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New study suggests what may have actually killed off dinosaurs

In simulations, dust from an asteroid impact lingered in Earth's atmosphere for 15 years, creating an "impact winter."
An artist image of a dinosaur is shown.
Posted at 3:58 PM, Oct 31, 2023

Despite being extinct for more than 65 million years, dinosaurs still fascinate the world: Humans marvel each time paleontologists discover ancient fossils in scientific digs, unearthing the remains of previously unknown dinosaur species.

But how did these giant creatures disappear from the planet so long ago?

Many scientists agree that an asteroid impact off the coast of modern-day Mexico sparked the dinosaurs' demise. But was it the actual impact, or the resulting global natural disaster it triggered — like tsunamis, earthquakes and a massive volcanic eruption — or vaporized sulfur from the impact?

A new study looked to answer this question, and it possibly found an answer as to what killed off the dinosaurs.

In the study published in Nature Geoscience, Belgian scientists say there was a cataclysmic domino effect caused by the asteroid collision with Earth. 

After extensive simulation studies, the researchers concluded a massive cloud of debris from the collision pushed the planet into a prolonged "global impact winter," with dark clouds of dust and sulfur blocking the sun's rays and plunging temperatures and light below levels of survival.

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To reach this conclusion, the scientific team took fossilized dust samples from an ancient lake bed in North Dakota, dated to shortly after the initial asteroid impact, and used them to create a series of computer situations.

Simulation models showed that about 2,000 gigatons of dust shot up into the atmosphere following the impact, creating a dust blanket that likely lasted about 15 years after the initial collision. 

The researchers concluded that this dust cloud prohibiting the sun from reaching the planet caused Earth’s temperature to fall by as much as 59 degrees Fahrenheit and likely affected how the sun's radiation reached the planet. 

Within two weeks of impact, this lesser amount of radiation meant plants couldn't perform photosynthesis, and without this process, most plants would die. Once vegetation goes away, plant-eating dinosaurs would die off. And when those dinosaurs began to die off, other dinosaur species, like those that eat herbivores, would also be affected.

"Dust could shut down photosynthesis for such a long time that it could pose severe challenges," Cem Berk Senel, a planetary scientist at the Royal Observatory of Belgium who led the study, told The Washington Post. "It could result in a chain reaction of extinction to all species in the food chain."

It took almost two years for plants to regain their ability to photosynthesize, according to the researchers' models. By then, the damage to the dinosaur life cycle was done, but other animals survived.

"Fauna and flora that could enter a dormant phase — for example, through seeds, cysts or hibernation in burrows — and were able to adapt to a generalistic lifestyle not dependent on one particular food source generally survived better, like small mammals," study co-author Özgür Karatekin, a Royal Observatory of Belgium planetary scientist, told Reuters.

This story was originally published by Marie Rossiter on Simplemost.