Opportunity Sees Tiny Spheres in Martian Soil
February 4, 2004
NASA's Opportunity has examined its first patch of soil in
the small crater where the rover landed on Mars and found
strikingly spherical pebbles among the mix of particles
there.
"There are features in this soil unlike anything ever seen on
Mars before," said Dr. Steve Squyres of Cornell University,
Ithaca, N.Y., principal investigator for the science
instruments on the two Mars Exploration Rovers.
For better understanding of the soil, mission controllers at
NASA's Jet Propulsion Laboratory, Pasadena, Calif., plan to
use Opportunity's wheels later this week to scoop a trench to
expose deeper material. One front wheel will rotate to dig
the hole while the other five wheels hold still.
The spherical particles appear in new pictures from
Opportunity's microscopic imager, the last of 20 cameras to
be used on the two rover missions. Other particles in the
image have jagged shapes. "The variety of shapes and colors
indicates we're having particles brought in from a variety of
sources," said Dr. Ken Herkenhoff of the U.S. Geological
Survey's Astrogeology Team, Flagstaff, Ariz.
The shapes by themselves don't reveal the particles' origin
with certainty. "A number of straightforward geological
processes can yield round shapes," said Dr. Hap McSween, a
rover science team member from the University of Tennessee,
Knoxville. They include accretion under water, but apparent
pores in the particles make alternative possibilities of
meteor impacts or volcanic eruptions more likely origins, he
said.
A new mineral map of Opportunity's surroundings, the first
ever done from the surface of another planet, shows that
concentrations of coarse-grained hematite vary in different
parts of the crater. The soil patch in the new microscopic
images is in an area low in hematite. The map shows higher
hematite concentrations inside the crater in a layer above an
outcrop of bedrock and on the slope just under the outcrop.
Hematite usually forms in association with liquid water, so
it holds special interest for the scientists trying to
determine whether the rover landing sites ever had watery
environments possibly suitable for sustaining life. The map
uses data from Opportunity's miniature thermal emission
spectrometer, which identifies rock types from a distance.
"We're seeing little bits and pieces of this mystery, but we
haven't pieced all the clues together yet," Squyres said.
Opportunity's Moessbauer spectrometer, an instrument on the
rover's robotic arm designed to identify the types of iron-
bearing minerals in a target, found a strong signal in the
soil patch for olivine. Olivine is a common ingredient in
volcanic rocks. A few days of analysis may be needed to
discern whether any fainter signals are from hematite, said
Dr. Franz Renz, science team member from the University of
Mainz, Germany.
To get a better look at the hematite closer to the outcrop,
Opportunity will go there. It will begin by driving about 3
meters (10 feet) tomorrow, taking it about halfway to the
outcrop. On Friday it will dig a trench with one of its
front wheels, said JPL's Dr. Mark Adler, mission manager.
Opportunity's twin, Spirit, today is reformatting its flash
memory, a preventive measure that had been planned for
earlier in the week. "We spent the last four days in the
testbed testing this," Adler said. "It's not an operation we
do lightly. We've got to be sure it works right." Tomorrow,
Spirit will resume examining a rock called Adirondack after a
two-week interruption by computer memory problems.
Controllers plan to tell Spirit to brush dust off of a rock
and examine the cleaned surface tomorrow.
Each martian day, or "sol," lasts about 40 minutes longer
than an Earth day. Spirit begins its 33rd sol on Mars at
2:43 a.m. Thursday, Pacific Standard Time. Opportunity
begins its 13th sol on Mars at 3:04 p.m. Thursday, PST.
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, D.C. Images and additional information
about the project are available from JPL at
http://marsrovers.jpl.nasa.gov and from Cornell
University at http://athena.cornell.edu.
