New information provided by a worldwide network of sensors has allowedscientists...

http://www.nasa.gov/mission_pages/as...d20130215.html


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.