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Asteroid strike spurred quick chill that led to dinosaurs’ demise

Ocean temperatures fell 2 degrees after Chicxulub impact

BIG IMPACT  New evidence of global cooling after the asteroid impact 66 million years ago in what’s now Chicxulub, Mexico, supports the idea that photosynthesis stopped. The lack of food coupled with acid rain and greenhouse gases drove most organisms to extinction.

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A space rock slammed into Earth 66 million years ago, setting off a chain of events that led to the demise of the dinosaurs. New evidence supports the idea that the impact caused global cooling in the months to decades afterward that drove mass extinction.

The huge asteroid collided with Earth near what is now Chicxulub, Mexico. Johan Vellekoop of Utrecht University in the Netherlands and colleagues studied lipids from ocean microbes preserved in silt and sand in the Brazos River region of central Texas to reconstruct sea surface temperatures from around the time of the asteroid’s impact. Before the impact, the waters were warm, around 30° Celsius. But in the months to decades afterward, sea surface temperatures fell an average of 2 degrees, scientists report May 12 in the Proceedings of the National Academy of Sciences.

This result supports the idea that the impact shot dust and other particles into the air, blocking light and heat from the sun, the scientists say. The analysis also shows that sea surface temperatures then warmed to roughly 32° C just a few decades to a century after the impact.

Such a quick, dark chill followed by a period of global warming, acid rain and increased greenhouse gases matches the pattern of extinction of organisms from tiny plankton all the way up to tyrannosaurs and pterosaurs, the authors write.

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