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Getting set to deflect asteroids that may one day head for the earth

David Adam

NASA evokes Hollywood in bold bid to avoid a possible catastrophe — to land an astronaut on an asteroid as it hurtles through space

It is the stuff of nightmares and, until now, Hollywood thrillers. A huge asteroid is on a catastrophic collision course with the earth and mankind is poised to go the way of the dinosaurs.

To save the day, the National Aeronautics and Space Administration (NASA) now plans to go where only Bruce Willis has gone before. The U.S. space agency is drawing up plans to land an astronaut on an asteroid hurtling through space at more than 30,000 mph. It wants to know whether humans could master techniques needed to deflect such a doomsday object when it is identified.

The proposals are at an early stage, and a spacecraft needed just to send an astronaut that far into space exists only on the drawing board, but they are deadly serious. A smallish asteroid called Apophis has already been identified as a possible threat to the earth in 2036.

Chris McKay of the Johnson Space Centre in Houston told the website Space.com: "There's a lot of public resonance with the notion that NASA ought to be doing something about killer asteroids... to be able to send serious equipment to an asteroid. The public wants us to have mastered the problem of dealing with asteroids. So being able to have astronauts go out there and sort of poke one with a stick would be scientifically valuable as well as demonstrate human capabilities."

A one billion tonne asteroid just 1 km across striking the earth at a 45 degree angle could generate the equivalent of a 50,000 megatonne thermonuclear explosion. Attempting to break it up with an atomic warhead might only generate thousands of smaller objects on a similar course, which could have time to reform. Scientists agree that the best approach, given enough warning, would be to nudge the object gently into a safer orbit.

"A human mission to a near earth asteroid would be scientifically worthwhile," Dr. McKay said. "There could be testing of various approaches. We don't know enough about asteroids right now to know the best strategy for mitigation."

In 2005, NASA's Deep Impact mission tested another technique by placing an object into the path of a comet.

Europe has its own efforts to tackle asteroids. Its planned Don Quijote mission will launch two robot spacecraft, one to tilt at a harmless passing space rock, and a second to film the collision and watch for any deviation in the asteroid's path.

© Guardian Newspapers Limited 2006

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