Guy Webster/Veronica McGregor 818-354-5011
Jet Propulsion Laboratory,
Pasadena, Calif.
guy.webster@xxxxxxxxxxxx,
veronica.mcgregor@xxxxxxxxxxxx
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@xxxxxxxx
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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