This is Scientific American's 60-second Science, I'm Julia Rosen.We all know the story: 66 million years ago, a giant asteroid crashed into Earth, killing off three quarters of all species, including most of the dinosaurs.Researchers suspect that the impact caused the extinction by kicking up a cloud of dust and tiny droplets called aerosols that plunged the planet into something like a nuclear winter.“These components in the atmosphere drove global cooling and darkness that would have stopped photosynthesis from occurring, ultimately shutting down the food chain.”Shelby Lyons, a recent Ph.D. graduate from Penn State University.But scientists have also found lots of soot in the geologic layers deposited immediately after the asteroid impact.And the soot may have been part of the killing mechanism too―depending on where it came from.Some of the soot probably came from wildfires that erupted around the planet following the impact.But most of these particles would have lingered in the lower atmosphere for only a few weeks and wouldn’t have had much of an effect on global climate.But scientists hypothesize that soot may also have come from the very rocks that the asteroid pulverized when it struck.If those rocks contained significant amounts of organic matter―such as the remains of marine organisms―it would have burned up on impact, sending soot shooting up into the stratosphere.In that case, soot would have spread around the globe in a matter of hours and stayed there for years. And it would have radically altered Earth’s climate.
