At what specific moment did the asteroid that killed the dinosaurs hit? About 66 million years ago, a 10 km wide asteroid crashed into Earth near the small town of Chicxulub, in what is now Mexico. The impact unleashed an incredible amount of climate-changing gases in the atmosphere, triggering a chain of events that led to the extinction of non-avian dinosaurs and 75% of life on the planet.
Specifying the exact moment of the impact event
Now, based on a histological and histoisotopic analysis of a unique set of fossil fish, scientists have inferred that the Chicxulub impact occurred during the late spring or early summer, shortly after the fish spawning season and the most continental species. This is the conclusion of a team led by the University of Manchester that studied the deposits at the Tanis fossil site in North Dakota that formed at the time of impact.
“The Chicxulub impact at the end of the Cretaceous triggered the last mass extinction on Earth, extinguishing about 75 percent of species diversity and facilitating a global ecological shift toward mammalian-dominated biomes ,” the team wrote in their paper. “The temporal details of the impact event on a fine scale (hour to day) […] have largely eluded previous studies.”
Knowing the exact moment of this impact is vital to gain a better understanding of the course of the mass extinction that followed this tragic collision, since it is not the same if it happens during the reproductive or hibernation season, for example. Time can affect which species go extinct and how well the others can recover. It can also help us predict how the life we have today might respond if a similar catastrophe were to occur on Earth in the future.
“The hindsight that the fossil record provides can produce critical data, which can be applied today, so that we can plan for tomorrow,” said paleontologist Phil Manning of the University of Manchester and leader of the work that publishes the journal Scientific Reports. .
Thus, the study found that the fish, turtles and dinosaurs buried there were in the main growing season when the disaster occurred. Many of the paddlefish and sturgeon fossils found at the site were young enough to have been recently born. And assuming that the fish in this area of the Cretaceous followed the same seasonal reproduction cycles as they do today, the researchers concluded that their deaths occurred in the spring or early summer.
“The time of year plays an important role in many biological functions such as reproduction, feeding strategies, host-parasite interactions, seasonal latency and reproduction patterns,” DePalma clarified. “It is therefore not surprising that the time of year when a global hazard occurs can play a significant role in the severity of its impact on life.”
Referencia: Robert A. DePalma et al, 2021. Seasonal calibration of the end-cretaceous Chicxulub impact event. Scientific Reports. 11, 23704; doi: 10.1038/s41598-021-03232-9
