Dust could have wiped out the dinosaurs | ET REALITY


On a spring day more than 66 million years ago, an asteroid crashed into the sea off the coast of present-day Mexico. Known as the Chicxulub impact, it unleashed a global shock wave, earthquakes and megatsunamis that exterminated non-avian dinosaurs and plunged the Earth into a long, dark winter.

TO study published on monday In the journal Nature Geoscience, a cause of this cold wave has been discovered: dust. The study’s authors say the fine, micrometer-sized silicate dust remained in the atmosphere for up to 15 years after the impact and contributed to global cooling. Additionally, they say, all photosynthetic activity on Earth may have completely ceased two weeks after the Chicxulub impact, largely due to fine dust.

Esteban BrusatteA paleontologist at the University of Edinburgh who was not involved in the research, said studies like this helped understand the period after the asteroid impact.

“They help us empathize with T. rex, Triceratops and the other dinosaurs that woke up in the morning at the top of the food chain but at the end of the day faced a world in chaos,” he said.

During field work in 2017, Pim Kaskes, a geologist at the Vrije Universiteit Brussel in Belgium and author of the new research, collected some fine-grained samples from a geological formation in North Dakota known as Tanis, which yielded a treasure trove of fossils. While Tanis is 2,000 miles from the Chicxulub impact, seismic waves created a mineral deposit known as the Cretaceous-Paleogene boundary. It is about four feet thick and corresponds to the event.

He shared the samples with Cem Berk Senela paleoclimate modeling researcher at the Royal Observatory of Belgium who was then a graduate student at the Free University of Brussels.

“One of the key questions we asked was what was the main determinant of the Chicxulub mass extinction because, in the literature, there have been various hypotheses addressing this phenomenon,” Dr. Senel said.

The role of dust has often been overlooked. Instead, scientists have focused on sulfur particles that the rocks released after the asteroid vaporized them, as well as soot from the impact and subsequent wildfires.

“The effects of the dust were not well known,” Dr. Kaskes said. “Most of the work that has been done used either very coarse-grained material that rains down very quickly from the atmosphere or extremely fine particles that also fall relatively quickly.”

Sulfur and soot were hypothesized, he said, to be better at absorbing and blocking sunlight compared to dust and were therefore the likely harbingers of winter’s impact.

According to Dr. Senel’s computer simulations, which incorporated data from sulfur particles, soot, and measurements of Dr. Kaskes’ samples, the fine dust was a major blow to the climate. After the asteroid, a cloud of fine dust thinner than a strand of hair clung to the atmosphere. Unlike sulfur and soot, which disappeared over time, these particles remained there for at least 15 years. This led to global average surface temperatures dropping as much as 59 degrees Fahrenheit.

Global photosynthesis was disrupted within two weeks, Dr. Senel said. Due to the fine dust, the photosynthesis of land plants was interrupted for 620 days after the impact. Four years passed before the atmosphere cleared, allowing the plants to receive enough sunlight to recover.

Jan SmithA paleontologist at the Vrije Universiteit Amsterdam who was not involved in the study, said the findings about the Earth’s cooling after the asteroid are “in the ballpark.”

But he said the idea that photosynthesis ceased for years, first proposed in the 1980s by father-son scientists Luis and Walter Alvarez, was controversial. Neither their hypothesis nor the new research explains how marine plants survived, although they may explain how dormant seeds and flowering plants recovered.

It will be necessary to incorporate fine dust measurements from more sites to draw more global conclusions. Dr. Senel and Kaskes say the computer simulation shows a slight difference in climate activity between the northern and southern hemispheres, but acknowledge that more research is needed.

“That’s something we would like to find out, to see if there are differences around the world, maybe some regions that were less affected by the meteorite impact and why some groups survived and others didn’t,” Dr. Kaskes said. “I think this is just a starting point for some interesting research and finding fossil evidence of this global response.”

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