Material matters: Shooting stars - mining meteorites?
As people across the UK sat down to dinner on the evening of Friday 15 February, the 50-metre diameter Asteroid 2012 DA14 passed just 27,700km above their heads – 8,000km closer than the geostationary orbit of some communications satellites.
Following close on the heels of a meteorite that crashed to earth in the Russian Urals only a few days before, it gave rise to the speculation of just how great is the risk of a collision with these interplanetary canonballs. High enough for NASA to maintain Sentry, an automated collision monitoring system that continually scans the most current asteroid catalogue for possibilities of future impact with Earth over the next 100 years. Most of the current crop have a less than one-in-a-million chance of impact, I am pleased to report.
It was also interesting to learn what we can do to prevent an end-of-the-world-as-we-know-it catastrophe that would follow a much larger meteor strike. Opinion is divided as to whether the Bruce Willis approach of blasting to smithereens with a nuclear weapon is practical or desirable, as the damage from millions of pieces of irradiated asteroid striking Earth would be as catastrophic as the impact of the asteroid itself.
Another strategy with more scientific merit is to slam a spacecraft into the object to knock it off course. A more refined version could be to land a spacecraft on the asteroid, fire retro rockets and slowly push the object off trajectory. Yet another, more intriguing, idea is to cover the asteroid in light-coloured reflective paint. The pressure of light particles bouncing off the reflective coating, acting over time, would apparently divert the rock off its path.
Notwithstanding the fact that many asteroids and meteors are undetectable until within a few weeks and sometimes only hours from impact, all of these methods are perfectly feasible with respect to the fundamental laws of Newtonian and particle physics. This has given rise to another area of research: capturing asteroids into low Earth orbit to mine them for nickel, cobalt and other non-ferrous metals. Asteroids are the detritus of inter-planetary collisions billions of years ago, and most comprise just rock and ice. But a few formed are known to comprise around 90% iron, 8% nickel and perhaps 0.5% cobalt, with smaller fractions of rare earths and precious metals.
It may be physically possible to capture asteroids, but would such an enterprise be economically viable? At first glance the numbers are attractive. Let’s take asteroid 2012 DA14, which was a relatively small 50-metre diameter and about 50,000m3 volume, or 390,000 tonnes mass. This would be about 31,000 tonnes of nickel and 2,000 tonnes cobalt, valued at around US$565 and US$50 million at today’s prices. But space missions don’t come cheap – the Space Shuttle’s programme of 130 missions cost more than US$200 billion, so that’s around 350 DA14s just to break even. More practically, as many Earth-bound mining projects struggle to find the corporate finance, even when the resource is at a known and fixed location with a verified assay, what chance do our budding space miners have where the resource often is only apparent with a few weeks’ notice and may turn out to be just rock and ice?
Last month, I wrote about the scrap metal industry – a mine above the ground – perhaps my 22nd Century successors will write about the mine above Earth. Much as I would like this to be so, somehow I doubt it.