'Armageddon' asteroid-busting mission may lift off for real

The U.S. space agency is even considering landing a man on a harmless asteroid in the hope that the mission would provide clues on how to divert a dangerous one.

The proposals are at an early stage and a spacecraft to send an astronaut far into space and on to a piece of rock travelling at more than 30,000mph does not yet exist.

But the agency is deadly serious about its plans. It points out that a small asteroid called Apophis has already been identified as a possible threat to Earth in 2036.

"A human mission to a near-Earth asteroid would be scientifically worthwhile," said Chris McKay at Nasa's Johnson Space Centre. "It could be part of an overall programme of understanding these objects.

"Also, it would be useful, instrumentally, in terms of understanding the threat they pose to the Earth.

"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."

The plans are being drawn up at Nasa's Ames Research Centre in California's Silicon Valley. An asteroid six-tenths of a mile across, striking the Earth at a 45 degree angle, could generate the equivalent of a 50,000 megaton nuclear explosion.

But an attempt to break it up with a missile warhead might just create thousands of smaller asteroids on a similar course.

A better option could be to nudge it away from collision course and into a safer orbit. Gianmarco Radice, an asteroid expert at Glasgow University, said the best approach would be to land a device to dig into the object.

Over the course of 20 years, mirrors and lights could change the way it absorbed light and heat sufficiently to shift its direction.