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Scientists reveal what led to the extinction of dinosaurs 66 million years ago

By CM Chaney · October 31, 2023

In brief…

  • Asteroid impact didn't directly kill dinosaurs 66MYA, but dust it ejected played key role
  • Dust blocked sunlight up to 15 years, disrupting photosynthesis and starving species
  • New models show dust made up 75% of material blasted into atmosphere after impact
  • Research gives insight into mass extinctions, including potential future ones
Scientists have determined the dust and debris thrown into the atmosphere by the asteroid impact 66 million years ago led to catastrophic climate changes that caused the extinction of dinosaurs.  Killdevil / Wikimedia

The asteroid impact 66 million years ago did not directly cause the extinction of the dinosaurs, but the massive amount of debris it ejected into Earth’s atmosphere played a critical role, scientists announced Monday.

A team led by the Royal Observatory of Belgium determined that dust from pulverized rock clouded the atmosphere for up to 15 years after the impact, blocking sunlight and disrupting photosynthesis. “New modeling showed that the amount of dust was about 2,000 gigatonnes - exceeding 11 times the weight of Mt. Everest,” the researchers stated.

This worldwide “nuclear winter” caused vegetation die-offs, resulting in the starvation of many herbivorous species including some dinosaurs. This kickstarted the catastrophic mass extinction event that saw 75% of life on Earth disappear.

Scientists have long sought to unravel the mystery of what drove the dinosaurs into extinction after the discovery of the Chicxulub impact crater in 1978. The leading theory has been that soot or sulfur from the asteroid impact blocked sunlight.

But new research based on particles found at the Tanis fossil site in North Dakota points back to the impact dust hypothesis. Though 1,865 miles from the crater, Tanis has remarkable preserved finds from right after the impact in ancient lake sediment.

Researchers said the 0.8-8.0 micrometer dust particles could linger for 15 years. Entering this data into climate models showed dust likely played a bigger role than thought, making up 75% of material ejected, versus 24% sulfur and 1% soot.

Sean Gulick, a University of Texas geophysicist not involved in the study, said it makes an interesting case but doesn’t definitively solve the “hot question” of what caused the impact winter. However, Gulick noted understanding the mass extinction event helps us understand potential future ones.