Researchers hypothesize that the asteroid that gave the world over to mammals and birds hit Earth at a 60 degree angle, kicking up far more atmospheric dirt than a direct hit. The resulting climate change would be deadly for massive fauna and the ecosystems that depended on themas the fossil record shows.

Analysing the structure of the 200-kilometre-wide (125 mile) crater in southern Mexico where the asteroid hit, scientists ran a series of simulations. Lead author Gareth Collins of Imperial College London and colleagues at the University of Freiburg and the University of Texas at Austin looked at four possible impact angles - 90, 60, 45 and 30 degrees - and two impact speeds, 12 and 20 kilometres per second (7.5 and 12.4 miles per second). The best fit with the data from the crater was a 60 degree strike.

"Sixty degrees is a more lethal impact angle because it ejects a larger amount of material fast enough to engulf the planet," Collins told AFP.

Adds Collins: "a very bad day for the dinosaurs". Read the rest

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