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[music] Buried under a mile of ice,

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it's never been seen by human eyes.

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But using ice-penetrating radar, scientists have discovered a giant canyon

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carved into Greenland’s bedrock.

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More than 400 miles long and up to a half mile deep, shown here as the dark brown groove

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in the center of the island, the canyon is thought to pre-date

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Greenland's massive ice sheet.

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The hidden feature was discovered by a team led by the University of Bristol,

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using radar data from a number of airborne campaigns from

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the United Kingdom and Germany, and a NASA mission

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called Operation IceBridge, which surveys this region with

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a range of different instruments every year to monitor changes in the Greenland Ice Sheet.

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From the interior of Greenland,

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the canyon snakes around up to the fjord of the

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Petermann Glacier on the northern coast, and researchers suspect it may

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play a major role in transporting melt water below the ice