Airburst Explained- NASA Addresses the Russian Meteor Explosion

A small asteroid entered Earth’s atmosphere early Friday, February 15, 2013 over Chelyabinsk, Russia at about 9:20 am local Russian time. Initial estimates, according to Bill Cooke, lead for the Meteoroid Environments Office at NASA’s Marshall Space Flight Center, is that the asteroid was about 15 meters (50 feet) in diameter, with a weight of 7,000 metric tons. It hit the atmosphere at a shallow angle of about 20 degrees, at a speed of about 65,000 km/h (40,000 mph).

It traveled through the atmosphere for about 30 seconds before breaking apart and producing violent airburst ‘explosion’ about 20-14 km (12-15 miles) above Earth’s surface, producing an energy shockwave equivalent to a 300 kilotons explosion. That energy propagated down through the atmosphere, stuck the city below – the Chelyabinsk region has a population of about 1 million — and windows were broken, walls collapsed and there were other reports of minor damage throughout the city.
The official 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).
Cooke said that at this time, the known damage is not due to fragments of the bolide striking the ground but only from the airburst. “There are undoubtedly fragments on the ground, but at the current time no pieces have been recovered that we can verify with any certainty,” Cooke said during a media teleconference today.