Published 26 April 2024 at 17.50
Start page. A group of international scientists has found evidence of a meteorite impact that occurred approximately one billion years ago. The traces of the crater – likely hidden under the ice sheet if it is still preserved – are among the oldest found on Earth.
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Today, there are approximately 200 confirmed impact craters on Earth, eight of which are in Sweden and twelve in Finland. This means that ten percent of all known impact craters in the world are in these two countries. One reason why there are so many here is that the bedrock is relatively old and well preserved. Another reason is that other areas on Earth are not as well researched.
Despite Greenland being the world's largest non-continental island, only one confirmed impact crater has been found there. That's because nearly 80 percent of Greenland is covered by ice sheets. But now traces of a new impact crater in the form of a small stone have been discovered. The small rock was found along the edge of the ice sheet in the Inglefield Land region of northwest Greenland.
The sample was collected in Greenland in 2019 by an international research team, and the new study has been published in the journal Geology. When the sample was analyzed using modern electron imaging techniques at the National Museum of Natural History, the researchers were able to confirm that this sample was formed in an impact crater.
Investigations carried out at the NordSIMS ion microprobe laboratory, also at the National Museum of Natural History, showed that the impact occurred approximately one billion years ago. Back then the earth looked very different compared to today. Most of the Earth's landmass was gathered in the supercontinent Rodinia.
– We looked for zircon grains in the sample, as these uranium-bearing minerals can provide precise radiometric ages. Zircon is commonly used to date geological events, but during a meteorite impact, the enormous pressures and temperatures can cause zircon grains to “reset” and record the exact time of an impact, said William Hyde, lead author of the study, then a PhD student at the Globe Institute at the University of Copenhagen , in a press release.
Previously, members of the same research team found compelling evidence for another impact crater in Inglefield Land called the Hiawatha Crater Structure. The age of that crater was recently determined to be about 58 million years. Since the new sample is estimated to be about a billion years old, it is not from the same impact crater.
– Discovering traces of a new meteorite impact was really surprising. We planned to examine more impact samples collected in Inglefield Land to study the Hiawatha Crater structure. This sample was somewhat unexpected and exciting, says William Hyde.
Where the new sample comes from is still unknown, but there are many indications that it comes from an impact crater further inland, hidden under the Greenland ice sheet. The sample could come from a possible impact crater in northwest Greenland that Nasa scientist Joseph MacGregor, one of the authors of this new study, found traces of in 2019. So far, however, it has only been identified via remote sensing and is not a confirmed impact crater. But its location lends itself well to explaining the origin of the sample.
– The study shows that it is possible to discover new impact craters by looking for loose material on the ground. This is especially needed in inaccessible places on Earth, such as the mostly ice-covered areas of Greenland and Antarctica, says William Hyde.