Asteroid did kill the dinosaurs after all
"Science": Scientists confirm impact theory / Doubters proven wrong
Münster (upm), March 5th 2010
Did the dinosaurs die out because an asteroid hit the Earth 65 million years ago? Some researchers doubt this. However, a new study just published in the noted magazine “Science” backs the so-called impact theory. “Scientists from a wide variety of disciplines are coming to the conclusion that it was the impact that set off the mass extinction. Traces of this event have now been substantiated worldwide,” says Prof. Alexander Deutsch from the Institute of Planetology at Münster University. He contributed to the success of this international project by making geochemical analyses and examinations of terrain.
“30 years ago the hypothesis was put forward that the Earth was hit by an asteroid with a diameter of ten kilometres, travelling at about 20 kilometres per second,” explains Alexander Deutsch. This event was said to have abruptly ushered in the end of the dinosaur age, and the relevant crater has been known for the last 20 years – the 200-kilometer wide Chicxulub crater in Yucatán, Mexico. Despite the sound evidence, scientists have doubted the theory from the beginning, with the greatest opposition to the theory coming from scientists at the University of Princeton, USA, a few years ago. They published studies which were designed to show that the asteroid impacted as much as 300,000 years before the mass extinction began on the Cretaceous-Tertiary boundary. They postulated that a phase of unusually strong volcanic activity, lasting around one million years in what is today India, was the cause of the mass extinction.
In order to look more closely at the doubts relating to the impact theory, a group of over 40 scientists from Europe, the USA, Mexico, Canada and Japan, headed by geologist Dr. Peter Schulte from the University of Erlangen, has evaluated relevant studies and analysed new data. The researchers, who include geophysicists, palaeontologists, geochemists and mineralogists have come to the conclusion that the meteorite impacted in Chicxulub at exactly the same time as the mass extinction of species began. The impact theory is the only theory which can provide a coherent explanation of the extinction that took place at the end of the Cretaceous period. “On the basis of detailed work on terrain and with the aid of elaborate laboratory investigations – and supported by the results of model calculations – we have now proven that this assumption is correct,” says Alexander Deutsch. “In some places we examined the top Cretaceous boundary layer millimetre by millimetre, using the most modern analytical techniques.”
Modellings of the asteroid impact show that the energy released by this event is millions of times greater than that of the biggest atomic bomb ever tested. With an impact of this size pieces of rock and molten particles are thrown up and distributed over the whole world. The Chicxulub impact triggered enormous earthquakes which led to chaotic rock sequences in what is today the Gulf of Mexico, say the researchers. For this reason the rock layers in the crater area are not suitable for explaining the exact sequence of events 65 million years ago. However, it was precisely on these layers that the American scientists had based their doubts.
According to the new study, strong volcanic activity in India cannot be assumed to be the cause of the extinction, either. The main phase of eruptions already began 500,000 years before the extinction, without the worldwide eco-systems showing any serious changes. The Chicxulub impact suddenly released huge amounts of sulphur dioxides, carbon dioxide, dust and soot, thus triggering drastic changes in the environment all over the world, such as darkness and a drop in temperatures. These sudden events led to an interruption of the food chain on the mainland and in the oceans – with catastrophic consequences for a large number of organisms.
