How To Capture An Asteroid (and Why)

August 30, 2011, 10:00am

Every now and again, Jupiter will get a cosmic couchsurfer of sorts in the form of an asteroid. Rocks of various sizes get snagged by the planet’s massive gravity, orbit around for a while, clean out the fridge, and then stumble back out into the solar system. Sometimes they do as little as one orbit around the planet, sometimes several.

Researchers at Bejing’s Tsinghua University decided to look and see if this could ever happen to Earth. Could we snag a comet satellite of our own? After looking at 6,000 near Earth objects (NEOs), the answer is no. But some come really close, close enough that we might be able to give one a sharp kick in a certain direction and it’ll wind up in our orbit.

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“It is possible for such an NEO to be temporarily captured by Earth; its orbit would thereby be changed and it would become an Earth-orbiting object after a small increase in its velocity,” they write in a paper recently posted to arXiv. One asteroid in particular, NEO 2008EA9, that’ll be in Earth’s neighborhood (well, within 1 million kilometers anyhow) in about 40 years gets singled out. If we gave it the right kick, we’ll have it in our orbit (at about twice the distance as the moon).

The researchers looked at a few different ways this kick could actually be delivered. One is simply smacking the thing the right way with a space probe, powered perhaps by a solar sail of the future. Or we could blow up a nuclear bomb in the right spot but, as the paper notes, that might just destroy it. Or maybe we could use the “slow push” method, e.g. by “[blasting it with thermal radiation], focused solar, gravity tractor, mass driver, pulsed laser, and space tug.”

But. . .why would we want to put a spectacular amount of effort into getting a small asteroid into our orbit? Mining. (Or maybe dumping nuclear fuel or trash or something.) Most of the valuable stuff in Earth’s crust, like gold and platinum, came from early-Earth asteroid collisions in the first place. Also, maybe we’ll find one made of diamond.