Beware the M-bomb


A meteor struck Chicxulub, southern Mexico, 66 million years ago triggering a climactic shift that doomed the dinosaurs. But the biggest extinction event, the Permian extinction, took place 252 million years ago, wiping out 90% of marine species and 70% of land species. Scientists thought a meteor was the culprit here too, since last year a crater in Brazil was dated close to that time. But it was too small, a mere 40 km wide compared to the 180 km of Chicxulub. It could not have caused a mass extinction unless there was something special about the place it landed. It turns out there was. The meteor seems to have detonated a methane bomb.

That’s the interpretation of Eric Tohver at the University of Western Australia and his team, who published their findings this October in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

Tohver’s team dated the crater last year. Now, after a geological survey, they found the meteor struck what was then a methane-rich shallow seabed. Based on the size of the meteor and the geology of the area, they calculated that multiple earthquakes about magnitude 9.9 would have followed the strike, shaking the sediment and freeing around 2,000 gigatonnes of methane, instantly and dramatically overheating the plant to cause the mass extinction.

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