Wednesday, February 20, 2013

Update: Russian Meteor Was Even Bigger, Rarer Than First Estimated

Reports are still coming in about the brilliant meteor (technically known as a bolide) that slammed into the atmosphere over Russia, causing injuries that sent hundreds of people to the hospital. In any breaking story like this, not all of the information is reliable and details keep getting updated as more facts come in. Here’s the latest.
Debris area of the meteor that struck the atmosphere over Chelyabinsk, Russia, at 3:20 UTC on February 15. (Credit: Google Earth, NASA/JPL-Caltech)
* No, it was not related to asteroid 2012 DA, which streaked close past the Earth earlier today. As strange as it sounds, the Russian event seems to have been coincidental. The observed path of the Russian bolide was totally different than the path of 2012 DA.
* The original mass of the rock that hit over Russia may be much larger than originally estimated. Calculations by astronomer Margaret Campbell-Brown at the University of Western Ontario in London, reported in the journal Nature, put its mass at 7,000 metric tons. At a density of 3 grams per cubic centimeter (typical of a stony meteorite), that means the parent body was about 15 meters (50 feet) wide. The total blast energy may have been the equivalent of 300 kilotons of TNT. These numbers are still rough estimates. Early reports pegged it as being much smaller, probably because the vast majority of the meteor disintegrated in the atmosphere.
* Most of the injuries and damage seem to have been caused by shock waves–sonic booms–from the meteor streaking through and breaking up in the atmosphere. Bits of it hit the ground, but they did not cause significant destruction, based on early reports. The bulk of the injuries seem to have come from shattered glass from broken windows.
* Just as scientists kept revising their estimate of the mass of the meteor, so they kept changing their estimates of how often objects of similar size strike our planet. Early news stories stated that similar bolides occur a few times a year. Others stated once every decade. Now Nature is reporting that this was the largest meteor strike since the Tunguska event of 1908.
* At present, we have no way to detect meteors this size before they reach the Earth. But Deep Space Industries, one of the private companies angling to build a fleet that could monitor asteroids and ultimately mine them for resources, is eager to change that. Planetary Resources, a competing company, has made a similar pitch. And you can help collect statistics by keeping a watch on meteor events from the ground (the American Meteor Society offers some tips).

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