JapanвЂ™s Hayabusa2 satellite spent six years and 16.4 billion yen ($157 million) recovering a single gram of material from the asteroid Ryugu. Bringing material back to Earth would raise the costs even more. Power demands rise sharply once you move from exploration drilling to mining and processing. That drill would need a similar-sized power plant. The international space station, with 35,000 sq ft of solar arrays, generates up to 120 kilowatts of electricity. Still, at those prices just lofting a single half-tonne drilling rig to the asteroid belt would use up the annual exploration budget of a small mining firm. On Falcon Heavy, the large rocket being developed by Elon MuskвЂ™s SpaceX, transporting a payload to the orbit of Mars comes to as little as $5,357 per kilogram, a drastic reduction in normal launch costs.

Escaping EarthвЂ™s gravitational field makes transporting the volumes of material needed in a mining operation hugely expensive. As a result, the cornucopia of minerals the globe attracted as it coalesced is as rich as will be found this side of Alpha Centauri. Earth is the largest rocky planet orbiting the sun. On one hand, it guarantees that most of the solar systemвЂ™s best mineral resources are to be found under our feet. One factor rules out most space mining at the outset: gravity.

Space engineers finding uranium