TOEFL: A discussion on the effects of the asteroid event that caused the extinction of the dinosaurs.
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It was the one event which irrevocably changed our world. Sixty six billion years ago, a giant rock moving at 18 kilometers per second came out of the Northeastern sky and slammed into a shallow sea where today there is the Gulf of Mexico. The fallout from the impact resulted in the demise of three quarters of all plant and animal species including the dinosaurs. Precisely what happened on that day is now coming into clearer focus thanks to a project to drill into the crater made by the asteroid. Our science correspondent Jonathan Amos has been speaking to the lead researchers Joe Morgan and Sean Gulick.
One of our targets actually was to look at the earliest sediments that filled the crater because they're going to tell us about the recovery of life actually at the impact site. So we might have expected life to grow very very slowly here because there was probably quite a toxic environment. The ocean was probably was full of vents of hydrothermal circulation and all these sort of metals that were being put into the oceans. So we were expecting sort of life to recover very very slowly, and we were quite surprised. So we get really amazing fast recovery, high productivity sort of almost straight after the impact. Similar to the fastest recovery at other sites around the world.
Sean, you've been able to put the day back together in a sense.
Yeah, what's super exciting as just the energy of an impact crater. So I mean they're hitting at something like 10 billion Hiroshimas worth of energy. And so that creates an instantaneous hole that has a rim with mountains that are Himalayan in size. But then all that collapses within minutes in order to infill the crater and result in something that's almost twice as wide when the final crater forms, and not very deep, only maybe a kilometer deep.
It was a bad day for planet Earth, a bad day for the dinosaurs, a bad day for a lot of life on Earth. And you can say now some of the way that it was a bad day because of the nature of the rocks that this impactor hit and what it did to the climate.
Yeah that's right. So we now know a lot more about the target site We know a lot more about the sediments that were essentially degassed when the asteroid hits. So a very high pressure shock wave passes through the sediments, releases these gases sulfur and carbon dioxide injected into the Earth's atmosphere and all around the globe. So they have a dramatic effect all around the globe. So we think that the Sulfur itself cooled the Earth's surface by about 25 degrees centigrade for that first year after the impact. So that's an amazing sort of cold earth for us. And that lasted probably 3 to 16 years of these subfreezing temperatures. So life would have a big sort of struggle at that point. You know it would be nothing like life normally sort of previous to the impact that the temperatures had been like. We also have a little bit better idea of the soot and the dust that was up in the atmosphere and stayed there itself for several years. And that cuts out sunlight. So we think photosynthesis was seriously inhibiting for at least a year. So were cutting out the primary food chain basically - the organisms that photosynthesize and make the food that everything else eats off. So that's serious for all life on Earth.
Joe Morgan and Sean Gulick talking to Jonathan Amos.