MOSCOW — With a blinding flash and a booming shock wave, a meteor blazed across the Siberian sky Friday and exploded with the force of 20 atomic bombs, injuring more than 1,000 people as it blasted out windows and spread panic in a city of 1 million.
NASA estimated that the meteor was about the size of a bus and weighed an estimated 7,000 tons before it hit the atmosphere, but the fireball it produced was dramatic.
Video shot by residents of the city of Chelyabinsk showed its streaming contrails as it arced toward the horizon just after sunrise, looking like something from a world-ending science-fiction movie.
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.
The meteor above western Siberia entered Earth's atmosphere at about 9:20 a.m. local time at a hypersonic speed of at least 33,000 mph and shattered into pieces about 18 to 32 miles above Earth's surface, the Russian Academy of Sciences said.
NASA estimated its speed at about 40,000 mph and said it exploded about 12 to 15 miles up, 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, and we heard a really loud, thundering sound."
The shock wave blew in more than 1 million square feet of glass, according to city officials, who said 3,000 buildings in Chelyabinsk were damaged. At a zinc factory, part of the roof collapsed.
The Interior Ministry said about 1,100 people sought medical care after the shock wave and 48 were hospitalized. Most of the injuries were caused by flying glass, officials said.
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 might have shattered windows, but "the atmosphere absorbed the vast majority of that energy," she said.
There was no word on any deaths or anyone struck by meteorite fragments.
President Vladimir 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.
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.
Meteors typically cause sizable sonic booms when they enter the atmosphere because they are traveling so much faster than the speed of sound. Injuries on the scale reported Friday, however, are extraordinarily rare.
"I went to see what that flash in the sky was about," said resident Marat Lobkovsky. "And then the window glass shattered, bouncing back on me. My beard was cut open, but not deep. They patched me up. It's OK now."
Q&A on Meteors
Q: How often do meteors hit Earth?
A: Experts say smaller strikes happen five to 10 times a year. Large meteors such as the one Friday in Russia are rarer but still occur about every five years, according to Addi Bischoff, a mineralogist at the University of Muenster in Germany. Most of them fall over uninhabited areas.
Q: When was the last event like this?
A: In 2008, astronomers spotted a meteor similar to the one in Russia heading toward Earth about 20 hours before it entered the atmosphere. It exploded over Sudan, causing no known injuries. The largest known meteor in recent times caused the "Tunguska event" — flattening thousands of square miles of forest in Siberia in 1908. Nobody was injured by the meteor blast, or by the Sikhote-Alin meteorite that fell in eastern Siberia in 1947. Scientists think that a far larger meteor strike on what today is Mexico's Yucatan Peninsula might have been responsible for the extinction of the dinosaurs about 66 million years ago.
Q: What can scientists learn from Friday's strike?
A: Bischoff says scientists and treasure hunters are already racing to find pieces of the space rock. Some meteorites can be valuable, selling for up to $670 per gram. Because meteors have remained largely unchanged for billions of years — unlike rocks on Earth affected by erosion and volcanic outbreaks — scientists will study the fragments to learn more about the early universe.
Q&A Earth-striking meteors