London, Oct 5 : The best defence against an asteroid on course to a collision with Earth, is a swarm of mirrors flying in formation in space, according to a new study by a researcher from the University of Glasgow, Scotland.

Mirrors in space, or “solar concentrators”, would direct the Sun’s rays against a small area of the rock, no more than 1.5 metres across, to generate temperatures of at least 2,100C (3,812F), enough to heat the surface to turn it into gas.

The evaporating gases would shoot into space, creating the thrust needed to divert the asteroid and prevent a deadly impact, said lead researcher Dr. Massimiliano Vasile.

He said the technique was most feasible of several options, including exploding a nuclear device.

During modelling tests, the team found that this technique had a high chance of success in pushing asteroids of any size off course.

On the other hand, exploding a nuclear device, as seen in the 1998 film Armageddon, was found to be highly successful in dealing with large asteroids, such as the one believed to have wiped out the dinosaurs 65 million years ago.

However, there was the risk of debris falling back on Earth, as also of an explosion during take-off.

The most serious asteroid threat to the planet identified by astronomers is Apophis, which is estimated to be at least 150 metres in diameter and to have a one in 45,000 chance of colliding with the Earth.

In 2029 Apophis’s orbit will take it close enough to Earth for the planet’s gravity to possibly alter its trajectory and dramatically increase the chances of an impact on April 13, 2036. The explosion caused by the impact of Apophis, a medium-sized asteroid, would be big enough to destroy a city the size of London.

“Asteroid impacts are a real threat. In the past 30 years there have been quite a number of technologies suggested to deflect asteroids. We’ve tried to analyse them to see which are the most effective,” said Dr. Vasile.

He said a large asteroid with a diameter of 1,000 metres would have the potential to cause mass extinctions, adding that it was a 10km meteor that ended the reign of the dinosaurs and created the Chicxulub crater.

“An asteroid big enough to cause the extinction of the dinosaurs hits Earth on average every 26 million years. It would take 5,000 mirrors operating for three years to deflect,” the Times quoted Dr. Vasile, as saying.

Dr. Vasile presented his study at a conference at the University of Manchester’s Jodrell Bank Observatory, held to celebrate the 50th anniversary of the start of the Space Age with the launch of Sputnik 1 by the Soviet Union. (ANI)