CenturiesOld Impact Crater Hidden Under Greenland Ice Sheet

first_imgStay on target Researchers discovered an impact crater bigger than Paris buried beneath an ice sheet in northern Greenland.Measuring more than 31 kilometers (19 miles) in diameter, the cavity was formed when an iron meteorite smashed into the area, which has since been hidden under nearly a kilometer of ice.“The crater is exceptionally well-preserved, and that is surprising, because glacier ice is an incredibly efficient erosive agent that would have quickly removed traces of the impact,” Kurt Kjær, a professor at the Natural History Museum of Denmark, said in a statement. “But that means the crater must be rather young from a geological perspective.”While scientists have no yet been able to date the crater directly, its condition suggests it formed after ice began to cover Greenland.“So, younger than 3 million years,” Kjær said, “and possibly as recent as 12,000 years ago—toward the end of the last ice age.”Close-up of the northwestern ice-sheet margin in Inglefield Land (via Natural History Museum of Denmark)In July 2015, during inspection of a new topographical map of Greenland’s ice sheet, researchers spotted what they called an “enormous,” but previously undetected, circular depression under Hiawatha Glacier.“We immediately knew this was something special, but at the same time it became clear that it would be difficult to confirm the origin of the depression,” Kjær explained.In the courtyard of the Geological Museum in Copenhagen, just outside the windows of the Center for GeoGenetics, sits a 22-ton iron meteorite, found in North Greenland, not far from the Hiawatha Glacier.“It was therefore not such a leap to infer that the depression could be a previously undescribed meteorite crater,” Aarhus University associate professor Nicolaj Larsen said. “But initially we lacked the evidence.”Map of the bedrock topography beneath the ice sheet and the ice-free land surrounding the Hiawatha impact crater (via Natural History Museum of Denmark)Their suspicion was confirmed when the team personally visited the Hiawatha Glacier, mapping the area with a powerful ice radar.“A distinctly circular rim, central uplift, disturbed and undisturbed ice layering, and basal debris. It’s all there,” according to Joseph MacGregor, a NASA glaciologist who participated in the study.The unnamed pit—among the planet’s 25 largest impact craters—is described further in a study published by the journal Science Advances.This marks the first time a crater of any size has been found under one of Earth’s continental ice sheets.“The next step in the investigation will be to confidently date the impact,” Kjær said. “This will be a challenge, because it will probably require recovering material that melted during the impact from the bottom of the structure, but this is crucial if we are to understand how the Hiawatha impact affected life on Earth.”More coverage on Geek.com:Ancient Meteorites Shed Light on Early Solar System470-Million-Year-Old Meteorite Crater Confirmed in IowaFormer Barn Doorstop Actually $100,000 Meteorite Scientists Uncover New Evidence of Asteroid That Killed DinosaursWWII Bomb Explodes in German Barley Field, Creates Giant Crater last_img

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