Earth hides its scars well; the planet has endured countless millennia of eruptions and collisions, but scientists are still stumbling upon the evidence of all that geologic drama.
Now, one such team has announced that it spotted a scar hidden below Greenland’s ice, a giant crater nearly 20 miles (31 kilometers) wide. The researchers said a giant iron meteorite likely created the mark by slamming into Earth sometime in the past 3 million years.
Other scientists aren’t necessarily sold yet that a space rock created the feature. “I think that the authors have presented some intriguing evidence of a possible impact site, and I think that’s the right word—intrigued,” David Kring, who studies impact craters at the Lunar and Planetary Institute in Houston and who wasn’t involved with the new research, told Space.com. “I’m intrigued. I’m not wholly convinced that this is an impact crater.” [In Pictures: The Giant Crater Beneath Greenland Explained]
Seems to match the younger Dryas Impact hypothesis though: A Comet at about 11,000 BC.
(Kjær said that, depending on when precisely the feature formed, it may match the sharp cooling of the Younger Dryas period, which ended about 11,500 years ago, but that it’s certainly too early to say.)
We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. This depression has an elevated rim that cross-cuts tributary subglacial channels and a subdued central uplift that appears to be actively eroding. From ground investigations of the deglaciated foreland, we identify overprinted structures within Precambrian bedrock along the ice margin that strike tangent to the subglacial rim. Glaciofluvial sediment from the largest river draining the crater contains shocked quartz and other impact-related grains. Geochemical analysis of this sediment indicates that the impactor was a fractionated iron asteroid, which must have been more than a kilometer wide to produce the identified crater. Radiostratigraphy of the ice in the crater shows that the Holocene ice is continuous and conformable, but all deeper and older ice appears to be debris rich or heavily disturbed. The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet.