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this from NASA/JPL
NEWS RELEASE: 2008-166 August 26, 2008
NASA's Mars Rover Opportunity Climbing out of Crater
PASADENA, Calif. -- NASA's Mars Exploration rover Opportunity is heading back out
to the Red Planet's surrounding plains nearly a year after descending into a large Martian
crater to examine exposed ancient rock layers.
"We've done everything we entered Victoria Crater to do and more," said Bruce Banerdt,
of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Banerdt is project scientist for
Opportunity and its rover twin, Spirit.
Having completed its job in the crater, Opportunity is now preparing to inspect loose
cobbles on the plains. Some of these rocks, approximately fist-size and larger, were
thrown long distances when objects hitting Mars blasted craters deeper than Victoria into
the Red Planet. Opportunity has driven past scores of cobbles but examined only a few.
"Our experience tells us there's lots of diversity among the cobbles," said Scott
McLennan of the State University of New York, Stony Brook. McLennan is a long-term
planning leader for the rover science team. "We want to get a better characterization of
them. A statistical sampling from examining more of them will be important for
understanding the geology of the area."
Opportunity entered Victoria Crater on Sept. 11, 2007, after a year of scouting from the
rim. Once a drivable inner slope was identified, the rover used contact instruments on its
robotic arm to inspect the composition and textures of accessible layers.
The rover then drove close to the base of a cliff called "Cape Verde," part of the crater
rim, to capture detailed images of a stack of layers 6 meters (20 feet) tall. The
information Opportunity has returned about the layers in Victoria suggest the sediments
were deposited by wind and then altered by groundwater.
"The patterns broadly resemble what we saw at the smaller craters Opportunity explored
earlier," McLennan said. "By looking deeper into the layering, we are looking farther
back in time." The crater stretches approximately 800 meters (half a mile) in diameter
and is deeper than any other seen by Opportunity.
Engineers are programming Opportunity to climb out of the crater at the same place it
entered. A spike in electric current drawn by the rover's left front wheel last month
quickly settled discussions about whether to keep trying to edge even closer to the base of
Cape Verde on a steep slope. The spike resembled one seen on Spirit when that rover lost
the use of its right front wheel in 2006. Opportunity's six wheels are all still working after
10 times more use than they were designed to perform, but the team took the spike in
current as a reminder that one could quit.
"If Opportunity were driving with only five wheels, like Spirit, it probably would never
get out of Victoria Crater," said JPL's Bill Nelson, a rover mission manager. "We also
know from experience with Spirit that if Opportunity were to lose the use of a wheel after
it is out on the level ground, mobility should not be a problem."
Opportunity now drives with its robotic arm out of the stowed position. A shoulder motor
has degraded over the years to the point where the rover team chose not to risk having it
stop working while the arm is stowed on a hook. If the motor were to stop working with
the arm unstowed, the arm would remain usable.
Spirit has resumed observations after surviving the harshest weeks of southern Martian
winter. The rover won't move from its winter haven until the amount of solar energy
available to it increases a few months from now. The rover has completed half of a full-
circle color panorama from its sun-facing location on the north edge of a low plateau
called "Home Plate."
"Both rovers show signs of aging, but they are both still capable of exciting exploration
and scientific discovery," said JPL's John Callas, project manager for Spirit and
Opportunity.
The team's plan for future months is to drive Spirit south of Home Plate to an area where
the rover last year found some bright, silica-rich soil. This could be possible evidence of
effects of hot water.
For images and information about NASA's Opportunity and Spirit Mars rovers, visit
http://www.nasa.gov/rovers .
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