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ZL2VAL > ROVERS 04.03.05 11:14l 121 Lines 5940 Bytes #999 (0) @ WW
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Subj: Press release 2nd March
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From: ZL2VAL@ZL2AB.#46.NZL.OC
To : ROVERS@WW
NEWS RELEASE: 2005-038
March 02, 2005
Mars Rovers Break Driving Records, Examine Salty Soil
On three consecutive days, NASA's Mars Exploration Rover Opportunity
accomplished unprecedented feats of martian motion, covering more total
ground in that period than either Opportunity or its twin, Spirit, did
in their first 70 days on Mars.
Spirit, meanwhile, has uncovered soil that is more than half salt,
adding to the evidence for Mars' wet past. The golf-cart-size robots
successfully completed their three-month primary missions in April 2004
and are continuing extended mission operations.
Opportunity set a one-day distance record for martian driving, 177.5
meters (582 feet), on Feb. 19. That was the first day of a three-day
plan transmitted to the rover as a combined set of weekend instructions.
During the preceding week, engineers at NASA's Jet Propulsion Laboratory
had sent Opportunity and Spirit an upgrade of the rovers' software,
onboard intelligence the rovers use for carrying out day-to-day commands.
The new record exceeded a two-week old former best by 13 percent. As on
all previous long drives by either rover, the traverse began with
"blind" driving, in which the rover followed a route determined in
advance by rover planners at JPL using stereo images. That portion
lasted an hour and covered most of the day's distance. Then Opportunity
switched to "autonomous" driving for two and a half hours, pausing every
2 meters (6.6 feet) to look ahead for obstacles as it chose its own
route ahead.
The next day, Opportunity used its new software to start another drive
navigating for itself. "This is the first time either rover has picked
up on a second day with continued autonomous driving," said Dr. Mark
Maimone, rover mobility software engineer at JPL. "It's good to sit back
and let the rover do the driving for us."
Not only did Opportunity avoid obstacles for four hours of driving, it
covered more ground than a football field. Opportunity has a favorable
power situation, due to relatively clean solar panels and increasing
minutes of daylight each day as spring approaches in Mars' southern
hemisphere. This allows several hours of operations daily.
On the third day of the three-day plan, the robotic geologist continued
navigating itself and drove even farther, 109 meters (357 feet), pushing
the three-day total to 390 meters (nearly a quarter mile). In one long
weekend, Opportunity covered a distance equivalent to more than half of
the 600 meters that had been part of each rover's original
mission-success criteria during their first three months on Mars.
Opportunity has now driven 3,014 meters (1.87 miles) since landing;
Spirit even farther, 4,157 meters (2.58 miles). Opportunity is heading
south toward a rugged landscape called "etched terrain," where it might
find exposures of deeper layers of bedrock than it has seen so far.
Spirit is climbing "Husband Hill," with a pause on a ridge overlooking a
valley north of the summit to see whether any potential targets below
warrant a side trip.
As Spirit struggled up the slope approaching the ridgeline, the rover's
wheels churned up soil that grabbed scientists' attention. "This was an
absolutely serendipitous discovery," said Dr. Steve Squyres of Cornell
University, Ithaca, N.Y., principal investigator for the rovers' science
instruments. "We said, 'My gosh, that soil looks very bright. Before we
go away, we should at least take a taste."
The bright patch of disturbed soil, dubbed "Paso Robles," has the
highest salt concentration of any rock or soil ever examined on Mars.
Combined information gained from inspecting it with Spirit's three
spectrometers and panoramic camera suggests its main ingredient is an
iron sulfate salt with water molecules bound into the mineral. The soil
patch is also rich in phosphorus, but not otherwise like a
high-phosphorus rock, called "Wishstone," that Spirit examined in
December. "We're still trying to work out what this means, but clearly,
with this much salt around, water had a hand here," Squyres said.
Meanwhile, scientists are re-calibrating data from both rovers' alpha
particle X-ray spectrometers. These instruments are used to assess
targets' elemental composition. The sensor heads for the two instruments
were switched before launch. Therefore, data that Opportunity's
spectrometer has collected have been analyzed using calibration files
for Spirit's, and vice-versa. Fortunately, because the sensor heads are
nearly identical, the effect on the elemental abundances determined by
the instruments was very small. The scientists have taken this
opportunity to go back and review the results for the mission so far and
re-compute using correct calibration files. "The effect in all cases was
less than the uncertainties in results, so none of our science
conclusions are affected," Squyres said.
JPL, a division of the California Institute of Technology in Pasadena,
has managed NASA's Mars Exploration Rover project since it began in
2000. Images and additional information about the rovers and their
discoveries are available on the Internet at:
http://www.nasa.gov/vision/universe/solarsystem/mer_main.html
and: http://marsrovers.jpl.nasa.gov
-=###=-
73, Alan
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