A shallow ocean off the coast of present-day Mexico was struck by a city-sized asteroid 66 million years ago, putting an end to the reign of the dinosaurs. However, the precise trajectory of the mass extinction that claimed 75% of the world’s species in the years following the cataclysmic impact remains unknown.
Prior studies have hypothesized that the impact, which resulted in the formation of the Chicxulub crater measuring 128 kilometers in width, discharged sulfur and ash from wildfires, which precipitated a worldwide winter characterized by record low temperatures.
A new study, however, published in Nature Geoscience on Monday, indicates that fine dust composed of disintegrated rock that was released into the atmosphere of Earth in the aftermath of the impact probably played a more significant role. Almost two years later, plants were incapable of photosynthesizing, an essential biological process, due to the degree to which this material obscured the sun.
“The cessation of photosynthetic activity for nearly two years following the impact posed significant obstacles for life,” explained Cem Berk Senel, the postdoctoral researcher at the Royal Observatory of Belgium and principal author of the study and a planetary scientist. “The food web collapsed, precipitating a series of extinctions.”
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An unanticipated lethal mechanism
Scientists devised a novel computer model to simulate the worldwide climate subsequent to the asteroid impact in order to arrive at their conclusions. In conjunction with newly collected sedimentary data from the Tanis fossil site in North Dakota, which spanned a two-decade period in the wake of the impact, the model was constructed using previously published climatic information at that juncture.
The Tanis fossil site provides a unique record of what was perhaps the most significant event in the history of life on our planet. According to fossilized fish discovered at the site, the asteroid made landfall in the springtime off the Yucatán Peninsula of Mexico. Other fossils discovered there provide unprecedented detail regarding the events of that catastrophic day.
The sample obtained from the location that was examined in the recent research comprised silicate dust particles, which were propelled into the atmosphere via an ejecta plume prior to their descent back to Earth.
This fine material may have remained in the atmosphere for as long as fifteen years following the asteroid impact, according to the team’s estimation. The researchers hypothesized that there was a potential 15-degree Celsius decrease in the global climate.
Their research represented the initial comprehensive examination of these dust particles.
“Extreme cold was long believed to have been the primary killing mechanism after the Chicxulub impact,” Senel explained. “However, the cessation of photosynthesis is certainly a mechanism in and of itself.”
“Within weeks or months of the impact, photosynthesis ceased globally,” Senel continued. “This state persisted for nearly two years, during which time photosynthesis was entirely absent.” “After two years, it then begins to recuperate once more… A full recovery occurs within a span of three to four years.
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Mysteries surrounding mass extinction
The model, according to Senel, demonstrated that the cessation of photosynthesis—the process through which plants generate oxygen and energy from carbon dioxide, water, and sunlight—was directly attributable to the fine particles emitted into the atmosphere, which obstructed the sun.
The study, according to paleontologist Alfio Alessandro Chiarenza, assisted in the resolution of certain enigmas associated with the mass extinction.
Chiarenza, a postdoctoral research fellow at the University of Vigo in Spain, stated, “The primary takeaway from this paper is that it provides more precise constraints on the composition, properties, and duration of the fine dust component ejected from the impact site, which contributed to the worldwide darkness that accompanied the impact winter.” He did not participate in the research.
Chiarenza further stated, “This newly acquired data allows for a more thorough examination of the processes and duration involved, illuminating the mechanisms that led to the cessation of photosynthesis and a substantial decrease in temperatures below what was habitable, such as for non-avian dinosaurs.”
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Source: CNN
