Chelyabinsk-class impacts more frequent that previously thought
Posted: Thu, Nov 7, 2013, 7:26 AM ET (1226 GMT)
Meteors like the one that exploded above the Russian city of Chelyabinsk earlier this year may be more frequent that previously thought, raising the impact risk to society. The Chelyabinsk event involved an asteroid nearly 20 meters in diameter that broke up in the upper atmosphere, releasing energy the equivalent of about 500 kilotons of TNT. The explosion shattered windows in the city and injured more than one thousand people, but killed no one. Scientists reporting in the journal Nature this week said that an analysis of 20 years of data collected by "infrasound" sensors monitoring pressure waves in the atmosphere detected far more meteors than previously thought. Those other events had gone unnoticed because they took place because they occurred over remote locations. A Chelyabinsk-class event, previously thought to take place only every 120-150 years on average, may instead take place as often as every 30 years.
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