Finally, he's found: More than a year after millionaire adventurer Steve Fossett disappeared somewhere over Nevada, Madero County Sheriff John Anderson announced that searchers had discovered the wreckage of his single-engine Bellanca 10,000 feet up a mountainside near Mammoth Lakes, California. Soon after, the National Transportation Safety Board discovered remains at the scene.

THE MEMBERS OF Team Adventure Science are playing air guitar and singing Iron Maiden's "Run to the Hills" as they form a phalanx, keeping within shouting distance of each other while fanning out into the Sierra Nevada scrub. Half a dozen of North America's top adventure racers, strapped with heart-rate monitors and slathered with BodyGlide, synchronize their compass watches and set out at high speed across ridges, down canyons, and over bare mineral earth, all while keeping critical spacing and overlapping visuals to achieve a probability of detection (POD) of at least 70 percent.

They cover the ground like grasshoppers. "Simon, there's something shiny at two o'clock to your left, a hundred meters up,"says Paul "Turbocock" Trebilcock, 42. Simon Donato, 32, clad in a multipocketed racing vest and camo surf trunks, is the team leader and founder of the Canadian Adventure Racing Association. He sprints over to what turns out to be a white PVC mining-claim post. Not what he was hoping for.

What we're looking for, Donato told us at base camp the hot July night we arrived, is probably the size of two crumpled shopping carts: a hunk of steel frame, maybe an engine block, and possibly some human remains. Donato has let me tag along with the team of six elite athletes-along with a documentary filmmaker, two base-camp coordinators, and a paramedic-that he's gathered for a grueling week of scrambling, searching, and extreme jogging through the area surrounding Bridgeport, California, near the Nevada state line. They'll comb these mountains at 60 percent of maximum exertion for 11 hours a day, pushing their heart rates and their luck in a hunt for a clue, any clue, to the biggest mystery in American aviation since skyjacker D.B. Cooper stepped out of a 727 over Washington State in 1971: the whereabouts of lost adventurer Steve Fossett, last seen somewhere over Nevada on September 3, 2007.

It's scavenger hunting on a grand scale, as exhausting as any adventure race-or, according to these guys, even more exhausting.

"When you're racing, you're not looking," says Eco-Challenge veteran Jim Mandelli, 47, old-school in Frank Shorter-style running shorts and low gaiters, as we scurry through the junipers. "We're not just playing and training in the mountains. We're looking."

Team Adventure Science, trackable via their Spot GPS transmitters, is playing on the ultimate course, the roughest corners of the 20,000-square-mile grid outlined when Fossett first went down. Twenty percent of that original search terrain, Donato figures, is ideal adventure-racer habitat-forbidding ground where the wreckage could be hidden under a juniper canopy or some cliffy bit of geological chicanery-and he's zeroed in on a rough circle, with a 62-mile radius, about 130 miles south of Reno. By Donato's own calculations, the odds of finding the millionaire or his airplane are south of 1 percent. But for these optimistic athletes, the wreckage has become the ultimate geocache, a corporeal poker run with Steve Fossett as the prize.