MOSCOW - With a blinding flash and a booming shock wave, a meteor blazed across the western 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.
While NASA estimated the meteor was only about the size of a bus and weighed an estimated 7,000 tons, the fireball it produced was dramatic. Video shot by startled residents 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 event 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 atmosphere about 9:20 a.m. local time (8:20 p.m. Tucson time Thursday) at a hypersonic speed of at least 33,000 mph and shattered about 18 to 32 miles high, the Russian Academy of Sciences said.
NASA estimated its speed at 40,000 mph, 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, and we heard a really loud, thundering sound," he told The Associated Press by telephone.
The shock wave blew in an estimated 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 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 meteor 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.
Some fragments fell in a reservoir outside the town of Chebarkul, the regional Interior Ministry office said. The crash left a 26-foot hole 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.
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," recalled 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."
Another resident, Valya Kazakov, said some elderly women in his neighborhood started crying out that the world was ending.
NASA said the Russian fireball was the largest reported since 1908, when a meteorite hit Tunguska, Siberia, and flattened an estimated 80 million trees. Chelyabinsk is about 3,000 miles west of Tunguska. The Tunguska blast, attributed to a comet or asteroid fragment, is generally estimated to have been equal to about 10 megatons.
Scientists believe that a far larger meteorite strike on what today is Mexico's Yucatan Peninsula may have been responsible for the extinction of the dinosaurs about 65 million years ago. According to that theory, the impact would have thrown up vast amounts of dust that blanketed the sky for decades and altered the climate.
Meanwhile, the 150-foot space rock that safely hurtled past Earth at 12:25 p.m. Tucson 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 of the world. But in Australia, astronomers used binoculars and telescopes to watch the point of light speed across the clear night sky.
Jim Green, NASA's director of planetary science, called the back-to-back celestial events an amazing display.
"This is indeed very rare, and it is historic," he said on NASA TV. "These fireballs happen about once a day or so, but we just don't see them because many of them fall over the ocean or in remote areas."
The U.S. bomb dropped over Hiroshima during World War II had an explosive force of about 15,000 tons of TNT, but it detonated just 2,000 feet above a densely populated city. The Russian fireball exploded miles above a sparsely populated area, causing less damage.
On StarNet: To see NASA video of an asteroid's flyby and video from Russia of the meteor streaking across the sky, go to azstarnet.com/video