About 66 million years ago, an asteroid broke into the earth, triggering a mass extinction that ended dinosaur rule and wiped out 75 percent of its life.
Although the asteroid killed species, new research led by the University of Texas at Austin found that the crater he left harbored a marine life less than a decade after impact, and a thriving ecosystem within 30,000 years had. a much faster recovery than other locations around the world.
Scientists were surprised by the results that undermined a theory that reclamation at sites closest to the crater is the slowest due to environmental contaminants such as toxic metals. Instead, the findings suggest that global recovery has been driven primarily by local factors, a result that could impact the environment today shaken by climate change.
"We found life really fast, surprisingly fast, within a few years of impact," said Chris Lowery, a postdoctoral fellow at the University of Texas Institute of Geophysics (UTIG), who led the research. "It shows that there is generally no great predictability of recovery."
The research was published on May 30 in the journal Nature . UTIG researchers Gail Christeson and Sean Gulick and postdoctoral fellow Cornelia Rasmussen, along with a team of international scientists, are co-authors of the article. UTIG is a research unit of the Jackson School of Geosciences.
The evidence of life comes primarily in the form of microfossils – the remnants of unicellular organisms such as algae and plankton – as well as the caverns of larger organisms found in rocks recovered during the recent scientific drilling of the crater International Ocean Research Program and International Continental Drilling Program
The tiny fossils are strong evidence that organisms inhabited the crater, but also a general indicator of habitability in the environment, years after impact. The rapid recovery suggests that other life forms than the microscopic ones live in the crater shortly after impact.
"Microfossils leave you with this complete picture of what's going on," Lowery said. "You get a piece of rock and there are thousands of microfossils so we can look at changes in the population with a very high degree of confidence … and we can use that as a sort of proxy for the organisms on a larger scale."
Two to three years after the impact, the scientists found first indications of the appearance of life. The evidence includes caves of small shrimp or worms. Thirty thousand years after impact, there was a thriving ecosystem in the crater, with thriving phytoplankton (microscopic plants) supporting a diverse community of organisms in surface water and seabed. In contrast, other areas around the world, including the North Atlantic and other areas of the Gulf of Mexico, similarly needed up to 300,000 years to recover.
The core, which contained the fossil evidence, was launched during a 2016 expedition led by the Jackson School. In this study, the scientists have established a unique core section that captures the seabed after impact in unprecedented detail. While core samples from other parts of the ocean have deposited only millimeter of material in the moments after impact, the section of the crater used in this study contains more than 130 meters of this material, of which the top 30 inches are slowly from the surface put off cloudy water. This material provides a record that captures the seabed environment days to years after impact.
"At this core one can see layers, while in others they are generally mixed, meaning that the records of fossils and materials are churned up and one can not resolve tiny time intervals," said co-author Timothy Bralower, professor of Micropaleontology at Pennsylvania State University. "We have a fossil record here where we can resolve daily, weekly, monthly and yearly changes."
Ellen Thomas, a senior geology and geophysics researcher at Yale University who was not part of the study, said that although she believes that the paper speaks for a speedy recovery, she expects the larger scientific community to attend will be interested in researching the data for themselves.
"In my opinion, we will see a considerable debate about the character, age, sedimentation rate, and microfossil content … especially the speculation that burrowing animals may have returned within years of impact," Thomas said.
The relatively rapid recovery of life in the crater suggests that the asteroid caused extinction It did not hinder recovery. The scientists point out that local factors such as water circulation, interactions between organisms and the availability of ecological niches have the greatest impact on the recovery rate of a given ecosystem.
The results suggest that recovery from a global catastrophe could be a local affair.
The expedition will search the crater of the dinosaur-deadly asteroid
Christopher M. Lowery et al. Rapid Recovery of Life at the Zero Point of Cretaceous Mass Extinction, Nature (2018). DOI: 10.1038 / s41586-018-0163-6