The Homestake Gold Mine is played out, but state officials think there's billions of dollars worth of pay dirt left in its 8,000-feet-deep maze of shafts and tunnels. Cosmic pay dirt.
South Dakota is trying to convince the National Science Foundation that the nation's deepest mine, one of two finalists for a proposed national underground lab, is the perfect place to hunt neutrinos and other elusive particles that could help scientists better understand the universe.
The state has fronted $35 million for an interim lab, hoping to improve its odds of building a high-tech boomtown around the mine, which produced 10 percent of all gold ever found in the United States before closing in 2001.
"It's brightened the coffee-shop talk," said Kay Jorgensen, a businesswoman in nearby Spearfish. "They're saying, 'Think of what's possible.'"
Last year the NSF selected Homestake and Colorado's Henderson Mine as the finalists for the Deep Underground Science and Engineering Laboratory.
After receiving conceptual designs due in late June, the foundation could pick a site later this year, and would seek congressional funding after the winner prepares a detailed proposal.
Physicists want to go deep underground to conduct experiments aimed at increasing their understanding of the universe's composition, its beginning and its future. More than a mile of rock would filter out many of the cosmic rays that would otherwise interfere with the study of fundamental particles such as neutrinos.
"The reason for going underground is the same reason why astronomers look at stars at night," said Ken Lande, a University of Pennsylvania physicist who manages a small existing underground lab at Homestake.
Homestake's proposed national lab, at 7,400 feet, would be about 600 feet deeper than a Canadian lab that is now the world's deepest.
"It will be the greatest depth and the lowest background, so it will be capable of having the most sensitive experiments," Lande said.
Homestake already holds an important place in the short history of neutrino research, thanks to Ray Davis Jr.
The Brookhaven National Laboratory physicist's work at the mine beginning in the late 1960s helped him demonstrate that neutrinos are created in the sun as the result of nuclear fusion, earning Davis a share of the 2002 Nobel Prize in physics.
Scientists now want to study how the three types of neutrinos change from one kind to another, Lande said.
They also want to use a deep underground lab to study dark matter, which has gravitational force but is not visible. Other experiments would study whether protons decay, which the NSF says would provide evidence that all the fundamental forces are united at some very high energy.
The proposed Henderson Mine lab in Colorado also would extend to 7,400 feet underground, although the still-operating mine there is not that deep.
The molybdenum mine is close to three universities and Denver International Airport, and studies have confirmed its rock conditions are favorable, said Stony Brook University physicist Chang Kee Jung. He noted that the Homestake mine is relatively remote from amenities.
Homestake backers point to its sturdy hard rock, its more than 350 miles of horizontal tunnels and its immediate availability. Because it no longer has an operating mine, there would be no conflicts between science and mining operations, Lande said.
South Dakota has helped encourage research by funding the interim lab, which could be open for experiments by late next year. Even at 4,850 feet it will be the deepest in the nation.
"If we can get the first experiments in and get them established," Gov. Mike Rounds said, "it seems to be a very logical conclusion that others will follow in the future and with them will come long-term jobs, technical jobs, research jobs and engineering jobs."
No official cost estimates or staffing levels have been mentioned yet for the national lab.
Rounds said a national lab could bring billions of dollars in economic activity to western South Dakota, which relies on tourism fueled by legalized gambling in Deadwood.
Lande said a national lab would offer more than economic benefits.
"From the point of view of South Dakota, it's a tremendous opportunity," Lande said. "Not only South Dakota but the whole Plains area, because this will become a laboratory that will be the center of science activities and science education for the whole region."