The cataclysmic asteroid impact that occurred 66 million years ago triggered planetwide combustion that incinerated most animals within hours, followed by a global winter that eliminated any survivors, according to new research from Purdue University.
The study aims to settle a long-standing debate about the precise sequence of events that led to the mass extinction of the dinosaurs. Scientists have previously understood that the six-to-nine-mile-wide Chicxulub asteroid struck Mexico's Yucatan Peninsula, ejecting an enormous cloud of dust and vaporized rock into the atmosphere.
Previous theories suggested that hot rock droplets, known as spherules, falling back to Earth could have burned animals without shelter. However, this was not considered sufficient to explain the widespread devastation. The Purdue University team proposes that a significant portion of this rock vapor did not condense into spherules but lingered in the atmosphere as a fine dust.
This "dust blanket" trapped thermal radiation, effectively charbroiling the surface and everything on it. Researchers estimate this increased surface temperature by 3.5 times, making the falling spherules hot enough to ignite vegetation and cause widespread wildfires. "With the dust cloud trapping thermal radiation, it was like the surface and everything on it was being charbroiled," explained Professor Brandon Johnson, lead author of the study.
These fires would have consumed most animals, with many others likely succumbing to smoke inhalation. The dust also reduced sunlight, plunging the planet into darkness and a prolonged winter. "The clouds would have blocked daylight so to any animal, like humans, that don't see far into the infrared, the surface would have probably looked dark," Johnson said. "You would only have been able to see a reddish glow from the wildfires."
Once the fires subsided and the spherules finished falling, the persistent dust layer would have blocked solar warmth for decades, leading to a global winter. This environmental collapse would have starved any remaining creatures.
Researchers are now seeking geological evidence of these global wildfires to further validate their findings. Paleontologist Alfio Alessandro Chiarenza, who was not involved in the study, noted the importance of understanding which animals survived the immediate impact and their biological traits, as this could explain why some species, unlike the dinosaurs, ultimately endured extinction events.
Mass extinctions, where a vast majority of the world's life is extinguished, have occurred five times in Earth's history. The End-Cretaceous event, which ended the reign of the dinosaurs, is the most famous among them.