Scientists have reevaluated the catastrophic impact of the Chicxulub asteroid that struck 66 million years ago, revising the estimated sulfur release and its effects on the Earth’s climate.
This new data suggests a milder impact winter, offering insights into how some species might have survived the drastic changes.
Asteroid Impact and Mass Extinction
About 66 million years ago, a massive asteroid, known as the Chicxulub impactor, crashed into what is now the Yucatán Peninsula in Mexico. Measuring between 10 and 15 kilometers in diameter, the asteroid created a colossal crater about 200 kilometers wide.
The impact triggered a series of catastrophic events, including rapid climate changes that ultimately led to the extinction of the non-avian dinosaurs and approximately 75% of all species on Earth. Scientists believe the primary cause of this mass extinction was an “impact winter.
This phenomenon occurred when enormous amounts of dust, soot, and sulfur were ejected into the atmosphere, blocking sunlight, plunging temperatures, and disrupting global photosynthesis. These effects persisted for years, even decades, severely impacting ecosystems.
Reevaluating the Impact’s Aftermath
In the past, researchers largely attributed the global cooling and extinction to the sulfur released during the impact. However, estimates of the amount of sulfur-bearing aerosols released into the atmosphere have varied widely — by as much as two orders of magnitude — across different studies. This uncertainty stems from several factors, including variations in the composition of the impacted rocks, the asteroid’s size, speed, and angle of impact, as well as the pressures generated during the collision that influenced how sulfur-bearing minerals vaporized.
In the new study, Katarina Rodiouchkina and colleagues used sulfur concentrations and isotopic compositions from new drill cores of impact rocks within the crater region, combined with detailed chemical profiles across K-Pg boundary sediments around the world. This way, the authors were able to empirically estimate, for the first time, the total amount of sulfur released into the atmosphere due to the Chicxulub asteroid impact event.
New Insights into Sulfur’s Role
“Instead of focusing on the impact event itself, we focused on the aftermath of the impact,” explains chemist Katerina Rodiouchkina. “We first analyzed the sulfur fingerprint of the rocks within the crater region that were the source of sulfate aerosols released into the atmosphere. These sulfate aerosols were distributed globally and were eventually deposited from the atmosphere back onto the Earth’s surface in the months to years after impact. The sulfur was deposited around the K-Pg boundary layer in sedimentary profiles all over the world. We used the corresponding change in the isotopic composition of sulfur to distinguish impact-related sulfur from natural sources and the total amount of sulfur released was calculated through mass balance.”
Revising the “Impact Winter” Scenario
The scientists revealed that a total of 67 (± 39) billion tons of sulfur were released, approximately five times less than previously estimated in numerical models. This suggests a milder “impact winter” than previously believed, leading to a less severe temperature decline and faster climate recovery, which could have contributed to the survival of at least 25% of species on Earth following the event. While sulfur remains the primary driver of global cooling, it is important to note that a recent study by the Royal Observatory of Belgium and VUB suggests a massive plume of micrometer-sized fine dust may have played a crucial role in creating a two-year-long dark period, blocking photosynthesis and further compounding the environmental impacts.
Reference: “Reduced contribution of sulfur to the mass extinction associated with the Chicxulub impact event” by Katerina Rodiouchkina, Steven Goderis, Cem Berk Senel, Pim Kaskes, Özgür Karatekin, Michael Ernst Böttcher, Ilia Rodushkin, Johan Vellekoop, Philippe Claeys and Frank Vanhaecke, 16 January 2025, Nature Communications.
DOI: 10.1038/s41467-024-55145-6
The study was a collaboration between Luleå University of Technology, Ghent University (UGent), Vrije Universiteit Brussel (VUB), Royal Observatory of Belgium (ROB), Université Libre de Bruxelles (ULB), Leibniz-Institute for Baltic Sea Research Warnemünde (IOW), University of Greifswald, University of Rostock, Australian Laboratory Services (ALS) Scandinavia AB, Katholieke Universiteit Leuven (KU Leuven), and the Royal Belgian Institute of Natural Sciences (RBINS). This research was supported by the Research Foundation Flanders (FWO) through the EOS-Excellence of Science program (project ET-HoME) and Hercules funding for the acquisition of a multi-collector ICP-mass spectrometer at UGent, VUB Strategic Research Program, Chicxulub BRAIN-be (Belgian Research Action through Interdisciplinary Networks) and the FED-tWIN project MicroPAST both through the Belgian Science Policy Office (BELSPO).
