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In a remote area of Northwest Greenland,

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an international team of scientists have made a stunning discovery

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buried beneath a kilometer of ice. It's an impact crater

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300 meters deep, 31 kilometers wide 

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much bigger than Washington D.C.,

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even bigger than Paris,

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and it's probably one of the youngest large impact craters on Earth.

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In May 2016, the team sent the German research plane Polar 6 

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to fly over Hiawatha glacier with a powerful new ice-penetrating radar.

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Radar waves can travel through ice 
measuring its thickness and internal structure.

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Studying data from this airborne survey,

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the scientists confirmed the tell-tale bowl shape 

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and central peaks beneath Hiawatha Glacier. 

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They also found that the oldest ice in the crater was
actually fairly young, by Greenland standards,

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and had experienced a great disturbance in its flow 

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towards the end of the last ice age.

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The Hiawatha crater is one of the 25 largest known impact craters on Earth,

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and the first found under any of our planet's ice sheets. 

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The data as a whole suggests it's quite young, geologically speaking.

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An impact of this size is unlikely to happen again soon, 

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but evidence that it might have happened not so long ago in Earth's history 

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is essential to assessing the risk today.

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