Greenland: New giant crater discovered under the ice
For the second time in a short time researchers in Greenland want to have found the remains of a gigantic meteorite impact. It may not be the last discovery of its kind.
Little time? At the end of the text there is a summary.
There are a few places on earth where you can experience first-hand what primordial forces occur when a meteorite impacts. The Barringer Crater in the Arizona Desert is such a place. About 50,000 years ago, a chunk of space consisting mainly of iron was crashed into space. With about 45 meters in diameter, he was not really big. But if you stand on the edge of the 1.2-kilometer-wide and 180-meter-deep hole that he has hit, then you still feel the force of the impact at that time can almost feel physically.
Other, often much larger and far older impact craters on Earth are not so easy to spot. They betray themselves on satellite imagery as much as they do
- the once up to 320 kilometers long and 180 kilometers wide Vredefort crater in South Africa,
- the Manicouagan Crater in the Canadian province of Quebec,
- the Chicxulub crater off the coast of the Mexican Yucatán Peninsula
- or the Nördlinger Ries and the Steinheimer basin in Germany.
At the bottom of the North Sea, researchers have discovered evidence of former impacts, under the ice of the Antarctic - and also in the frosty Greenland. Scientists now want to have found another copy near a collapse crater on the Hiawata glacier in the northeast of the island, which was publicly presented only last November. In the journal "Geophysical Research Letters," a group around Joseph MacGregor from the Goddard Space Flight Center in Greenbelt, Maryland, reports on the evidence that points to it.
"Exciting that such discoveries are still possible"
"We've studied the Earth in many different ways, from land, air and space - it's exciting that such discoveries are still possible," says MacGregor. After finding the first crater, he had targeted satellite data from Greenland, hoping for more finds.
And in fact, the measurements of the "Modis" spectrometer on the Nasa satellites "Terra" and "Aqua" as well as on the altitude model "ArcticDEM", which was produced from commercially available satellite data, gave indications of another impact. Radar and gravitational data from aircraft-operated "Operation IceBridge" underpinned the suspicion.
Jonathan Bamber from the University of Bristol, who was not involved in the current work, but is also looking for possible impact craters in Greenland with his team, praised the approach to close from satellites height data to the underlying structures under the ice. If one could combine this with radar measurements from airplanes, it would be "quite likely" that in this way also further interesting structures could be found.
Also Olaf iron from the Alfred Wegener Institute for Polar and Marine Research (AWI) in Bremerhaven, also not concerned with the current publication, praises the work, calls the data basis "plausible" and the interpretation "in order". Particularly striking: The now discovered area is located only about 180 kilometers from the impact point announced in November, not far from the former, under the ice hidden US military base "Camp Century". Both craters seem to be of comparable size. The newly discovered crater should have a diameter of about 35 kilometers, the specimen under the Hiawata Glacier is estimated at about 31 kilometers.
However, MacGregor and his colleagues do not believe that both craters go back to the same cosmic event. As an argument they cite, among other things, the ice that can be found above the respective geological structures. In the case of the first discovered Hiawata Crater, the current estimate is that it has been undisturbed for approximately the last 12,000 years. In the newly discovered formation, however, the team expects at least 79,000 years.
Twin craters from other parts of the world known
This information can not be easily converted into a time of impact - after all, theoretically it would also be possible for the impact of smashed and confused ice to drain into the Arctic Ocean over the years and be replaced by undisturbed ice from inside the island.
"The questions of dating are particularly challenging," says Brit Bamber. Indications include simulations of the erosion of the observed formations - and here, the scientists even come to a presumed age of 100,000 to even one million years for the currently discovered crater.
Even if the hints seem convincing: The team can not be completely sure that the discovered anomaly actually goes back to an impact. But the evidence suggests, "The only circular structure that would approach such a size would be a collapsed volcanic caldera," says MacGregor. "But the areas of known volcanic activity in Greenland are several hundred kilometers away."
In addition, a volcanic origin of the geological formation should be able to measure a magnetic anomaly there. And that was not the case, says the MacGregor. "The last security is missing," comments his AWI colleague Eisen. "But that's what the team did."
And that two unrelated impact craters are in such close proximity may indeed seem unlikely. But that is not unknown on earth. So you know examples from the Ukraine and Canada. As MacGregor says, "Overall, our evidence suggests that the new structure is likely to be an impact crater, but currently it looks unlikely that it is a twin of Hiawata."
In a nutshell: within a few months, researchers have discovered for the second time tracks under the ice of Greenland, suggesting that a large meteorite is smashed there. Even though the two formations are less than 200 kilometers apart, the team assumes that they were two separate events.