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, targeting them costs less fuel and money than going to the moon, Anderson said in a phone interview.

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 of them have water and other valuable minerals. “A depot within a decade seems incredible. I hope there will be someone to use it,” said Andrew Cheng at Johns 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.”