Science Daily invites us to the opening chapter of an alien invasion story, as international researchers explain how they just found a 31-kilometer-wide crater from an ancient meteorite collision under the continental ice shelf:
The crater measures more than 31 km in diameter, corresponding to an area bigger than Paris, and placing it among the 25 largest impact craters on Earth. The crater formed when a kilometre-wide iron meteorite smashed into northern Greenland, but has since been hidden under nearly a kilometre of ice.
“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. But that means the crater must be rather young from a geological perspective. So far, it has not been possible to date the crater directly, but its condition strongly suggests that it formed after ice began to cover Greenland, so younger than 3 million years old and possibly as recently as 12,000 years ago — toward the end of the last ice age” says Professor Kurt H. Kjær from the Center for GeoGenetics at the Natural History Museum of Denmark.
Joseph MacGregor, a glaciologist at NASA, who participated in the study and is an expert in ice radar measurements adds:
“Previous radar measurements of Hiawatha Glacier were part of a long-term NASA effort to map Greenland’s changing ice cover. What we really needed to test our hypothesis was a dense and focused radar survey there. Our colleagues at the Alfred Wegener Institute and University of Kansas did exactly that with a next-generation radar system that exceeded all expectations and imaged the depression in stunning detail. A distinctly circular rim, central uplift, disturbed and undisturbed ice layering, and basal debris. It’s all there.”
In the summers of 2016 and 2017, the research team returned to the site to map tectonic structures in the rock near the foot of the glacier and collect samples of sediments washed out from the depression through a meltwater channel.
“Some of the quartz sand washed from the crater had planar deformation features indicative of a violent impact, and this is conclusive evidence that the depression beneath the Hiawatha Glacier is a meteorite crater, ” says Professor Larsen.