The cone-shaped top of the 250-pound meteorite known as "Big Lew" sits behind glass in a dust-proof lab at NASA's Johnson Space Center in Houston. Big Lew is the largest meteorite found in Antarctica since the United States began collecting them in 1975. (Pat Sullivan/Associated Press)

The geologist who conceived it called it the poor man’s space program. Sen. John McCain (R-Ariz.) fumed that it was a waste of taxpayer dollars. Meteorite hunter Ralph Harvey simply calls it work.

For the 35th year, the United States is mounting its annual campaign to gather space rocks from the wind-hammered icefields of Antarctica.

“We’ll be living two to a tent for six weeks, and everybody’s got a snowmobile,” said Harvey, a geologist at Case Western Reserve University who is leading the expedition for the 21st time. “I guess we’re almost like cowboys trying to round up cows.”

Except these cows don’t moo. They hunker on the blue ice, half-buried, dark and inert. In the 24-hour sunshine of the austral summer — starting now — meteorites stick out like Angus among Holsteins.

“If you want to find stuff falling out of the sky, get a big white sheet,” Harvey said during a phone call from McMurdo Station, the U.S. research base on the continent. “We’ve got a white sheet as big as the continental United States.”

Getting to that sheet is a feat of logistical largesse. The eight-person expedition requires 20,000 pounds of gear, hauled first to McMurdo. From there, three giant C-130 transport planes plop the tents, food, water, fuel, snowmobiles, generators and spare parts on the ice halfway to the final destination. From there, many flights of a smaller Otter plane shuttle the expedition to its camp site, which this year is near the Miller Range along the Transantarctic Mountains.

“I feel more like I’m moving a city than doing science,” Harvey said. “It will be a three- or four-day process” that will begin Wednesday or Thursday.

Scientists say meteorites bombard the Earth from all directions, falling everywhere in roughly equal proportions. But geologic forces concentrate them at the foot of Antarctica’s mountains.

Giant ice sheets push against these peaks, churning fallen meteorites toward the surface. Harsh winds knifing down the mountains blow off a layer of snow and ice each year, exposing a new batch. The whole process is a meteorite-generating machine. The expedition collects hundreds each year.

“The ice continues to produce more and more meteorites that have been buried below,” said Linda Welzenbach, manager of the National Meteorite Collection at the Smithsonian Institution, where most of the Antarctic finds eventually reside.

As a bonus, the continent serves as a natural deep-freeze, keeping the ancient space rocks nearly pristine.

Finding them is as straightforward as riding out across the ice with open eyes. Because few Earthly minerals exist out there, anything rocky is bound to come from space.

Of every 1,000 meteorites picked off the ice, about 50 hold “outstanding interest to a broad range of scientists,” Harvey said.

The smallest are marbles. The largest weigh hundreds of pounds. Some originate at asteroids. Others are free-floating detritus from the birth of the solar system some 4.6 billion years ago. A few — the rarest and, to many scientific minds, the most precious — come from the moon and Mars. An asteroid or comet blasted them into space on an improbable trajectory that eventually landed them at the bottom of the Earth.

Nobody knew the Antarctic held such otherworldly wealth until 1969, when a Japanese expedition stumbled on nine unusual rocks near the Queen Fabiola Mountains. It took a few years for Japanese scientists to realize that the rocks hailed from space. (Since then, an ongoing Japanese campaign has collected 30,000 meteorites from Antarctica. Italy, Belgium and China have more recently launched smaller collection programs.)

In 1974, word of the Japanese discovery reached William Cassidy, then a geologist at the University of Pittsburgh, who ran the program until 1991. “I realized there had to be some previously unknown process concentrating meteorites in Antarctica,” he wrote in an e-mail.

With a grant from the National Science Foundation, Cassidy launched ANSMET, as the program is known. The NSF, NASA and the Smithsonian jointly run it. The ANSMET logo is playful: A penguin in a baseball hat running across the continent, a flaming space rock falling into his glove.

Harvey and other scientists credit the program’s longevity to Cassidy’s vision: He insisted that all finds be made available to any scientist in the world. “It almost sounds ridiculous,” said Harvey. “Who goes out and finds a new Egyptian pyramid and says, ‘Hey, you guys study it and I’ll watch’? That’s basically what it is.”

Harvey pinned the cost of ANSMET at about $1 million a year. He said it’s a bargain; Cassidy called it “the poor man’s space program.” Sending robots or humans into space to collect such rocks would costs tens of billions. “It’s a unique way to explore the solar system, and we are doing it inexpensively, minimizing risk, and bringing home the bacon,” said Harvey. “In this case, the bacon is space rocks.”

To McCain and Sen. Tom Coburn (R-Okla.), though, that bacon smells like pork. In August 2010, the pair listed what they called the 100 most wasteful projects funded by the 2009 stimulus act. A $600,000 grant to ANSMET clocked in at No. 75. The report suggested that the program had collected enough meteorites already.

Meteorite scientists argue that isn’t true. Each year brings unexpected finds, they say. The 2006-2007 season returned two chunks whose origins are still unknown, which is unusual, said Welzenbach. The rare Martian rocks hold special interest, too, as one found in 1981 generated excitement in 1996 when a NASA scientist asserted that it showed evidence of fossil microbes — life on Mars. That claim has since been roundly rejected.

But there is no doubt that the program has found tons and tons of space rocks. Just this month, the Smithsonian finished upgrading the meteorite storage facility in its Museum Support Center in Suitland to hold them all. Inside a clean room with triple-filtered air, 14 gleaming NASA-designed cabinets — each creepily outfitted with six white gloves sticking straight out, inflated by a constant flow of inert nitrogen gas — stand ready to accept thousands more meteorites. The Smithsonian recently spent about $500,000 to buy 10 new cabinets.

Harvey expects this year’s expedition to hit a special mark. When they find their 299th meteorite of the season, “it will be as close as we can estimate to our 20,000th” since 1976, he said. Then “the team will break out our, uh, grape juice.”