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Geologists Find Clues In Crater Left By Dinosaur-Killing Asteroid

Written by GEOFF BRUMFIEL

Scientists have had a literal breakthrough off the coast of Mexico.

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After weeks of drilling from an offshore platform in the Gulf of Mexico, they have reached rocks left over from the day the Earth was hit by a killer asteroid.

The cataclysm is believed to have wiped out the dinosaurs. “This was probably the most important event in the last 100 million years,” says Joanna Morgan, a geophysicist at Imperial College in London and a leader of the expedition.

Since the 1980s, researchers have known about the impact site, located near the present-day Yucatan Peninsula. Known as Chicxulub, the crater is approximately 125 miles across. It was created when an asteroid the size of Staten Island, N.Y., struck Earth around 66 million years ago. The initial explosion from the impact would have made a nuclear bomb look like a firecracker. The searing heat started wildfires many hundreds of miles away.

After that, came an unscheduled winter. Sulfur, ash and debris clouded the sky. Darkness fell and, for a while, Earth was not itself.

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“I think it was a bad few months, really,” Morgan says.

That’s an understatement: Scientists believe 75 percent of life went extinct during this dark chapter in Earth’s history, including the dinosaurs.

Researchers have sampled Chicxulub before, but this expedition by the European Consortium for Ocean Research Drilling precisely targets a key part of the crater yet to be studied: a ring of mountains left by the asteroid. This “peak ring” is a fundamental feature of the strike and should tell researchers much more about it, says Sean Gulick, a geophysicist at the University of Texas at Austin, who co-leads the team with Morgan.

For weeks, they’ve been drilling — and going back in time. Each layer of rock they pass through is connected to a part of Earth’s history.

“We went through a remarkable amount of the post-impact world. All the way into theEocene times — so between 50 and 55 million years ago,” Gulick says.

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The rocks they’ve pulled out show how life began to recover after the cataclysm, Gulick says. “We’ve got all these limestones and rocks that contain the fossils from the world after the impact, all the things that evolved from the few organisms that survived.”

The research team finally reached the top of the peak ring this week. It appears to be a thick layer of broken, melted rock just beneath a layer of sandstone that may be the leavings of a huge tsunami that was triggered when the asteroid struck.

Gulick thinks the rocks hold clues. For example, if any microscopic organisms survived near the site of the strike, their fossils might be in these samples. In June, the rock cores will be sent back to a lab in Germany for further study.

The asteroid strike marked the end of an era. But the creatures that made it through that catastrophe went on to shape the world again, says Morgan.

“The mammals survived,” she says. “And that led on to our own evolution.”

Read more at npr.org

Comments (1)

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    Rosco

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    If anything is capable of producing a “runaway greenhouse effect” then surely the impact of a huge “red hot” asteroid in the ocean would be a decent candidate.

    Such an impact must have vaporised a huge amount of water vastly increasing the amount of the principal “greenhouse gas” in the atmosphere

    Such an increase – probably to levels many times higher than today’s atmospheric water vapor levels must have been significant especially if alarmists are terrified of another increase of 0.04% CO2 beyond today’s levels. CO2 is “transparent” compared to water vapour.

    The Gulf of Mexico can’t have been dry at the time – apparently there was no ice on the planet during the age of the dinosaurs meaning the seas were up to a hundred or so metres deeper than today – perhaps more – if you believe contemporary climate alarm.

    Like most thought bubbles in climate research I find it inconceivable that huge amounts of water would not have been vaporised when an asteroid heated by atmospheric friction hit what must have been deeper water than presently experienced and yet there is no mention of even the possibility of an increased “greenhouse effect” due to such an impact – quite the opposite in fact. Even if the initial impact simply displaced the water it would have easily boiled as it flowed back into the crater.

    Air temperatures were higher, there was no ice on Earth, the oceans deeper than today, the amount of water vapor would have been higher than today anyway and the capacity of the atmosphere to “hold” even higher levels of water vapor was significantly higher than today and along comes an asteroid which clearly melted rock and vaporising huge quantities of the principal greenhouse gas and the result is death by cold ?

    As credible as “snowball Earth” to me.

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