Scientists from Purdue University have proposed a refined sequence of events for the extinction of the dinosaurs, asserting that the asteroid impact 66 million years ago triggered planetwide fires that killed most animals within hours, before a global winter eliminated any survivors. This research aims to settle a long-standing debate among scientists regarding the primary cause of the mass extinction.
The study, led by Professor Brandon Johnson, suggests that the impact of the Chicxulub asteroid, a space rock estimated to be six to nine miles wide, created an enormous cloud of dust and vapor. While some of this vapor cooled into small rock droplets known as spherules that fell back to Earth, the researchers believe a significant portion of fine dust lingered in the atmosphere. This "dust blanket," according to the study, trapped thermal radiation, significantly increasing surface temperatures and igniting widespread wildfires.
"With the dust cloud trapping thermal radiation, it was like the surface and everything on it was being charbroiled," Professor Johnson explained. "And that's what killed the dinosaurs and all the other animals."
Previous theories posited that while the falling spherules were hot, they were not hot enough to cause widespread spontaneous combustion, leading some scientists to doubt the immediate impact as the sole cause of extinction. However, the Purdue team's research, based on new evidence from rock layers, indicates that the lingering dust intensified the heat from the spherules. This combination, they argue, was sufficient to ignite vegetation like grass, pine needles, and even wood, leading to fires that would have killed animals not sheltered underground or in water.
Alexandria Johnson, a researcher specializing in clouds and part of the study, noted that even survivors of the intense heat would have faced dire consequences from smoke inhalation. "Even if critters were to survive the charbroiling, they would likely have had lasting health effects from these particulates as well," she stated. "But when you look at the time scales of the cooking versus the inhalation risks, the cooking is much faster."
Following the initial hours of intense heat and fire, the persistent dust cloud would have blocked sunlight for decades, ushering in a period of global winter. This prolonged darkness and cold would have led to starvation for any animals that managed to survive the initial inferno, completing the extinction event.
The researchers intend to seek further evidence of these global wildfires to support their findings. Paleontologist Alfio Alessandro Chiarenza, who was not involved in the study, expressed interest in identifying the biological traits of any species that survived the immediate impact, which could shed light on the differential survival rates during mass extinction events.