The Chicxulub impact, believed to have caused the mass extinction 66 million years ago, may have resulted in a 15°C global cooling, primarily due to micrometric silicate dust, according to a new study from the Royal Observatory of Belgium. This dust could have disrupted photosynthesis for almost two years, contributing to the extinction event.
Fine dust from pulverized rock generated by the Chicxulub impact likely played a dominant role in global climate cooling and the disruption of photosynthesisPhotosynthesis is how plants and some microorganisms use sunlight to synthesize carbohydrates from carbon dioxide and water.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>photosynthesis following the event. This is suggested by a new study published in Nature Geoscience<span class="st"> Nature Geoscience is a monthly peer-reviewed scientific journal published by the Nature Publishing Group that covers all aspects of the Earth sciences, including theoretical research, modeling, and fieldwork. Other related work is also published in fields that include atmospheric sciences, geology, geophysics, climatology, oceanography, paleontology, and space science. </span><span class="st">It was established in January 2008.
</span>” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Nature Geoscience, in which researchers Cem Berk Cenel, Özgür Karatekin, and Orkun Temel of the Royal Observatory of Belgium contributed.
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 speciesA species is a group of living organisms that share a set of common characteristics and are able to breed and produce fertile offspring. The concept of a species is important in biology as it is used to classify and organize the diversity of life. There are different ways to define a species, but the most widely accepted one is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable offspring in nature. This definition is widely used in evolutionary biology and ecology to identify and classify living organisms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>species on Earth at the CretaceousThe Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era. It ended with the Cretaceous–Paleogene extinction event.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Cretaceous-Palaeogene (K-Pg) boundary 66 million years ago. 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, and not the ejection of silicate dust into the atmosphere. However, this hypothesis was based so far on a limited knowledge of the actual size properties of the dust particles.
Paleoart reconstruction depicting North Dakota in the first months following the Chicxulub impact event 66 million years ago, showing a dark, dusty, and cold world in which the last non-avian dinosaurs, illustrated with a Dakotaraptor steini, were on the edge of extinction. Credit: Mark A. Garlick
New Insights from the Royal Observatory of Belgium
To evaluate the roles of sulfur, soot, and silicate dust on the post-impact climate, Cem Berk Senel, Orkun Temel, and Özgür Karatekin, scientists from the Royal Observatory of Belgium (ROB), developed a new paleoclimate model, specialized to simulate the climate and biotic response following the Chicxulub impact. These simulations were carried out by incorporating new, high-resolution geological field data from a location in North Dakota, USA.
Sediment samples were collected and measured using laser-diffraction grain-size analysis by Pim Kaskes and colleagues at Archaeology, Environmental Changes & Geo-chemistry (AMGC) at the Vrije Universiteit Brussel (VUB) and the Vrije Universiteit Amsterdam (VUA).
“We specifically sampled the uppermost millimeter-thin interval of the Cretaceous-Paleogene boundary layer. This interval revealed a very fine and uniform grain-size distribution, which we interpret to represent the final atmospheric fall-out of ultrafine dust related to the Chicxulub impact event. The new results show much finer grain-size values than previously used in climate models and this aspect had important consequences for our climate reconstructions,” explains Kaskes.
Conceptual model of the Chicxulub impact plume showing different stages of (a) production, and (b) transport and deposition of the impact-generated ejecta (not to scale). (c) Paleoclimate model simulations showcasing the time evolution of the dust-induced photosynthetic active radiation flux across the planet following the Chicxulub impact 66 million years ago. Credit: Modified from Senel et al., 2023; Nature Geoscience
The Role of Silicate Debris
The researchers discovered that the size distribution of silicate debris (approximately 0.8–8.0 µm) revealed a larger role for fine dust than previously appreciated.
Cem Berk Senel (ROB), the lead author, describes: “The new paleoclimate simulations show that such a plume of micrometric silicate dust could have remained in the atmosphere for up to 15 years after the event, contributing to global cooling of the Earth’s surface by as much as 15 °C in the initial aftermath of the impact.”
