Powerful Impact: Researchers in Greenland have discovered the traits of a massive meteor impact. Under the ice of a glacier in the northwest of the island is a crater about 31 kilometers in diameter. According to the analysis, the projectile of space must be at least one kilometer in size – and may have had serious consequences for life on our planet. However, it is still unclear when the meteorite crashed on Earth, as the team reports in the journal Science Advances.
© Museum of Natural History of Denmark
Like all the inner planets of the solar system, Earth has been repeatedly targeted by asteroids and meteorites throughout its history. These space missiles would probably bring vital life elements like carbon and hydrogen to our planet, but they also triggered global disasters – such as the disappearance of dinosaurs. Many of these craters are still witness to numerous craters.
Circle under the ice
This trail of past impact researchers discovered in Greenland: hidden under the ice. On the trail of this crater, Kurt Kjær of the University of Copenhagen and his colleagues analyzed the radar. "We've collected a lot of data over the past few decades to find out how Greenland is under the ice," says co-author John Paden of the University of Kansas in Lawrence.
One day, the team of researchers noticed a crater-like depression about 31 kilometers in diameter and 320 meters below the Hiawatha glacier in northwestern Greenland. In satellite images, too, a circular structure was visible at this time. Was there really an impact here? In order to get to the bottom of this question, the scientists conducted further investigations of targeted radars – and confirmed their suspicions.
© Museum of Natural History of Denmark
An iron meteorite?
The data revealed that the young ice on the job in question is flawless. At about a kilometer deep, however, they show clear traces of destruction and the ice is interspersed with debris. Samples of sediments from a riverbed flowing out of the Hiawatha glacier, among other things, brought quartz grains to light – minerals that showed distinct shock characteristics.
In further investigations, the researchers also noted high concentrations of nickel, cobalt, chromium and gold in the river sediment. In his view, this suggests that the impact was caused by a rare iron meteorite. Such meteorites probably come from the nucleus of ancient asteroids and are estimated to represent only about five percent of all meteorites.
In addition, the size of the projectile may limit the crew to approximately. According to his calculations, the meteorite that left the huge crater under the ice sheet could have a diameter of at least one kilometer. It would have been as large as the Brocken, which struck 15 million years ago in Nördlinger Ries.
However, it is not yet clear when exactly the meteorite fell to the ground. "We could not date directly," says Kjær. "Because the crater is exceptionally well preserved, despite the enormous erosion forces of icy ice, we assume that it is still relatively young geologically." Specifically, the researchers classify the impact of Hiawatha in the Pleistocene era. Thus, the meteorite could have been taken a little less than three million years ago, but also only 12,000 years ago.
But whenever it fell, it seems clear that the consequences for life on Earth could have been enormous. "Wrecks were released into the atmosphere, affected the climate – and possibly caused a thaw, which could have caused a sudden impact on freshwater in the Nares Strait between Canada and Greenland, which could have affected the ocean currents in the region" says Paden.
"The next step will now be to accurately date the impact before we can understand how the impact of Hiawatha has affected our planet," Kjær said. (Science Advances, 2018; doi: 10.1126 / sciadv.aar8173)