Estimates of their abundance on some asteroids, such as the enigmatic Psyche 16 beyond the orbit of Mars, suggest concentrations several times higher than can be found in terrestrial mines. Because of their affinity for iron, these so-called siderophile elements mostly sunk toward the metallic core of our planet early in its formation, and are relatively scarce in the Earth’s crust. The more promising commodities are platinum, palladium, gold and a handful of rare related metals. Copper, which typically costs about $4,500 per metric tonne (ppm) to refine, has an average ore grade of about 6,000 ppm. Still, the concentrations of 100 to 412 parts per million are extraordinarily low by terrestrial standards. The discovery in October of ice molecules in craters on the Moon was taken as a major breakthrough. What might you want to mine from space? Water is an essential component of most earth-bound mining operations and a potential raw material for hydrogen-oxygen fuel that could be used in space. Japan’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 Musk’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 Earth’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 system’s best mineral resources are to be found under our feet. One factor rules out most space mining at the outset: gravity.
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