In November, scientists discovered the first crater ever found under an ice sheet — an enormous, bowl-shaped dent nestled beneath the Hiawatha Glacier in northwest Greenland. At the time, scientists marveled at the discovery because it was so rare. It’s unusual enough to find a crater of that size, and doubly so if it’s under ice. Now, a team led by NASA scientists has made another dazzling announcement: There’s likely another impact crater buried in Greenland, and it’s only 114 miles away from Hiawatha.
This crater is even larger than the first. At 22 miles wide, it’ll be the 22nd-largest impact crater found on Earth if it’s ultimately confirmed as a result of a meteorite impact. In a study published Monday in Geophysical Research Letters, scientists say the crater is buried under nearly 1.2 miles of ice — layers that are unambiguously older than those covering the Hiawatha crater.
“It is increasingly rare to find new large impact craters on Earth, let alone such craters buried beneath ice,” the scientists write. “Our study expands knowledge of the impact history of the Earth and raises the question as to how many other impact craters buried beneath ice have yet to be found.”
For decades, the obstacle created by the polar ice sheets has made it tricky for scientists to know the exact geology of Earth’s remote polar regions. Now humans are beginning to see what’s going on in that part of the world for two reasons — one that scientists like, and another that they are afraid of. The latter is climate change: Melting ice has revealed an Arctic landscape that hasn’t seen the light of day in thousands of years. The former is new technology, which is how the NASA-led team was able to find this crater.
NASA glaciologist Joe MacGregor, Ph.D., explains that after he helped discover the Hiawatha crater, he asked himself whether or not there could be another. He scoured topographic maps of Greenland, searching for signs of a crater, and, after examining imagery of the ice surface taken by the Moderate Resolution Imaging Spectroradiometer instruments aboard NASA’s Terra and Aqua satellites, noticed a circular pattern.
Radar images of the bedrock beneath the ice collected by NASA’s Operation IceBridge confirmed that the pattern contained distinctive impact crater features: a bowl-like depression, an elevated rim, and centrally located peaks. There was also a negative gravity anomaly surrounding the region, which is another characteristic linked to impact craters.
Researchers then collected ice cores, which revealed that the ice nestled into the crater is at least 79,000 year old — which implies that the structure was created prior to that timestamp. The range of when exactly the impact happened is still wide, though: The team believes the crater formed sometime between 100,000 and 100 million years ago. Because the process of ice erosion can make using ice cores challenging as a means of dating, it’s difficult to pinpoint an exact date.
While both this new crater and the Hiawatha crater are technically described as “potential” impact craters, the scientists behind the discoveries appear confident that both craters were formed by asteroid hits. And those events, Hiawatha crater project leader Kurt Kjær, Ph.D., told Inverse in November, were far from pleasant.
“Imagine 12 billion tons of iron coming down,” explained the University of Copenhagen professor. “Just the energy released on impact would be equal the energy from 45 Hiroshima atom bombs, creating strong earthquakes 100 kilometers [62 miles] away from the impact site and covering large areas with hot ejecta material. It would instantly kill life in the large surrounding area.”
Abstract: Following the discovery of the Hiawatha impact crater beneath the northwest margin of the Greenland Ice Sheet, we explored satellite and aerogeophysical data in search of additional such craters. Here we report the discovery of a possible second subglacial impact crater that is 36.5‐km wide and 183 km southeast of the Hiawatha impact crater. Although buried by 2 km of ice, the structure’s rim induces a conspicuously circular surface expression, it possesses a central uplift, and it causes a negative gravity anomaly. The existence of two closely spaced and similarly sized complex craters raises the possibility that they formed during related impact events. However, the second structure’s morphology is shallower, its overlying ice is conformal and older, and such an event can be explained by chance. We conclude that the identified structure is very likely an impact crater, but it is unlikely to be a twin of the Hiawatha impact crater.