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About 1.2 billion years ago, an asteroid measuring over one kilometer wide crashed in northwestern Scotland. The problem is that scientists do not know exactly where the meteorite fell, because the traces of the crater have long since disappeared. With new research, however, scientists are beginning to focus on the area of impact.
According to a study conducted by Kenneth Amor of the Department of Earth Sciences at Oxford University, an asteroid measuring between 1 and 2 kilometers wide would crash into the Scottish Minch Basin in Scotland there are about 1.2 billion years. The estimated location of this old collision is just off the Highland coast, about 15 to 20 kilometers west of Enard Bay.
The crater is no longer visible on the seabed after being buried by newer rocks over the course of hundreds of millions of years. Traces of the old impact were detected in the reddish rocks of the Stac Fada deposit on nearby shores. The analysis of these minerals allowed Amor and his colleagues to triangulate the location of the crater, which they describe in a research published today in the Journal of the Geological Society.
"This marks another interesting chapter in the crater research of the enigmatic deposits of Stac Fada in northwestern Scotland," a geologist at Western University in London, Ontario told Gizmodo in an email. , Canada. . "If the authors are right, this would be the first confirmed crater in the UK."
The data presented in the new article suggests that the feature lies somewhere between the Scottish mainland and the western islands, but a geophysical survey will be needed to provide definitive proof. Amor and his colleagues estimated the crater size at a width of about 13 to 14 kilometers and at a depth of 3 kilometers.
"It's gratifying to know now that Britain has its own crater of impact, even though it's old enough," said Jay Melosh, professor of Earth Sciences, of the 39, atmosphere and planets at Purdue University, in an email addressed to Gizmodo. "Unfortunately, the crater itself should not become a tourist attraction like the Meteor Arizona crater of the United States, as it is completely buried under thick layers of younger rocks," said Melosh, who n & # 39; 39; also did not participate in the new study.
Insiders of this ancient collision first appeared in 2008 when Amor, together with researchers from the University of Aberdeen, found evidence of what appeared to be the debris field of 39; an old asteroid impact. The precise location of the crater however could not be determined.
In 2015, a gravitational analysis of the area suggested that the crater was about 50 km wide and was located east of the outcrop of Stac Fada, a narrow band of 39; extending about 50 km to the north and south along the northwest coast of Scotland. .
"However, this new study revises this estimate and, based on flow models in the deposit, suggests that the crater is only 12 kilometers in diameter and that it is located in the west. from the outcrop! "wrote Melosh. "This uncertainty illustrates the difficulty of reconstructing the entire crater from a narrow band of its ejected material. But it also illustrates the importance of a careful analysis of the flow directions from subtle indices in the deposit. "
Indeed, the crater may be invisible, but associated rocks on the shore have provided important clues to the cataclysmic event. The approximate location of the crater has been deduced from two indirect ways.
"When the asteroid struck thunder in formation, tons of pulverized and molten rock, mixed with hot gases, were thrown at high speed in all directions," Amor explained in an email to Gizmodo. . "These debris flows [traveled] great distances at a speed of several hundred kilometers at the hour. They eventually stopped, especially if they encountered an obstacle such as a hill. On one of the outcrops, we saw evidence showing that the debris flow stopped, but that the material behind was still trying to progress and that it was was pushed over the blocked material. This gave a very good directional information for the origin of the crater.
Amor and his colleagues also examined the alignment of magnetic particles in the rock.
"The mixture of hot gas and powdered rock behaves like a high-density fluid," said Amor. "Alignment of mineral grains can give directional information about the current direction. This technique has been successfully applied to determine current directions in ancient river systems and volcanic ash deposits, but it is the first time that it is used for a meteorite impact. "
This particular impact occurred while life was still in its infancy. No plants or animals lived on dry land, but there was some life in the oceans, such as microbes and the first forms of multicellular complex life. In addition, Scotland was closer to the equator at the time and had a semi-arid environment. "The landscape of the Earth would have looked a bit like Mars when there was water on the surface," said a statement from Oxford University about the research.
"Once we were able to locate the crater, we were able to conduct a focused geophysical survey to determine the actual dimensions of the crater," said Amor. "The impact craters on Earth are extremely rare and are quickly destroyed by erosion and plate tectonics or buried by sediments. The better we can understand how they formed and the better we can understand the observations on the planets and the rocky moons of the solar system. "
Ideally, Amor would like to conduct a high-resolution 3D seismic survey in the Minch Basin between mainland Scotland and the outer western islands. But "to be abroad it would be very expensive," he said.
Finally, Melosh said that the presence of this crater in the UK is a good illustration of the fact that no part of our planet is immune to meteorite impacts.
"Sooner or later, most of us hope later, a significant impact will occur where we live," he said.
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