Nuclear weapons to blast dangerous asteroids?

US researchers are looking into the possibility of using nuclear weapons to protect Earth from the threat of incoming asteroids.
Scientists at Los Alamos, the US government's atomic weapons research centre in New Mexico, say that the threat of an asteroid impact is far greater than had been realised and research was required to work out the best way to destroy or deflect them.
"The goal is to study the effectiveness of using a nuclear explosive to alter the orbit, or destroy, a potentially harmful object," said Robert Weaver at Los Alamos in an abstract submitted to the American Geophysical Union's annual meeting in San Francisco.

Weaver and his colleagues plan to create computer simulations of a nuclear device detonating above an asteroid to work out the ideal height to deflect it, 'The Times' reported.
It was believed that impacts by large asteroids were rare, but sensor networks set up to monitor illicit nuclear tests have recorded a large number of mysterious explosions now known to be caused by asteroids hitting the Earth, usually in remote areas.
Weaver said a larger impact could be disastrous.
The risks include "a direct hit in an urban area (potentially catastrophic but highly unlikely); the generation of a tsunami from an ocean impact close to a coastline; and regional and global effects from medium to large impactors," he said.

In 2013, a small asteroid of about 13,000 tonnes exploded above Chelyabinsk in Russia, damaging 7,000 buildings and leaving 1,500 people injured.