Asteroid to defend earth from stray rocks?

In a scene straight from a sci-fi movie, scientists are now planning to park an asteroid near the earth in the space to shield our planet from stray asteroids.

NASA scientists have been evolving measures to avoid asteroids on a collision course with earth.

One such technique is the gravity tractor method in which, a robotic probe flies alongside an asteroid for months or even years pulling the rock off course through gravitational force.

The greater the robot's mass, the stronger is its gravitational pull.

"We would go into this enhanced gravity tractor position after we retrieve the boulder and demonstrate that we have even more gravity attraction capability by doing that," said Lindley Johnson, an executive for NASA's Near-Earth Object (NEO) observations programme.

NASA officials are working on the details of the mission and have already identified about 12 candidates for the asteroid-capture mission.

The best target for the asteroid-grab mission may be 'Itokawa' - a 1,750-foot-long space rock that was visited by Japan's Hayabusa probe in 2005, according to a Fox News report.

The US space agency hopes to have a basic mission concept in place by the end of the year.