Sixty-six million years ago, only 13 per cent of Earth’s surface contained enough organic material to generate this doomsday soot, the authors concluded in the new study. Had the asteroid hit the other 87 per cent of Earth, Kaiho said, “I think dinosaurs could be alive today.”

Timothy Bralower, a Penn State paleoceanographer who was not involved with this work, applauded the researchers for their “innovative way of thinking.” But Bralower said he doubted that a soot cloud alone could explain why the asteroid was so lethal.

“The 13 per cent number they’re quoting has a lot of assumptions based around it,” said Sean Gulick, a geophysicist at the University of Texas at Austin. The asteroid churned up soot, he said, but soot was “not the driver” that killed the dinosaurs.

The extinction asteroid theory, widely accepted as the most plausible explanation for the dinosaurs’ disappearance, is the result of four decades of research. In the late 1970s, scientists Luis and Walter Alvarez, a father-son duo at the University of California at Berkeley, began to investigate rocks on the border between the Cretaceous and Paleogene geologic periods. The Alvarez team discovered the element iridium, at levels found only in asteroids, in Italian clay that dated to the ancient divide. Cretaceous soot, too, was mixed in with the red clay.


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