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 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
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
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.