Just months after revealing an impact crater the size of Washington, D.C., buried under the ice of northwestern Greenland, a team of scientists has discovered that it has company: a large depression 180 kilometers away that may also be an asteroid or comet impact crater.

Greenland crater, Greenland impact crater
Greenland crater discovered under the ice. Topography under Hiawatha glacier in Greenland, mapped with airborne radar data (1997 to 2014, NASA; 2016 Alfred Wegener Institute).

Several years ago, after researchers spotted the first crater hiding in plain sight under Greenland’s Hiawatha Glacier, they began to scour satellite records and ice-penetrating radar profiles for other circular deformations.

Profiles from NASA’s IceBridge research flights revealed a 36-kilometer-wide, bowl-shaped depression surrounded by a rim, with a collection of raised peaks in the center resembling the uplift left after an asteroid or comet strikes Earth’s surface.

But unlike the Hiawatha crater, the basin hasn’t yet yielded shocked quartz crystals, considered to be the best evidence of an extraterrestrial impact. The basin appears eroded and filled with ice older than Hiawatha’s crater, both of which suggest that, if it is a crater, it likely came from a different impact.

Although that may seem an implausible coincidence, other unrelated impact pairs have been found in Ukraine and Canada. And the rate of cosmic collisions needed to achieve such a coincidence is possible, given recent studies charting an uptick in Earth’s bombardment by extraterrestrial objects over the past 300 million years.

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[AGU, Science]

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