April 28, 2004

Donald Savage 
Headquarters, Washington 
(Phone: 202/358-1547)

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-6278)

RELEASE: 04-142

MARS ROVERS FINISH PRIMARY MISSION AND ROLL ONWARD

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?" he questioned.

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, 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 an arrival 
planned for mid to late June.

For images and additional information about the project on the 
Internet, visit: 

http://marsrovers.jpl.nasa.gov/ 
& 
http://athena.cornell.edu 

	
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