This timescale, according to co-authors Steven Goderis and Philippe Claeys (both VUB-AMGC), is consistent with the recent global iridium layer observations from the Chicxulub impact structure, where the final atmospheric settling of fine-grained impactor material in the dust cloud was estimated to be less than 20 years.
Paleoclimate model simulations show the rapid dust transport across the planet, indicating thatthe Paleogene world was encircled by the silicate dust ejecta within a few days following the Chicxulub impact event. Credit: Simulations by Cem Berk Senel
Furthermore, the authors find that dust-induced changes in solar irradiance may have shut down photosynthesis for almost two years post-impact. The prolonged disruption in photosynthesis constitutes a sufficiently long timescale to pose severe challenges for both terrestrial and marine habitats. Biotic groups that were not adapted to survive the dark, cold, and food-deprived conditions for almost two years would have experienced mass extinctions.
This matches the paleontological records, according to co-author Johan Vellekoop (KU Leuven and Royal Belgian Institute of Natural Sciences), which show that fauna and flora that could enter a dormant phase (for example, through seeds, cysts, or hibernation in burrows) and were able to adapt to an omnivorous diet, not dependent on one particular food source (for example, deposit feeders), generally better survived the K-Pg event.
The authors suggest that the silicate dust, along with soot and sulfur, played a major role in blocking photosynthesis and sustaining an impact winter long enough to cause the catastrophic collapse of primary productivity, triggering a chain reaction of extinctions.
Overview of the Cretaceous-Paleogene boundary in North Dakota (USA). The sediments indicate a river and swamp-like environment at the end of the age of the dinosaurs. The pink-brown layer yields ejecta debris derived from the Chicxulub impact event and the grain-size data from this interval were used as input parameters for the paleoclimate modeling study. Credit: Pim Kaskes
Implications and Planetary Defense
“The Chicxulub-sized impacts by kilometer-sized asteroids causing mass extinction events are rare, however, small- and medium-sized asteroids in the range of 100 meters are far more common in the Solar System and can cause destruction on a regional to national scale,” says Özgür Karatekin (ROB).
The European Space AgencyThe European Space Agency (ESA) is an intergovernmental organization dedicated to the exploration and study of space. ESA was established in 1975 and has 22 member states, with its headquarters located in Paris, France. ESA is responsible for the development and coordination of Europe's space activities, including the design, construction, and launch of spacecraft and satellites for scientific research and Earth observation. Some of ESA's flagship missions have included the Rosetta mission to study a comet, the Gaia mission to create a 3D map of the Milky Way, and the ExoMars mission to search for evidence of past or present life on Mars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>European Space Agency’s Hera asteroid mission for planetary defense is Europe’s contribution to an international planetary defense experiment to which authors of the present research from the Royal Observatory of Belgium and VUB are contributing. The Hera mission will validate the kinetic impactor asteroid deflection technique and provide scientific information, thereby increasing our understanding of asteroid geophysics and impact processes.
The HELOS laser-diffraction grain-size analyzer at the Sedimentology Lab of the Vrije Universiteit Amsterdam. This instrument was used to measure the size properties of the Cretaceous-Paleogene boundary sediments depicted in the foreground. Credit: Pim Kaskes
Reference: “Chicxulub impact winter sustained by fine silicate dust” by Cem Berk Senel, Pim Kaskes, Orkun Temel, Johan Vellekoop, Steven Goderis, Robert DePalma, Maarten A. Prins, Philippe Claeys and Özgür Karatekin, 30 October 2023, Nature Geoscience.
DOI: 10.1038/s41561-023-01290-4
This research has been supported by Belgian Federal Science Policy (BELSPO) through the Chicxulub BRAIN-be (Belgian Research Action through Interdisciplinary Networks) project, which is a collaboration between the Royal Observatory of Belgium, Vrije Universiteit Brussel, and the Royal Belgian Institute of Natural Sciences. The authors also acknowledge the support of Research Foundation-Flanders (FWO) grants as well as a FED-tWIN project.
Source: SciTechDaily
