Life recovered rapidly at site of dino-killing asteroid: A hydrothermal system may have helped

But the crater it left behind in the Gulf of Mexico was a literal hotbed for life enriching the overlying ocean for at least 700,000 years, according to research published today in Nature Communications.

Scientists have discovered that a hydrothermal system created by the asteroid impact may have helped marine life flourish at the impact site by generating and circulating nutrients in the crater environment.

"After the asteroid impact, the Gulf of Mexico records an ecological recovery process that is quite different from that of the global ocean, as continuous hydrothermal activity has created a unique marine environment," said the study's lead author Honami Sato, an assistant professor at Japan's Kyushu University.

Sean Gulick, a research professor at The University of Texas at Austin's Jackson School of Geosciences, is a co-author on the study. In 2016, he co-led a scientific drilling expedition to the impact site, which is called Chicxulub, that recovered core samples from the crater.

The study is the latest discovery to come from research on the 829 meters of core retrieved by the international team of researchers.

Previous research already determined that life returned to the site of the crater within a matter of years. The new study presents evidence that a hydrothermal system created by the asteroid impact and its melt sheet buried beneath the seafloor likely played a role in its recovery and sustenance for hundreds of thousands of years.

"We are increasingly learning about the importance of impact-generated hydrothermal systems for life," Gulick said. "This paper is a step forward in showing the potential of an impact event to affect the overlying ocean for hundreds of thousands of years."

The research hinges on a chemical element called osmium. A particular ratio of osmium is associated with asteroid materials. The researchers found evidence that osmium from the asteroid buried kilometers beneath the impact crater was continuously released in the Gulf of Mexico due to submarine hydrothermal activity.

In other words, as hot water moved beneath the seafloor and up toward the surface, so did traces of the asteroid. As the hydrothermal fluid cooled over time, the asteroid traces exited the water and precipitated into sediment. The researchers analyzed the sediment, which was brought to the surface in the core samples, and used it to determine the extent of the hydrothermal system and how long the enrichment of osmium lasted.

The researchers also found that as the hydrothermal system ceased releasing osmium from the asteroid, the types of marine life living at the crater site changed. They found that when the hydrothermal system was releasing this osmium, the type of plankton found living in the environment were associated with high-nutrient environments. When the osmium returned to pre-impact levels, the plankton were associated with low-nutrient environments.

This finding indicates that the ecosystem was no longer being sustained by the nutrients from the hydrothermal system being released into the overlying ocean. However, beneath the seafloor the hydrothermal system continued to persist for many millions of years; it just became ever more deeply buried by millions of years of sedimentation.

"This study reveals that impact cratering events, while primarily destructive, can in some cases also lead to significant hydrothermal activity," said co-author Steven Goderis, a research professor at the Vrije Universiteit Brussel, in Belgium. "In the case of Chicxulub, this process played a vital role in the rapid recovery of marine ecosystems."

With the demise of the dinosaurs, the Chicxulub impact is well known for its link to causing mass extinction. Gulick said that this research is important because it shows that this impact can be a catalyst for life, too. At the UT Center for Planetary Systems Habitability, Gulick is leading research on whether large impacts elsewhere in the solar system could help generate conditions that could sustain life on other planets or moons.

The science team included researchers from Kyushu University; the University of Texas at Austin's Jackson School of Geosciences' Department of Earth and Planetary Sciences and Institute for Geophysics; the Japan Agency for Marine-Earth Science and Technology; Vrije Universiteit Brussel, Belgium; Institute of Science Tokyo; Universidad de Zaragoza, Zaragoza, Spain; Universitat de Barcelona, Barcelona, Spain; and Imperial College London.