The asteroid that caused the extinction of the dinosaurs probably hit Earth in the spring

Being filter fillers, paddlefish, for example, retain signs of changes in their food chemistry in their bones. The photosynthetic plankton they ate was more productive in spring and summer than in autumn or winter. As the productivity of plankton increases, so does the relative amount of carbon-13, an isotope slightly heavier than the more common isotope carbon-12. Analyzing the chemical composition of each layer of paddlefish bone, Doing’s team observed that when the animal died, its carbon-13 value increased but did not rise to the top, a sign that death had come in the spring.

The team also analyzed the type of bone growth. Using the European Synchrotron facility in Grenoble, France, a particle accelerator that produces the brightest X-rays in the world, Doing and his colleagues subjected the bones to computed tomography. Their goal was to analyze in detail the seasonal changes in bone microstructure.

In spring and summer, when there is more food, the fish grow faster, so the bone parts formed during that period become more spongy and porous. During the weakening of autumn and winter, however, the growth of the fish slows down, resulting in a hard layer in the bone called the ‘stunting line’. Over time the team measured these variations from the inner layer of bone to the outer and most recent layer. As a result, all fish die at one stage of the growing growth rate, which has not yet peaked, a period consistent with spring.

With both streams of evidence pointing to the same season, researchers are more confident in their conclusions. “That’s why I think our research has achieved an amazing result in narrowing the possibilities in just one season,” explained Dennis Votten, a co-author of the study and a researcher at Uppsala University.

Life in different hemispheres

The study of the new fish in Tanis is not the only one of its kind: in December 2021, a prominent team led by Dipalmar published their analysis of the immortal season in Tanis in the journal Scientific report. The two works are based on different fossils and use different techniques, yet they reach similar conclusions. DePalma’s findings suggest that Chicxulub hit in the spring or summer, in line with During’s more specific conclusion that the effect occurred in the spring.

“We welcome the research and analysis activities, and we are pleased that these projects complement each other for a better understanding of the prehistoric world,” said Diploma, a professor. Florida Atlantic University And a PhD student at the University of Manchester, in an e-mailed statement.

The authors of the new study hope that this information will lead to further analysis of extinction events that occurred at the end of the Cretaceous period. For example, frightening signals from some sites in the Southern Hemisphere suggest that after Chicxulub, the southern hemisphere of the world has recovered twice as fast as the northern hemisphere. To what extent can these signals be affected by the season in which the effect occurred?

More clues may await us in the Southern Hemisphere fossil record, which has been studied less than in the Northern Hemisphere. “I believe that a real treasure in the Southern Hemisphere will be uncovered if we can get more funding for data-less countries,” Time explained. “It’s a gap of enough proportions.”

Kirk Johnson, director of the Smithsonian’s National Museum of Natural History, noted that although the Tanis fish undoubtedly showed a seasonal indication, 66 million years ago there were fewer marked seasonal fluctuations on Earth than there are today. At that time, there was no permanent polar ice cap and the deciduous forest touched the two poles. Therefore, scientists suspect that plants and animals in the South would benefit from surviving the immediate consequences of the effects.

Johnson, a paleontologist who specializes in Hell Creek Formation, said: “It’s better if the bomb explodes when you’re already at the shelter than when you’re out fixing the roof of the house, no question.” “But I don’t think the proponents of this argument are considering the reduced season of Cretaceous, then. [la stagione] It’s less suggestive, though not completely irrelevant. “

Johnson added that future research may cast doubt on this assumption. As the tennis site now serves as their landmark, Johnson and others are re-evaluating other sites in the Hell Creek formation, looking for similar treasures that may themselves contain surprisingly detailed evidence of dinosaur extinction.

“We find the discoveries made on the Tanis site very useful, because they reveal something unusual,” Johnson concluded. “They opened up a scene we didn’t consider.”

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