PASADENA, Calif. -- While engineers here at the Jet Propulsion Laboratory (JPL) try to sort out what ails the Spirit Mars rover, the robot patient is at least lending a helping hand in the diagnosis.

Still locked within Spirits memory is science data, including its "last picture show" -- images taken by the robot from its position near a science target -- the football-sized rock that scientists have nicknamed "Adirondack".

Preparations were underway to scientifically inspect Adirondacks makeup, as well as use the robots Rock Abrasion Tool, or RAT, to probe the internal composition of the object.

Also received within the Spirit data via Mars Odyssey were several frames of "fill data". These are sets of intentionally random numbers that do not provide information.

Despite repeated "go to bed" orders from controllers here at JPL, the Spirit rover refuses to listen to parental command. It did not go to sleep even after ground controllers sent commands twice for it to do so.

Spirit had not communicated successfully through Odyssey since the rover's communications difficulties began last Wednesday.

At a press briefing yesterday, JPLs Peter Theisinger, rover project manager, said Spirit's flight software is not functioning normally. It appears to have rebooted the rover's computer more than 60 times in the past three days.

Despite the new engineering information from Spirit relayed via the Mars Odyssey, what troubles Spirit is still unknown.

There is a growing feeling here that the robot may have been taxed too much  that is, too many "do this, do that" instructions were sent. That multi-tasking could have sparked the problem, according to sources here.

Prior to its troubles on Mars, Spirit was being put through its paces -- doing things that were not tested with as much vigor here at JPL before being launched.

Spirit does not have a huge track record of testing, a source said, for fear of damaging the robot and not meeting an unforgiving launch window.

Theisinger said that the prospects for quick restoration of Spirit is not in the cards, a situation that could be the case for many days, into weeks -- even in the best of circumstances.

"We believe, based on everything we know now, we can sustain the current state of the spacecraft from a health standpoint for an indefinite amount of time," Theisinger said. That will give troubleshooting teams time to work on the problem.

While experts attempt to mend Spirit, sister ship Opportunity arrives at Mars tonight, landing at 12:05 a.m. EST. That robot is headed for a landing spot on the opposite side of the planet from Spirit -- Meridiani Planum.

Meridiani Planum promises to offer a landscape unlike that seen by any previous lander. This smooth, flat region of Mars is within an Oklahoma-sized outcropping of gray hematite.

That mineral can form in the presence of water. Opportunitys scientific gear is expected to resolve whether the gray hematite layer comes from sediments of a long-gone ocean, from volcanic deposits altered by hot water, or from other ancient environmental conditions.

Scientists also think that this region could offer clues as to the habitability of Mars by microbial life at some point in the planets past.

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