Asteroid strikes more likely, says scientists

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Asteroid strikes more likely, says scientists
BY JOHN MINER,THE LONDON FREE PRESS
FIRST POSTED: WEDNESDAY, NOVEMBER 06, 2013 03:03 PM EST | UPDATED: WEDNESDAY, NOVEMBER 06, 2013 03:39 PM EST
LONDON, Ont. — The chances of asteroids exploding in Earth’s atmosphere, such as the detonation that damaged buildings in Russia earlier this year, are far greater than previously believed, Western University scientists reported Wednesday.
Instead of one hitting about once every 120 to 150 years, researchers are now calculating we can expect such damaging airbursts once every 30 to 40 years.
The research by Western University’s Centre for Planetary Science and Exploration Peter Brown, Margaret Campbell-Brown, Paul Wiegert and David Clark was published Wednesday in the journal Nature.
A 19-metre diameter asteroid that exploded over Chelyabinsk, Russia, on Feb. 15 and injured hundreds of people had an explosive force of about 500 kilotons of TNT. Its brightness was 30 times more than the sun.
While scientists have discovered and projected the orbit of almost all the one-kilometre and larger diameter asteroids, it isn’t practical to do the same for Chelyabinsk-sized ones, Brown said.
“There are millions of these things. There would be no practical way without expending a huge amount of money to catalogue and get orbits for all of them,” he said.
Instead, Brown suggests a ground-based detection system that would allow authorities to issue a warning.
“At the very least perhaps authorities could say at such and such a time don’t go over near your windows, there will be a blast wave that could cause damage and could cause injuries,” he said.
The good news is there is virtually no prospect of Earth being hit within the next 100 years by a far more devastating one-kilometre sized asteroid. That happens about once every 500,000 to one million years, said Brown.

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Asteroid strikes more likely, says scientists | Canada | News | Toronto Sun