U.S. scientists reveal what likely responsible for dinosaur-killing extinction

(с) NASA
(с) NASA

New research finds soot from global fires ignited by an asteroid impact could have blocked sunlight long enough to drive the mass extinction that killed most life on Earth, including the dinosaurs, 66 million years ago.

A new study in AGU's journal Geophysical Research Letters simulates the contributions of the impact's sulfur, dust, and soot emissions to the extreme darkness and cold of the impact winter. The results show the cold would have been severe but likely not devastating enough to drive a mass extinction. However, soot emissions from global forest fires darkened the sky enough to kill off photosynthesizers at the base of the food web for well over a year, according to the study published on Phys.org.

The results help scientists better understand this intriguing mass extinction that ultimately paved the way for humans and other mammals to evolve. But the study also provides insight into what might happen in a nuclear winter scenario, according to Tabor.

In the new study, Tabor and his colleagues used a sophisticated climate model to simulate the climatic effects of soot, sulfates, and dust from the impact.

Their results suggest soot emissions from global fires absorbed the most sunlight for the longest amount of time. The model showed soot particles were so good at absorbing sunlight that photosynthesis levels dropped to below one percent of normal for well over a year.

The darkness would have been devastating to photosynthesizers and could explain the mass extinction through a collapse of the food web, according to the researchers. 

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