New research points to a comet as the source of the explosion that caused the extinction of dinosaurs, contradicting earlier theories blaming an asteroid.

Science Recorder reported on Friday that the findings from a team at Dartmouth College indicated that an asteroid would not have been capable of creating the Chicxulub crater in Mexico, long regarded as the collision point for the phenomenon that led to the destruction of 70 percent of animal species on the planet 65 million years ago.

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Lead study author Jason Moore and his fellow researchers presented their findings at the annual Lunar and Planetary Science Conference.

Moore said an analysis of iridium and osmium layers within the 180-kilometer wide crater revealed that the crash created less debris than an asteroid would have been able to produce.

“You’d need an asteroid of about 5km diameter to contribute that much iridium and osmium,” Moore said. “But an asteroid that size would not make a 200km-diameter crater. So we said: how do we get something that has enough energy to generate that size of crater, but has much less rocky material? That brings us to comets.”

The two elements, Moore said, could not have been generated within the crater naturally.

However, a researcher at Imperial College in London told the BBC that though the Dartmouth team’s work was “thought-provoking,” it did not entirely shut the door on possible asteroid involvement.

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“The authors suggest that 75 percent of the impactor mass is distributed globally, and hence arrive at quite a small-sized impactor,” said Gareth Collins “But in reality this fraction could be lower than 20 percent.”

Watch NewsyScience’s recap of the Dartmouth team’s findings, posted on Saturday, below.

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[Image by Mike Shaver via Flickr Creative Commons]