An asteroid impact is widely blamed for killing off the dinosaurs 65 million years ago. An asteroid 10 kilometers wide struck the Yucatan peninsula and left a giant crater. It also tossed up enough debris to catastrophically darken the sky and cool the Earth.
Now a study in the journal Nature indicates that such impacts may have been commonplace in Earth's history. As many as 70 asteroid impacts at least as severe as the one that did in the dinosaurs rocked the planet long after such impacts were thought to have petered out. [William F. Bottke et al., "An Archaean heavy bombardment from a destabilized extension of the asteroid belt"]
The culprit is a hypothesized collection of asteroids called the E belt, only a small remnant of which survives today. The E belt was closer to Earth than the main asteroid belt is now, and it was disrupted by the giant planets as they settled into their current orbits.
It had been thought that Earth’s heavy bombardment by asteroids and comets died down about 3.7 billion years ago. But E belt asteroids would have rained down frequently for another two billion years after that, with the occasional dino killer coming in even later on. All those impacts would have had major effects on life. Somehow, it all worked out for us—if not for the dinosaurs.
[The above text is a transcript of this podcast.]
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