Big Asteroid Passes
Earth In Close Call


Digital Illustration by Kenb - ©2002

PARIS (AFP) - An asteroid big enough to wipe out a major country gave the Earth a close shave Monday, passing less than twice the distance of the Moon from our planet, astronomers reported.
The space rock, designated 2001 YB5, measures between 220 and 490 metres (715-1,592 feet) and at its closest point, at 0737 GMT, hurtled past about 600,000 kilometers (375,000 miles) from the Earth, according to varying estimates on US and European specialist websites.
2001 YB5 was spotted in early December by a Near-Earth Asteroid Tracking (NEAT) survey telescope on Mount Palomar in California, NASA said on its Near-Earth Object (NEO) Programme website.
Although there had been no danger of collision from the asteroid, experts said the distance was a whisker in cosmic terms.
"Such an object could literally wipe out a medium-sized country if it impacted and lead to a global economic meltdown, unless we were extremely fortunate and it hit somewhere remote," Benny Peiser, an asteroid expert at Liverpool John Moores University, told AFP by phone.
Only one other identified asteroid, a rock called 1999 AN10, will come closer, making a flyby on August 7 2027 at about 389,000 kms (243,000 miles), about the distance from the Earth to the Moon.
An object 220-490 metres (715-1,592 ft) across would release energy equivalent to hundreds of atomic bombs if it wacked into the Earth.
A large object, believed to be up to 10 kilometers (six miles) long, smashed into Mexico's Yucatan peninsula 65 million years ago.
Scientists believe the object, either a comet or an asteroid, triggered a firestorm and then a dust cloud that obscured sunlight. It inflicted lasting climate change that destroyed vegetation and ended the long reign of the dinosaurs.
In 1908, an asteroid or comet about 60 metres (200 feet) long exploded over Siberia with the force of 600 times the Hiroshima bomb, reducing a 40-km (25-mile) wide patch of forest to matchwood.
2001 YB5 has been categorised by NEAT as a "potentially hazardous" asteroid.
Although it poses no danger at all to the Earth at the moment, that could theoretically change in the future if its orbit around the Sun is deflected by the gravitational pull of a nearby planet.
Its trajectory crosses the orbits of Mars, Earth, Venus, and Mercury, NEAT said.
Astronomers are becoming increasingly vocal about the risks of asteroid collision, saying Earth has simply had a long run of good luck in escaping big cosmic debris for so long.
NASA's main focus is on identifying asteroids between one km and 10 kms (0.6 to six miles) across.
The number of these bruisers was once put at 1,000-2,000, which translates into a roughly one-percent chance that one of them will smash into the Earth in the next thousand years. In January 2001, that estimate was downgraded to 700, plus or minus 230.
Even so, that leaves the vast majority of space objects, which are under one km (0.6 miles), still to be detected.
Noting the belated discovery of 2001 YB5, Peiser said, "had we discovered that the thing were on a collision course, there is nothing that we could have done... nothing has been done on planetary defence."
David Jewitt, an astronomer at the University of Hawaii at Honolulu, has estimated there is a one-percent statistical chance that the Earth will be struck by a 300-metre (715-feet) asteroid sometime this century.
"Such an impact would deliver a withering 1,000-megatonne explosion and cause perhaps 100,000 deaths," according to his assessment, adding that in a densely-populated area, such as the US eastern seaboard or Western Europe, the fatalities could rise into "tens of millions."
On January 1, the British government announced it was setting up a centre in Leicester, central England, to pool information about potentially hazardous asteroids.
It will also launch a pilot study to track asteroids using a telescope on the Canary Islands, in the central-eastern Atlantic.
New European Centers To Monitor Asteroid Threat

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