Asteroid Dust Caused 15-Year Winter That Killed Dinosaurs, Scientists Say

Around 66 million years ago, the Chicxulub asteroid caused a mass extinction event, killing three-quarters of life on Earth, including the dinosaurs. A new study suggests that fine silicate dust from the asteroid, which remained in the atmosphere for up to 15 years, played a more significant role in causing the impact winter and extinction than previously thought.

Fine silicate dust from pulverized rock would have stayed in the atmosphere for 15 years, dropping global temperatures by up to 15 degrees Celsius, researchers said in a study in the journal Nature Geoscience. [...] For the study, the international team of researchers was able to measure dust particles thought to be from right after the asteroid struck. The particles were found at the Tanis fossil site in the US state of North Dakota.

Though 3,000 kilometers (1,865 miles) away from the crater, the site has preserved a number of remarkable finds believed to be dated from directly after the asteroid impact in sediment layers of an ancient lake. The dust particles were around 0.8 to 8.0 -- micrometers -- just the right size to stick around in the atmosphere for up to 15 years, the researchers said.

Entering this data into climate models similar to those used for current-day Earth, the researchers determined that dust likely played a far greater role in the mass extinction than had previously been thought. Out of all the material that was shot into the atmosphere by the asteroid, they estimated that it was 75 percent dust, 24 percent sulfur and one percent soot. The dust particles "totally shut down photosynthesis" in plants for at least a year, causing a "catastrophic collapse" of life, [said Ozgur Karatekin, a researcher at the Royal Observatory of Belgium].

fine dust made from pulverized rock thrown up into Earth's atmosphere in the wake of the impact likely played a greater role. This dust blocked the sun to an extent that plants were unable to photosynthesize, a biological process critical for life, for almost two years afterward.

"Photosynthesis shutting down for almost two years after impact caused severe challenges (for life)," said lead study author and planetary scientist Cem Berk Senel, a postdoctoral researcher at the Royal Observatory of Belgium. "It collapsed the food web, creating a chain reaction of extinctions."