Impact statement

摘要

For the inhabitants of the Russian city of Chelyabinsk, the events of 15 February 2013 will never be forgotten. Just after 9.00am, as commuters made their way to work along snow-covered roads and schoolchildren settled down for their lessons, a 20m-diameter meteorite - travelling at an estimated 12 miles per second - exploded above the city with a force equivalent to 30 Hiroshima bombs. Amazingly, no one was killed. But the resulting Shockwave and shower of cosmic debris wreaked havoc over a wide area, damaging thousands of buildings, putting around 1,600 people in hospital, and drawing international attention to a risk that astronomers, scientists and Hollywood film-makers had been nervously contemplating for decades.