|Chelyabinsk meteor exploded with the energy of 500 kilotonnes of TNT|
|Thursday, 07 November 2013 17:33|
Scientists have published the most complete picture yet of the devastation caused by the meteor that exploded over the city of Chelyabinsk in Russia this year.
The 20-metre-wide space rock hurtled into the skies over the city in February and began to tear apart at an altitude of 28 miles. Travelling at a speed of 12 miles per second, the rock exploded with the energy of around 500 kilotonnes of TNT, researchers found.
Directly beneath the meteor's path, the shockwave was powerful enough to knock people off their feet. Windows were shattered in more than 3,600 apartment blocks, and a factory roof collapsed.
In the local library in Yemanzhelinsk, 30 miles away, a statue of Pushkin cracked when it was struck by a blown-out window frame. At least 1,210 people were treated for injuries, most from falling building debris and flying glass.
At its most intense, the streaking fireball glowed 30 times brighter than the sun, leaving people on the ground below with skin and retinal burns. One resident in Korkino, 18 miles from the point of peak brightness, lost skin from their face after being burned by radiation. The intense heat evaporated three quarters of the meteor. Around four to six tonnes reached the ground as meteorites, representing just 0.05% of the original rock.
The Chelyabinsk airburst was the largest since Tunguska in 1908, but unlike that and other historic events, the strike was recorded by a full suite of modern technology: satellites photographed the meteor from space; security and personal video cameras filmed the rock's violent path across the sky; and sensors picked up infrasound waves as lumps hit the ground.
The largest single piece, weighing around 650kg, punched a 7 metre-wide hole in ice 70cm thick on Lake Chebarkul, and was recovered from the lakebed in October.
An international team of researchers, led by Olga Popova at the Russian Academy of Sciences, visited Chelyabinsk and 50 nearby villages in the weeks after the event to map the extent of the destruction. The shockwave left a trail of damage 55 miles on either side of the rock's trajectory, according to a report in the journal, Science.
"Our goal was to understand all circumstances that resulted in the damaging shockwave that sent over 1,200 people to hospitals in the Chelyabinsk Oblast area that day," said Peter Jenniskens at Nasa's Ames Research Centre in California.
The unforeseen arrival of the meteor and the violence of its impact were a wake-up call, according to Qing-Zhu Yin, an author on the study at the University of California, Davis. "If humanity does not want to go the way of the dinosaurs, we need to study an event like this in detail," he said.
Further details of the Chelyabinsk strike appear in two reports in the journal Nature. The first, led by Jirí Borovicka at the Academy of Sciences of the Czech Republic, traces the orbit of the meteor back to another object, known as asteroid 86039. This asteroid has also orbited close to Earth and was probably once part of the same rock as the Chelyabinsk meteor.
The second Nature study, led by Peter Brown at the University of Western Ontario, calculated the energy of the Chelyabinsk airbust at 400 to 600 kilotonnes of TNT, but found that scientists' models for estimating damage from airbursts were off the mark. The glitch in the models means that the number of space rocks with sizes of the order of tens of metres, which pose a threat, may be ten times greater than previously thought.
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