UT-Austin researchers find link between asteroid, dinosaur extinction

Kevin Vu

UT researchers, in collaboration with experts around the world, discovered asteroid dust within a crater in the Yucatán Peninsula that links the extinction of 75% of life on Earth, including the dinosaurs, to a 66 million-year-old asteroid.
The researchers discovered high concentrations of iridium, an element not commonly found in Earth’s crust, that allowed them to determine an asteroid caused the crater which led to the mass extinction; they published their findings last month.
The researchers drilled into the Chicxulub crater, a 125-mile-wide impact crater found underneath the Yucatán Peninsula in Mexico, to collect different materials to discover what created the impact site, said Sean Gulick, the co-author of the research and geosciences research professor.
The impact that produced the crater caused severe regional damage and launched carbonate dust into the atmosphere, triggering global climate change that wiped out 75% of life, Gulick said. 
“(It) basically blanketed the Earth in a haze that blocks the sun,” Gulick said. “It dropped the global temperatures probably 25 degrees Celsius. So most of the world was spent freezing for most of the year after the impact to the point that you cut off photosynthesis. That meant land plants and planktons in the ocean all died. And because of that, the larger organisms all ultimately died.”

A 1980s study fueled the theory that an asteroid caused the event after scientists discovered an abundance of iridium in rocks during the age of the dinosaurs, Gulick said. 

“Iridium is one of those elements that was around in the building blocks of planets,” Gulick said. “You’d find it in asteroids … we have very little available to be observed at the surface of the Earth normally; however, if you go back to an asteroid, you’re kind of looking way back in time to what the building blocks of the solar systems originally look like, which was very enriched in iridium.”

Gulick said the 1980s research did not definitely determine an asteroid led to the impact event. He said with the recent study, they were able to close in on the asteroid theory and the precise date of the impact based on measuring sediment layers’ thicknesses. 

Research associate Cornelia Rasmussen said to ensure that the iridium found in the crater was from an asteroid, the team sent iridium samples to different labs across the globe to analyze certain elements. If those elements had the same concentration as the iridium, they could conclude they were from an asteroid since that concentration does not occur on Earth. 

In addition to the iridium and dust, the team also discovered evidence to the recovery of life after the impact in the form of planktons and microfossils, research associate Chris Lowery said.

“Things were already starting to come back in the crater within a few years of the impact,” Lowery said. “(This tells) us how insanely fast the end-Cretaceous mass extinction was and the environmental changes in it.”