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Dino-Killing Asteroid Fueled Global Wildfires, Study Says

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Derek
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« on: June 23, 2007, 03:16:16 am »

  Dino-Killing Asteroid Fueled Global Wildfires, Study Says
By SPACE.com Staff

posted: 09:35 am ET
04 September 2002


 

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.

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.

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.

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.

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.

"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."

Kring worked on the study with Daniel Durda of the Southwest Research Institute. Their results are detailed in the Journal of Geophysical Research - Planets.

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.

More than 75 percent of the planet's plant and animal species did not survive the era.

"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."

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.

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.

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.

"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."

Durda has turned the simulations into a movie that can be viewed at the Lunar and Planetary Lab Space Imagery Center web site.


http://www.space.com/scienceastronomy/asteroid_fires_020904.html
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