Talk of mining asteroids was once the preserve of corduroy-flare-clad, optimists of the Apollo era. Now the idea is making a comeback thanks to enterprising tech billionaires and a nascent commercial space industry.The company Planetary Resources is due to outline today in Seattle, Washington, its aims to mine near-Earth asteroids for precious metals. "The resources of Earth pale in comparison to the wealth of the solar system," company founder Eric Anderson, also of Space Adv