Powerful impact: Researchers in Greenland have discovered the traces of a massive meteoric impact. Under the ice of a glacier in the northwest of the island lies a crater of about 31 kilometers in diameter. According to the analysis, the projectile from space must have been at least one kilometer in size – and could have had serious consequences for life on our planet. But it is still unclear when the meteorite fell on earth, as the team reports in the journal Science Advances.
© Denmark's Natural History Museum
Like all inner planets in the solar system, the Earth has repeatedly been the target of asteroids and meteorites throughout their history. These space missiles were likely to have essential parts of life like coal and hydrogen to our planet, but they also triggered global disasters – such as the loss of dinosaurs. Many of these craters still testify to many craters.
Circle under the ice
Such a trail of former researchers has now discovered in Greenland: Hidden under the ice. On this crater, Kurt Kjær from the University of Copenhagen and his colleagues came to radar analysis. "We have collected a lot of data in recent decades to find out what Greenland looks like under the ice," said co-author John Paden of the University of Kansas in Lawrence.
One day, the research group discovered a crater-like depression of 31 kilometers in diameter and 320 meters deep below the Hiawatha glacier in northwestern Greenland. On satellite images, a circular structure was visible at this point. Had it really been an impact here? To get to the bottom of this question, the researchers then conducted further targeted radar investigations – and confirmed their suspicions.
© Denmark's Natural History Museum
An iron meteorite?
The data revealed that the young ice over the job in question is flawless. However, about a mile deep shows clear traces of destruction and the ice is bursting out of rubbish. Sediment samples from the bed of a river flowing out of the Hiawatha glacier, among other things, gave quartz grain to light minerals that showed distinct shock properties.
In further investigations, researchers also noted increased concentrations of nickel, cobalt, chromium and gold in the river sediment. According to her, this indicates that the effect was caused by a rare iron meteorite. Such meteorites probably come from the nucleus of previous asteroids and are estimated to represent only about five percent of all meteorites.
Even the size of the projectile can limit the team to approximately. According to her calculations, the meteorite who left the huge crater under the ice could have had a diameter of at least one kilometer. He had been about the same size as Brocken, who struck 15 million years ago in Nördlinger Ries.
But it is still unclear when exactly the meteorite fell to the ground. "We have not been able to date directly," says Kjær. "Because the crater is exceptionally well-preserved despite the Icelandic isosion forces, we assume that it is still relatively young from a geological point of view." Specifically, the researchers classify the Hiawatha effect in Pleistocen's age. Thus, the meteorite could have been taken little less than three million years ago, but also just 12,000 years ago.
But when he fell, it seems clear that the consequences for life on earth could have been enormous. "Wreckage slammed into the atmosphere, affected the climate – and possibly caused an ice melting that could have caused a sudden freshwater impact on the Naresundet between Canada and Greenland, which could have affected the ocean currents across the region, says Paden.
"The next step will now be relevant to the effect before we can understand how the Hiawatha impact has affected our planet," says Kjær. (Science Advances, 2018; doi: 10.1126 / sciadv.aar8173)