Near-miss asteroid could have wiped out Greater London area

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The Independent Online

An asteroid measuring nearly three miles across squeezed past Earth by the astronomical equivalent of a hair's breadth yesterday.

An asteroid measuring nearly three miles across squeezed past Earth by the astronomical equivalent of a hair's breadth yesterday.

The flypast, by the asteroid Toutatis, was the closest it will make this century, and one of the nearest by any "near-Earth object" for the next 180 years.

But astronomers warned that there are potentially thousands of much smaller objects that could devastate an area as large as the M25 region which are not being picked up because governments are failing to fund the detection of one of the greatest threats to the planet.

Toutatis is one of thousands of asteroids left over from the formation of the solar system six billion years ago which could still crash into the Earth.

Had Toutatis hit the Earth, it would have had the explosive impact of a one million megaton bomb, many times the total nuclear arsenal of the superpowers, and destroyed all life on the planet. But it's closeness is relative - it remained a little less than a million miles away.

But even smaller objects, as small as 100 to 200 metres across, could wipe out an area the size of London, warned Kevin Yates of the Near-Earth Objects group at the British National Space Centre. "Nasa has calculated that such an object will hit the Earth about once every 700 to 1,000 years," he said yesterday. "Such an object did hit the Earth in 1908, over Tunguska in Siberia, which devastated two thousand square kilometres of forest."

Dr Alan Fitzsimmons, an astronomer at Queen's University Belfast who wrote a report in 2000 detailing what the government should do to increase detection of such "near earth objects", said: "The search programmes now under way use relatively small telescopes, which means they can only see fairly bright objects that reflect sunlight; that means they can only detect things larger than about 200 metres across. Most of the effort, though, is being focussed on objects larger than one kilometre."

Toutatis posed little risk. The peculiar-shaped asteroid - described by one astronomer as looking like a "cosmic yam" - whizzed past at roughly four times the distance between the Earth and the Moon, precisely as astronomers had expected.

"Toutatis isn't any risk to the Earth," said Dr Yates. "It has an extremely well-known orbit, and has been observed with radio telescopes, which gives a pretty accurate prediction of where it's going."

Named after an obscure Celtic and Gallic god - whose name was then picked by the writers of the Asterix cartoon as an expletive - the asteroid measures 4.6 kilometres (2.9 miles) by 2.29 kilometres by 1.92 kilometres.

Its next close approach to the Earth will not come before 2100. The next close approach to the Earth by an identified near-Earth object will be on 26 January 2015 - when an object called 2004 BL86, discovered only this year, will pass just 800,000 miles from the Earth.