Dinosaur extinction: dust generated climate catastrophe – 10/30/2023 – Science

To use an understatement, it was a bad day for Earth when an asteroid struck Mexico’s Yucatan Peninsula 66 million years ago, causing a global calamity that led to the extinction of nearly three-quarters of the planet’s species and ended the Earth’s era. of Dinosaurs.

The asteroid’s immediate effects included massive fires, earthquakes, a huge shock wave in the air, and huge standing waves in the oceans. But the checkmate for many species was the climate catastrophe unleashed in the following years, when the skies darkened due to clouds of debris and temperatures plummeted.

Researchers revealed this Monday (30) the important role played by pulverized rock dust in extinctions by “suffocating” the atmosphere and preventing plants from using sunlight to obtain energy through photosynthesis.

The total amount of dust released by the impact was calculated by the group of researchers at 2,000 gigatons, which would be more than 11 times the mass of Mount Everest.

Scientists also ran paleoclimate simulations based on sediments unearthed in the U.S. state of North Dakota from a site called Tanis that preserved evidence about Earth’s post-impact conditions, including dust fallout.

Simulations showed that the dust could have blocked photosynthesis for up to two years, leaving the atmosphere opaque to the sun. The material may have remained in the air for 15 years, said planetary scientist Cem Berk Senel, from the Royal Observatory of Belgium and the Vrije Universiteit Brussel, author of the study published by the journal Nature Geoscience.

While previous studies have pointed to two factors in the extinction — sulfur released after the impact and soot from forest fires — this research indicated that dust played a larger role than previously known.

After the impact, Earth experienced a drop of about 15 degrees Celsius in surface temperature.

“It was cold and dark for years,” said Philippe Claeys, a scientist at Vrije Universiteit Brussel and co-author of the study.

The Earth then entered an “impact winter”, with temperatures falling and primary production — the process used by terrestrial and aquatic plants, as well as other organisms, to produce food from non-organic sources — collapsing, causing a chain reaction of extinctions.

Vegetables died, and herbivorous animals became hungry. The carnivores, in turn, lost their prey and died. In marine kingdoms, the disappearance of phytoplankton has ruined food chains.

“While the sulfur remained for about eight to nine years, the soot and silicate dust remained in the atmosphere for about 15 years after the impact. Full recovery from the impact winter took even longer, with temperature conditions returning to the earlier only about 20 years later,” said Royal Observatory of Belgium scientist and co-author Özgür Karatekin.

The asteroid, which was 10 to 15 kilometers in diameter, brought the cataclysm that ended the Cretaceous Period.

Dinosaurs became extinct, as well as marine reptiles that dominated the seas, among other groups. The greatest beneficiaries were mammals, which until then played a supporting role in the drama of life, but had the opportunity to become main characters.

Without the asteroid, dinosaurs could still rule the planet.

“They dominated Earth and were fine when the meteorite hit,” Claeys said.

“Without the impact, my estimate is that mammals — including us — would have little chance of becoming the dominant organisms on this planet.”