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Ice age impact

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Science  16 Nov 2018:
Vol. 362, Issue 6416, pp. 738-742
DOI: 10.1126/science.362.6416.738

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Summary

An international team of scientists this week reported a startling new discovery hidden beneath the Greenland Ice Sheet: a 31-kilometer-wide impact crater, big enough to swallow Washington, D.C., left after a 1.5-kilometer-wide asteroid slammed into Earth. One of the planet's 25 largest-known craters, it is also remarkably fresh, seemingly indicating a recent strike within the last few million years. Though not as cataclysmic as the dinosaur-killing Chicxulub impact 66 million years ago, the Hiawatha impactor, as it's known, may have left an imprint on the planet's history. The timing is still up for debate, but some researchers on the discovery team believe the asteroid struck at a crucial moment: roughly 13,000 years ago, just as the world was thawing from the last ice age. That would mean it crashed into Earth when mammoths and other megafauna were in decline and people were spreading across North America.