WEBVTT - How Did a Dinosaur Killing Asteroid Change The Environment?

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<v Speaker 1>Welcome to brain Stuff from how Stuff works. Hey, brain Stuff,

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<v Speaker 1>it's Christian Seger. Picture what it must have been like

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<v Speaker 1>for the dinosaurs just before they bought the proverbial farm.

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<v Speaker 1>You're probably familiar with the basics of what happened. Sixty

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<v Speaker 1>six million years ago. A massive asteroid hit Earth in

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<v Speaker 1>Mexico's Yucatan Peninsula, which was at the time a shallow sea,

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<v Speaker 1>and suddenly, relative to the long stretch of planetary history,

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<v Speaker 1>there were no more dinosaurs. At least that's the sanitized

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<v Speaker 1>version of the story. For some lucky organisms, death was quick,

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<v Speaker 1>but others probably had to spend some time staggering around

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<v Speaker 1>in a pitch dark nightmareland. It was probably terrible, but

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<v Speaker 1>we don't know much about what the environmental aftermath of

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<v Speaker 1>the asteroids impact was actually like, and that lack of

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<v Speaker 1>precise knowledge makes it tough to know much about why

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<v Speaker 1>some species died and others survived. A new study published

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<v Speaker 1>in the Proceedings of the National Academy of Sciences used

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<v Speaker 1>advanced computer modeling techniques to figure out exactly what kind

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<v Speaker 1>of wretched hellscape drove roughly three quarters of the planet

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<v Speaker 1>species to extinction. The researchers found that the cheek Salube

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<v Speaker 1>asteroid that ushered in the Cretaceous Paleogene extinction most likely

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<v Speaker 1>triggered all sorts of cataclysmic natural disasters like earthquakes, tsunamis,

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<v Speaker 1>and volcanic eruptions, in addition to wildfires ignited by the

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<v Speaker 1>vaporized molten rock that rained down on every corner of

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<v Speaker 1>the planet. The team wanted to look at the long

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<v Speaker 1>term consequences of the amount of soot they think was

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<v Speaker 1>created and what those consequences might have meant for the

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<v Speaker 1>animals that were left. It is not an insignificant amount

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<v Speaker 1>of soot we're talking about here. The scientists estimate that

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<v Speaker 1>these worldwide wildfires that started after the asteroid hit launched

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<v Speaker 1>around fifteen billion tons or thirteen point six billion metric

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<v Speaker 1>tons of fine soot into the atmosphere. Average temperatures on

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<v Speaker 1>Earth's surface and at sea plummeted with a fifty degree

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<v Speaker 1>fahrenheit or twenty eight degrees celsius drop over land and

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<v Speaker 1>a drop of twenty degrees fahrenheit or eleven degrees celsius

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<v Speaker 1>over the oceans for more than a year and a half.

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<v Speaker 1>Photosynthesis would have been impossible for the terrestrial plants that

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<v Speaker 1>weren't damaged or destroyed by the fires, and in the oceans,

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<v Speaker 1>the phytoplankton would have been hit hard enough to tank

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<v Speaker 1>the marine food chain for a few months, our planet's

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<v Speaker 1>energy source was removed and a lot of animals starved.

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<v Speaker 1>Interestingly enough, the research team's models found that a fraction

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<v Speaker 1>of soot in the atmosphere probably would have entirely shut

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<v Speaker 1>down photosynthesis for a year. Actually, only five billion tons

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<v Speaker 1>or four point five billion metric tons of soot would

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<v Speaker 1>have done the trick. They also found that as Earth

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<v Speaker 1>sees surface and lower atmosphere below the soot level cooled,

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<v Speaker 1>All that soot absorbed the Sun's light, heating and changing

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<v Speaker 1>the chemistry of the upper atmosphere, destroying the ozone layer

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<v Speaker 1>in the process. All the water in the atmosphere caused

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<v Speaker 1>by the sudden warming eventually condensed into ice, creating a

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<v Speaker 1>feedback loop that would very suddenly scour all the soot

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<v Speaker 1>out of the atmosphere over the course of just a

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<v Speaker 1>few months. Now For comparison, the lead author on this study,

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<v Speaker 1>Charles Bairdeen, says the amount of soot created by nuclear

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<v Speaker 1>warfare would be much less than what the planet saw

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<v Speaker 1>during this extinction. Today's episode was written by Jescelyn she Wilds,

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<v Speaker 1>produced by Dylan Fagan, and For more on this and

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<v Speaker 1>other topics, please visit us at how stuff works dot

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<v Speaker 1>com