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Earth’s 10 billion atomic bomb-blast: when an asteroid killed our planet (science news).

September 10, 2019 | By | Reply More

when the asteroid that called time on the dinosaurs smashed into the Earth, the impact set wildfires, triggered tsunamis and blasted so much sulphur into the atmosphere that it blocked the sun, which caused the global cooling that ultimately doomed the dinosaurs.

That’s the scenario scientists have hypothesised. Now, a new study led by The University of Texas at Austin has confirmed it by finding hard evidence in the hundreds of feet of rocks that filled the impact crater within the first 24 hours after impact.

The evidence includes bits of charcoal, jumbles of rock brought in by the tsunami’s backflow and conspicuously absent sulfur. They are all part of a rock record that offers the most detailed look yet into the aftermath of the catastrophe that ended the Age of Dinosaurs, said Sean Gulick, a research professor at the University of Texas Institute for Geophysics (UTIG) at the Jackson School of Geosciences.

“It’s an expanded record of events that we were able to recover from within ground zero,” said Gulick, who led the study and co-led the 2016 International Ocean Discovery Program scientific drilling mission that retrieved the rocks from the impact site offshore of the Yucatan Peninsula. “It tells us about impact processes from an eyewitness location.”

The research was published in the Proceedings of the National Academy of Sciences on Sept. 9TH 2019 and builds on earlier work co-led and led by the Jackson School that described how the crater formed and how life quickly recovered at the impact site.

Most of the material that filled the crater within hours of impact was produced at the impact site or was swept in by seawater pouring back into the crater from the surrounding Gulf of Mexico. Just one day deposited about 425 feet of material — a rate that’s among the highest ever encountered in the geologic record. This breakneck rate of accumulation means that the rocks record what was happening in the environment within and around the crater in the minutes and hours after impact and give clues about the longer-lasting effects of the impact that wiped out 75% of life on the planet.

Gulick described it as a short-lived inferno at the regional level, followed by a long period of global cooling.

“We fried them and then we froze them,” Gulick said. “Not all the dinosaurs died that day, but many dinosaurs did.”

Researchers estimate the asteroid hit with the equivalent power of 10 billion atomic bombs of the size used in World War II. The blast ignited trees and plants that were thousands of miles away and triggered a massive tsunami that reached as far inland as Illinois. Inside the crater, researchers found charcoal and a chemical biomarker associated with soil fungi within or just above layers of sand that shows signs of being deposited by resurging waters. This suggests that the charred landscape was pulled into the crater with the receding waters of the tsunami.

That finding supports a theory that the asteroid impact vaporized the sulfur-bearing minerals present at the impact site and released it into the atmosphere, where it wreaked havoc on the Earth’s climate, reflecting sunlight away from the planet and causing global cooling. Researchers estimate that at least 325 billion metric tons would have been released by the impact. To put that in perspective, that’s about four orders of magnitude greater than the sulfur that was spewed during the 1883 eruption of Krakatoa — which cooled the Earth’s climate by an average of 2.2 degrees Fahrenheit for five years.

Although the asteroid impact created mass destruction at the regional level, it was this global climate change that caused a mass extinction, killing off the dinosaurs along with most other life on the planet at the time.

“The real killer has got to be atmospheric,” Gulick said. “The only way you get a global mass extinction like this is an atmospheric effect.”

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Category: Science

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Colonel Frog is a long time science fiction and fantasy fan. He loves reading novels in the field, and he also enjoys watching movies (as well as reading lots of other genre books).

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