For two particularly harsh years after the dinosaur-killing asteroid slammed into Earth, the world darkened and temperatures plummeted.
Ultimately, the food web collapsed, wiping out starved terrestrial dinosaurs.
New research, published in the science journal Nature Geoscience, reveals a detailed view of what transpired after the roughly six-mile-wide rock collided with our planet. The impact hit around the Yucatan Peninsula, ejecting a nasty brew of soot, sulphur gases, and extremely fine dust into the atmosphere. Crucially, scientists found this dust proved extremely potent in blocking sunlight.
A long, callous winter, with vastly reduced light for some two years, followed.
“That shuts down photosynthesis. And breaks down the food chain,” David Fastovsky, a professor emeritus in the Department of Geosciences at the University of Rhode Island who has researched the dinosaur extinction, told Mashable. Fastovsky had no involvement in the new study.
In a well-known site that preserved fallout from the asteroid impact, the Hell Creek Formation in North Dakota, the researchers found a high abundance of these fine dust particles in the pinkish, uppermost layer where the last of the dust settled. Then they simulated, using advanced climate models, how such a high amount of dust would have behaved in the lofty skies. Global effects persisted for well over a decade, though they were greatest for the first couple years. It wasn’t just dark, but also cold.
“The new paleoclimate simulations show that such a plume of micrometric silicate dust could have remained in the atmosphere for up to 15 years after the event, contributing to global cooling of the Earth’s surface by as much as 15 °C [27 degrees Fahrenheit] in the initial aftermath of the impact,” Cem Berk Senel, a scientist at the Royal Observatory of Belgium who led the research, said in a statement.
A conception of the darkened, dusty world in the aftermath of the Chicxulub impact.
Credit: Mark A. Garlick
It takes the largest class of asteroid — a half-mile-wide or bigger — to potentially trigger such a worldwide effect. “To shut down an entire global ecosystem is truly astounding,” Fastovsky noted.
“To shut down an entire global ecosystem is truly astounding.”
This scale of rock hits Earth every 100 million years or so. Fortunately, astronomers are vigilantly scanning Earth’s solar system neighborhood for big asteroids, and have found no known threats of collision for the next century, and the likelihood of an impact in the next 1,000 years is exceedingly low. (Smaller asteroids, which are more common, hit more frequently: On average, a car-sized asteroid explodes in our skies each year, while impacts by objects around 460 feet in diameter occur every 10,000 to 20,000 years.)
The latest research adds to a preponderance of evidence that an asteroid collision triggered the Cretaceous-Tertiary Mass Extinction event, also known as the K-T event, 66 million years ago. (Some argue that potent, long-term volcanism in what’s now India could have driven the extinction.) Ultimately, some 75 percent of Earth’s species went extinct. The new study, pointing at the outsized role that dust played in collapsing the food web, fills in more of the picture of what happened so long ago. “It’s another step,” Fastovsky said.
A graphic showing how the ejecta from the asteroid collision vastly reduced the amount of sunlight on Earth.
Credit: Royal Observatory of Belgium / Modified from Senel et al., 2023; Nature Geoscience
Some life, of course, persevered. Some organisms could hibernate, some seeds could stay dormant. And some dinosaurs — avian species — survived, too. These birds, which have since evolved over millions of years, persisted, in part because they could gobble many different types of food (unlike, say, many carnivores).
Today, around 6,400 species of mammals roam Earth. Yet over 10,000 bird species inhabit the planet.
“You’re still living in the age of dinosaurs,” Fastovsky marveled.
