Fixing Spirit, from 125 million miles away

[Editor's note: The headline of the original version misstated the distance from Earth to Mars.]

At the moment, it seemed a glass-half-full grasp at optimism. Over a 24-hour period, America's model rover had gone completely mad. Spirit had astonished scientists with its flawless performance for weeks, but when it was asked to send scientific data last Wednesday, it spat out only jibberish. When asked to go to sleep, Spirit refused with the obstinacy of an 8-year-old at bedtime.

Amid the mounting clatter of despair and doom, though, mission manager Firouz Naderi paused as he addressed the media that day: "Gosh, don't give up on us yet."

It was the briefest look into a world unseen in all the recent photos of red rocks or craters of dun dust - yet in many ways no less remarkable. It was a glimpse into the can-do world of the engineers themselves, where disasters can be divined from endless strings of ones and zeroes, and cosmic fix-it jobs are performed from millions of miles away through keystrokes and creativity.

If the Russians became the gurus of space improvisation on manned missions, holding their Mir space station together with little more than duct tape and paper clips, then the Americans have become the Houdinis of robotic missions into the Great Beyond. Indeed, Spirit now appears to be on the road to an almost full recovery in two to three weeks.

But on numerous other missions as well, unmanned American spacecraft and their engineers have established a legacy of overcoming the unexpected - from jammed camera mounts to broken antennas - yet still returning groundbreaking science.

"It is a very common thread," says James Oberg, a former member of NASA mission control and now a commentator. "These spacecraft are built with a robustness that allows people to project their ingenuity millions of miles into space."

For most of the mission, the rover's robust design has been almost an afterthought. After Spirit arrived Jan. 4, it performed just as scientists had hoped it would, rolling off its lander, snapping pictures of Gusev Crater, and sampling the dust for signs that water was once there.

Halfway around Mars, its twin also landed perfectly Saturday night, coming to rest in a small crater on the dark and Gothic fields of Meridiani. The rover Opportunity should move off its lander in a week or so.

But one week ago, the wonder of scientific discovery was abruptly displaced by worldwide scrutiny of every circuit on the Spirit rover. One minute, the scientists' jolly robot geologist was preparing to use one of its sensors. The next, it had transformed into a recluse, crouched on its patch of Martian soil and offering up only jumbled strings of useless information.

The story of how engineers pieced together the fragmented clues of a mystery some 125 million miles away - and plan to fix it - is a parable of space-age derring-do in which bravado is measured in long hours of persistence and translated into lines of computer code.

At first, it was simply a process of engineers trying to concoct any possible scenario for the symptoms they saw. "It's an exercise in imagination," says Julie Townsend, an engineer at the Jet Propulsion Laboratory, which runs the two rovers. "You try to imagine all the sorts of things that could cause the signatures that you're seeing."

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