Sunday, November 1, 2009

An asteroid has hurled through space unnoticed by scientists and smashed into the earth's atmosphere with three times the energy of the Hiroshima nuclear bomb.

The space rock, estimated by NASA to be just 5-10m wide, detonated about 20km above the earth on October 8 over South Sulawesi, a rugged mountain province in western Indonesia, New Scientist magazine reports.

Locals in the town of Bone in the north of the province said they saw a fireball and heard a huge explosion while amateur video footage shows a trail of smoke typical of an exploding asteroid.

NASA estimated the force from the explosion was equivalent to 50,000 tons of TNT, making it one of the largest ever recorded asteroid explosions.

Dr Nick Lomb, curator of astronomy at Sydney Observatory, told ninemsn the asteroid went unnoticed because it was so small but that chunks of the rock may still have made it to the ground.

"It's very hard to find small asteroids — the main emphasis is to find big one which are 1km or more in diameter because they're the ones that cause global catastrophe," Dr Lomb said.

"But bits of this rock could have survived and somebody might be able to actually search for it ... it is extremely useful scientifically."

Dr Lomb said the asteroid exploded at such a high altitude because of the huge amounts of heated air piling in front of it.

If the asteroid exploded a few kilometres closer to earth, "you would be very unlucky to be in the blast area," he said.

Dr Lomb said the rock could have easily slipped by even if it was 100m-wide because the southern hemisphere is not closely watched for asteroids.

"Asteroids 100m-wide asteroids could destroy a city and if it's coming from the southern part of the sky, there's a good chance it would come in undiscovered," he said.

"There's only one small [asteroid watch] project at Coonabarabran in NSW which receives only a little bit of funding from NASA ... it's a single handed effort."

The report from NASA on the October 8 explosion said a "fireball event of this magnitude" occurs about once every two to 12 years.


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