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A massive crater hides under Greenland’s ice

Author: Carolyn Gramling / Source: Science News for Students

An artists illustration of incoming asteroids breaking up in Earth's atmosphere, as seen from Earth orbit
An iron-rich asteroid breaks up in Earth’s atmosphere in this artist’s conception. It suggests the event that long ago created a large crater in northwest Greenland.

Something big lurks beneath Greenland’s ice. Using ice-penetrating radar, scientists have discovered a crater larger than the city of Paris.

This 31-kilometer- (19.3-mile-) wide pit in northwest Greenland lies buried under as much as 930 meters (3,000 feet) of ice.

It was formed by a meteorite that slammed into Earth. Scientists now calculate that this space rock must have been about 1.5 kilometers (0.9 mile) across. One so big would have caused notable environmental damage across the entire Northern Hemisphere, a new analysis finds. Glaciologist Kurt Kjær led the team that found this crater. He works at the University of Copenhagen in Denmark.

a map showing where the crater was discovered and a radar image showing the crater
A crater has just been discovered at the edge of Greenland’s Hiawatha Glacier (upper image). Airborne radar data (lower image) show a round depression (green circle) under nearly a kilometer of ice. Deformed quartz minerals and other signatures of an ancient impact were found just outside the edge of the ice (black dot).

No one yet knows how old the crater is. But glacial debris and computer studies on rates of ice flow suggest the asteroid impact might have happened between 2.6 million and 11,700 years ago. That was during what is known as the Pleistocene Epoch (PLY-stuh-seen EP-ok).

The newfound crater could breathe new life into a controversial idea. It argues that an impact some 13,000 years ago triggered a mysterious 1,000-year cold snap. Scientists refer to that surprise cold period as the Younger Dryas.

Members of the research team first spotted hints of the crater in 2015. They were curious about a big rounded shape at the edge of Hiawatha Glacier in northwest Greenland. It showed up in a radar scan of the region. NASA’s Operation IceBridge was flying an aircraft over the area. It was part of a program to map the thickness of ice at Earth’s poles. The rounded shape looked like it might mark the edge of a crater, Kjær says.

His team decided to take a more detailed look. They hired a plane from Germany’s Alfred Wegener Institute. Its radar sent pulses of energy toward the ice at a large number of frequencies. Using data collected between 1997 and 2014 by several NASA programs, as well as lots of data collected in 2016 with this “ultra-wideband radar,” the team mapped its target.

The object is almost certainly an impact crater, Kjær says: “It became clear that our idea had been right from the beginning.” It is the first crater found in Greenland and one of the 25 or so largest ever spotted…

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