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Web Extra Friday, September 29, 2006

Opportunity reaches martian crater

Despite minor mechanical aches and pains, NASA's Mars rover Opportunity refuses to quit. During the last 21 months, the rover has traveled 9.2 kilometers, dodging rocks and climbing sand ridges along the way, to arrive Wednesday at the latest destination of geological interest — Victoria crater, located on a martian plain just 2 degrees south of the planet's equator.

Cameras aboard NASA's Mars rover Opportunity captured the vast expanse of Victoria crater. Image is courtesy of NASA/JPL-Caltech.

At more than 700 meters in diameter, Victoria is the third, and the largest, crater that Opportunity has successfully reached. It is about 40 times wider than the rover's landing site at Eagle crater and about five times wider than the previously visited Endurance crater, according to a Sept. 29 press release from Cornell University. The size, however, poses a formidable challenge for scientists trying to maneuver the rover's cameras close to an outcrop of rocks that could help them learn more about the red planet's environmental past.

"There are a couple of reasons to go to craters," says Matt Golombek, a geologist and principal scientist on the Mars Exploration Rover mission at NASA's Jet Propulsion Laboratory in Pasadena, Calif. One reason is that craters are "effectively a poor man's probe into the earth," because the layers hold records of past conditions on the planet at relative times during the planet's history, he says. At Endurance crater, for example, materials within 10 and 15 meters of layered rock revealed that the planet had undergone multiple fleeting wet periods.

Victoria crater, too, looks like it has an interesting exposure of outcrops, Golombek says. About 50 meters from Opportunity's current position, referred to by scientists as Duck Bay, exists a large cliff that looks like it might have "beautiful layers," he says. The next step is to get Opportunity closer and capture high resolution images needed to distinguish colors and textures, he says.

Getting Opportunity to reach the outcrops, however, is a daunting task. First, the team back on Earth plans to use the rover to circumnavigate some of the crater's rim, taking images and making maps, from which the researchers can best determine the safest approach. That could take months, if not years, Golombek says.

Despite its latest accomplishments, Opportunity has already been running 10 times longer than originally expected and is beginning to feel its age. Golombek compares it to a middle-aged person, who "has all these creaks and groans — not everything works like when you were 20, but pretty much everything works." Opportunity's front wheel has lost its steering capability, which means it has to drive mostly backward, he says.

Still, the steering should not affect the mission at Victoria crater, Golombek says. The team hopes the outcrop will reveal rock layers, so that they can learn more about how materials on Mars are deposited. But "more importantly," Golombek says, the team wants to find out if the deposit is above or below the layers previously observed at Endurance crater, and whether the deposit reveals a wetter or drier environment.

Right now, the answers are anyone's best guess. "We have just arrived," Golombek says. "It will be exciting for sure."

Kathryn Hansen

NASA/JPL Mars Exploration Rover mission
Geotimes Mars coverage

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