Now, a spacecraft to save Earth

Now, a spacecraft to save Earth

A team at British space company EADS Astrium has made the spacecraft, "gravity tractor", which will be deployed when an orbiting rock is detected on a collision course with Earth -- in fact, it will intercept the asteroid and position itself to fly alongside it, just 160 feet from its surface.

And, from this position, the ten-tonne craft is able to exert a small gravitational force on the rock, pulling the asteroid towards it. By gradually modifying its course, over several years, the gravity tractor is able to slowly shift the asteroid's trajectory enough to ensure it misses the Earth.

According to the scientists, the spacecraft could divert asteroids that are up to 430 yards across -- big enough to release 100,000 times more energy than the nuclear bomb dropped by the US on Hiroshima in 1945.

Dr Ralph Cordey of Astrium was quoted by 'The Daily Telegraph' as saying: "Anything bigger than 30 metres across is a real threat to the Earth. Unfortunately it is a matter of when rather than if one of them hits us.

"The gravity tractor exploits the principals of very basic physics -- every object with a mass has its own gravity that affects objects around it. It can move fairly large objects 300 metres to 400 metres across.

"These asteroids are hurtling around our solar system at 10 km per second, so when you scale that up, you just need a tiny nudge to send it off course."

The team has designed the gravity tractor and planned details of the mission. The craft can be built in a relatively short time, using existing technologies, if an asteroid was detected on a collision course. But, it's likely that it would require an international agreement to send a mission in space.

"We've designed the mission using the technology that we currently have available, so it could be put into practice at any time," Christian Trenkel, who has worked on the mission plans, said.

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