Close encounter prompts call for asteroid watch plea for new vigil system

In intergalactic terms, it was a close shave. An asteroid capable of causing widespread devastation narrowly missed the Earth yesterday.

In intergalactic terms, it was a close shave. An asteroid capable of causing widespread devastation narrowly missed the Earth yesterday.

Although the nearest the asteroid came to Earth was 390,000 miles, had it arrived four hours earlier on its journey around the Sun it would have scored a direct hit.

The asteroid – measuring 300 metres across and known as 2001 YB5 – passed Earth at 7.37am. For a moment, it was less than twice as far from the Earth as is the Moon.

Scientists were unaware of its approach until a month ago, when it was spotted by an American observatory dedicated to tracking near Earth objects (NEOs).

Astronomers insisted there was never any danger of a collision with Earth. But they warned that the asteroid was one of up to 400,000 small NEOs up to 1,000 metres wide that could strike Earth with little or no warning because of the absence of an adequate early- warning system.

The idea of a catastrophic asteroid strike has long been a source of morbid fascination, most recently manifesting itself in Hollywood disaster movies such as Armageddon and Deep Impact. The potential consequences are indeed apocalyptic, according to research on asteroid impacts. If a 300-metre asteroid hit London, it would destroy everything within a 95-mile radius and cause severe damage for a further 500 miles – wiping out the UK, the Low Countries and much of France.

In the more likely event of a similarly sized NEO landing in the sea (70 per cent of the Earth's surface is covered by water), it would trigger a series of tsunamis – massive waves – that would devastate coastal regions.

Jonathan Tate, director of Spaceguard UK, which campaigns for a British-funded telescope to watch for such asteroids as part of a global network, said: "YB5 is one of hundreds of thousands of objects which present an unknown risk to the planet.

"What limited resources exist for tracking asteroids are dedicated to spotting the 700 to 1,200 which are more than a kilometre in diameter and, if they hit the Earth, could wipe out the planet.

"That leaves very few resources for trying to trace the many more asteroids between 100 metres and 1,000 metres in diameter which still present a very significant risk.

"This particular asteroid passed us by without any danger but it remains that by the time it was spotted last month, there was nothing we could have done to avert a catastrophe had it been heading toward us."

YB5 was identified four weeks ago by scientists at the Near Earth Asteroid Tracking observatory on Mount Palomar, California, part of America's system for picking up large asteroids.

There are estimated to be about three or four "close encounters" with NEOs every month. The only known object that will pass nearer to Earth than YB5 is another asteroid, 1999 AN10, on 7 August 2027.

Astronomers say greater resources are required to provide long-range forecasting. Spaceguard UK estimates that the cost of British participation in a global early warning network would be £35m.

Dr Roderick Willstrop, of the Institute of Astronomy at Cambridge University, said: "Our knowledge of these smaller NEOs is rather sketchy. We don't have a system in place to spot them all."

Were a dangerous NEO to be spotted, however, fans of the Hollywood version of asteroid defence will be glad to know that the solution is straight out of the realms of fiction.

Dr Willstrop said: "The only way to deal with it is to give yourself enough time and launch rockets to stage an explosion in space which will deflect the asteroid sufficiently off course to avoid us."