- A new computer model lends further support to an idea
that global wildfires accompanied a devastating space-rock impact 65 million
years ago that led to the demise of dinosaurs.
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- The fires were ignited by high-velocity debris kicked
up when an asteroid or comet slammed into Earth, researchers suspect. The
debris rained down on the planet for three days.
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- The fires are now said to have spread over southern North
America, the Indian subcontinent and most of the equatorial part of the
world hours to days after impact, according to the new study.
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- Most scientists agree that an impact was a major contributor
to the dinosaurs' disappearance. The impact that blasted the immense Chicxulub
crater near Yucatan, Mexico, marked the end of the Age of Reptiles, the
Mesozoic, and heralded the Age of Mammals, the Cenozoic.
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- There has been much speculation about whether wildfires,
increased volcanic activity or both might have served as additional nails
for the giant coffin, into which many other species of animals and plants
also fell. Climate change and even giant tsunami have also been implicated.
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- "We've added more detail in re-evaluating the extent
of the wildfires," said David Kring of the University of Arizona.
"Our new calculations show that the fires were not ignited in a single
pulse, but in multiple pulses at different times around the world. We also
explored how the trajectory of the impacting object, which is still unknown,
may affect the distribution of these fires."
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- Kring worked on the study with Daniel Durda of the Southwest
Research Institute. Their results are detailed in the Journal of Geophysical
Research - Planets.
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- As far back as 1990, other researchers modeled global
wildfire scenarios from the horrific impact. The new, more detailed modeling
suggests pulses of misery for life on Earth during days after impact.
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- More than 75 percent of the planet's plant and animal
species did not survive the era.
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- "The fires were generated after debris ejected from
the crater was lofted far above the Earth's atmosphere and then rained
back down over a period of about four days," Kring said. "Like
countless trillions of meteors, the debris heated the atmosphere and surface
temperatures so intensely that ground vegetation spontaneously ignited."
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- The collision was so energetic -- 10 billion times more
energetic than the nuclear bombs that flattened Hiroshima and Nagasaki
in 1945 -- that 12 percent of the impact debris was launched beyond Earth
into the solar system, Kring said.
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- About 25 percent of the debris rained back through the
atmosphere within two hours of impact. Fifty-five percent fell back to
Earth within 8 hours of impact, and 85 percent showered down within 72
hours of impact, according to the new calculations.
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- Both physics and Earth's rotation determined the global
wildfire pattern. High-energy debris would have concentrated both around
the Chicxulub crater in Mexico and its global antipode -- which corresponded
to India and the Indian Ocean 65 million years ago.
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- "The way to think of this is, the material was launched
around Earth and headed on a return trajectory to its launch point,"
Kring explained. "Then, because the Earth rotates, it turned beneath
this returning plume of debris, and the fires migrated to the west. That's
what causes the wildfire pattern."
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- Durda has turned the simulations into a movie that can
be viewed at the Lunar and Planetary Lab Space Imagery Center.
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