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Pieces of asteroid that wiped out the dinosaurs tell their tale, 66 million years later

2019-09-10

Researchers have learned exactly what happened after a massive asteroid smashed into Earth 66 million years ago and decimated the dinosaurs, along with 75% of all species.

Studying material extracted from the Chicxulub crater off Mexico’s Yucatan Peninsula, a worldwide research team headed by the University of Texas at Austin have constructed a detailed timeline of the minutes and hours following the fatal hit.

The immediate impact of the blast equivalent to 10 billion World War II-sized atomic bombs caused wildfires thousands of miles away, tsunamis that reached as far inland as today’s Illinois, and blasted tons of sulfur into the atmosphere, according to a statement from the team.

And that was just in the first 24 hours, scientists at the University of Texas at Austin Jackson School of Geosciences found. What followed after the inferno and tidal wave was an extended period of intense global cooling, the statement said.

Scientists have long-thought this is how it went down, but now the hard evidence has come in.

More than two dozen scientists all over the world analyzed hundreds of feet of rock that tumbled into the impact crater within a day of the impact. Their findings were published Monday in Proceedings of the National Academy of Sciences.

The rocks were infused with charcoal bits, and sulfur was conspicuously absent, UT said in a statement. These and other signs tell the story of what happened to end the Age of Dinosaurs, said Sean Gulick, one of the lead authors and a co-leader of the International Ocean Discovery Program, the drilling mission in 2016 that unearthed the rocks from their impact site off Mexico’s Yucatan Peninsula.

“It’s an expanded record of events that we were able to recover from within ground zero,” said Gulick, a research professor at the University of Texas Institute for Geophysics (UTIG) at the Jackson School of Geosciences. “It tells us about impact processes from an eyewitness location.”

Scientists theorize that the asteroid’s impact vaporized the sulfur-bearing minerals, releasing the substance into the atmosphere, UT said. In the immediate aftermath, as National Geographic describes it, rock and water on the ocean floor were vaporized “in a flash,” sending shock waves that caused rock to churn like liquid. Then it all collapsed back into the crater, in both liquid and solid form.

Reflecting sunlight away, it prompted the global cooldown. It was this large-scale climate change, rather than the immediate blast, the caused the extinction, the scientists said.

“It was a momentous day in the history of life, and this is a very clear documentation of what happened at ground zero,” said Jay Melosh, a Purdue University professor and expert on impact cratering, who was not involved with this study.

The detailed sequence of events that the researchers gathered from the evidence left colleagues awestruck.

“They can put their fingers on moments in that event,” experimental geologist Jennifer Anderson, who studies impact cratering at Winona State University, told National Geographic. “The level of detail kind of blows you away.”