From The Drudge Report:
<font face="Verdana, Arial" size="2">An asteroid big enough to wipe out a major country gave the Earth a close shave yesterday, 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 and at its closest point, at 6:37pm, Sydney time, was about 600,000km 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) Program website.
Although there was no danger of collision from the asteroid, experts said the distance was a whisker in cosmic terms.
"Such an object would literally wipe out a medium-sized country 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.
An object 220-490 metres across would release energy equivalent to hundreds of atomic bombs if it hit the Earth.
A large object, believed to be up to 10km long, smashed into Mexico's Yucatan peninsula 65 million years ago, triggering a firestorm and a dust cloud that wiped out the dinosaurs, scientists believe.
In 1908, an asteroid or comet about 60 metres long exploded over Siberia with the force of 600 times the Hiroshima bomb, reducing a 40km 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.</font>