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Copenhagen (dpa) – researchers have an impact crater 31 km wide under Greenland Ice cover uncovered. With an area larger than Paris, it is one of the 25 largest known impact craters on the planet, reports the team in the journal Science Advances.
Never before has such a crater been discovered under any of the mainland continental ice sheets.
At one point, an iron meteorite one kilometer wide had to reach the target, according to researchers around Kurt Kjær of the GeoGenetics Center at the Natural History Museum of Copenhagen University. A dating of the ice crater under a kilometer was previously impossible. It was exceptionally well preserved. From a geological point of view, he could be very young.
It could even be 12,000 years ago, towards the end of the last ice age, according to Kjær. The timing of the impact was critical to understanding the impact of the impact on life on Earth. Large meteorite impacts can have a lasting effect on the climate.
The contours of the crater under the Hiawatha Glacier, in northern Greenland, were first discovered in 2015. At the edge of the ice, there was a huge circular depression. But scientists did not know at the beginning if it was really the mark of an impact. Only when the team at the Alfred Wegener Institute (AWI) in Bremerhaven mapped the area from the aircraft with a powerful ice radar confirmed this hypothesis.
"The new radar system of the AWI research aircraft was exactly the type of instrument we needed for measurements," said Olaf Eisen, a glaciologist at the Alfred Wegener Institute. The structure had to be recognized exactly. "A clearly circular boundary, a central elevation, above disturbed and undisturbed layers of ice and basal debris. All that characterizes the impact of a meteorite. "
During the summers of 2016 and 2017, the research team returned to the site to collect sediment samples and map the tectonic structures of the rock at the foot of the glacier. "Part of the quartz sand removed from the crater had only deformation characteristics that indicate a violent impact," said Nicolaj Larsen of Aarhus University. This is conclusive proof that depression under the glacier is a meteor crater.
The impact of an asteroid in North America some 66 million years ago probably contributed significantly to the extinction of dinosaurs. Its diameter is about 180 kilometers. According to a scenario presented at the beginning of the year in the journal "Current Biology", the detonation swept all the trees within a radius of about 1500 km. Others have disappeared during wildfires around the world. The emission of sulphurous vapors has probably resulted in acid rain, large amounts of soot have obstructed plant photosynthesis for years and cooled the world.
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