[meteorite-list] NASA Mars Rover Churns Up Questions With Sulfur-Rich Soil

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 14 Mar 2007 15:29:33 -0700 (PDT)
Message-ID: <200703142229.l2EMTYR17128_at_zagami.jpl.nasa.gov>

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

News Release: 2007-029 March 14, 2007

NASA Mars Rover Churns Up Questions With Sulfur-Rich Soil

Some bright Martian soil containing lots of sulfur and a trace of water
intrigues researchers who are studying information provided by NASA's
Spirit rover.

"This material could have been left behind by water that dissolved these
minerals underground, then came to the surface and evaporated, or it
could be a volcanic deposit formed around ancient gas vents," said Dr.
Ray Arvidson of Washington University, St. Louis. He is the deputy
principal investigator for NASA's twin Mars rovers, Spirit and Opportunity.

Determining which of those two hypotheses is correct would strengthen
understanding of the environmental history of the Columbia Hills region
that Spirit has been exploring since a few months after landing on Mars
in January 2004. However, investigating the bright soil presents a
challenge for the rover team, because the loose material could entrap
the rover.

The bright white and yellow material was hidden under a layer of
normal-looking soil until Spirit's wheels churned it up while the rover
was struggling to cross a patch of unexpectedly soft soil nearly a year
ago. The right front wheel had stopped working a week earlier.
Controllers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., were
trying to maneuver the rover backwards, dragging that wheel, to the
north slope of a hill in order to spend the southern-hemisphere winter
with solar panels tilted toward the sun.

Due to the difficulty crossing that patch, informally named "Tyrone,"
the team chose to drive Spirit to a smaller but more accessible slope
for the winter. Spirit stayed put in its winter haven for nearly seven
months. Tyrone was one of several targets Spirit examined from a
distance during that period, using an infrared spectrometer to check
their composition. The instrument detected small amounts of water bound
to minerals in the soil.

The rover resumed driving in late 2006 when the Martian season brought
sufficient daily sunshine to the solar panels. Some of the bright soil
from Tyrone was dragged to the winter site by the right front wheel, and
Spirit spent some time measuring the composition and mineralogy of these
materials. The material is sulfur-rich and consists of sulfate salts
associated with iron, and likely calcium. "These salts could have been
concentrated by hydrothermal liquid or vapor moving through the local
rocks," said rover science team member Dr. Albert Yen, a geochemist at
JPL. Two other patches of bright soil uncovered by Spirit before Tyrone
were also sulfur-rich, but each had similarities to local rock
compositions that were different at the three sites, suggesting
localized origins.

Researchers will watch for more patches of bright soil. "If we find them
along fractures, that would suggest they were deposited at ancient gas
vents," Arvidson said. "If they are at the saddles between hills, that
would suggest the deposits formed where groundwater came to the surface."

Scientists are describing recent findings by Spirit and Opportunity at
the Lunar and Planetary Science Conference this week in League City, Texas.

Spirit has driven away from the Tyrone area for a clockwise circuit
around a plateau called "Home Plate." Researchers want to learn more
about Home Plate, which Spirit visited briefly in early 2006. They are
checking a hypothesis that explosive volcanism, driven by the
interaction of magma with water, formed Home Plate and similar features.

Halfway around Mars, Opportunity is exploring clockwise around "Victoria
Crater," a bowl about 800 meters (half a mile) across. Cliff-like
promontories alternate with more gradually sloped alcoves around the
scalloped rim. The impact that dug the crater exposed layers that had
been buried.

"The images are breathtaking," said Dr. Steve Squyres of Cornell
University, principal investigator for the rovers. "Every promontory
we've seen has the kinds of layering expected for ancient wind-blown
sand deposits."

The layers consist of sulfate-rich sandstone similar to other bedrock
Opportunity has been finding in Mars' Meridiani region for more than
three years. The minerals come from a wet period in the region's ancient
past. While exploring Victoria's rim with Opportunity, researchers have
been on the lookout for rocks that might have been tossed out from
layers deeper and older than the sulfates.

"We found one group of cobbles that were clearly more resistant to
erosion than the sulfate blocks thrown out onto the rim," Squyres said.
"We checked the composition of one that we called Santa Catarina. Our
suspicion now is that Santa Catarina is a piece of a meteorite." That
would be the fifth meteorite found by the rovers.

More than three years into what was planned as a three-month mission on
Mars, both Spirit and Opportunity remain in good health, though with
signs of aging. "The team has learned how to drive Spirit very well with
just five wheels," said JPL's Dr. John Callas, rover project manager.
"We could accomplish longer drives if there were more energy, but
Spirit's solar panels have gotten really dusty. We would welcome another
wind-related cleaning event." It's about the same time of year on Mars
now as it was when winds blew dust off Spirit and its solar panels in
2005, increasing energy output.

JPL, a division of the California Institute of Technology, Pasadena,
manages the Mars Exploration Rover project for NASA's Science Mission
Directorate. For images and information about the rovers, visit
http://www.nasa.gov/rovers .
Received on Wed 14 Mar 2007 06:29:33 PM PDT