About 66 million years ago, an asteroid approximately 12 kilometers long struck the Yucatan Peninsula, located in what we now know as Mexico, and its impact vaporized rocks, started fires of unimaginable proportions and created a giant cloud of soot that covered the Earth, whose cooling caused the extinction of 76% of the planet’s species, including dinosaurs.
Until then, it was thought that the harsh conditions responsible for the annihilation of much of life had been generated only by the incineration of surface elements, but new research published in the journal Proceedings of the National Academy of Sciences brings an unprecedented theory.
Scientists decided to investigate the chemical composition of sediments from the Chicxulub crater, the “landing” point for the space object, and from two distant places on the seabed, one in the South Atlantic Ocean and the other in the Indian Ocean. With that, they found that the initial wave of carbon came from rapidly heated fossil sources, which suggests that the soot from forest fires, despite not having helped in the situation, potentiated the global winter and prolonged it.
Dinosaurs would not have been extinguished “only” by superficial fires.Source: Pixabay
For decades, materials from that time were found in several samples, including coal, soot and chemicals called polycyclic aromatic hydrocarbons (PAHs). “These compounds are usually formed when things are heated,” explains Shelby Lyons, a geologist at Pennsylvania State University and co-author of the study.
“You can find them when grilling meat, in the exhaust of a car, in the smoke of forest fires in California, in the abandoned coal. There were several processes in progress that culminated in extinction”, adds the researcher. Still, a difficult question remains to be answered: how intense was the heat pulse from the impact and the resulting forest fires?
Compounds originate from any type of heating.Source: Pixabay
Clay Tabor, a paleoclimatologist at the University of Connecticut who did not participate in the project, acknowledges that the hypothesis is well founded and that it is “an important step in clarifying the sources of the burning markers”, but questions the exemption, even if minimal, of the role of habitat destruction resulting from the event. Lyons and his team, however, remain firm.
This is because, in the analysis of PAHs, peculiar formats were identified. According to Lyons, those originating from forest fires would have a different chemical structure. “The material had properties that seemed to burn extremely quickly, but the initial source was old carbon.” Complementing the idea, she describes that most of the plant fragments would have remained in the lowest part of the atmosphere and had been removed by precipitation, slowing the accumulation in higher parts. Estimates, of course, are part of the package.
Soot’s chemical composition may indicate where it came from.Source: Unsplash
According to the research, a weight equivalent to the 7,550 Empire Carbon buildings of the old carbon would have been launched into the sky and circulated around the globe in a matter of hours. This soot, together with large amounts of dust and sulfur-containing compounds from the vaporized rock, would have blocked the sunlight and started winter. “She would have settled in the upper atmosphere and stayed there for years,” says Lyons.
“The burnt material of the target rock is placed in the upper atmosphere of the Earth in a few hours, while that of forest fires can take months. It is possible that even a small part was the most impactful”, concludes the scientist.