Exploding Russian Meteor: An Asteroid Fragment?

The meteor which exploded over the Urals of Russia on 15 February 2013 entered the Earth's atmosphere within hours of the closest approach ever recorded of an asteroid to the Earth, named 2012 DA14.

The above video of the event is quite spectacular, with a number of dash cams in and around Chelyabinsk, Russia capturing the meteor's trail. The meteor was initially estimated by the Russian Academy of Sciences to weigh about 10 tons, which caused buildings to be damaged from the shock wave, and hundreds of injuries from flying glass. (As we shall see, 10 tons was a gross underestimate).

The video suggests that the meteor became brighter than the sun as atmospheric friction super-heated the fast-travelling space rock.

The following statement as made on JPL's Asteroid Watch website late on 15 February 2013:

February 15, 2013
Update: February 15, 2013 7pm PST

New information provided by a worldwide network of sensors has allowed scientists to refine their estimates for the size of the object that entered that atmosphere and disintegrated in the skies over Chelyabinsk, Russia, at 7:20:26 p.m. PST, or 10:20:26 p.m. EST on Feb. 14 (3:20:26 UTC on Feb. 15).

The estimated size of the object, prior to entering Earth's atmosphere, has been revised upward from 49 feet (15 meters) to 55 feet (17 meters), and its estimated mass has increased from 7,000 to 10,000 tons. Also, the estimate for energy released during the event has increased by 30 kilotons to nearly 500 kilotons of energy released.

These new estimates were generated using new data that had been collected by five additional infrasound stations located around the world - the first recording of the event being in Alaska, over 6,500 kilometers away from Chelyabinsk. The infrasound data indicates that the event, from atmospheric entry to the meteor's airborne disintegration took 32.5 seconds. The calculations using the infrasound data were performed by Peter Brown at the University of Western Ontario, Canada.

"We would expect an event of this magnitude to occur once every 100 years on average," said Paul Chodas of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. "When you have a fireball of this size we would expect a large number of meteorites to reach the surface and in this case there were probably some large ones."

The trajectory of the Russia meteor was significantly different than the trajectory of the asteroid 2012 DA14, which hours later made its flyby of Earth, making it a completely unrelated object. The Russia meteor is the largest reported since 1908, when a meteor hit Tunguska, Siberia.

This event will likely lead to renewed calls for government programs to deal with the potential threat of an asteroid collision with the Earth, a threat which space experts have been saying is very real. It's only a matter of time before an asteroid large enough to cause substantial damage will reach the Earth.
Interesting facts:
The 1908 Tunguska Event: On June 30 1908, what is believed to be an exploding meteor leveled over 800 sq. miles of forest in rural Russia. The size of the meteor or cometary fragment has been estimated to be around 100 m (320 ft) in diameter, which is somewhat larger than the 2012 DA14 asteroid (50 m, or 160 ft.) which made its closest approach to Earth on 15 February 2013, and larger still than the Feb. 15 2013 exploding Russian meteor, which is now estimated to have been 17 m (55 ft.) in diameter. Note that the total mass of the meteor, and so its potential energy (if travving at the same speed), goes up as the 3rd power of its diameter, so the asteroid passing by the Earth on Feb. 15 had about 25 times the mass of the exploding Russian meteor.
(page last updated 2/18/2013)
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