News outlets worldwide trumpeted the news in January as the rovers bounced to a stop south of the equator and on opposite sides of Mars, each with its solar panels, six wheels, flexible arm, and instrument mast folded snugly inside a cocoon of air bags. But it is the daily grind since then that has made history with an up-close Martian scouting trip far more fruitful than the pioneering but immobile Viking landers of 1976 or the shoebox-size Sojourner rover of 1997 that stayed within about 30 feet of its base station.
They are far past their nominal three-month lifetimes. While half a mile’s travel was considered a decent goal, Spirit has already gone more than 2. Even better, operators say with fingers crossed, despite signs of wear they could keep rolling for another Earth year after a brief pause during the looming Martian southern hemisphere winter with its weak sunlight and bitter cold as deep as minus 157 degrees Fahrenheit.
They are well into science gravy time with their IMAX-quality pictures, mineral analyses, and weather reports. Opportunity has essentially proved that water once soaked now desiccated dirt on Mars. That builds the case that when young, it and Earth were much alike. Mars, too, may have supported life. More robots are to follow, including a bigger, nuclear-powered rover as soon as 2009. But the upshot of this year’s visit is a quantum leap toward NASA’s multibillion-dollar aim to put people on the next planet out from the sun to learn lessons on life’s place in the universe.
Discovery. Any job must get boring sometime. But Spirit team member Larry Crumpler, a geologist from the New Mexico Museum of Natural History and Science, widens his eyes in disbelief as a visitor comments sympathetically that it must have been a tad tedious from April to mid-June. That’s when Spirit made a nearly straight-line trek across the desolation of volcanic debris filling its landing site, a vast depression called Gusev Crater. “Boring? Are you kidding?” Crumpler exclaims, jumping from the seat in front of his computer in the rover’s “war room,” a broad space with walls and tables covered in blowup images of Mars’s rubbly terrain. “Every day I can’t wait to wake up; every day I see something new.” He bubbles about the constantly shifting textures of the soil and boulders, especially a meteor crater named Missoula.
Geologists call a straight-line reconnaissance of virgin terrain a transect. To make the first transect on another world is, to a man like Crumpler, sublime. Prospects for great discovery now beckon to Spirit’s operators from the rounded, yellow Columbia Hills where it has been since mid-June and quickly spotted odd rock formations and stones that seemed to be rotting from the inside. The team dubbed one boulder “Plymouth Rock” in tribute to the rovers’ arrival at a promising new world. Another, studded with strange mineral nuggets on stalks, got the name “Pot of Gold.” Opportunity for its part is examining the interior of a larger crater called Endurance, where it is finding that the thin layers of water-altered minerals at its landing site continue many feet into underlying rock.
“I just love this stuff, love it,” says Steve Squyres, the project’s lean, hyperkinetic overseer of the science instruments and Cornell University planetary sciences professor. Sleeves rolled up, he hustles down the stairs between a large science team meeting and an intimate confab over data. The electrically driven wheels on the machines and the arrays of transmitters and mineral analysis tools were designed for three months’ work. By now, fears were that worn parts, the cold of a Martian winter, dust on the solar panels, or all three would shut them down for good. Hard of hearing and a bit arthritic, Spirit indeed is showing its age--a balky front right wheel requires three times normal current to get it turning, and a radio receiver drifts off tune in the cold. For both rovers, solar power is under 40 percent what it was at landing. In mid-September, the rovers may be put on standby, using as little power as possible, parked on slopes as sunny as can be found. The cold is apt to crack the optics of one instrument, rendering it useless. But project manager Jim Erickson now says the two could revive by October and run into September next year.
“Trust the vehicles.” Nobody knows how far into the hills Spirit may go, nor whether Opportunity will live out its days in deep Endurance Crater. Squyres constantly exhorts his teams to “trust the vehicles” but is amazed by their sturdiness. “You can’t believe how many gears, wheels, hinges, motors, and other gizmos all had to work just right,” he says in his office, a futon next to him on the floor where he catches an occasional wink. Other than an overloaded computer memory that hobbled Spirit for a few weeks in the early going and was fixed by a change in procedure, showstoppers have been few.
In 1997, Squyres joined forces with Ray Arvidson, a planetary scientist at Washington University in St. Louis and onetime rival for NASA projects, to propose a Mars rover expedition. Arvidson is now his second in command of the rover science packages. Their teams of researchers, engineers, and students spent thousands of hours over several years driving practice rovers with names like FIDO (for Field Integrated Design and Operations) and K-9 across the deserts of California, Arizona, and Nevada. And while Spirit and Opportunity were en route to Mars last year, they drilled on engineering models over simulated Mars terrain at JPL. Upon landing, says Arvidson, “we had this eerie feeling we’d been there before.” There is no guidebook to running robots on Mars, Squyres says, but the team is “unbelievably good at doing this now.” Their skill, he says, laughing, has no other, earthly use.
For the first three months of the expedition, the 400-plus scientists and engineers split into two shifts for round-the-clock work. Arizona State University geologist Jim Rice worked both Spirit and Opportunity for all three months, catching two hours’ sleep at each shift change. At 45, he has been a space nut all his life and hopes he is still fit enough in his 60s or even 70s to go to Mars himself. “We’re the 21st-century Corps of Discovery,” he says, invoking the Lewis and Clark expedition. The pace has slowed down somewhat, with rover workers sticking to Earth-based shifts and adjusting their tasks daily according to which rover is active.
Experts continue to debate whether it makes sense to explore other planets with robots or people, but here the experts are in consensus. “Robots are impressive,” Bethany Ehlmann, of Washington University, says, “but really, science has a much bigger payoff with people.” Squyres says simply: “Not for a very long time will robots do what humans do. I can’t imagine robots running a deep drilling operation on Mars.”
In a weekend a human geologist could do what either of the rovers has done in half a year. “What we’re learning with robots is just laying the groundwork,” he says. “And when the scientists get there, they’ll have a much better idea what to do.”
Copyright 2004 U.S. News & World Report
Copyright © 2002 LexisNexis, a division of Reed Elsevier Inc.