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March 10, 2022 02:52 pm

Controversial Impact Crater Under Greenland's Ice is Surprisingly Ancient

An anonymous reader shares a report: In 2018, an international team of scientists announced a startling discovery: Buried beneath the thick ice of the Hiawatha Glacier in northwest Greenland is an impact crater 31 kilometers wide -- not as big as the crater from the dinosaur-killing impact 66 million years ago, but perhaps still big enough to mess with the climate. Scientists were especially excited by hints in the crater and the surrounding ice that the Hiawatha strike was recent -- perhaps within the past 100,000 years, when humans might have been around to witness it. But now, using dates gleaned from tiny mineral crystals in rocks shocked by the impact, the same team says the strike is much, much older. The researchers say it occurred 58 million years ago, a warm time when vast forests covered Greenland -- and humanity was not yet even a glimmer in evolution's eye. Kurt Kjaer, a geologist at the Natural History Museum of Denmark and a co-author of the new study, says the new date is at odds with the team's initial impression, gleaned from ice-penetrating radar. "But this is the way science works and should work," he says. The date is a blow to a group of scientists that for more than a decade has advanced a controversial hypothesis that the Younger Dryas, a drastic, 1000-year cooling about 12,800 years ago, was triggered when a comet struck Earth. They had seized on the first Hiawatha paper as a smoking gun: The crater seemed about the right age, and it was in the right place -- near a region of the North Atlantic Ocean that heavily influences Northern Hemisphere climate. Now, says Brandon Johnson, a co-author and impact modeler at Purdue University, West Lafayette, "It's probably safe to put the Younger Dryas impact hypothesis back to rest for a while."

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