Scientists say they have made an astonishing discovery of a large meteorite crater in Greenland – the first ever discovered there, and the first ever found under an ice sheet.
Published in the journal Science Advances, a team led by Kurt Kjaer from the University of Copenhagen in Denmark described how they found what's believed to be an impact crater hiding under 900 meters (3,000 feet) of ice beneath the Hiawatha Glacier in northwest Greenland.
The crater is thought to be 31 kilometers (19 miles) wide, making it one of the 25 largest impact craters on Earth. The object that caused it was likely an iron asteroid about 1.5 kilometers (0.9 miles) across, the size of a city, weighing 12 billion tonnes (13.2 billion tons). It's thought to have hit Greenland anywhere from 12,000 to 2 million years ago at a speed of about 20 kilometers (12 miles) per second.
“It was hiding in plain sight,” Kjaer told IFLScience. “How often do you go out in the world and make a discovery like this? It’s mind-boggling.”
The crater was first spotted in 2015, when radar was used to map the Greenland ice sheet. Looking at the map, Kjaer and his team noticed there was a large depression towards the northwest of the island.
In May 2016, a German research plane flew back over the area, taking new ice radar images. These started to show that the researchers were right – there was a circular feature hundreds of meters under the ice with a rim around it.