The asteroid that wiped out most life on Earth was a hotbed for bacteria. They were the first organisms to bounce back
Posted February 4, 2020 11:41 a.m. EST
CNN — The asteroid that wiped out the dinosaurs some 66 million years ago almost took all of life on Earth along with it.
The impact of the Chicxulub asteroid devastated 76% of all species and nearly all of the planet's vegetation. Because dust clouded the atmosphere and blocked the sun, photosynthesis slowed and phytoplankton in oceans stopped producing oxygen.
It was dark, extremely hot in the crater left by the asteroid and extremely cold everywhere else -- conditions that made it impossible for most life to thrive.
But in the days, weeks and decades after the catastrophic event, microbacteria were swept back into the crater.
"We're talking about organisms recovering within days to decades,"said Timothy Bralower, professor of geosciences at Pennsylvania State University. "From a geological viewpoint, that discovery is pretty major."
Millions of years after the asteroid struck, geologists drilled into the asteroid's peak ring -- the center of the crater -- and based on the biomarkers left behind by microbacteria millions of years earlier, they knit together a timeline of how life returned after the asteroid hit.
The findings were published last month in the journal Geology.
"(Bacteria) bounced right back," Bralower, coauthor of the paper, told CNN. "This is very consistent with what we know about bacteria today -- they can grow anywhere."
A giant tsunami deposited the first bacteria
Bacteria are some of the most resilient organisms on Earth. They've been found lodged within ice, in deep underground caves and hidden within hot springs.
So it's no wonder they were able to survive in the Chicxulub crater, buried in Mexico's Yucatan Peninsula. What's rarer, Bralower said, is how quickly the microbes were able to return.
After the asteroid struck Earth around 66 million years ago, it triggered a massive tsunami, thought to be 300 feet tall, that deposited sediment into the asteroid.
Among that sediment was cyanobacteria, microorganisms capable of photosynthesis and an important player in the nitrogen cycle. The geological record shows that these microbes were deposited immediately after the crater was formed.
"Basically the first survivors, the first inhabitants of the crater, were microbes," Bralower said.
The microbial communities in the crater remained in a "constant state of dynamic flux" in the millions of years that followed, the authors wrote.
Eventually, after dust that clouded the sun settled, phytoplankton rapidly recovered and began to photosynthesize and produce more oxygen, largely in part to the resurgence of land plants.
"Microbes kind of paved the way for higher orders of life," Bralower said.
Kliti Grice, paper coauthor and director of the Western Australian Organic and Isotope Geochemistry Centre, called the activity in the crater "post-apocalyptic microbial mayhem."
"The development and productivity of phytoplankton was accompanied by major transitions in nutrient and oxygen supplies that shaped the recovery of microbial life," Grice, a Curtin University professor, said. "There was so much going on in such a short time frame."