Chase Stone
Rock samples collected from the site where the Chicxulub asteroid fell show that the collision didn’t just cause widespread destruction: it also created a vast underground ecosystem, filled with warm water, where microbial life found refuge.
The asteroid impact that wiped out almost all dinosaur species was so violent that the collision site took at least eight million years coolingcreating a warm underground ecosystem where microscopic life forms were able to thrive.
The asteroid, which hit Earth 66 million years ago in the region that today corresponds to Mexico, would have been around 15 km in diameter. The impact caused climate disruption so profound that it led to the extinction of 3/4 of the planet’s species.
All the dinosaurs disappearedwith the exception of the bird ancestors, and the Earth was plunged into a nuclear winter that would have lasted at least 15 years.
The effects of the collision were felt also at great depth. “The Chicxulub impact was large enough to cause deformations at least 35 kilometers below the Earth’s surface, detectable through geophysical surveys,” it says Annemarie Pickersgillfrom the University of Glasgow, in the United Kingdom, cited by .
According to the researcher, the impact mixed approximately 10 thousand km³ of rock. The combination of molten rock and seawater created porous materialfilled with small pockets of hot water — what is called a hydrothermal system.
The presence of minerals that only form when there is liquid water and heat shows that the asteroid would have created hydrothermal environments at depths of several kilometers. But the size and duration of the heating, as well as the resulting hydrothermal system, appear to have been heavily underestimated.
Until now, it was thought that the impact site took just two million years to cool. Pickersgill and his colleagues now argue that this process It may have taken at least four times as longgiving hydrothermal life much more time to develop.
“One of the biggest unknowns about all impact-generated hydrothermal systems — and Chicxulub in particular — is how long heat keeps water circulating through the structure,” explains Pickersgill.
To understand this, the team drilled a kilometer into the crater and collected rock samples. As the potassium present in rocks transforms, over time, into argon gas, the researchers were able to measure the amount of argon retained in the samples and determine their age.
The results were presented in an article published this Tuesday in Communications Earth & Environment.
“We obtained a series of ages ranging from the moment of impact, 66 million years ago, until about 58 million years ago” says Pickersgill. “This showed us that hydrothermal activity was still ongoing in at least part of the Chicxulub structure eight million years after the impact.”
Os sulfur isotopes present in the samples provide evidence that there was microbial life in hydrothermal system and that it recovered quickly after the impact.
The results suggest that the first impact craters on young Earthand perhaps other worlds as well, may have had habitable hydrothermal systems during longer than previously thought.
“IThis gives life more opportunities to develop, evolve and spread“, says Pickersgill. “It reinforces the idea that primitive life on Earth may have found a lasting home in impact craters — and possibly also life on other planets where these huge craters are dominant surface features.”
Chris Kirklandfrom Curtin University in Perth, Australia, says that while there is “no completely unambiguous record of ongoing hydrothermal activity” at Chicxulub, there is strong evidence that the impact site remained hot for millions of years.
“Major impacts are not limited to destroying environments“, he emphasizes. “They can also create long-lived underground systems where hot fluids circulate through fractured rock,” says Kirkland.
“These environments, rich in chemical compounds, can provide protected habitats for microbes and perhaps even favorable conditions for some of the first chemical steps on the path to life”, he concludes.
