NASA’s Spirit will begin trekking toward hills on its eastern horizon
in the next few days, entering a new phase of the rover’s exploration
of Mars just before its prime three-month mission ends and its
extended mission begins, rover team members said today.
The range of peaks named “Columbia Hills” is an island of older rock
surrounded by a younger volcanic layer which surfaces the plain that
Spirit has been crossing, said Dr. Ray Arvidson of Washington
University, St. Louis. He is deputy principal investigator for the
science payload on both Spirit and its twin rover, Opportunity.
Older rocks may hold evidence of an ancient body of water thought to
have once filled Gusev Crater. Spirit landed inside that
150-kilometer-wide (95-mile-wide) crater 12 weeks ago, and the rover’s
main task is to find geological clues about whether the region ever
had a wet environment. Spirit has spent much of its time since
landing driving toward a 200-meter-wide (660-foot-wide) crater
nicknamed “Bonneville.” Rover scientists had anticipated that the
impact that excavated Bonneville might have ejected rocks old enough
to hold clues about whether Gusev held water.
“The ejecta from Bonneville didn’t get excavated from deep enough to
get below the volcanic layer,” Arvidson said. So, after finishing an
examination of a light-colored rock on the crater’s rim, Spirit will
head for the hills.
NASA’s Jet Propulsion Laboratory, Pasadena, Calif., built each of the
two Mars Exploration Rovers for a prime mission of 90 martian days of
operation. Both rovers are healthy and could operate for several
additional months, said JPL’s Matt Wallace, mission manager. A martian
day, or sol, lasts about 40 minutes longer than an Earth day, and
Spirit’s 82nd sol began on Friday. “Spirit will start driving toward
the hills on sol 84 or a little after that,” Wallace said.
Scientists have examined the terrain between Bonneville Crater and
Columbia Hills in photographs taken from orbit by NASA’s Mars Global
Surveyor and found several features to inspect along the route. These
include some small craters and a dark streak apparently left by a
whirlwind that removed dust.
Science team member Dr. Larry Crumpler of New Mexico Museum of Natural
History, Albuquerque, said, “It won’t be a continuous drive, like a
bad road trip. We’ll actually get out and do some touristy things
along the way.”
With stops for “traverse science” along the way, the trip of about 2.3
kilometers (1.3 miles) to the near edge of Columbia Hills will
probably take 60 to 90 sols, Arvidson said.
Beginning next week and continuing into the extended mission, Spirit’s
controllers will switch from working on Mars time – with schedules set
to coincide with day or night at Gusev crater – to an Earth time
schedule easier to maintain for the long haul. The Opportunity team
will shift the following week, Wallace said.
Opportunity is also at the start of a trek. This week, it climbed out
of the small impact crater informally named “Eagle Crater” that it had
been examining since it landed nine weeks ago. Rocks in an outcrop
within the crater have provided evidence that the site was once under
flowing water. In coming weeks, Opportunity will drive about 750
meters (nearly half a mile) to a crater nicknamed “Endurance,” where
scientists hope to find and examine a thicker set of bedrock layers to
learn more about the duration of the region’s wet history.
Before leaving Eagle Crater, Opportunity inspected the soil at five
sites in the opposite half of the crater from the outcrop. The target
patches show a diversity of particle sizes and shapes on the surface.
“We’re seeing the effects of differences in wind speed,” said Bethany
Ehlmann, a science team collaborator from the University of
Washington, St. Louis. In some patches more than others, winds have
removed small particles and left large particles behind, she said.
Spherical gray particles that have been fancifully called blueberries
are plentiful in some soil patches higher on the inner slope of the
crater than near the center of the crater. A reading by Opportunity’s
Moessbauer spectrometer on one of the higher patches found the highest
concentration of hematite seen so far in the mission, reported Dr.
Goestar Klingelhoefer of the University of Mainz, Germany. He is the
lead scientist for that instrument, which is used for identifying
iron-containing minerals. The type of hematite Opportunity has been
finding usually forms on Earth under wet environmental conditions.
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.
