(CN) – A 19-mile-wide crater hidden under a half-mile of ice likely came from a kilometer-wide iron asteroid that crashed into Greenland perhaps in the last 12,000 years, according to nearly two decades of surveys finally released Wednesday.
Researchers found sediment that included glass from a river in the center of the crater, which was likely formed when the asteroid crashed and melted rocks in the earth, according to the paper published in Science Advances.
Researchers found the big craterlike depression beneath the Hiawatha Glacier in remote northwest Greenland, and only after looking at satellite imagery did they see circular patterns in the crater.
That information, along with data collected between 1997 and 2014 by researchers at the University of Kansas’ Center for the Remote Sensing of Ice Sheets, presented a strong case for the site being an impact crater.
Co-author John Paden, associate professor of electrical engineering and computer science with Kansas University, helped develop the Multichannel Coherent Radar Depth Sounder to collect radar information over that last couple of decades.
Paden said Danish researchers looked over the map and saw the circular pattern, which led to a May 2016 survey with more recent technology. Then Paden flew over the site to get a better idea of the crater’s dimensions.
“You can see the rounded structure at the edge of the ice sheet, especially when flying high enough,” he said. “For the most part the crater isn’t visible out the airplane window. It’s funny that until now nobody thought, ‘Hey, what’s that semicircular feature there?’
“From the airplane it is subtle and hard to see unless you already know it’s there,” he continued. “Using satellite imagery taken at a low sun angle that accentuates hills and valleys in the ice sheet’s terrain – you can really see the circle of the whole crater in these images.”
Melting glacier streams and sediment from the site drained into a large river, and from there researchers found “shocked quartz and other impact-related grains” or rocks. That included glass, which was likely formed by the impact and high heat melting the rocks.
Researchers are still working to narrow down the exact timing of the asteroid’s impact, but they believe the Hiawatha impact crater formed during the Pleistocene, from 2.58 million years ago to 11,700 years ago ending with the last glacial period on earth. That’s a wide window befitting a wider search: The team is now looking at debris launched from the asteroid’s impact, which could shed light on the impact’s effect on the atmosphere and climate.
A large influx of fresh water from the melting of a large portion of a glacier would have gone through the Nares Straight between Canada and Greenland. That in turn would have affected ocean flow for the entire region, said Paden.
“The evidence indicates that the impact probably happened after the Greenland Ice Sheet formed, but the research team is still working on the precise dating,” he said.