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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.
—John Matson
[The above text is a transcript of this podcast.]
Scientific American is part of the Nature Publishing Group.
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3 Comments
Add CommentVery selective asteroid that killed off the dino. I noticed that you did not mention if the asteroid killed off the dino all around the world. If it didn't kill off the dino all around the world, then maybe those were the wrong two words to use. If it was big enough to wipe out the dino, then why didn't it kill every living warm blooded thing on this planet? The asteroid would also vaporize tender plant life and the heat would destroy the lungs of all breathing animals that was above ground, and then the very long and the very cold spell that followed would kill the rest of the animals because they wouldn't be able to find anything to eat. You may want to consider revising your sentence and say, "killed off some or most or just those in the Yucatan peninsula and the rest of the dino magically down sized themselves so there would be enough food for everyone and since there was no Bargain Barns built yet, they all huddled together to keep warm.
Reply | Report Abuse | Link to thisActually there are several really good theories to explain why dinosaurs could have been killed off while other species lived on... and why the devastation could have reached so far beyond the Yucatan... do a little quick research and I'm sure you'll turn up plenty of info.
Reply | Report Abuse | Link to thisIt might be worth a quick read before you mockingly dismiss an idea based on a "common sense" explanation that doesn't hold up any where near as well to scrutiny as does that alternatives widely available. Just a thought...
Technically, birds ARE therapod dinosaurs. So you could say the asteroid-caused mass extinction killed dinosaur megafauna but spared some smaller families of dinosaurs.
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