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Spirit panorama
This amazing panorama of the martian surface at Columbia Hills was taken by the Spirit rover. Expert narration is provided by camera scientist Jim Bell. (2min 12sec file)
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Update on Mars rovers
Mars Exploration Rover project manager Jim Erickson and panoramic camera lead scientist Jim Bell offer comments on the status of the Spirit and Opportunity missions (1min 33sec file)
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Delta rocket assembly
The first stage of Boeing's Delta 2 rocket that will launch NASA's Swift gamma-ray burst detection observatory in November is erected on pad 17A at Cape Canaveral, Florida. (4min 52sec file)
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Solid boosters arrive
The three solid-fueled rocket boosters for the Boeing Delta 2 vehicle that will launch the Swift satellite are hoisted into the pad 17A mobile service tower. (4min 55sec file)
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SRBs go for attachment
The mobile service tower carries the solid boosters into position for attachment to the Delta 2 rocket's first stage. (3min 08sec file)
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Swift nose cone
The two halves of the 10-foot diameter rocket nose cone that will enclose NASA's Swift satellite during launch aboard a Boeing Delta 2 vehicle are lifted into the pad 17A tower. (4min 26sec file)
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ISS talk with students
The International Space Station crew holds an educational event to answers questions live with students at the Maryland Science Center. (24min 01sec file)
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Genesis to Houston
The solar wind samples retrieved by NASA's Genesis spacecraft finally arrive at Johnson Space Center facilities from the Utah landing site. (2min 51sec file)
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Spirit adds clues about history of rocks in hills
Posted: November 4, 2004

All the scientific tools on NASA's two Mars Exploration Rovers are still working well, a full 10 months after Spirit's dramatic landing.

The ones on Spirit are adding fresh evidence about the history of layered bedrock in a hill the rover is climbing.

"Our leading hypothesis is that these rocks originated as volcanic ash that fell from the air or moved in ground-hugging ash flows, and that minerals in them were altered by water," said Dr. Ray Arvidson of Washington University, St. Louis, deputy principal investigator for the mission.

"This is still a working hypothesis, not a firm conclusion, but all the instruments have contributed clues that fit," he said. "However, it is important to point out that we have just begun to characterize the textures, mineralogy and chemistry of these layered rocks. Other hypotheses for their origin focus on the role of transport and deposition by water. In fact, it may turn out that volcanism, water and wind have produced the rocks that Spirit is examining. We are just beginning to put together the big picture."

Both rovers completed three-month primary missions in April. NASA has extended their missions twice because they have remained productive longer than anticipated.

"We're still making good progress even though Spirit has two types of problems with its wheels," said Jim Erickson, rover project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are working around those problems successfully, but they might be a sign of things to come, as mechanical parts wear out during our exploration of Mars."

One question for continuing investigations as Spirit heads for rocks higher in the "Columbia Hills," is what the environment was like when water altered the minerals. Possibilities include water in the volcanic magma mixture before the ash erupted, surface water transporting the ash while it was still loose after the eruption, and ground water soaking through the rocks that solidified from the accumulated ash.

Some clues for a volcanic-ash origin come from a layered rock dubbed "Uchben." Researchers pointed Spirit's microscopic imager at a spot on Uchben scoured with the rock abrasion tool. The images reveal sand-size particles, many of them sharply angular in shape and some quite rounded. The angularity is consistent with transport by an eruption. Particles carried across the surface by wind or water usually tumble together and become more rounded. Uchben's rounded particles may be volcanic clumps, may be concretions similar to what Opportunity has found, or may be particles tumbled in a water environment.

Evidence for alteration by water comes mainly from identification of minerals and elements in the rocks by the rover's Moessbauer spectrometer and alpha particle X-ray spectrometer.

The rovers' principal investigator, Dr. Steve Squyres of Cornell University, Ithaca, N.Y., said, "We have really made headway just in the last several weeks in understanding these rocks. The most likely origin is debris that blasted out of a volcano, was transported by air or water to its present location, and settled out in layers."

Opportunity, meanwhile, examined a lumpy boulder called "Wopmay" inside "Endurance Crater." The slope of the ground and loose surface material around the rock prevented Opportunity from getting firm enough footing to use its rock abrasion tool. Evidence from the spectrometers and microscopic imager is consistent with scientists' earlier hypothesis that rocks near the bottom of the crater were affected by water both before and after the crater formed. The evidence is still not conclusive, Squyres said.

Opportunity is heading toward the base of "Burns Cliff," a tall exposure of layered rock in the wall of the crater. However, if the rover encounters more of the poor traction found around Wopmay, planners may change course and drive up out of the crater.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Science Mission Directorate, Washington.