rover recently finished a two-year investigation of a half-mile wide crater called Victoria and now is
headed toward Endeavor crater, which is approximately seven miles from Victoria and nearly 14 miles
across. Since landing, Opportunity has driven more than 11 miles and returned more than 132,000
images.

JPL manages the rovers for NASA's Science Mission Directorate in Washington.

For more information about the rovers, visit: http://www.nasa.gov/rovers or
http://marsrovers.jpl.nasa.gov

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