[meteorite-list] NASA Rovers Continue Unique Exploration of Mars

[Ron Baalke]

Dwayne Brown 
Headquarters,Washington                     June 8, 2004
(Phone: 202/358-1726)

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

RELEASE: 04-184

NASA ROVERS CONTINUE UNIQUE EXPLORATION OF MARS

     NASA's Mars Opportunity rover began its latest adventure 
today inside the martian crater informally called Endurance. 
Opportunity will roll in with all six wheels, then back out 
to the rim to check traction by looking at its own track 
marks. 

"We're going in, but we're doing it cautiously," said Jim 
Erickson, deputy project manager for the Mars Exploration 
Rovers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, 
Calif. Barring any surprises, Opportunity will enter the 
stadium-sized crater Wednesday for two to three weeks of 
scientific studies.

"NASA has made a careful decision. The potential science 
benefits of sending Opportunity into the crater are well 
worth the calculated risk the rover might not be able to 
climb back out," said JPL's Dr. Firouz Naderi, manager of 
NASA's Mars Exploration Program. "Inside the Endurance crater 
waits the possibility for the most compelling science 
investigations Opportunity could add to what it has already 
accomplished. We have done the ground testing necessary to 
evaluate the likelihood of exiting the crater afterwards," he 
said.

"Spirit and Opportunity are well into their bonus periods 
after successfully completing their three-month primary 
missions in April," Naderi said. "Both rovers are starting 
new chapters. Spirit is within a stone's throw of Columbia 
Hills, and Opportunity is entering the crater."

Dr. Steve Squyres of Cornell University, Ithaca, N.Y., the 
rovers' principal investigator, said, "We expect the science 
return of going a short way into Endurance to be very high." 
The target for inspection within the crater is an exposure of 
rock layers beneath a layer that corresponds to rocks 
Opportunity previously examined in the shallower Eagle 
crater, where the rover landed in January.

The sulfur-rich layer seen in Eagle yielded evidence a body 
of gently flowing water once covered the area. The underlying 
layers come from an earlier period. Opportunity's 
observations from the rim of Endurance already have shown 
their composition differs from the Eagle crater's layers. 

"If there was a change in rock type, there was a change in 
environment," Squyres said. "This unit will tell us what came 
before the salty water environment the Eagle crater unit told 
us about. We want to get to the contact between the two units 
to see how the environment changed. Is it gradual? Is it 
abrupt?" Even if the lower layers formed under dry 
conditions, they may have been exposed to water later. The 
water's effect on them could have left telltale evidence of 
that interaction," he said.

One section of the target outcrop is only five to seven 
meters (16 to 23 feet) from the rim in an area dubbed 
Karatepe. The rover team's plan is to get there, examine the 
rocks for several days, and then exit the crater. Reaching 
lower-priority targets, like at the bottom of the crater, 
would entail driving on sand, with a higher risk of not 
getting out again.

The strategy for driving on the crater's inner slope is to 
keep wheels on rock surfaces instead of sand, said JPL rover-
mobility engineer Randy Lindemann. The team ran trials with a 
test rover on a surface specifically built to simulate 
Karatepe's surface conditions. "The tests indicate we have a 
substantial margin of safety for going up a rocky slope of 25 
degrees," Lindemann said. Opportunity's observations from the 
rim at the top of the planned entry route show a slope of 
less than 20 degrees.

Spirit, launched one year ago Thursday, has driven more than 
3.2 kilometers (2 miles) inside the Gusev Crater. A trench it 
dug in May exposed soil with relatively high levels of sulfur 
and magnesium, reported Dr. Johannes Brueckner, of Max-
Planck-Institut fuer Chemie, Mainz, Germany. Spirit's alpha 
particle X-ray spectrometer showed concentrations of these 
two elements varied in parallel at different locations in the 
trench, suggesting they may be paired as a magnesium sulfate 
salt.

Squyres said, "The most likely explanation is water 
percolated through the subsurface and dissolved out minerals. 
As the water evaporated near the surface, it left 
concentrated salts behind. I'm not talking about a standing 
body of water like we saw signs of at Eagle crater, but we 
also have an emerging story of subsurface water at Gusev," he 
said.

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.

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

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

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