|  |  | | |
| |  | | | | Rocks Tell Stories in Reports of Spirit's First 90 Martian Days
|
08.05.04
|
Scientific findings from the NASA rover Spirit's first three
months on Mars will be published Friday, marking the start of a
flood of peer-reviewed discoveries in scientific journals from
the continuing two-rover adventure.
Image above: One of Spirit's first views of its landing site at Gusev Crater on Mars.+ Click for full image Image Credit: NASA/JPL/Cornell.
Researchers using Spirit's toolkit of geological instruments
from early January into April read the record from rocks and
soils in the rover’s landing area and found a history of
volcanic blanketing, impact cratering, wind effects and
possible past episodes of scant underground liquid water.
Evidence for the water comes from mineral alteration in the
veins, inclusions and coatings of some rocks. Eleven reports
with 120 collaborating authors from around the world lay out
details in the Aug. 6 issue of the journal Science.
"This is the first batch," said Dr. Steve Squyres of Cornell
University, Ithaca, N.Y., principal investigator for the
science payload on both Mars Exploration Rovers. "You'll be
seeing a lot more publications in months ahead and, no doubt,
for many years to come based on information from Spirit and
Opportunity. These machines just keep going and going, so the
science just keeps coming and coming." Dr. Jim Garvin, NASA’s
Chief Scientist for Mars added, “This is the basis for
beginning the remarkable scientific legacy of the rovers that
will not only rewrite our textbooks about Mars, but also pave
the way for human exploration.”
The rovers completed three-month primary missions in April,
then began bonus exploration in extended science missions.
"Spirit and Opportunity have really done yeoman's work, still
operating after more than twice as long as their original
assignments. We don't know how much longer they'll keep
working, but while they do we promise to keep them busy," said
Jim Erickson, project manager at NASA's Jet Propulsion
Laboratory, Pasadena, Calif.
Both rovers were equipped and targeted to collect evidence
about past environmental history, especially any history of
liquid water, since life as we know it depends on water. Spirit
is exploring inside Gusev Crater, an ancient Connecticut-sized
impact basin that was selected as a landing site because it may
have once held a giant lake fed by flows of water though a
large valley that empties into the crater.
The new reports state that, in its first three months, Spirit
found no evidence of lake-related (lacustrine) deposits. "Any
lacustrine sediments that may exist at this location within
Gusev apparently have been buried by lavas that have undergone
subsequent impact disruption," says the leadoff paper by
Squyres and 49 other rover science team members. Spirit has
subsequently driven to a different location -- nearby hills
over 3 kilometers (2 miles) away -- to continue exploring.
Dr. John Grant of the National Air and Space Museum,
Washington, and co-authors report that the rocks on the plain
that Spirit explored during its primary mission increased about
fivefold in maximum size as the rover got closer to an old 210-
meter (690-foot-wide) impact crater. The impact that excavated
the crater brought volcanic rocks to the surface from as deep
as 10 meters (33 feet). Several papers give evidence that rocks
in the area are a volcanic type called basalt and bear the
mineral olivine. These include reports by Cornell's Dr. Jim
Bell with collaborators using Spirit's panoramic camera and by
Dr. Dick Morris of NASA Johnson Space Center, Houston, with
collaborators using the Moessbauer spectrometer. Dr. Hap
McSween of the University of Tennessee, Knoxville, and co-
authors state, "These basalts extend the known range of rock
compositions comprising the martian crust."
Dr. Ken Herkenhoff of Flagstaff, Ariz., offices of the U.S.
Geological Survey and other scientists using Spirit's
microscopic imager offer findings that rocks cut into by the
rover’s rock abrasion tool have coatings and bright veins
apparently from mineral alteration after the rocks formed. Dr.
Ralf Gellert of Max-Planck-Insitut-fur-Chemie in Mainz,
Germany, and other users of Spirit's alpha-particle X-ray
spectrometer report that bromine in the veins suggests the
alteration resulted from exposure to water. Dr. Phil
Christensen of Arizona State University, Tempe, and
collaborators using Spirit's miniature thermal emission
spectrometer say the rock's coatings are consistent with
exposure to moisture while buried. Dr. Ray Arvidson of
Washington University, St. Louis, and co-authors describe
cohesive texture in soils and rock coatings, which they suggest
could result from brief moist periods in the past.
Magnet experiments indicate almost all sampled dust particles
in Mars' atmosphere contain magnetic minerals, according to a
paper by Dr. Preben Bertelsen of the Niels Bohr Institute,
Copenhagen, Denmark, and others. Dr. Ron Greeley of Arizona
State University and co-authors found that winds from the
northwest grooved some rock surfaces and shaped sand ripples in
the past. They report that the way rock dust accumulates during
grinding by Spirit's rock abrasion tool shows that wind still
comes from the same direction.
JPL, a division of the California Institute of Technology in
Pasadena, manages the Mars Exploration Rover project for NASA's
Science Mission Directorate, Washington. Images and additional
information about the project are available from JPL at
http://marsrovers.jpl.nasa.gov and from Cornell University,
Ithaca, N.Y., at http://athena.cornell.edu.
Guy Webster
NASA's Jet Propulsion Laboratory
Donald Savage
NASA Headquarters, Washington
2004-194
|
| |
|
