Meteor dwarfs atom bomb

Tests on the meteor fragments (below) after the explosion in the skies over the Siberian city of Chelyabinsk (above) in February show the rock was about the same age as the Earth. Photo / AP

The meteor that exploded over the Siberian city of Chelyabinsk in February released more than 30 times the explosive energy of the Hiroshima bomb, a study has found.
Scientists calculated that the blast caused by the disintegration of the space rock as it ploughed through the atmosphere at 19km a second was equivalent to between 500,000 and 600,000 tonnes of TNT - compared with the 16,000-tonne explosion at Hiroshima in 1945.
People directly under the meteor's flight were knocked over and many others suffered sunburn or eye damage as they looked at the intense fireball.
It was the biggest meteor blast since the devastating explosion over Tunguska, also in Siberia, in 1908, which flattened forests for hundreds of kilometres around and was reckoned to have released energy equivalent to between five million and 15 million tonnes of TNT.
The Chelyabinsk meteorite - the part of the meteor that fell to Earth - belongs to the most common class of space rock, known as ordinary chondrites. It is these that are most likely to cause a meteorite catastrophe, says Professor Qing-Zhu Yin of 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. Chelyabinsk serves as a unique calibration point for high-energy meteorite impact events for our future studies," Yin said.
Two independent studies, published in the journals Nature and Science, agree closely on the strength of the explosive force as the meteor disintegrated south of Chelyabinsk, punching an 8m-wide hole in the frozen surface of a lake.
Calculations suggest the meteor broke into smaller pieces at altitudes of 45km and then 30km, preventing more serious injuries and damage on the ground. Even so, windows were shattered for kilometres around, the scientists said.
"Our goal was to understand all circumstances that resulted in the damaging shockwave," said Peter Jenniskens, of Nasa, one of dozens of researchers who took part in the studies.
Olga Popova of the Russian Academy of Sciences in Moscow, who led one of the studies, said: "Our [meteor] entry modelling showed that the impact was caused by a 20-metre chunk of rock that fragmented at 30km." At that point the space rock glowed brighter than the sun.
Tests showed the meteor was about 4567 million years old - about the same age as the Earth.
- Independent