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

Researchers from the University of British Columbia studying material from the mysterious dinosaur-killer meteorite that wiped out 75% of Earth’s species, including non-avian dinosaurs, have determined the doomsday space rock was likely a rare type of carbonaceous chondrite.

Although the international team behind the discovery, which includes researchers from Paris, Brussels, and Vienna, said the evidence for this category of “oddball” meteorite offers a viable solution to its mysterious composition, they note that the rarity of chondrite meteorites makes its origin a new mystery that needs to be solved by future research.

They also note that a chondrite meteorite impact would have much less effect on atmospheric sulfur, which is critical to most extinction models, potentially casting doubt on its central role in dinosaur extinction.

Many Details About the Dinosaur Killer Meteorite Remain a Mystery

According to a statement, the Cretaceous-Paleogene impactor resulted in one of the largest extinction events in the planet’s history. While most scientists agree that the event played a significant role in ending the dinosaurs’ reign, the study’s authors note that “the exact mechanism and the extent of the impact-extinction link are debated.” They also note that the origin and composition of the dinosaur killer have remained a mystery.

An analysis of the Chicxulub impact structure reveals that the doomsday dinosaur-killer meteorite was between 10 and 15 kilometers (approximately 6 to 9 miles) wide. Estimates also suggest it impacted Earth at 64,000 km/m (40,000 mph) beneath the modern-day Yucatán Peninsula in Mexico.

Although previous studies identified the meteorite as similar to carbonaceous chondrites, the researchers said that carbonaceous chondrites are a diverse class of space rock, “leaving the exact nature of the impactor unclear.”

“Carbonaceous chondrites of the Ornans class (CO) are definitely not like the typical meteors you find in museum collections,” explained study co-author and visiting professor Dr. Philippe Claeys.

For example, the professor explained, a CO contains fewer volatile elements, such as zinc, carbon, Sulphur, and H20 “than other classes of meteorites we’ve discovered so far on Earth.”

One Mystery Solved

To try to unravel the mystery of the dinosaur-killer meteorite, the researchers teamed up with scientists from the Institut de Physique du Globe and the Université de Paris to conduct high-precision nickel isotope measurements of meteor samples from the event that have been collected over the years from the thin, worldwide layer of clay created by the explosive impact.

Dr. Claeys, a professor at Vrije Universiteit Brussel, currently visiting the Pacific Center for Isotopic and Geochemical Research in Earth, Ocean and Atmospheric Sciences at UBC, noted the challenging nature of the isotopic analysis, primarily due to the limited number of samples.

“Only a minute fraction of the projectile is preserved in the planet’s KT clay layer because the entire meteorite vaporized upon impact,” the researcher explained.

Still, the study authors explain, evaluating Nickel isotopes offers several advantages over other testing methods. For example, Nickel has five isotopes that the researchers note  “allow for up to three separate internally normalized signatures.” They also highlight the availability of Nickel in “virtually all types of available early Solar System solids,” including iron meteorites, which allows for comparison with a wide variety of potential impactors.

Finally, they write, CI chondrites have a distinct Ni isotope signature from the rest of the class, therefore “making it possible to distinguish a CI-like impactor clearly” from other meteorite types.

After completing an isotopic analysis of samples of marine clays containing microscopic pieces of the ejecta, the team said their results “constrain the impactor to one group of carbonaceous chondrites, CO chondrites, “ as well as some evidence for “ungrouped chondrites.”

“By combining our new Ni isotope data with the existing evidence, we demonstrate that the composition of the Chicxulub impactor was most likely CO chondrite-like,” the researchers write, adding that this identification is possible “given nickel’s high abundance in primitive meteorites compared to the Earth’s crust and the distinct isotope compositions they record.”

A New Mystery is Created

While the isotopic analysis offers a compelling solution to the composition of the famed dinosaur-killer that slammed into Earth millions of years ago, the team said the identification casts doubt on the extent of its role in the dinosaurs’ extinction. Specifically, they note that CO chondrites are “dry” compared to others in their class, meaning they contain much less of the volatiles that most extinction theories cite as a significant mechanism.

“As highly volatile elements, such as C, N, and S, in CO chondrites are less abundant than in the typical CCs, questions arise whether the impactor was an essential contributor to the volatiles released during the impact,” they explained.

The most important volatile in most extinction theories is Sulfur (S). However, the authors note, CO chondrites would deliver “approximately half as much S” as more common types.

If the new analysis is correct, it also puts the dinosaur-killer’s origin in question. The authors note that possible sources include distant, debris-rich regions of the outer Solar System or even the outer area of the asteroid belt near Jupiter.

Combined with the compositional analysis lacking volatiles, the team notes that their findings allow “further studies of the mechanism behind the extinction.”

Finding “Doesn’t Alter Our Theory” of What Caused Land Dinosaur Extinction

When discussing the potential implications of their findings, the researchers said their study “highlights the extraterrestrial origin of the K-Pg mass extinction and the isotopes of Ni as a well-suited tool to characterize the nature of extraterrestrial material on Earth.” They also note that the composition of the dinosaur-killer “opens the door for further research into the connection between the impact and the mass extinction.”

From a scientific perspective, the research said their work “highlights the use of Ni isotopes in fingerprinting extraterrestrial materials on Earth,” and helps evaluate the risks associated with “potential future impact events and their consequences.” The study also shows how even an uncommon type of space rock can permanently alter the planet’s history.

“Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were,” Dr. Claeys said.

The researcher also noted that the lack of volatiles in this category of meteorite “doesn’t alter our theory of what caused the extinction event.” However, he notes, if correct, the result “makes it less likely that Sulphur contained in the impactor was the smoking gun.”  Instead, the fine debris “thrown into the atmosphere” by the forceful impact would have been the primary factor in the end of the dinosaurs.

The study “The origin of Cretaceous-Palaeogene impactor revealed by nickel isotopes” was published in Science Advances.

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