Mars Rovers Break Driving Records, Examine Salty Soil
Guy Webster and Dolores Beasley
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.
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.
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
Mars Exploration Rover Spirit used its navigation camera to
take the images combined into this 360-degree view of the
rover’s surroundings on Spirit’s 409th martian day, or sol
(Feb. 26, 2005). Spirit had driven 2 meters (7 feet) on this
sol to get in position on "Cumberland Ridge" for
looking into "Tennessee Valley" to the east. This
location is catalogued as Spirit’s Site 108. Rover-wheel tracks
from climbing the ridge are visible on the right. The summit
of "Husband Hill" is at the center, to the south.
This view is presented in a cylindrical projection with geometric
and brightness seam correction.
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
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.
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."
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.
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,"
Related to the Spirit and Opportunity Rovers:
Craft Spirit Taking in ‘Tennessee Valley’
** Opportunity Gets
New Flight Software
Craft Spirit Taking in ‘Tennessee Valley’
Spirit has spent the last 70 sols climbing up
the "Columbia Hills" to reach "Larry’s Lookout,"
a point on "Cumberland Ridge." Having accomplished the
trek up to Larry’s Lookout, Spirit is getting into position to
shoot a panorama of the "Tennessee Valley" located below.
Spirit is still in excellent health.
Sols 401 and
402 were planned in a single planning cycle. On sol 401, Spirit
placed the Mössbauer spectrometer on a target of disturbed
soil called "Paso Robles" and collected data for most
of sols 401 and 402. Spirit also performed about three hours of
remote-sensing observations, including imaging of Phobos, one
of the moons of Mars.
Sols 403 through
405 were planned in another single planning cycle, to allow the
Earthlings to take President’s Day holiday off. Sol 403 was spent
continuing the very long Mössbauer spectrometer integration
on Paso Robles. Spirit stowed the rover arm, and then moved back
about a meter (3 feet) to allow imaging of Paso Robles with the
miniature thermal emission spectrometer and panoramic camera.
Spirit then began moving closer to Larry’s Lookout, covering 16
meters (52 feet). On sol 405, Spirit spent over two hours performing
remote-sensing observations and recharging the batteries.
still closer to Larry’s Lookout on sol 406, driving another 14
meters (46 feet) uphill. By the end of the drive, Spirit was within
5 meters (16 meters) of the crest. Spirit also performed another
On sol 407,
Spirit reached Larry’s Lookout, driving another 3.5 meters (11
feet). Spirit performed an hour of post-drive imaging and was
ready to begin observations of Tennessee Valley.
as of sol 407 is 4,157 meters (2.58 miles).
Gets New Flight Software
Opportunity received a software tuneup that should
improve its mobility capabilities. With the new load on board,
Opportunity booted into it and began an initial checkout. After
a short test drive with promising results, there remains more
checkout to do before blessing the load and having the rover’s
sister craft, Spirit, boot up the new software. Atmospheric opacity
has been stable, with tau around 0.9. Solar power is still relatively
plentiful and Opportunity continues to be in excellent health.
Sols 374 through
376 were used to load the files for the new flight software, so
Opportunity did not move during this operation. There were a few
hours of remote-sensing observations on sols 374 and 375. Opportunity
successfully booted into the new flight software on sol 376.
slowly, Opportunity performed three hours of remote-sensing activities
on sol 377.
Sol 378 was
the first driving sol using the improved flight software. The
drive employed various methods, such as blind driving, auto-navigation,
and visual-odometry driving to exercise the rover’s new software.
Opportunity traversed approximately 25 meters (82 feet) this sol.
the drive on sol 378, Opportunity had a very nice rock target
just outside its front right wheel. On sol 379, Opportunity performed
two hours of remote sensing and then turned to 170 degrees, putting
the rock target "Russet" perfectly in the rover’s work
volume. Sol 379 ended on Feb. 16, with Opportunity’s total odometry
at 2,559.88 meters (1.59 miles).