A meteor that exploded in the skies above Russia's Ural Mountains was the largest since the Tunguska blast in Siberia in 1908 and released about 33 times the energy of the atomic bomb that destroyed Hiroshima.
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The meteor, which hit 16 hours before an asteroid half the length of a football field hurtled past Earth, has prompted calls to be more vigilant about the risks of strikes from space. Every day, 100 tons of dust and sand-size particles enter the Earth's atmosphere, most of which burns up.
"We would expect an event of this magnitude to occur once every 100 years on average," Paul Chodas of NASA's Near-Earth Object Program Office said in the statement about Friday's explosion. The Chelyabinsk meteor released 500 kilotons of energy when it disintegrated above the city of Chelyabinsk at about 9:20 a.m. local time, according to NASA.
Unrelated to asteroid 2012 DA14, which flew past by Earth safely, the Chelyabinsk meteor hit the atmosphere at a speed of 18 kilometers per second (40,000 miles per hour) and broke apart 15 kilometers to 25 kilometers above the Russian city, according to NASA.
The shock wave from the meteor blew out in 3,700 buildings windows in and around Chelyabinsk, the regional government said in a statement. About 1,150 people sought medical attention, of whom more than 50 were hospitalized, the Health Ministry said.
Burning streaks lit up the sky in videos that were caught by drivers on dashboard cameras, broadcast on Russian television and posted on YouTube. The force destroyed a warehouse wall at the OAO Chelyabinsk Zinc Plant and disrupted service by Russia's second-biggest mobile operator, OAO MegaFon.
A piece of the meteor probably hit a frozen lake about 80 kilometers (50 miles) west of Chelyabinsk, Vadim Kolesnik, an Interior Ministry official, said Friday by phone. A hole 8 meters in diameter was found in the ice, national television channel Rossiya 24 reported. There are two other possible impact sites, he said.
Divers exploring the lake haven't found any pieces of meteorite, Rossiya 24 reported Saturday.
The Tunguska event, which was the most powerful natural explosion in the modern era, leveled about 800 square miles (2,100 square kilometers) of forest in Siberia, while leaving no crater, according to NASA. The asteroid that scientists say plowed into Earth about 66 million years ago, wiping out the dinosaurs, may have been about 6 miles in diameter.
A United Nations team met in Vienna this week to come up with recommendations on how best to track, and someday deflect or destroy, orbiting space rocks.