NASA's Durable Spirit Sends Intriguing New Images From Mars

"When the images came down and we could see horizon all the wayaround, that was every bit as exhilarating as getting to the top of anymountain I've climbed on Earth," said Chris Leger, a rover planner atNASA's Jet Propulsion Laboratory, Pasadena, Calif.

The summit sits 82 meters (269 feet) above the edge of thesurrounding plains. It is 106 meters (348 feet) higher than the sitewhere Spirit landed nearly 20 months ago. Spirit and twin rover,Opportunity, successfully completed their three-month prime missions inApril 2004. They have inspected dozens of rocks and soil targets sincethen, continuing their pursuit of geological evidence about formerlywet conditions on Mars.

"Spirit has climbed to the hilltop and looked over the other side,but NASA did not do this just to say we can do it. The Mars rovers areaddressing fundamental questions about Martian history and planetaryenvironments," said NASA's Mars Exploration Program Director DougMcCuistion.

The crest of "Husband Hill" offers Spirit's views of possible routesinto a basin to the south with apparently layered outcrops. Shortlyafter Spirit landed, it observed a cluster of seven hills about 3kilometers (2 miles) east of its landing site. NASA proposed naming therange "Columbia Hills" in tribute to the last crew of Space ShuttleColumbia. The tallest of the hills commemorates Rick Husband,Columbia's commander.

Volcanic rocks covering the plain Spirit crossed on its way to thehills bore evidence of only slight alteration by water. When Spiritreached the base of the hills five months after landing, it immediatelybegan finding rocks with wetter histories.

"This climb was motivated by science," said Steve Squyres of CornellUniversity, Ithaca, N.Y. Squyres is principal investigator for therovers' science instruments. "Every time Spirit has gained altitude,we've found different rock types. Also, we're doing what any fieldgeologist would do in an area like this: climbing to a good vantagepoint for plotting a route."

Researchers are viewing possible routes south to apparently layeredledges and to a feature dubbed "home plate," which might be a plateauof older rock or a filled-in crater.

The landing site and the Columbia Hills are within Gusev Crater, abowl about 150 kilometers (95 miles) in diameter. The crater wasselected as the landing site for the Spirit rover because the shape ofthe terrain suggests the crater once held a lake. Volcanic depositsappear to have covered any sign of ancient lakebed geology out on theplain, but scientists say the hills expose older layers that have beenlifted and tipped by a meteorite impact or other event.

"We're finding abundant evidence for alteration of rocks in a waterenvironment," said Ray Arvidson of Washington University, St. Louis,Mo. Arvidson is deputy principal investigator for the rovers' scienceinstruments. "What we want to do is figure out which layers were on topof which other layers. To do that it has been helpful to keep climbingfor good views of how the layers are tilted to varying degrees.Understanding the sequence of layers is equivalent to having a deepdrill core from drilling beneath the plains."

Both Spirit and Opportunity have been extremely successful. Theirsolar panels are generating plenty of energy thanks to repeateddust-cleaning events. Spirit has driven 4,827 meters (3.00 miles), andOpportunity 5,737 meters (3.56 miles).

JPL manages the Mars Exploration Rover project for NASA's ScienceMission Directorate. For images and information about the rovers andtheir discoveries on the Web, visit: http://www.nasa.gov/vision/universe/solarsystem/mer_main.html or http://marsrovers.jpl.nasa.gov.

For information about NASA and agency programs on the Internet, visit: http://www.nasa.gov/home .