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Earth's asteroid impact rate took a sudden jump 290 million years ago

27 Jul 2020, 13:00 UTC
Earth's asteroid impact rate took a sudden jump 290 million years ago
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Looking at impact craters on both the Earth and Moon, a team of scientists found that there may have been a sudden increase in big impact events starting around 290 million years ago. At around that time, they think, asteroid impacts became as much as 2.6 times more common.

That’s a big jump.

Mind you — because some folks worry about this sort of thing — this doesn’t affect anything now. It’s not like we’re suddenly seeing more than twice as many impacts since, like, yesterday. We’re talking about an increase that started before the dinosaurs even got their start.

But why? And how did they figure this out?

Rocks ejected by a nearby impact litter the lunar landscape. They erode over millions of years, allowing planetary scientists to measure their age. For scale, this image is 500 meters wide. Credit: NASA/GSFC/Arizona State University

Second things first. We know that there’s a lack of old craters on the Earth, and it’s always been assumed that’s due to erosion. Wind, water, geologic activity: Over long stretches of time our Earth remakes itself, scrubbing the surface of blemishes like impacts*.

But the evidence for this is lacking. That’s what initially motivated the ...

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