The effects of asteroid have rotted the Earth over its history of 4.5 billion years, and some have been responsible for global extensions such as the rest of the dinosaurs around 66 million years ago. But the planet suffers scarcities of a few hundred of these effects due to weathering processes such as erosion.
Now, using intense ice radar measurements, researchers have found a huge impact crater that has been well preserved beneath a kilometer of glacial ice in the north west. By analyzing crater size and crater deposits, they estimate that the asteroid that is turned to the Earth is more than a diameter of a diameter, has composed it mainly of iron. This finding suggests that the Earth can offer more signs of a wonderful history under its ice glaciers and leaflets.
Mark Fahnestock, a glacier at the University of Alaska Fairbanks, and his colleagues did not try to find an asteroid effect. They used archival measurements from the Greenland Ice Sheet to study their ice flows and basic baptismal rock. But when a group of Danish researchers noticed a cyclical depression in the fund on the northwestern edge of the ice sheet, under the Hiawatha Rain, their curiosity was piqued.
"Fahnestock said there are only a few ways in which you can get depressed. "River can not do that." A likely asthma was an asteroid effect, and some of the Danish researchers at the Copenhagen Museum of Natural History of Denmark, which home to a collection of iron meteorites of the Greenland, have occurred. The hunting went on.
The data clearly revealed that round depression is approximately 31km in diameter with a high edge and an area enriched near its center.
By May 2016, the researchers had secured support from a private organization to fund a series of trips over the mysterious depression in the Hiawatha Glaciate. Go at an altitude of just 350 meters in an adapted DC-3 plane, used by the researchers ice penetration radar to correctly map the layers of ice and rock under the Hiawatha Glacier. The data clearly revealed that round diameter is approximately 31km in diameter with a high edge and a rich area near its center, a geometric feature of impact grater.
Grain and Gold Cut
In order to better restrict whether this depression had actually caused by the asteroid effect, Fahnestock and her colleagues collected sandy sediments that had drained out under the Hiawatha Revolution. Back in the laboratory, the scientists found that some of the quartz grain in the sediments show evidence that a high pressure shock wave has passed through the rocks.
"There's a diagnostic effect," said Fahnestock. Along with the scary quartz grains, scientists also found high levels of elements such as nickel, cobalt, chromium, and gold, elemental signs that show iron meteorite.
This crater, if confirmed, will be the largest 25 crater on Earth according to the Earth Impact Database, the team wrote in their paper, published last week in Science Feedback. Based on its size, researchers estimated that the asteroid that created this crater was approximately 1.5km in diameter. In comparison, it has been calculated that the asteroid that spent the dinosaurs and the creation of a Chicxulub crater in the Yucatan Peninsula is approximately 10 kilometers diameter.
A permanent mystery is the lack of any rock ejecta that is associated with this cataclysm, which would have dispersed plates far and wide. Four deep chickens have been drilled in central and northern Poland, but no-one has expelled ejecta.
"The careful work done on deep ice colors would not have lost an ejecta blanket," said Fahnestock.
One theory to explain this inconsistency is that an asteroid hit the Blue Country, when traveling to the north, which would contain dispersed debris mainly to the north and in producing disproportionate layer of projection. It is not known that any of the iron metabolites held at the University of Copenhagen came from this event.
Fahnestock says it is very difficult to say that this crater is difficult, but it is possible to set junior and older boundaries. The crater can not be younger than about 11,000 years because the deposited river during the Holocene period is not disturbed; If the asteroid had hit during the Holocene, those layers would have been destroyed.
And finding a shocked grain still being taken away from the bottom of the glacier suggests that the crater was probably not over a million years ago, said Fahnestock. "Os [the crater] glacier over and over, that type of sediment would have gone. "
Chris Lowery, a paleoceanographer at the Geophysics Foundation at the University of Texas in Austin who has studied the Chicxulub crater, suggests that this crater even turns to the sea. "I hope that someone will intend to take extracts of marine sediments nearby to install the ejecta crater to the exact context of the climate records held in marine sediments," said Lowery, who was not part of the # 39; the research.
Regardless of the precise age of the crater, the impact was likely to have a significant impact on the environment. The huge number of heat produced in the adjacent ice ice effect would be. The flow of fresh water-to-sea water could then affect global patterns of sea circulation, which the researchers offer.
"This effect is very likely to have significant environmental consequences in the North Hemisphere and possibly globally."
Because fresh water is more lively than salt water, glacial melting intake could slow down or prevent cold, thick water hacking in North Atlantic. This sinking is an essential element of sea circulation and, by extension, planet weather patterns. "This effect is very likely to have significant environmental consequences in the North Hemisphere and possibly globally," the team wrote in their paper.
Fahnestock and his colleagues are hoping to return to the Blue Island. Their previous fieldwork turned briefly – just a few days – and they are eager to thread more details about the crater. "If you want to know age and geochemical signatures on the effect," said Fahnestock, "you probably want to drill the ice and recover the rock."
-Katherine Kornei (e-mail: [email protected]; @katherinekornei), Freelance Science Journalist
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doi: 10.1029 /.