About 66 million years ago, a massive asteroid crashed into Earth near the site of the small town of Chicxulub in what is now Mexico. The impact eradicated roughly 75% of the animal and plant species on Earth, including whole groups like non-avian dinosaurs and ammonites. Fine silicate dust from pulverized rock generated by the impact played a dominant role in global climate cooling and the disruption of photosynthesis following the event, according to new research.
This painting depicts an asteroid slamming into tropical, shallow seas of the sulfur-rich Yucatan Peninsula in what is today southeast Mexico. The aftermath of this immense asteroid collision, which occurred approximately 65 million years ago, is believed to have caused the extinction of the dinosaurs and many other species on Earth. Shown in this painting are pterodactyls, flying reptiles with wingspans of up to 50 feet, gliding above low tropical clouds. Image credit: Donald E. Davis / NASA.
The Chicxulub impact has long been thought to have triggered a global winter 66 million years ago, which led to the demise of the dinosaurs and around 75% of species on Earth.
However, what effect the various types of debris ejected from the crater had on the climate is debated, and exactly what caused the mass extinction remains unclear.
Previous research has suggested that sulfur released during the impact and soot from post-impact wildfires constituted the main drivers of an impact winter, but the size of silicate dust particles ejected into the atmosphere has not been considered to be a major contributor.
“The Chicxulub asteroid impact event 66 million years ago showcases a unique opportunity to examine the rate, magnitude and mechanisms of extreme and abrupt climate change in Earth’s history,” said Dr. Cem Berk Senel, a researcher at the Royal Observatory of Belgium and Vrije Universiteit Brussel, and his colleagues.
“The 45-60° inclined impact of a 10- to 15-km-sized carbonaceous chondrite on the Yucatán Peninsula in Mexico triggered a chain reaction of events ultimately responsible for the end-Cretaceous mass extinction and the demise of 75% of species, including the iconic non-avian dinosaurs.”
“Yet the climatic consequences of the various debris injected into the atmosphere following the Chicxulub impact remain unclear, and the exact killing mechanisms of the mass extinction remain poorly constrained.”
To evaluate the roles of sulfur, soot and silicate dust on the post-impact climate, Dr. Senel and co-authors produced paleoclimate simulations based on an analysis of fine-grained material emplaced at a well-preserved impact deposit from a site in North Dakota, the United States.
They found that the size distribution of silicate debris (approximately 0.8-8 micrometers) revealed a larger contribution of fine dust than previously appreciated.
They inputted the measured size distribution into a climate model and estimated that such fine dust could have remained in the atmosphere for up to 15 years after the event, contributing to global cooling the Earth’s surface by as much as 15 degrees Celsius.
They suggest that dust-induced changes in solar radiation may also have shut down photosynthesis for almost two years post-impact.
“Our simulations of the atmospheric injection of such a plume of micrometer-sized silicate dust suggest a long atmospheric lifetime of 15 years, contributing to a global-average surface temperature falling by as much as 15 degrees Celsius,” the authors said.
“Simulated changes in photosynthetic active solar radiation support a dust-induced photosynthetic shut-down for almost 2 years post-impact.”
“We suggest that, together with additional cooling contributions from soot and sulfur, this is consistent with the catastrophic collapse of primary productivity in the aftermath of the Chicxulub impact.”
The results appear in the journal Nature Geoscience.
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C.B. Senel et al. Chicxulub impact winter sustained by fine silicate dust. Nat. Geosci, published online October 30, 2023; doi: 10.1038/s41561-023-01290-4
