The crater under the ice of Greenland could arise in the time of humans
The crater under the ice of Greenland could arise in the time of humans
.For the first time an international team of scientists, led from the Museum of Natural History of Denmark (University of Copenhagen), has discovered a crater produced by the impact of a meteorite under the continental ice of the Earth. It is located in the northeast of Greenland, hidden by the Hiawatha glacier.
The discovery was made in 2015 and for three years researchers have worked to verify their discovery, which they just announced in the journal Science Advances. In the study explain that the crater is more than 31 km in diameter, which corresponds to an area as large as the entire metropolitan area of Madrid, and places it among the 25 largest impact craters on our planet.
The crater was formed when an iron meteorite, about one kilometer or 1.5 km wide, crashed into that area of Greenland, but has since been hidden under almost a kilometer of ice.
"It is exceptionally well preserved and that is surprising, because the ice of the glacier is an incredibly efficient erosive agent that would have quickly eliminated the footprints of the impact, but that means that this crater must be quite young from a geological point of view", explains the Professor Kurt H. Kjær of the Geogenetics Center at the Natural History Museum of Denmark.
So far, it has not been possible to date the crater directly, but its characteristics indicate that it was formed after the ice sheets began to cover Greenland. This indicates that it is only between three million years old and a date as close as 12,000 years ago, towards the end of the last ice age.
A 1.5-kilometer asteroid, whole or in pieces, crashed into an ice sheet in northwest Greenland in geologically recent times. (Photo: NASA Scientific Visualization Studio)
"We are inclined to think that the impact occurred in the most recent part of this time range," Kjær points out to Sinc, adding: "Humans may not have come to see the impact, but they may feel its consequences, like a change climate. Hurricane winds and earthquakes would occur within a radius of 500 km. "
The professor admits that they have tried different radiometric methods to try to date the crater, "but unfortunately the grains used were contaminated". His team, along with other experts, will continue to study and discuss this issue, as well as the possible links between the meteorite shock and some evolutionary change that could be detected in ancient human populations through DNA.
The crater was first discovered in July 2015 when investigators inspected the topography that hid the Greenland ice sheet. It was then that they noticed a huge circular depression under the Hiawatha Glacier. "We immediately knew that this was something special, but at the same time it was clear that it would be difficult to confirm its origin," recalls Professor Kjær.
In the courtyard of the Geological Museum in Copenhagen, next to the windows of the Geogenetics Center, is a 20-ton iron meteorite recovered in northern Greenland, not far from the Hiawatha glacier. "It was not very difficult to deduce that the depression could be a meteorite crater not described above, although initially we did not have evidence," says co-author Nicolaj K. Larsen, a professor at the University of Aarhus.
To confirm their suspicions, the team sent a German research aircraft from the Alfred Wegener Institute to fly over the Hiawatha glacier and map the crater and ice that covered it with a new and powerful ice radar.
Joseph MacGregor, a NASA glaciologist who participated in the study, comments: "Previous radar measurements of this glacier were part of a long-term study by NASA to map the changing ice cover of Greenland. What we really needed to test our hypothesis was exhaustive radar sounding focused there. "
"Our colleagues at the Alfred Wegener Institute and the University of Kansas did just that," he adds, "with a state-of-the-art radar system that exceeded all expectations and recorded the depression with astonishing details. A clearly circular border, central bulge, altered and undisturbed layers of ice, and basal debris. It was all there. "
During the summers of 2016 and 2017, the team returned to the area to map the tectonic structures in the rock near the foot of the glacier and collect samples of sediment carried from the depression through a melt water channel.
"Part of the 'washed' quartz sand of the crater had planar deformation characteristics (planes arranged in parallel in vitreous materials) indicative of a violent impact, and this is conclusive proof that the concavity beneath the Hiawatha glacier is a crater of meteorite ", highlights Professor Larsen.
Previous studies have shown that large impacts can profoundly affect Earth's climate, with important consequences for life on Earth after the collision. An example is the one that killed the dinosaurs. Therefore, the authors consider it important to investigate when and how the glacier crater was produced.
"The next step will be to date it exactly," insists Kjær, who concludes: "It will be a challenge, because it will probably be necessary to recover the material that melted at the bottom of the structure, but the results will be crucial to understand how the impact of Hiawatha affected life on Earth. " (Source: Museum of Natural History of Denmark)
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