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Ask a Scientist: If a Comet Hits Earth

Hi My name is Leila and I'm in 4th grade. My question is, if a comet hit Earth, how deadly would it be?

Steve Chesley, EPOXI, NASA/JPL:
Well if a large comet did hit the Earth, it would be a very bad day for all of us. The damage could be, depending on the size of the comet, either local damage or global damage. A smaller comet, say the size of Hartley 2, would create a huge crater and maybe disrupt the climate of the Earth for years, while a much larger comet could cause a mass extinction like the one that killed off the dinosaurs 65 million years ago. The good news is that these things happen very rarely and they're separated by millions, even billions of years.

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