Finally, the detector whines and Arnold slams the brakes. "That is so good," he says.
Arnold jumps out, pinpoints the location with a smaller detector and starts digging. The world-renowned meteorite hunter is hoping for a big score. He has had three false hits today, unearthing a bit of barbed wire, a fragment of a plow, a squashed Dr. Pepper can.
"What's the definition of insanity?" Arnold asks. "Doing the same thing over and over again."
All over the world.
He has dodged police in Oman, had his truck break down in a desert in Chile, and bicycled the streets of suburban Chicago holding a broomstick with a magnet tied to its end -- searching for space rock.
But it was here in Kansas that he found the meteorite that would make him famous.
In 2005, Arnold began to systematically search the meteorite-rich prairies of western Kansas. Within two weeks, he unearthed the world's biggest intact pallasite. Weighing 1,400 pounds, the pallasite -- the rarest, most sought-after type of meteorite, composed of iron streaked with dazzling crystals -- is believed to be worth between $600,000 and $1 million. It will be featured in the first all-meteorite auction, scheduled for this Sunday in New York.
The world of space rocks attracts all sorts. Professionals like Arnold comb the tundra of Siberia and Norway and the deserts of South America. Nomads in the Sahara search for rocks to sell to avid collectors looking for the perfect piece of intergalactic debris. Some collectors are drawn to meteorites for purely aesthetic reasons -- the rocks can be startlingly colorful -- but many are also captivated by the scientific novelty of the pieces.
"It's from outer space," said Darryl Pitt, who curates a major meteorite collection. Ten pieces from that collection will also be auctioned Sunday. "There's a romantic notion of being able to have something from between Mars and Jupiter."
Unlike many meteorite mavens, Arnold is not in it for the science. "I'm a treasure hunter, not a scientist," he says repeatedly.
Arnold, 41, grew up in a small town in eastern Kansas, and knew nothing about meteorites. What he did know was that he wanted to be his own boss.
His parents operated their own businesses: his father, an accounting office; his stepmother, a bookstore. Arnold went to Oral Roberts University in Tulsa, Okla. -- not for religious reasons but because he liked its business program. He met and married his wife, Qynne at the school, and after graduation pressured-cleaned houses in Tulsa to make ends meet while trying to figure out what to do with his life. One day in 1992, he wandered into a Barnes & Noble and spotted a book on treasure hunting.
In a chapter on finding buried caches of coins on old homesteads, the book advised checking historical records to locate areas where epidemics or drought wiped out the population. Arnold went to the Kansas Historical Society in Topeka and began to thumb through newspapers. In the yellowing pages, he found stories about farmers digging up meteorites. "I realized, 'Oh my God, these are treasure maps,'|" Arnold said.
He began driving to rural communities in Kansas and offering to buy meteorites from farmers. Then he sold them to retailers or collectors. As the years passed, he spent less time acting as a middleman and more time hunting the rocks himself.
Meteorites are extraterrestrial debris from asteroids and comets that collide with the Earth. As the rocks fall through the atmosphere, the heat and pressure can mold them into odd shapes. Some land with a huge impact, creating enormous holes such as the Barringer crater in northern Arizona, which is nearly a mile wide and more than 500 feet deep.
Treasure hunters like Arnold are generally on the prowl for meteorites that break up as they fall through the atmosphere and scatter across what is called a "strewn field." These are simplest to find in dry, flat places where the dark rocks are preserved and easy to spot, like the Great Plains or the basins of the American Southwest.
In 1995 Arnold went to the Atacama Desert in northern Chile, considered the driest place on the planet. He drove a rented truck for hours into the desert and got stuck in a sand drift. It took four hours for Arnold and his companions to free the truck by excavating limestone slabs to create a ramp.
"Nothing ever gets him down," said Geoff Notkin, a science journalist and meteorite aficionado who accompanied Arnold on the Chile trip. "In 11 years of digging holes and getting lost and getting soaked, I've hardly ever seen him annoyed."