PASADENA, Calif. -- At far-flung locations on Mars, two wheeled robots have begun a history-making quest to explore the red planet.

Mars exploration is, factually, on a roll as never before.

With the Opportunity Mars Exploration Rover (MER) rolling from its lander hardware onto the soil of Mars Meridiani Planum January 31, the robot joined its sister craft -- Spirit -- halfway around Mars parked at Gusev Crater.

Software and hardware teams here at the Jet Propulsion Laboratory (JPL) have put Spirit back in working order, with the rover restarting science-gathering duties.

There is growing confidence in restoring Spirits work schedule at Gusev Crater after it encountered a confounding computer glitch.

Software and hardware specialists have isolated the problem, they believe. Far too many files were being held within Spirits computer system, said JPLs Mark Adler, MER Mission Manager.

Reviving Spirit meant deleting thousands of files from the rover's flash memory -- a type of rewritable electronic memory that retains information even when power is off. Among the erased files: leftover information from the seven-month flight from Florida to Mars.

The bottom line is that onboard software couldnt properly manage the flash memory, prompting Spirit's computer to reset itself about once an hour.

Adler said that files have been deleted from Spirits flash memory. A rebooting of the flash file system is slated, perhaps for Monday. Wiping it out and starting over should prevent the robot from encountering a computer problem for the next week or two, he said today during a telephone briefing with reporters.

Once every one to two weeks, the flash memory could be reformatted to assure that the issue does not crop up again, Adler told SPACE.com . The computer is now stable even when operating in the normal mode, which uses the flash memory, he said.

"Whatever workarounds we develop, well apply to both Spirit and Opportunity," Adler said. "Theres no difference in the vehicles with respect to this anomaly."

On Sunday, Spirit used its Panoramic Camera and conducted a checkout of its Mini-Thermal Emission Spectrometer (Mini-TES) -- to ready the hardware for reactivation since the computer foul-up halted its use.

Spirit is also scheduled on Sunday to once again make coordinated observations with Europes Mars Express as it flies overhead. The European Space Agency (ESA) orbiter will look down with sensors through the atmosphere at Gusev Crater while Spirit looks up using science instruments.

Meanwhile, Spirit has been commanded to transmit priority data remaining in the flash memory. That information includes data from coordinated atmospheric observations made January 16 between the rover and ESAs Mars Express.

Lastly, Spirit is being readied to pick up where it left off -- examine the interior of the rock dubbed Adirondack. Scientists are expected to call for brushing off the rock using stiff bristles that are part of the Rock Abrasion Tool, or RAT, mounted on the robots mechanical arm.

After giving the rock the brush-off, the RAT would be used, Adler said, followed by inspection of the rock utilizing a microscope and two spectrometers.

In about a weeks time, Spirit should be roving again, Adler said. The robot may head off to a white rock for close-up scrutiny, and eventually wheel over to the crater nicknamed Bonneville, Adler reported.

MER mission control operators were overjoyed here early Saturday morning with Opportunitys roll-off from its lander. The flight team needed a week to get the rover on Mars, contrasted to 12 days for Spirit to wheel onto martian soil.

Ground controllers here at JPL have begun checking out the overall condition of the Opportunity rover after its short drive onto Mars, such as exercising its Instrument Deployment Device, or IDD. This robot arm is loaded with science instruments to examine selected rock or patch of soil.

One pesky concern is the status of a failed heater switch on Opportunity. The switch is not working as planned, causing a drawdown of battery power each night on the robot.

There are ideas to potentially correct the problem, said Matt Wallace, MER Mission Manager at JPL, or coping with the switch issue on a long-term basis. He told SPACE.com that the problem should not cut into Opportunitys chances of working beyond a targeted 90 martian days of work at Meridiani Planum.

The soil at the Opportunity site contains hematite -- confirmed by the rovers Mini-TES. That mineral, a crystalline hematite, covers most of the crater floor.

Phil Christensen, Lead Scientist for the Mini-TES onboard both rovers, announced the finding at an early Saturday morning press briefing. More work using Opportunity is necessary to clarify if, like in most cases on Earth, the hematite seen on Mars is a byproduct of wet environmental conditions.

Typically, the grey hematite found by Opportunity forms in the presence of water - at the bottom of lakes, springs and other bodies of standing water. But it can also arise without water in volcanic regions.

New clues about the hematite may come from the Germanys Mssbauer spectrometer, designed to identify iron-containing minerals. Christensen said that the Mssbauer should help decipher whether the hematite is a coating on the grains of soil, or in the grains.

Now that Opportunity has its wheels down inside the small crater, scientists are keen on taking their time inspecting the martian soil.

"We want to see what other minerals are present," said Steve Squyres, MER Principal Investigator from Cornell University. By using Opportunitys science instruments to analyze the soil, those results would help sort out the hematite story at Meridiani Planum, he said.

"Were going to take our time on the soil," Squyres told SPACE.com . "That could really, really be crucial to understanding this whole situation," he said.

The soil on which Opportunity sits has been found to be loaded with hematite, Squyres explained. Careful characterization of the soil will be "crucial to understanding the whole story," he said.

Squyres said several days are likely to be spent on "beating on the soil with everything weve got" before the rover rolls over to the exposed rock outcrop. "Then well do a thorough job on the outcrop. And then well climb out of this crater andwho knows what were going to find."

Its history in the making, Squyres said.

"We can go from the global scale to the microscopic scaleand every step in-between. That has never been done before. Its going to be really something."

Mars Rovers: Complete Coverage

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