MIT boffins plan for asteroidal doom

Researchers at MIT say they know what the near-Earth asteroid Apophis is made of, information that could be vital if we need to divert or pulverise the space-rock in 2036.

By analysing its spectrum and comparing it with meteorites that have already landed on Earth, the team has "nailed" its composition, says Richard Binzel, professor of planetary sciences in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS).

Apophis is a 270-metre-wide chunk of debris left over from the solar system's heady days of planet formation. In 2029 it will pass within 22,000 miles of Earth, well inside the lunar orbit, and edging close to some of our satellites. In 2036, it'll pass the Earth again, and there is a very tiny (one in 45,000) chance that the earlier encounter will have knocked it onto a collision course.

So, to be fully prepared for this potentially planet-smashing encounter, MIT unleashed its finest asteroid analysers to find out exactly what it is that probably won't crash into us in 29 years' time. The info could also be useful for any other possible mission to the asteroid, the boffins say.

"Basic characterisation is the first line of defence," Binzel said. "We've got to know the enemy."

Even though the chances of it hitting us are remote, the damage a head-on collision with Apophis could do makes it worth thinking about. A 270-metre asteroid could devastate a region the size of France, or create huge, coast-engulfing tsunamis.

So Binzel and his team turned the IT Magellan telescope in Chile and NASA's Infrared Telescope Facility in Hawaii towards Apophis, and set about analysing the results. Happily, enough meteorites have fallen on Earth that the team was able to find a near-exact match.

Their work suggests that Apophis is a rare type, known as LL chondrite. Just seven per cent of the space rocks that land on Earth are a match to this pyroxene and olivine-rich rock, the team says.

"The beauty of having found a meteorite match for Apophis is that because we have laboratory measurements for the density and strength of these meteorites, we can infer many of the same properties for the asteroid Apophis itself," Binzel said.

Knowing the asteroid's composition will help those preparing planetary defence to choose the best method from the array of sci-fi options, such as lasers, nukes or space tugboats, to manoeuvre it out of harm's way. ®