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Russian meteor blast had force of 300-kiloton nuclear warhead (+video)

Using sensors designed to detect rogue nuclear tests, scientists have learned more about the meteor that exploded over Russia. It was much bigger than they first thought. 

By Staff writer / February 15, 2013

A meteor streaks through the sky over Chelyabinsk, Russia, Friday.

AP

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The meteor that exploded over the Ural Mountains in Russia Friday now appears to have been a small asteroid clearly unrelated to 2012 DA14, which flitted past Earth Friday afternoon.

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A 10-ton meteor exploded over Russia, shattering windows and injuring hundreds.

Initially, the Russian Academy of Science estimated the object's mass at about 10 metric tons (11 US tons). With more data in hand, researchers now say the object had a mass of 7,000 metric tons (7,700 US tons) and a diameter of about 50 feet.

The blast released energy comparable to a 300- to 500-kiloton nuclear warhead, says Bill Cooke, who heads the meteoroid environment office at NASA's Marshall Space Flight Center in Hunstville, Ala. By Comparison, the Nagasaki nuclear bomb had a yield of 20 to 22 kilotons.

The asteroid's breakup at an altitude some 12 to 15 miles above Russia's Chelyabinsk region represents the largest recorded asteroid encounter since 1908, when another asteroid or comet exploded over the Tunguska River in Siberia, leveling some 820 square miles of forest, says Paul Chodas, a scientist with the near-Earth object program at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

The shock waves from what appear to have been multiple blasts, perhaps triggered as large initial fragments underwent their own disruption, broke windows in the three major cities in the region, including Chelyabinsk. At least 950 people were injured, although most of the injuries were minor, according to reports from the area.

"What an amazing day for near-Earth objects. By an incredible coincidence we have two rare events happening on the very same day," Dr. Chodas said during a briefing Friday afternoon.

Asteroid 2012 DA14 set a record for the closest approach to Earth of an asteroid in its size class humans so far have detected. And the Chelyabinsk blast occurs on average once every hundred years, based on the revised size and mass estimate for the asteroid that triggered it.

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