A METEOR the size of San Francisco hurtles towards the Earth at 20 kilometres a second, smashes into the tropical lagoons of the Gulf of Mexico and gouges a hole 20 times as deep as the Grand Canyon. The mammoth crater quickly collapses and a tidal wave surges outwards. Fires sweep across North and South America and tonnes of debris are ejected into the atmosphere, blocking out the Sun and plunging the Earth into a frigid darkness that lasts for months.
This is the classic explanation for the event that wiped out the dinosaurs 65 million years ago, but is it true? Everyone agrees that the Earth suffered a large impact towards the end of the Cretaceous. Yet more than 20 years after a meteor was proposed as the cause of the Cretaceous-Tertiary (K/T) mass extinction, scientists are still arguing over what really killed the dinosaurs.
On one side are ...
20:00 03 July 2008
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