Asteroid Impact Sulfur Release Less Lethal in Dinosaur Extinction
Previous studies posited that the mass extinction that wiped out the dinosaurs was caused by large volumes of sulfur released from rocks within the Chicxulub crater following the asteroid impact. A new paper published in the journal Nature Communications questions this scenario. The authors, including Cem Berk Senel and Özgür Karatekin of the Royal Observatory of Belgium, used groundbreaking empirical measurements of sulfur within the related Cretaceous-Paleogene (K-Pg) boundary layer. They demonstrated that the role of sulfur during the extinction is overestimated.
Paleoart reconstruction depicting the Chicxulub impact event 66 million years ago and a post-impact cold, barren, and cloudy landscape where the transition between the ‘Age of the Dinosaurs’ to the ‘Age of the Mammals’ is illustrated – surviving ground-dwelling mam-maliaformes are present next to skeletons of the extinct Triceratops horridus and Dakotaraptor steini. Artwork by Aleksei Rodushkin.
The Chicxulub Impact and the Role of Sulfur
The Chicxulub meteorite impact has long been thought to have triggered a global impact winter, which led to the demise of the dinosaurs and around 75% of species 66 million years ago. In 2023, a groundbreaking study led by Cem Berk Senel of the ROB demonstrated the major role of impact-generated dust in the dinosaur’s demise. Together with Özgür Karatekin, he participated in a new study led by Katerina Rodiouchkina (associated to Luleå University of Technology in Sweden, and UGent and VUB in Belgium) to examine the role of sulfur that was released by the same impact.
Most previous studies considered sulfur as the most crucial factor in driving the cooling and extinction after the impact event. However, estimates of the volume of sulfate aerosols released from the vaporization of the impacted rocks in Mexico have varied widely over two orders of magnitude from one study to another. This is because such estimates are largely based on uncertain parameters, such as the proportion of sulfur-bearing rocks at the impact location, the size, velocity, and impact angle of the asteroid, and the resulting shock pressures of sulfur-bearing minerals.
Current-day map showing the impact site of Chicxulub and different Cretaceous-Paleogene sites analyzed in this study (modified from Rodiouchkina et al., 2025).
Estimating of the Amount of Sulfur Released 66 Millions of Years Ago
In the new study, the researchers 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.
‘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 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.’
Comparing estimates of the amount of sulfur (S) (in billion tonnes or gigatonnes; Gt) vaporized following the Chicxulub impact event determined in the current study (empirical, black triangle markers) to previously published values (numerical, blue square markers). The empirical S estimations are based on S isotope ratios and S-concentration values from various K-Pg (Cretaceous-Paleogene) boundary sites. The purple shadowed region shows the average of all these 5 terrestrial K-Pg boundary sites (67 ± 39 Gt), excluding the marine Brazos River site due to the corresponding large uncertainties. Previously published numerical estimates are included. (Modified from Rodiouchkina et al., 2025.)
A Milder Impact Winter Caused by Sulfur
The scientists revealed that a total of 67 ± 39 billion tons of sulfur was released, approximately five times less than previously considered . 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 the 2023 study led by Cem Berk Senel of the ROB 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.
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).
Reference
Katerina Rodiouchkina, Steven Goderis, Cem Berk Senel, Pim Kaskes, Özgür Karatekin, Michael Ernst Böttcher, Ilia Rodushkin, Johan Vellekoop, Philippe Claeys, Frank Vanhaecke. Reduced contribution of sulfur to the mass extinction associated with the Chicxulub impact event. Nature Communications (2025). DOI: 10.1038/s41467-024-55145-6.