The largest recorded meteor strike in more than a century occurred hours before a 150-foot asteroid passed within about 17,000 miles of Earth. The European Space Agency said its experts had determined there was no connection between the asteroid and the Russian meteor - just cosmic coincidence.
The meteor above western Siberia entered the Earth's atmosphere about 9:20 a.m. local time (10:20 p.m. EST Thursday) at a hypersonic speed of at least 33,000 m.p.h. and shattered into pieces about 18 to 32 miles high, the Russian Academy of Sciences said. NASA estimated its speed at 40,000 m.p.h., said it exploded about 12 to 15 miles high, released 300 to 500 kilotons of energy, and left a trail 300 miles long.
"There was panic. People had no idea what was happening," said Sergey Hametov of Chelyabinsk, about 930 miles east of Moscow in the Ural Mountains.
"We saw a big burst of light, then went outside to see what it was," he said, "and we heard a really loud, thundering sound."
The shock wave blew out more than one million square feet of glass, according to city officials, who said 3,000 buildings in Chelyabinsk were damaged.
The Interior Ministry said that about 1,100 people sought medical care after the shock wave and that 48 were hospitalized. Most of the injuries were caused by flying glass.
Scientists estimated the meteor unleashed a force 20 times more powerful than the Hiroshima bomb, although the space rock exploded at a much higher altitude. Amy Mainzer, a scientist at NASA's Jet Propulsion Laboratory, said the atmosphere acted as a shield.
The shock wave may have shattered windows, but "the atmosphere absorbed the vast majority of that energy," she said.
Emergency Situations Ministry spokesman Vladimir Purgin said many of the injured were cut as they flocked to windows to see what caused the intense flash of light, which momentarily was brighter than the sun.
There was no immediate word on any deaths or anyone struck by space fragments.
President Vladimir V. Putin summoned the nation's emergencies minister and ordered immediate repairs. "We need to think how to help the people and do it immediately," he said.
Some meteorite fragments fell in a reservoir outside the town of Chebarkul, the regional Interior Ministry office said. The crash left a 26-foot crater in the ice.
Lessons had just started at Chelyabinsk schools when the meteor exploded, and officials said 258 children were among those injured. Amateur video showed a teacher speaking to her class as a powerful shock wave hit the room.
The many broken windows exposed residents to the bitter cold as temperatures in the city were expected to plummet to minus 4 degrees Fahrenheit overnight. The regional governor put out a call for any workers who knew how to repair windows.
Vladimir Zhirinovsky, a nationalist leader noted for his vehement statements, blamed the Americans.
"It's not meteors falling. It's the test of a new weapon by the Americans," the RIA Novosti news agency quoted him as saying.
NASA said the Russian fireball was the largest reported since 1908, when a meteor hit Tunguska, Siberia, and flattened an estimated 80 million trees. Chelyabinsk is about 3,000 miles west of Tunguska.
The 150-foot space rock that safely hurtled past Earth at 2:25 p.m. Philadelphia time Friday was dubbed Asteroid 2012 DA14 and was discovered a year ago. It came closer than many communication and weather satellites that orbit 22,300 miles up.
The asteroid was invisible to astronomers in the United States at the time of its closest approach on the opposite side of the world. But in Australia, astronomers used telescopes to watch the point of light speed across the clear night sky.
Derrick Pitts, chief astronomer for the Franklin Institute, discusses the threat from space at www.philly.com/
Good news for homeowners: Your insurance probably covers a meteor strike. A10.