- YAXCOPOIL, Mexico (Reuters)
- One minute you're a big T-Rex, the next you're toast.
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- Challenging conventional theory, new scientific research
suggests the dinosaurs may have been scorched into extinction by an asteroid
collision 65 million years ago that unleashed 10 billion times more power
than the Hiroshima nuclear bomb.
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- Earth's temperatures soared, the sky turned red and trees
all over the planet burst into flames, said atmospheric physicist Brian
Toon of the University of Colorado.
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- Among the few survivors would have been animals living
in water or burrowed in the ground like turtles, small mammals and crocodiles.
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- "Essentially, if you were exposed you were broiled
alive. That is probably what happened to the dinosaurs. They were big creatures
that didn't have anywhere to hide," said Toon.
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- Scholarly debate over how the dinosaurs died is fierce
and the theory put forward by Toon and others adds one more twist to the
greatest forensic mystery of all time.
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- Despite opposition from some scientists, the idea that
the dinosaurs were killed by an asteroid that slammed into Mexico's Yucatan
peninsula has won general acceptance since it was first mooted in the early
1990s.
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- Under that argument, academics say the giant reptiles
mostly froze or starved to death when a huge cloud of particles kicked
up by the meteorite blocked the world's sunlight for months.
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- But Toon, the co-author of a study published in the Geological
Society of America Bulletin in May, reckons the dinosaurs' end was even
more dramatic.
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- Creatures living near ground zero would have been vaporized
immediately while those in the Caribbean area and southern United States
would have drowned in 330-feet-high (100-meter) tsunamis when the asteroid
impacted near today's Gulf of Mexico shoreline at a speed of 33,750 mph
(54,000 kph).
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- Then, a column of red-hot steam and dust soared thousands
of miles into space and most of it fell back toward Earth within a few
hours, turning the heavens into hell.
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- GIANT FIRE
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- "The entire sky would be radiating at you. It would
be like standing next to a giant fire; you'd be burned very severely,"
Toon said, whose research is based on mathematical and computer models.
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- Land dinosaurs all around the world perished from the
intense heat of several hundred degrees Fahrenheit, said Toon.
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- He agrees with other scientists that the dust cloud later
cooled and blocked out the sun, but says the land dinosaurs were already
history by that time.
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- The darkness finished off many of the remaining marine
reptiles and fish by killing plankton and disrupting the food chain, said
Toon.
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- But those views are being challenged by some researchers
who say the Yucatan meteorite was not as great a catastrophe as first thought.
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- A theory gaining ground is that global warming combined
with another asteroid collision in an unknown location other than the Yucatan
was what cut short the dinosaurs' reign.
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- The academics are unlikely to agree soon on what caused
the demise of the Triceratops, Sauropods and their kin but in the jungly
Yucatan peninsula, locals are in no doubt.
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- "Everyone knows that the asteroid here killed the
dinosaurs. They teach it in the schools," said Isabel Lopez, a shop
owner in the village of Yaxcopoil.
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- "It's a shame what happened," said schoolboy
Daniel Tzeu, 11, lamenting the dinosaurs' end. He was standing near a bore
hole in the village dug by University of Arizona scientists probing for
rock samples in a crater caused by the asteroid.
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- The crater, around 100 miles in radius is now buried
1/2 mile underground, partly beneath the sea.
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- The University of Arizona has found "shocked"
rocks it says could only have been damaged by an asteroid collision.
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- David Kring, one of the University of Arizona scientists
who proved the Yucatan crater was the asteroid crash site, agrees the catastrophe
killed off the land dinosaurs but doubts they all burned to death.
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- Many starved when plants were destroyed by fires, a subsequent
period of global darkness and acid rain.
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- "If you knock out the vegetation you really have
undermined the food chain," he said.
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- WRONG ASTEROID?
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- But Princeton University geologist Gerta Keller disagrees
that the asteroid put paid to the dinosaurs. She says asteroid debris,
known as ejecta, found embedded in ancient rocks shows the Yucatan meteorite
hit Earth many millennial before the dinosaurs vanished.
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- "The ejecta everywhere is in sediment layers that
pre-date the mass extinction by about 300,000 years," she said.
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- Global warming caused by 400,000 years of repeated volcanic
eruptions in western India weakened the dinosaurs and then another asteroid
struck earth, although scientists have yet to find its crater, Keller said.
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- "It's a double whammy at that point," she said.
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- A combination of the two disasters deprived the Earth
of oxygen and the dinosaurs probably suffocated to death, she said.
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