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ZL2VAL > ROVERS 17.07.04 05:21l 105 Lines 5133 Bytes #999 (0) @ WW
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Subj: NEWS RELEASE: 2004-184
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From: ZL2VAL@ZL2AB.#46.NZL.OC
To : ROVERS@WW
July 16, 2004
NASA's Mars Rovers Roll Into Martian Winter
As winter approaches on Mars, NASA's Opportunity rover continues to inch
deeper into the stadium-sized crater dubbed "Endurance." On the other
side of the planet, the Spirit rover found an intriguing patch of rock
outcrop while preparing to climb up the "Columbia Hills" backward. This
unusual approach to driving is part of a creative plan to accommodate
Spirit's aging front wheel.
Spirit, with an odometer reading of over 3.5 kilometers (2.2 miles), has
already traveled six times its designed capacity. Its right front wheel
has been experiencing increased internal resistance, and recent efforts
to mitigate the problem by redistributing the wheel's lubricant through
rest and heating have been only partially successful.
To cope with the condition, rover planners have devised a roundabout
strategy. They will drive the rover backward on five wheels, rotating
the sixth wheel only sparingly to ensure its availability for demanding
terrain. "Driving may take us a little bit longer because it is like
dragging an anchor," said Joe Melko, a rover engineer at NASA's Jet
Propulsion Laboratory, Pasadena, Calif. "However, this approach will
allow us to continue doing science much longer than we ever thought
possible."
On Thursday, July 15, Spirit successfully drove 8 meters (26 feet) north
along the base of the Columbia Hills backward, dragging its faulty
wheel. The wheel was activated about 10 percent of the time to surmount
obstacles and to pull the rover out of trenches dug by the immobile wheel.
Along the way, Spirit drove over what scientists had been hoping to find
in the hills -- a slab of rock outcrop that may represent some of the
oldest rocks observed in the mission so far. Spirit will continue to
drive north, where it likely will encounter more outcrop. Ultimately,
the rover will drive east and hike up the hills backward using all six
wheels.
"A few months ago, we weren't sure if we'd make it to the hills, and now
here we are preparing to drive up into them," said Dr. Matt Golombek, a
rover science-team member from JPL. "It's very exciting."
For the past month, the Spirit rover has been parked near several
hematite-containing rocks, including "Pot of Gold," conducting science
studies and undergoing a long-distance "tuneup" for its right front wheel.
Driving with the wheel disabled means that corrections might have to be
made to the rover's steering if it veers off its planned path. This
limits Spirit's accuracy, but rover planners working at JPL's rover test
facility have come up with some creative commands that allow the rover
to auto-correct itself to a limited degree.
As Spirit prepares to climb upward, Opportunity is rolling downward.
Probing increasingly deep layers of bedrock lining the walls of
Endurance Crater at Meridiani Planum, the rover has observed a puzzling
increase in the amount of chlorine. Data from Opportunity's alpha
particle X-ray spectrometer show that chlorine is the only element that
dramatically rises with deepening layers, leaving scientists to wonder
how it got there. "We do not know yet which element is bound to the
chlorine," said Dr. Jutta Zipfel, a rover science-team member from the
Max Planck Institute for Chemistry, Mainz, Germany.
Opportunity will roll down even farther into the crater in the next few
days to see if this trend continues. It also will investigate a row of
sharp, teeth-like features dubbed "Razorback," which may have formed
when fluid flowed through cracks, depositing hard minerals. Scientists
hope the new data will help put together the pieces of Meridiani's
mysterious and watery past. "Razorback may tell us more about the
history of water at Endurance Crater," said Dr. Jack Farmer, a rover
science-team member from Arizona State University, Tempe.
Rover planners are also preparing for the coming Martian winter, which
peaks in mid-September. Dwindling daily sunshine means the rovers will
have less solar power and take longer to recharge. Periods of rest and
"deep sleep" will allow the rovers to keep working through the winter at
lower activity levels. Orienting the rovers' solar panels toward the
north will also elevate power supplies. "The rovers might work a little
bit more every day, or a little bit more every other day. We will see
how things go and remain flexible," said Jim Erickson, project manager
for the Mars Exploration Rover mission at JPL.
JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA's Office of Space
Science, Washington.
Images and additional information about the project are available on the
Internet at http://marsrovers.jpl.nasa.gov and http://athena.cornell.edu
=========================
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