Massive Crater Discovered Under Greenland Ice

An international team of scientists came together to unravel the mystery of Greenland’s Hiawatha crater, which is buried in ice, yet reveals its circular outline. Chemical evidence indicates that the impactor was an iron asteroid more than a kilometer (half-mile) across. NASA/Jefferson Beck

There are 190 confirmed impact structures on the Earth. Er, make that 191. An international team of researchers, including a NASA glaciologist, has discovered a new crater hiding beneath more than a half-mile of ice in northwest Greenland. The crater — the first of any size found under the Greenland ice sheet — is one of the 25 largest impact craters on Earth, measuring roughly 1,000 feet (305 meters) deep and more than 19 miles (31 km) in diameter.

Using ground-penetrating radar data from NASA, the team mapped the topography of the rock and crater beneath the ice sheet. NASA / Cindy Starr

The European researchers made the discovery using data from NASA’s ice-penetrating radar used on the P3 aircraft, first spotting the crater in July 2015. The scientists noticed an enormous, previously unstudied circular depression under Hiawatha Glacier, along the edge of the ice sheet in northwestern Greenland. They backed up this data with satellite imagery from NASA’s Terra and Aqua satellites, which found evidence of a circular pattern on the ice surface that matched the one observed in the terrain below the ice by radar.

To further confirm their suspicions, the team sent a research plane with even more elaborate ice-penetrating radar, which imaged the depression in great detail showing a circular rim, central uplift (from rock rebounding after the impact) and disturbed ice on the crater’s bottom topped by normal ice.

Radar data from an intensive aerial survey of the Hiawatha crater in May 2016 is shown here in aqua-colored curtains. A blue arrow points to the central peak of the crater. NASA/Cindy Starr

The crater formed less than 3 million years ago, according to the study, when an iron meteorite more than half a mile wide smashed into northwest Greenland. The resulting depression was subsequently covered by ice. The team’s research was inspired in part by the Cape York meteorite, a heavy hunk of iron meteorite weighing 22.4 tons collected decades ago from northwestern Greenland that may be related to the impact. A large slice is on display inside the Geological Museum of the University of Copenhagen, while the main mass still sits outside in the weather. The largest Cape York, a 31-ton behemoth, resides in the American Museum of Natural History in New York City.

The Agpalilik iron, a large fragment of the Cape York meteorite, sits outside the Geological Museum in Copenhagen. It may be a piece of the small asteroid that gouged out the huge crater found in Greenland. Michael B.H. / CC BY-SA 3.0

When the researchers performed an on-site survey at the glacier during the summers of 2016 and 2017, they collected pieces of quartz from sediments that washed out from the crater through a meltwater channel. Examination revealed classic shock structures that could have been produced by the enormous pressures generated by a violent impact.

This simulation shows a small asteroid breaking up on hitting the atmosphere over Greenland long ago. NASA

“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,” said Kurt Kjær, a professor at the Center for GeoGenetics at the Natural History Museum of Denmark and lead author of the study.

This is an aerial view of the Hiawatha Glacier (center) emerging from its semicircular parent ice lobe in northwestern Greenland. NASA

That preservation may indicate that the impact occurred as some 12,000-115,000 years ago — as recently as the end of the last ice age — making the crater one of the youngest on Earth. For more on the new discovery, click the video or read the scientific paper here. The researchers plan to continue their work and will focus on how the meteorite impact may have affected the planet.