Russian meteor explosion as powerful as 600k tonnes of TNT

The giant meteorite that smashed into a remote region of Russia in February exploded with a power of about 600 thousand tonnes of TNT, appearing brighter than the Sun, NASA and international scientists have found.
The 20-metre Chelyabinsk meteoroid strike that injured around 1200 people was "a wake-up call," according to a University of California, Davis scientist.
"If humanity does not want to go the way of the dinosaurs, we need to study an event like this in detail," said researcher Qing-Zhu Yin, who participated in the study.
Chelyabinsk was the largest meteoroid strike since the Tunguska event of 1908, and modern technology provides an unprecedented opportunity to study such an event, researchers said.

The Chelyabinsk meteorite belongs to the most common type of meteorite, an "ordinary chondrite." If a catastrophic meteorite strike were to occur in the future, it would most likely be an object of this type, Yin said.
"Our goal was to understand all circumstances that resulted in the damaging shock wave that sent over 1200 people to hospitals in the Chelyabinsk Oblast area that day," said Jenniskens.

"The explosion was equivalent to about 600 thousand tonnes of TNT, 150 times bigger than the 2012 Sutter's Mill meteorite in California," said researchers.
Based on viewing angles from videos of the fireball, the team led by Olga Popova of the Russian Academy of Sciences, and by NASA Ames and SETI Institute meteor astronomer Peter Jenniskens, calculated that the meteoroid entered Earth's atmosphere at just over 19 kilometres per second, slightly faster than had previously been reported.

"Our meteoroid entry modelling showed that the impact was caused by a 20-metre sized single chunk of rock that efficiently fragmented at 30 km altitude," Popova said.
The meteor's brightness peaked at an altitude of 29.7 km as the object exploded. For nearby observers it briefly appeared brighter than the Sun and caused some severe sunburns.
The team estimated that about three-quarters of the meteoroid evaporated at that point. Most of the rest converted to dust and only a small fraction - 4,000 to 6,000 kilogrammes, or less than 0.05 per cent - fell to the ground as meteorites. The dust cloud was so hot it glowed orange.

The largest single piece, weighing about 650 kilogrammes, was recovered from the bed of Lake Chebarkul in October by a team from Ural Federal University.
Shockwaves from the air-burst broke windows, rattled buildings and even knocked people from their feet. Popova and Jenniskens visited over 50 villages in the area and found that the shockwave caused damage about 90 kilometres on either side of the trajectory.