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.
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 .
