AN asteroid the size of a house that exploded with the power of an atom bomb over Antarctica last year may help scientists prepare for the entrance of larger bodies into the Earth's atmosphere. The 1000-tonne asteroid crashed to Earth in millions of pieces last September, 900km from the nearest humans at Japan's Syowa station. A trail of dust recorded by a physicist 1500km away at Australia's Davis station shows that if the asteroid had not fragmented into tiny pieces when it hit the Earth's atmosphere, it would have had an impact similar to the bombing of Hiroshima. Dr Andrew...