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
