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From the WSJ (NASA JPL Statement follows):
The meteor that crashed to earth in Russia was about 55 feet in diameter, weighed around 10,000 tons and was made from a stony material, scientists said, making it the largest such object to hit the Earth in more than a century.
Large pieces of the meteor have yet to be found. However, a team from the Urals Federal University, which is based in Yekaterinburg, collected 53 fragments, the largest of which was 7 millimeters, according to Viktor Grokhovsky, a scientist at the university.
Data from a global network of sensors indicated that the disintegration of the Russia fireball unleashed nearly 500 kilotons of energy, more than 30 times the energy of the Hiroshima atomic bomb.
It is the largest reported meteor since the one that hit Tunguska, Siberia, in 1908, according to the U.S. National Aeronautics and Space Administration. The agency’s new gauge of the meteor’s size was a marked increase from its initial estimate.
Here is the NASA JPL statement:
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.
Preliminary information indicates that a meteor in Chelyabinsk, Russia, is not related to asteroid 2012 DA14, which is flying by Earth safely today.
The Russia meteor is the largest reported since 1908, when a meteor hit Tunguska, Siberia. The meteor entered the atmosphere at about 40,000 mph (18 kilometers per second). The impact time was 7:20:26 p.m. PST, or 10:20:26 p.m. EST on Feb. 14 (3:20:26 UTC on Feb. 15), and the energy released by the impact was in the hundreds of kilotons.
Based on the duration of the event, it was a very shallow entry. It was larger than the meteor over Indonesia on Oct. 8, 2009. Measurements are still coming in, and a more precise measure of the energy may be available later. The size of the object before hitting the atmosphere was about 49 feet (15 meters) and had a mass of about 7,000 tons.
The meteor, which was about one-third the diameter of asteroid 2012 DA14, was brighter than the sun. Its trail was visible for about 30 seconds, so it was a grazing impact through the atmosphere.
It is important to note that this estimate is preliminary, and may be revised as more data is obtained.
Jet Propulsion Laboratory, Pasadena, Calif.