Monday, July 2, 2012

Asteroid that hit Earth 65 million years ago - New Discovery

The asteroid that hit Earth 65 million years ago and wiped out the dinosaur was at least six miles across and left behind a crater over 110 miles across. But that's nothing compared to a possibly newly discovered impact site.

It's not confirmed yet, but a potential crater site in Greenland would be the oldest, biggest impact ever observed on Earth. The original asteroid would have been about 18 miles across - that's about half the length of Rhode Island, which is pretty damn huge by asteroid standards - and the crater it initially created would have been nearly 375 miles wide and over 15 miles deep. While we've seen evidence of impacts on that scale elsewhere in the solar system, we've never seen anything like this on Earth.

So why are we only discovering something this big now? Part of it is its immense age - when this asteroid hit, Earth was only a third its current size. Most of the crater has since been worn away by three billion years of erosion, meaning only the rocks from the very bottom of the original impact site are still there. Besides, part of the reason we know so much about the Chicxulub crater is because it killed the dinosaurs - it left behind plenty of clues in the fossil and geological record that there was something there worth searching for, whereas this massive crater smashed into a relatively empty Earth. The fact that this site is in Greenland instead of Mexico also probably doesn't help.

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