Cosmic influence dated –

Much earlier than previously thought: the huge Hiawatha crater beneath the Greenland ice was formed 58 million years ago, and therefore not only when humans already existed, as previously assumed. This is due to the analysis of the rock material that was formed during the asteroid impact. New dating now raises questions about the impact of hell on the world then. Scientists say further insights could therefore lead to a better understanding of how Earth evolved during the postdinosaur era.

There was still a hellish fracture: many asteroids struck our planet in the history of the Earth and caused local or far-reaching consequences. The most famous example is the massive blow that drove the dinosaurs out of their evolutionary stage some 66 million years ago. The massive remains of the Chicxulub Crater in the Mexican Yucatan Peninsula are testimony to this impact. In addition to this particularly large scar, other scars of considerable size are also known. However, a particularly spectacular crater was only discovered in 2015: The structures of the Hiawatha Crater were only revealed during a radar investigation, as it lies dormant under a thick layer of ice in northwest Greenland.

How old is the crater under the ice?

According to research, the Hiawatha crater has a diameter of approximately 31 kilometers, making it one of the 25 largest known impact craters on Earth. It is understandable that this influence once had far-reaching consequences for the Earth’s climate. But when was that? So far, relatively few weathered structures suggested that the crater might still be young. This led to some speculation: It seemed possible that the asteroid had hit Earth just 13,000 years ago. So, perhaps he was responsible for the nearly 1000-year global cooling known as the Younger Dryas, speculates.

But as the new dating suggests, the influence of Hiawath may not have been a glacial climatic factor that may have also influenced the fate of our ancestors. The results of the international research team are based on analyzes of sand and rock that have been revealed by water flowing from the glacier subsurface in the crater area. “Since we discovered the crater seven years ago, we’ve worked hard to date it. We did several field trips to the area to collect samples from the Hiawath impact, ”says co-author Nicolaj Larsen of the University of Copenhagen. In particular, the samples currently tested are material that was produced directly by the impact.

It crashed 58 million years ago

As the scientists explain, shock overheating and melting led to changes in some substances that allow for a chronological classification by determining the decay processes. Argon tests on sand were carried out at the Natural History Museum of Denmark in Copenhagen – dated 40Ar / 39Ar. At the same time, the mineral zircon in rock samples was subjected to uranium-lead dating at the Swedish Museum of Natural History in Stockholm.

According to the scientists, the results of both approaches referred to the Palaeocene – more specifically, to a period approximately 58 million years ago. This means that Hiawatha Crater is much older than previously thought. “The age finding surprised us all,” says lead author Gavin Kenny of the Swedish Museum of Natural History. His colleague Michael Storey from the Danish Natural History Museum says: “Since both laboratories came to the same conclusion using different dating methods, I am convinced that we have established the actual age of the crater.”

The new dating now also shows the circumstances under which the impact took place: when the Hiawatha asteroid struck the Earth’s surface, the area of ​​what is now northwestern Greenland was not yet covered by a layer of ice one kilometer thick. Temperatures were rather mild there, and the region was wooded and inhabited by animals, the researchers say. The world of life on our planet was just recovering from the catastrophic effects of the Chicxulub impact eight million years earlier.

While the Hiawatha impact was far from that magnitude, it certainly devastated the region and potentially had a far-reaching impact on the Earth’s climate and nature. So far, however, no clear traces of such an effect have been detected. But it still could come: scientists say further research could possibly reveal the palaeoecological and climatic consequences of this impact in the future.

Source: University of Copenhagen – Faculty of Science, Article: Science Advances, doi: 10.1126 / sciadv.abm2434

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