The Dinosaur-Killing Asteroid Hit an Exceptionally Unlucky Spot

The asteroid that ended the dinosaur era hit sulfur- and hydrocarbon-rich ground, helping fill the sky with soot and trigger global cooling and mass extinction.

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About 66 million years ago, a roughly 9 kilometer wide asteroid struck what is now the Yucatan Peninsula in Mexico and formed the enormous Chicxulub crater. The impact itself was catastrophic, but research has highlighted an important detail about where it happened. The rocks at the impact site contained substantial sulfur-bearing material and hydrocarbons, which could be blasted high into the atmosphere and contribute to soot and sulfate aerosols that blocked sunlight. The resulting cooling and disruption of plant growth would have placed enormous stress on ecosystems and food webs. One influential study estimated that only about 13 percent of Earths surface had enough hydrocarbon-rich material to produce the level of atmospheric soot associated with a mass extinction from an impact of this kind. That does not mean the asteroid would have been harmless elsewhere. The collision would still have caused enormous local and regional destruction, and the exact balance among dust, soot, sulfur aerosols, carbon dioxide, wildfires, and other effects remains an active area of research. More recent studies have also revised estimates of how much sulfur entered the atmosphere, showing why the details of the impact winter are still being refined. The broad scientific picture remains that the Chicxulub impact was the principal trigger of the end-Cretaceous mass extinction, which eliminated about 75 percent of species and ended the dominance of non-avian dinosaurs. The location of the impact appears to have strongly influenced how severe its global environmental consequences became.

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