Our asteroid belt is the debris left over from the formation of the Solar System. The cowboy builders responsible didn’t clear up their mess. They simply swept it out beyond Mars, where the powerful gravity of Jupiter kept it all stirred up and prevented it from clumping into new planets.
The baby Earth and her siblings, Mercury, Venus and Mars, must have passed some threshold in their formation, picking up enough matter to be stable, so that further collisions caused them to accumulate material rather than being broken up. Eventually, they swept up everything, entirely clearing the inner system.
But it was a close-run thing for Earth. When she had almost finished gathering up her building materials, she was struck by another massive proto-planet and the resulting mess split into two chunks. The bigger part is our Earth today, and the smaller, our Moon.
Other fledgeling planets weren’t so lucky. When a growing planet has acquired enough matter to be molten, it tends to fractionate out: heavy metals sink to the core, while lighter, rocky minerals float on top. That’s how we know that some of the asteroids are the wreckage of destroyed worlds: some of them are made of rock and some of metal, the different parts of something that already had a planetary structure.
It’s the metal ones which have been in the news recently, specifically about the possibility of mining them. Of course, Earth is mostly made of metal too, but the majority of it is inconveniently buried under hundreds of kilometres of rock. The easily-accessible remainder, brought to the surface by volcanic events, is being used up and hence increasing in price. Has asteroid-mining become economically viable?
The idea was previously explored in the optimistic 1960s and 1970s, when people thought that progress in space exploration would continue at the same, heady rates. One visionary of the time was the physicist Gerard K O’Neill (whose title I have stolen), who proposed space habitats and space factories, and mining the Moon and asteroids for materials to build them. At a Congressional hearing on the issue, he recited his catchphrase: “Is the surface of a planet really the right place for an expanding technological civilization?”.
That highlights a significant difference between what was envisioned back then and the ideas in circulation now. It’s not progress which interests people, it’s money; and one little one-kilometre metallic asteroid contains enough valuable metals (the nickel content especially) to pay for the combined, post-financial-crisis national debts of the EU and the USA.
Such wealth is tempting, or at least tempting some people, the rich investors who have formed the company Planetary Resources. These are heavyweights, including at least three Google billionaires (Page, Schmidt and Shriram), the CEO of the X-Prize Foundation, the Chairman of Space Adventures (who use Russian facilities to fly space tourists) and a former Goldman-Sachs CEO. As well as a raft of very serious academic advisors, the company has recruited film-maker James Cameron, presumably for his abilities to fund and develop exploration technology — for the deep seas, so far.
The concept behind Planetary Resources is to use near-Earth asteroids. Why travel all the way to the Asteroid Belt (given that even getting to Mars is pretty tough) when you can just wait for one to fly by? They say that there are currently 9,000 identified asteroids with orbits within, or crossing, Earth’s orbit; and 981 of them are known to be larger than one kilometre. In fact, two near-Earth bodies have already been inspected by Earthly spacecraft. 433 Eros was visited by NASA’s NEAR mission, and 25143 Itokawa by Japan’s Hayabusa craft. NASA is currently working on the OSIRIS-REx mission to visit the carbonaceous asteroid 1999 RQ36 in 2019.
That provides a reality check for Planetary Resources. OSIRIS-REx, planned for launch in 2016, is currently budgeted at a round billion dollars, and is to sample and return to Earth as much asteroid material as it can collect, up to a maximum of 2 kilos. Asteroid 1999 RQ36 is a soft, crumbly carbonaceous lump, about half a kilometre long, so collecting a sample of surface material ought to be feasible. Although the rendezvous is in 2019, the return capsule won’t arrive back on Earth until 2023.
Planetary Resources say that they will be able to create robotic spacecraft at a tenth of NASA’s pork-barrel prices, and I can believe that. But even a mere hundred million dollars for a crumbly lump of space gunk seems expensive if it’s not the scientific content you’re interested in. At today’s commodity price for nickel, just under 20 dollars per kilo, you’d need to recover five thousand tonnes of the pure metal just to break even on a hundred million dollar mission. (That would only be a house-sized lump, but how would they land it?)
And suppose you could do it, bring a plentiful supply of nickel, cobalt and platinum to Earth, that would affect the market price and undermine (“mine”, oh dear) the economics of the operation. I’d love to believe in an advance into space, but I just can’t, on these terms. For me, the only plausible scenario is a return to the ideas of the 1970s: forget Earth — use the stuff up there to build stuff up there, and live on it.