Elevating this from a mention in my previous Newsworthy Items post.
From ScienceNews
Whether the impact is related to a period of cooling called the Younger Dryas is unknown
By Carolyn Gramling 2:00pm, November 14, 2018
There’s something big lurking beneath Greenland’s ice. Using airborne ice-penetrating radar, scientists have discovered a 31-kilometer-wide crater — larger than the city of Paris — buried under as much as 930 meters of ice in northwest Greenland.
The meteorite that slammed into Earth and formed the pit would have been about 1.5 kilometers across, researchers say. That’s large enough to have caused significant environmental damage across the Northern Hemisphere, a team led by glaciologist Kurt Kjær of the University of Copenhagen reports November 14 in Science Advances.
Although the crater has not been dated, data from glacial debris as well as ice-flow simulations suggest that the impact may have happened during the Pleistocene Epoch, between 2.6 million and 11,700 years ago. The discovery could breathe new life into a controversial hypothesis that suggests that an impact about 13,000 years ago triggered a mysterious 1,000-year cold snap known as the Younger Dryas (SN: 7/7/18, p. 18).
Members of the research team first spotted a curiously rounded shape at the edge of Hiawatha Glacier in northwest Greenland in 2015, during a scan of the region by NASA’s Operation IceBridge. The mission uses airborne radar to map the thickness of ice at Earth’s poles. The researchers immediately suspected that the rounded shape represented the edge of a crater, Kjær says.
For a more detailed look, the team hired an aircraft from Germany’s Alfred Wegener Institute that was equipped with ultra-wideband radar, which can send pulses of energy toward the ice at a large number of frequencies. Using data collected from 1997 to 2014 from Operation Icebridge and NASA’s Program for Arctic Regional Climate Assessment, as well as 1,600 kilometers’ worth of data collected in 2016 using the ultra-wideband radar, the team mapped out the inner and outer contours of their target.
The object is almost certainly an impact crater, the researchers say. “It became clear that our idea had been right from the beginning,” Kjær says. What’s more, it is not only the first crater found in Greenland, but also one of the 25 or so largest craters yet spotted on Earth. And it has held its shape beautifully, from its elevated rim to its bowl-shaped depression.
“It’s so conspicuous in the satellite imagery now,” says John Paden, an electrical engineer at the University of Kansas in Lawrence and a member of the team. “There’s not another good explanation.”
On the ground, the team hunted for geochemical and geologic signatures of an asteroid impact within nearby sediments. Sampling from within the crater itself was impossible, as it remains covered by ice. But just beyond the edge of the ice, meltwater from the base of the glacier had, over the years, deposited sediment. The scientists collected a sediment sample from within that glacial outwash and several from just outside of it.
The outwash sample contained several telltale signs of an impact: “shocked” quartz grains with deformed crystal lattices and glassy grains that may represent flash-melted rock. The sample also contained elevated concentrations of certain elements, including nickel, cobalt, platinum and gold, relative to what’s normally found in Earth’s crust. That elemental profile points not only to an asteroid impact, the researchers say, but also suggests that the impactor was a relatively rare iron meteorite.
Read the full article at the source here:
HT/David Hagen, ResourceGuy, Fred Nicol and maybe some I missed.
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There is an excellent chance that the Hiawatha iron impactor is associated with the Cape York meteorite(s), which were discovered and exploited for their iron by the Inuit centuries ago. The Hiawatha Crater and Cape York are only about 200 miles apart (straddling Thule AFB), and the Cape York objects have already been dated to roughly 10,000 BP. (There are 60 tons of Cape York iron on public display in New York and Copenhagen.)
Since It will be many years before the Hiawatha crater itself can be precisely dated, we should proceed with high confidence that the crater is the same age as the Cape York objects. If that turns out to be wrong, then we will know how Hillary Clinton feels.
The impressive thing here isn’t the crater discovered.
It’s the implications of the ultrawide band radar sensor that found this impact’s potential for finding a lot of other such impacts under the ice.