11:15 a.m. January 30, 2004

PASADENA – Scientists were trying Friday to determine whether NASA's Opportunity rover spotted a mineral that typically forms in water, a finding that would provide a clue that the now dry and dusty martian landing site may once have been a wetter place.

NASA also said the six-wheeled rover should roll off its lander early Saturday, less than a week after it safely landed on the opposite side of Mars from its twin, Spirit. It was the second time in two days that NASA moved up the time.

Word whether the roll-off was a success should arrive by 3:30 a.m. PST, rover systems engineer Daniel Limonadi said.

Scientists were cautious but smiling during a Jet Propulsion Laboratory press conference when asked if Opportunity had discovered a mineral called gray hematite by using its mini-thermal emissions spectrometer, an instrument that measures infrared radiation. Gray hematite is an iron-rich mineral that typically – but not always – forms in liquid water.

Preliminary evidence suggests Opportunity has spied the mineral in the ground around the lander. But confirmation of the discovery should take a few days, as scientists work to "check and double check" the new measurements, said Ray Arvidson of Washington University, the deputy main scientist for the mission. Other data are required to corroborate the initial analysis.

"They will be able in a couple of days to confirm the presence of hematite," Arvidson told reporters.

Another NASA spacecraft, a satellite called the Mars Global Surveyor, previously identified the presence of the mineral at Opportunity's landing site. Scientists believe the mineral covers an estimated 15 percent to 20 percent of the surface at Meridiani Planum, an area hundreds of miles across.

Arvidson emphasized the complexity of the spectrometer instrument, dubbed Mini-TES for short, and the difficulty of interpreting its data. "But if you look at any of the Mini-TES team members they have huge smiles on their faces," he said.

Spirit, meanwhile, is expected to return to full health by Sunday, after fixes of software problems that ground its mission to a temporary halt. NASA planned to reformat Spirit's flash memory on Saturday. That should pare down the number of files it contains and make it easier for the rover's random-access memory to manage.

"We're still trying to recover the full capabilities of the system," mission manager Mark Adler said.

On Friday, NASA showed new images taken by Spirit, including the first-ever microscopic image of a the surface of a rock on the surface of Mars. Spirit should begin drilling into that rock sometime in the next four days. That will allow its instruments to examine a freshly exposed, unweathered surface.

Initial measurements of the outside of the rock, dubbed "Adirondack," reveal it's an olivine-rich basalt, said scientist Bodo Bernhardt, of the University of Mainz, Germany.

The rock is the most common type found on the surface of Earth. Its volcanic origin doesn't require water to form, disappointing scientists eager to find geologic evidence Mars once was wetter.

"It is not the kind of smoking gun evidence we're looking for," Arvidson said.

Scientists mapped in 3-D the small crater that cradles Opportunity – the first time such a depression has been charted from the inside, said Ron Li, of Ohio State University. NASA still hasn't pinned down exactly which crater Opportunity ended up in, however.

Once Opportunity rolls onto the martian soil, it should spend several days studying the soil around it. Scientists want Opportunity then to strike out for an outcropping several yards off to the left of the rover. High-resolution images have revealed the presence of fine-scaled layering in the narrow band of bedrock.

The layers could have been laid down by water, wind or by ash settling out of the sky following successive volcanic eruptions. Opportunity could reach the low outcropping in a week, and then spend several more weeks studying it in detail, Arvidson said.

Scientists plan for Spirit to check out a few more rocks in its immediate vicinity and then begin rolling toward a large crater, called "Bonneville," that sits 250 yards away.

Scientists have begun naming craters at Spirit's landing site after lakes on Earth. They have yet to devise a naming convention for features at Opportunity's landing site, Arvidson said.

NASA sent the twin rovers on a $820 million mission to Mars to prospect for geologic evidence that its surface was once awash in enough water to sustain life.