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The second big bang

Scientists say cosmic collision killed 90 percent of life on earth

asteroid Earth
A comet or asteroid that slammed into Earth about 250 million years ago had dire consequences for the planet  

March 28, 2001
Web posted at: 6:17 PM EST (2317 GMT)


(CNN) -- Think of the worst natural disaster imaginable. Maybe it's a shocking earthquake, a torrential storm or an explosive volcano blast.

Then multiply that phenomenon's power and effect by a million. Even then, the impact will be less than that caused by a comet or asteroid scientists believe slammed into Earth about 250 million years ago, setting off a series of events that killed 90 percent of the planet's life forms.


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In a report in the journal "Science" last month, researchers said an asteroid four to eight miles across slammed into Earth a quarter billion years ago, spurring volcanic eruptions that covered the planet in lava and kicked up so much dust and ash to block the sun's rays for centuries. The cataclysmic event that ended the life of many earth forms, scientists said, advanced the rise of dinosaurs and eventually humans many million years later.

The lack of light, damaged vegetation and overall poor conditions left species scrambling to adapt. Ninety percent of the Earth's 15,000 species became extinct in the aftermath, including many shellfish, as well as trilobites - a cockroach-like creature that once canvassed the planet.

Scientists arrived at this conclusion after unearthing gases normally found in outer space, which they traced to the enormous collision. They combined this research, gathered from several countries with evidence of massive volcanic activity around this time to theorize the idea of an collision-induced big bang -- around 185 million years before a like event spurred the end of dinosaurs on Earth.

"We're not sure of all the environmental consequences, but with both the impact and with the volcanic activity, we do know that the Earth was not a happy place," study researcher Robert Poreda, associate professor of earth and environmental sciences at the University of Rochester in New York, said in a statement.

"It may be that the combined effects of impact and volcanism are necessary to cause such a tremendous extinction."

'Space gases' hold the key

The breakthrough came after scientists discovered carbon molecules called "buckyballs" deep in the Earth  

A giant crater in the Yucatan peninsula, north of Guatemala in southeast Mexico, is a visual reminder of a cosmic collision 65 million years ago that scientists say wiped out the dinosaurs. But unlike that event, the researchers in this study do not know where the giant space object touched down 250 million years ago.

But deep in the Earth, researchers did find a layer of small carbon molecules called buckminsterfullerenes, or Buckyballs. The soccer ball-shaped spheres contained helium and argon gases. Both are isotopes, suggesting they came from space, the report said.

"These things form in carbon stars. That's what's exciting about finding (buckminsterfullerenes) as a tracer," said Luann Becker, assistant professor of earth and space sciences at the University of Washington, who also worked on the paper.

The spheres, gathered at sites in Japan, China and Hungary, were found at the sedimentary layer of the earth's crust -- dating them to 250 million years ago, roughly between Permian and Triassic periods of the Earth's history.

The "space gases" correspond with other evidence from layers dating back to that period, which also signals a mass extinction. For instance, some of the most extensive volcanic activity ever, in what is now Siberia, laid down enough lava to cover the entire planet with 10 feet (three meters) of rock over a one-million year period.

What's a 'buckyball?'

Named for Buckminster Fuller, designer of the geodesic dome, fullerenes have been the subject of intense study since their discovery in 1985.

A third form of pure carbon after diamonds and graphite, so-called buckyballs are composed of carbon atoms that have bonded together into hollow, geodesic "cages."

They possess unusual properties that researchers hope to exploit in everything from superconductors to superlubricants to microscopic "nanotubes."

Robert Curl, Harold Kroto and Richard Smalley, who first produced fullerenes in the laboratory, shared the 1996 Nobel Prize in chemistry for their work. Since then scientists have discovered naturally existing fullerenes.

Effects felt everywhere

Researchers said the huge initial collision effected the entire Earth, below and above its crust. Massive earthquakes, tidal waves, volcanic activity -- all could have been triggered by the impact.

15000 species became extinct after earth's last asteroid collision  

"The impact ... releases an amount of energy that is basically about one million times the largest earthquake recorded during the last century," Podera said.

Researchers said the jolt's most devastating effects came well after the collision, as the dust and ash from the collision and volcanoes shielded the sun's rays. The world was left to face centuries of unnatural dark and cold -- unable to support most of the life on it.

"If the species cannot adjust, they perish," said Becker. "It's a survival-of-the-fittest sort of thing."

Like the trilobites, 70 percent of land vertebrates and 90 percent of all marine creatures became extinct following the cosmic collision. Fish fared better than most, Bambach said.

"These very active animals actually made it through with only 40 percent rather than 90 percent extinction," he said.

Cosmic collision coming soon?

Life did come back, giving rise to the rich collection of animals that thrived during the Triassic, Jurassic and Cretaceous periods. Mammals evolved, as did dinosaurs -- although another, later, cosmic collision is thought to have led to their extinction.

Asteroids hit the earth every million years  

So are more colliding asteroids or comets - and subsequent extinctions -- in the Earth's near future? Not to worry, scientists say, calculating an asteroid hits the planet every million years or so.

Experts know where the big asteroids are, said Chris Chyba of Stanford University, and people would have plenty of notice even if a smaller one was targeted for Earth.

"We would almost have decades, if not centuries, to go before that impact would happen," Chyba said. "So we would have a long time to think about what to do about it."



violent stream of a liquid; stormy; severe, typically describing hard downpours



relating to an event characterized by overwhelming upheaval and demolition



any of two or more variations of atoms of a given chemical element (with the same atomic number and nearly identical chemical behavior), but with differing atomic mass or mass number and different physical properties

CNN Science and Technology Correspondent Ann Kellan and Reuters contributed to this report.

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Scientists discover large asteroid between Neptune, Pluto
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July 13, 2000
Glass holds grains of truth about Earth's meteor history
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Outer space gas trapped on Earth in 'buckyballs'
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'Nomad' combs no-man's-land for meteors
January 24, 2000

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