Asteroid wiped out dinosaurs: Scientists

A panel of 41 international experts, including researchers from Cambridge, Imperial College London, University College London and the Open University, reviewed 20 years' of research to determine the cause of the Cretaceous-Tertiary (KT) extinction, which happened around 65 million years ago. The review, published in this week's Science, shows the extinction was caused by a massive asteroid around 15 kilometres wide slamming into Earth at Chicxulub, Mexico.

The asteroid is believed to have hit Earth with a force one billion times more powerful than the atomic bomb at Hiroshima. It would have blasted material at high velocity into the atmosphere, triggering a chain of events that caused a global winter, wiping out much of life on Earth in a matter of days, the panel said.

Scientific opinion was split over whether the extinction was caused by an asteroid or by volcanic activity in the Deccan Traps in what is now India, where there were a series of super volcanic eruptions that lasted around 1.5 million years.

In 2005, scientists from the Department of Earth Sciences at the University of Cambridge spent two months on board the US research vessel R/V Ewing collecting seismic data off the coast of Mexico. Their data, part of the evidence reviewed in the new Science paper, revealed the structures preserved in the interior of the crater.

This allowed them to use computer models to predict how much rock was vapourised or ejected by the impact. Dr Penny Barton, who led the seismic survey and co-authored the review, said: "Our work lets us visualise the astonishing events of the few minutes after impact. The front of the asteroid hit the Earth while the far side was still out in the upper atmosphere, punching a hole though the Earth's atmosphere.

"As the asteroid vapourised explosively, it created a crater 30 km deep and 100 km across, with sides as high as the Himalayas. However within only two minutes the sides collapsed inwards and the deepest parts of the crater rebounded upwards to leave a wide, shallow hollow. "These terrifying events led to darkness and a global winter, resulting in the extinction of more than 70 per cent of known species.

"The tiny shrew-like mammals which were around at that time proved better adapted to survival than the cumbersome dinosaurs, and the removal of these dominant animals paved the way for the radiation of the mammals and eventual emergence of humans on Earth."

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