Those free-flying asteroids — ranging from a couple of dozen feet wide to nearly 10 miles long — are the ones being targeted for rare Earth platinum metals that are used in batteries, electronics and medical devices, Diamandis said.
In the past couple of years, NASA and other space agencies have shifted their attention from the moon and other planets toward asteroids. Because asteroids don't have any substantial gravity, going after them costs less fuel and money than going to the moon, Anderson said.
There are probably 1,500 asteroids that pass near Earth that would be good initial targets. They are at least 160 feet (50 meters) wide, and Anderson figures 10 percent have water and valuable minerals.
"A depot within a decade seems incredible. I hope there will be someone to use it," said Andrew Cheng at John Hopkins University's Applied Physics Lab, who was the chief scientist for a NASA mission to an asteroid a decade ago. "And I have high hopes that commercial uses of space will become profitable beyond Earth orbit. Maybe the time has come."
Diamandis and Anderson would not disclose how much the project will cost overall. By building and launching quickly, their company hopes to operate much more cheaply than NASA.
Harvard's Tim Spahr, director of the Minor Planet Center, said getting drilling equipment into space and operating safely sounds "expensive and difficult."
"It would be awfully hard to make money on it," Spahr said.
Richard Binzel, professor of planetary science at the Massachusetts Institute of Technology, said the effort "may be many decades ahead of its time. But you have to start somewhere."
Anderson said the benefit to humanity — and investors — is worth it.
"We do understand that the pot of gold at the end of this rainbow, if it's successful, will be big."
Borenstein, who reported from Washington, can be followed at http://twitter.com/borenbears .
Planetary Resources Inc.: http://www.planetaryresources.com/
NASA's 2016 asteroid sampling mission: http://osiris-rex.lpl.arizona.edu/