Mars Rovers Finish Primary Mission and Roll Onward
April 28, 2004
Both of NASA's Mars Exploration Rovers have completed their
originally planned mission and are tackling extra-credit
assignments.
"Spirit and Opportunity have completed all the primary
objectives of the mission. The terrific success achieved is a
tribute to a superb team whose commitment to excellence, and
keeping the public engaged, is hard to match," said Orlando
Figueroa, director of the Mars Exploration Program, NASA
Headquarters, Washington.
Opportunity finished its 90th martian day of surface
operations on Monday. That was the last of several criteria
set in advance for full mission success. Spirit passed its 90-
day mark on April 5. Both rovers have met all goals for
numbers of locations examined in detail, distances traveled,
and scientific measurements with all instruments. Both rovers
are healthy. In early April, NASA approved funding for
extending operation of Spirit and Opportunity through
September.
"This brings Opportunity's primary mission at Meridiani
Planum to a resounding and successful close. It's stunning to
think through the short history of this vehicle," said Matt
Wallace, Opportunity mission manger at NASA's Jet Propulsion
Laboratory, Pasadena, Calif., where rover assembly began
barely two years ago. In its three-month primary mission,
Opportunity drove 811 meters (more than half a mile) and sent
home 15.2 gigabits of data about Mars, including 12,429
images.
Opportunity found other rock exposures in recent days similar
to the ones near its landing site that yielded evidence for a
body of salty water covering the area long ago. Instead of
spending many days to examine those rocks, controllers told
the rover to go to the rim of a 130-meter-wide (approximately
430-foot-wide) crater informally named "Endurance."
When Opportunity sends home a view into Endurance Crater,
expected within a few days, scientists and engineers will
begin deciding whether the rover should try to enter that
crater. "We're coming up on a major branch point in the
mission," said Dr. Scott McLennan of the State University of
New York, Stony Brook, N.Y., a member of the rovers' science
team. "Can we get down into Endurance? Can we get back out?"
Last week, Opportunity paused beside a crater dubbed "Fram,"
less than one-tenth the size of Endurance Crater. It examined
a rock studded with small, iron-rich spherules that are one
part of the evidence for past water in the region. The rover
used its rock abrasion tool to grind a hole. This allowed
examination of the interior of the rock, called "Pilbara."
McLennan said, "Pilbara is a dead ringer for McKittrick," a
rock target in the outcrop Opportunity examined in February
and March. Another rock at Fram showed hints that it might
provide the best-yet evidence about how minerals precipitated
out of solution as the ancient body of water evaporated.
"It's something that would be of interest to come back and
study more if we don't see something of even greater interest
along our way," he said. Images of Endurance Crater from a
distance seem to show much thicker layers of outcrop than
Opportunity has been able to reach so far.
Improvement to the rovers' mobility from new software has
expanded options for planning their explorations. Spirit and
Opportunity have driven farther in April than in the previous
three months combined. Spirit has traveled more that 1.2
kilometers (three-fourths of a mile), and has another 1.8
kilometers (more than a mile) to go before reaching highlands
informally named "Columbia Hills." Scientists hope to examine
rock layers older than the volcanic plain Spirit has been
crossing. This week, Spirit is crossing from an area
dominated by material dispersed by crater-forming impacts
into an area with fewer rocks.
"We are transitioning into a geologically different region.
Nothing could be more striking evidence of this than the view
ahead of a landscape that has fewer and smaller rocks than
the region explored so far," said Dr. Dave Des Marais, a
rover science team member from NASA Ames Research Center,
Moffett Field, Calif. Scientists are using Spirit's
observations at ground level to check ideas about the
region's geology based on observations from orbiting
spacecraft. That could improve interpretation of orbital data
for the whole planet. Spirit will systematically survey the
soils, rocks and other features on the plain as it continues
toward Columbia Hills, with arrival planned for mid to late
June.
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, Ithaca, N.Y., at http://athena.cornell.edu.
