February 16, 2013

Fire in the sky

By SERGEI L. LOIKO AND MONTE MORIN Los Angeles Times

(Continued from page 1)

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The meteorite leaves a contrail over Chelyabinsk, Russia, on Friday before it exploded. Dozens of witnesses posted photos and videos of the event on the Internet, providing much data for scientists.

The Associated Press

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A hole in the ice of Chebarkul Lake indicates where the space rock may have struck Earth.

The Associated Press

Additional Photos Below

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Q&A ON METEORS

Q. What's the difference between a meteor and a meteorite?

A. Meteors are pieces of space rock, usually from larger comets or asteroids, which enter the Earth's atmosphere. Many are burned up by friction and the heat of the atmosphere, but those that survive and strike the Earth are called meteorites. They often hit the ground at tremendous speed -- up to 18,650 mph -- releasing a huge amount of energy.

Q: How often do meteorites hit Earth?

A: Experts say smaller strikes happen five to 10 times a year. Large meteors such as the one in Russia on Friday are rarer, but still occur about every five years, scientists say.

Q: How big was Friday's meteor and why did it cause so many injuries?

A: Before it entered the atmosphere, the meteor was about 49 feet in diameter, NASA says. The space agency also says the fireball from it, which was brighter than the sun, is the biggest reported in more than a century, since a 1908 event in Siberia. The blast released the equivalent of hundreds of thousands of tons of TNT. The huge release of energy shattered windows and sent loose objects flying. The blast produced 20 times or more the explosive force of the U.S. bomb dropped over Hiroshima during World War II. But the bomb detonated just 2,000 feet above a densely populated city, while the Russian fireball exploded miles in the air, reducing the potential damage.

Q: Is there any link between this meteor and the larger asteroid that passed Earth later on Friday?

A: No, it's just cosmic coincidence. According to NASA, the trajectory of the Russian meteorite was significantly different from that of asteroid 2012 DA14.

– The Associated Press

Mikhail Yurevich, the regional governor of Chelyabinsk, estimated that the material damage had exceeded $33 million, Interfax reported.

Tatiana Borisevich, the science secretary of the Pulkovo Observatory in St. Petersburg, called the explosion over Chelyabinsk a unique study case for scientists. The last time scientists observed a similar-size object was in 2009 when one crashed in South Sudan. No remnants of it were ever retrieved, she said.

"Of course, we are sorry that so many people suffered from the explosion (Friday), but as scientists we are excited because now we have this unique study case using many existing videos of the incident to calculate its orbit to answer some questions we couldn't answer before," Borisevich said. "We also hope that now some parts of it can be found to determine its composition, whether it was stone, metal or ice."

Although as a rule big asteroids in space can be detected in advance, smaller objects can often enter Earth's atmosphere with little warning, Borisevich added.

The smaller asteroid was traveling in a very different trajectory and much faster than 2012 DA14, indicating they were not related, according to Paul Chodas, research scientist in the Near-Earth Object Program office at NASA's Jet Propulsion Laboratory in La Canada Flintridge, Calif.

"I would call this a tiny asteroid," Chodas said. "This is the largest recorded event since the Tunguska explosion in 1908."

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Additional Photos

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Municipal workers in Chelyabinsk, Russia, repair a damaged electric power circuit outside a zinc factory building where the roof collapsed after a meteorite exploded over the region Friday. The region’s governor estimated damages at more than $33 million.

The Associated Press

injured man
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A man identifying himself only as Viktor has his face bandaged at a hospital in Chelyabinsk, Russia, where he sought treatment of injuries sustained after a meteorite exploded over the Ural Mountains on Friday, creating a shock wave that blew out windows and caused other damage. No one was killed.

Andrei Kuzmin/Reuters

 


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