As the current brouhaha about asteroid mining shows, visionaries may toil quietly until famous or rich people decide to enact an idea. With others, the director James Cameron (Avatar) and the founders of Google are now setting out to bring back valuable metals from near-earth asteroids (NEAs). The firm is called Planetary Resources, apparently implying not that the resources are to be found on this planet, but that they will be brought back to it.
What is involved in asteroid mining? The go-to source is Space Wealth; and the key paper, "Profitable Asteroid Mining: A Pragmatic Policy Goal?" The author is BC Crandall, who edited early books on nanotechnology for MIT Press (1992 and 1996) and earned an MBA from Cal Poly. He answers his question about the policy goal was a resounding yes.
Asteroids seem far away, except when viewers of a Hollywood movie worry about one crashing into Earth, but many near-Earth asteroids are easier to go to than the moon. A Japanese craft has already brought back a sample of the surface of an asteroid called Itokawa. According to Crandall, some asteroids are rich in platinum-group metals. Patinum now sells for more than $1500/ounce.
One of the technologies necessary for asteroid mining would be robotics, with obvious applications also on Earth. It is not inconceivable that new robotics patents may in themselves provide a substantial income.
In an era of uncertain support for space ventures, successful asteroid mining would keep alive and extend the skills necessary for eventual habitats in space. Crandall and others hope that profitable asteroid mining might open a path to a viable future off of the Earth. In the words of Stephen Hawking, "The human race shouldn't have all its eggs in on basket, or on one planet."