WEST LAFAYETTE — A new study from Purdue University is offering fresh insight into how the asteroid impact that ended the age of the dinosaurs became a global catastrophe.
Researchers found that when the massive asteroid struck Earth roughly 66 million years ago, it launched a blanket of fine dust into the atmosphere that trapped heat near the planet’s surface. The result was intense thermal radiation that baked much of Earth’s surface, contributing to the extinction of about 75% of all living species.
The findings, published in the Journal of Geophysical Research: Biogeosciences, suggest the dust cloud played a far greater role than the initial explosion itself.
“That much kinetic energy has to go somewhere, and eventually it is converted to heat,” said Brandon Johnson, the study’s lead author and a professor in Purdue’s Department of Earth, Atmospheric, and Planetary Sciences. “With the dust cloud trapping thermal radiation, it was like the surface, and everything on it was being charbroiled.”
The asteroid struck near what is now Mexico’s Yucatán Peninsula, creating the Chicxulub crater. While the impact caused immediate destruction, Johnson said the worldwide effects of the dust cloud transformed the event into a mass extinction.
According to the research team, the collision vaporized more than 1,000 cubic kilometers of rock and other material, sending it high above Earth’s atmosphere. As the vapor cooled, it separated into two forms: larger molten rock droplets known as spherules and much finer dust particles.
As the spherules fell back through the atmosphere, they reheated from air resistance, adding even more heat to the planet. Meanwhile, the finer dust spread around the globe, creating a layer that trapped thermal radiation instead of allowing it to escape into space.
Researchers estimate the trapped heat exposed animals living on the surface to thermal radiation about 17 times greater than the amount considered lethal to humans. The extreme temperatures likely ignited widespread wildfires and made survival nearly impossible for most plants and animals that could not find shelter underground, underwater or in other protected environments.
Alexandria Johnson, a Purdue assistant professor and co-author of the study, analyzed how the dust cloud interacted with heat.
“We found that the cloud layer was so impermeable that it trapped almost all of the heat from the falling spherules near the surface of the planet,” she said. “The dust is essentially acting like a lid on a pot.”
Photo by Purdue University
She noted that burrowing underground or taking refuge underwater would have provided protection from the intense heat because those environments warm much more slowly than the atmosphere.
The study also suggests the dust cloud lingered in Earth’s atmosphere for years or even decades. The tiny particles, measuring about 2.5 micrometers across, are similar in size to the smoke particles produced by modern wildfires and could have posed long-term health risks to surviving organisms by entering their lungs and bloodstream.
Johnson said the research highlights that the devastating global effects came not from the initial blast alone, but from the planet-wide blanket of dust that trapped heat and turned an already catastrophic impact into a mass extinction event.
The researchers believe the findings provide a better understanding of one of Earth’s most significant extinction events and the powerful role atmospheric conditions can play in shaping the planet’s history.
