A meteor that exploded over Russia in February was "a wake-up call" for humanity, according to scientists who have been studying the event.
Researchers believe they have discovered new details about the meteorite, which was the largest object to hit the Earth since the Tunguska event of 1908, when an exploding asteroid destroyed 2,000 square kilometres of Siberian forest.
After studying the remains of the meteorite and examining the damaged caused by the shock wave which came from the rock scientists now believe it was bigger than first estimated and also moved faster than thought.
The rock was 20 metres in diameter
Caused a blast equivalent to 600,000 tons of TNT
It blew apart 18.5 miles above the city of Chelyabinsk
Entering the Earth's atmosphere at just over 19 kilometres per second
Three quarters of the rock evaporated in the explosion
The largest single fragment, weighing about 650kg, was recovered from the bed of Lake Chebarkul
*1,200 *attended hospital after the impact
Scientists estimated the rock to have been more than 4 billion years old
Analysis showed that the rock was a common type known as a "chondrite" - the kind most likely to cause a major extinction event in the future.
Professor Qing-Zhu Yin, from the Department of Earth and Planetary Sciences at the University of California in the US said: "If humanity does not want to go the way of the dinosaurs, we need to study an event like this in detail."
Most of the massive rock evaporated on impact with the atmosphere. Some of what was left then became a glowing orange dust cloud and only a small fraction - still weighing 4,000 to 6,000kg - fell to the ground.
The researchers, whose findings are reported in the journal Science, found that shock waves from the airburst smashed windows, rattled buildings, and knocked people off their feet.
Researchers visiting villages in the area found a region of shock-wave damage extending some 50 miles on either side of the meteor's trajectory path.
Major impact events such as Tunguska or Chelyabinsk occur more frequently than is commonly thought, said Prof Yin. He pointed out that four tons of material was recovered from a meteor shower in Jilin, China, in 1970.
"Chelyabinsk serves as a unique calibration point for high-energy meteorite impact events for our future studies," Prof Yin added.