New analysis of dust deposits left after the massive asteroid hit Earth around 66 million years ago suggests the event created a thick, worldwide dust blanket that drove heat down toward the planet’s surface, resulting in global wildfires.
The researchers behind the new study said the evidence for a post-impact dust blanket and resulting heat wave adds new fuel to the debate about what role, if any, the Chicxulub asteroid played in their extinction, by suggesting most unsheltered animals would have died instantly.
Scientists Debate Connection Between Asteroid Impact and Dinosaur Extinction
While scientists agree that a massive chunk of space rock slammed into Mexico’s Yucatan Peninsula 66 million years ago, they have continued to debate the event’s impact on the end of the dinosaurs‘ reign. Still, the timing of the two events, and the evidence for a mass extinction of animals incapable of seeking the necessary shelter to survive the asteroid’s impact, has led most to connect the two events to some degree.
Further studies of the impact have shown that the event’s immense heat and pressure vaporized a massive amount of rock, resulting in a huge cloud of dust and rock vapor high into the Earth’s atmosphere. As some of that dust condensed into tiny rock ‘spherules’ and slammed back into the surface, the friction between them and the air generated a corresponding heat pulse.
According to the authors of the new study, many theories suggested that this heat pulse acted like a planetary-wide broiler, including “radiating enough heat to sizzle thin-skinned animals without shelter,” but not enough for plants to suddenly burst into flames. The team said that this result temporarily caused researchers to move away from the idea that the immediate impact event caused the dinosaur’s extinction rather than a longer, more drawn-out event.
Now, after years of new ideas, the team said that a 2023 discovery once again changed the debate, leading to their new proposal.
Atmospheric Layer of ‘Post-Impact’ Dust Would Have Magnified Heat Wave 3.5 Times
According to the team’s statement, the 2023 discovery involved a layer of “extremely fine post-impact dust” that could have formed from rock vapor that did not condense into spherules.
“It reinvigorated my interest in what happened to the leftover vapor,” explained Brandon Johnson, a planetary scientist at Purdue University and lead author of the study detailing the new theory, “that’s where this work started.”
To determine what effect such a post-impact dust layer might have had on dinosaurs and other terrestrial animals, the team plugged the new data into previous simulations of the Chicxulub event. Johnson and colleagues especially wanted to know how the dust layer would boost Earth’s retention and release of heat energy generated by the falling rock spherules.
After running several simulations, the team determined that the dust layer would have increased the surface heat by 3.5 times compared to an event that only included the falling spherules. Unlike earlier models, this new version with the dust layer included showed that the heat pulse would have been enough to “kill animals and start spontaneous forest fires.”
“We’re in the realm where we might be essentially killing off everything within that first hour or two,” Johnson explained.
Notably, the researcher said his team’s concept is not unlike alternative extinction theories that credit a global post-impact winter for the eventual mass extinction of dinosaurs and other lifeforms.
“It seems counterintuitive,” Johnson said, “but actually it’s the same effect.”
The research compared the idea to how an insulated mug can keep hot coffee hot and iced coffee cold.
“Once the spherules finished falling and the fires petered out, massive dust clouds could have blocked warmth from the Sun for years to decades and caused a global winter,” the authors explained.
Results Could Help Unravel Why Some Animals Survived, and Others Didn’t
When discussing how the team’s findings might affect the ongoing debate about dinosaur extinction, Johnson said the work seems to offer strong support to the impact extinction theory.
“This work of ours supports this idea that it really is the impact that was devastating to terrestrial life and caused the mass extinction,” the researcher explained.
Although the team suspects that the global fires caused by the dust amplified the heat wave, they point out that a more complete geological record would likely be needed to provide confirmation. Alfio Alessandro Chiarenza, a paleontologist at University College London who was not involved with this study, said researchers could find a record of global wildfires, but “we just don’t have it so far.”
“It would be great to figure out which animals survived right at the impact and what their biological features were,” Chiarenza added. “This could finally tell us why some animals made it when others, like the dinosaurs, didn’t.”
The study “Heat and wildfires during the K-Pg mass extinction enhanced by fine dust” was published in the Journal of Geophysical Research: Biogeosciences.
Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org