Fires From Asteroid May Have Spared Some Regions

John Roach
for National Geographic News
September 16, 2002

About 65 million years ago a space rock slammed into Mexico's Yucatan Peninsula and scattered high-velocity debris around Earth, igniting wildfires in North America, the Indian subcontinent, and most of the equatorial part of the world.

However, northern Asia, Europe, Antarctica and possibly much of Australia may have been spared the inferno, according to a new computer simulation of how the wildfires spread around the world.

The wildfires are thought to be a key ingredient in the concoction of environmental changes that killed more than 75 percent of all plant and animal life on Earth, including the dinosaurs.

"Our calculations suggest fires may have been more intense in some parts of the world than in others and that some areas may have been spared fires altogether," said David Kring, a planetary scientist at the University of Arizona in Tucson. "However, other environmental effects would have affected the spared regions."

For example, dust and smoke from the impact and fires would have obscured sunlight causing global temperatures to plummet and acid rain to fall. Then, the increased concentrations of carbon dioxide and other pollutants in the air may have led to global warming.

The impact event, which created a 110 to 180 mile (180 to 300 kilometer) diameter crater in Mexico's Yucatan Peninsula, marks the transition of the Cretaceous Period to the Tertiary Period where mammals replaced dinosaurs as the dominant species on Earth.

Kring along with his colleague Daniel Durda at the Southwest Research Institute in Boulder, Colorado, detail the spread of the wildfires in the September issue of the Journal of Geophysical Research—Planets.

Fire Model

The global wildfires sparked by the impact event that formed the Chicxulub crater were first modeled in 1990 by planetary scientist Jay Melosh at the University of Arizona and colleagues. Their calculation indicated that the fires spread around the world in a single pulse.

The model developed by Kring and Durda, which they say builds on the earlier research, shows that the fires were ignited in multiple pulses.

The impact was 10 billion times more energetic than the nuclear bombs dropped on Hiroshima and Nagasaki, Japan in World War II, the scientists said.

Most of the material from the collision collected around the impact site, but according to the researchers' calculations, some 12 percent of the debris was launched beyond Earth's atmosphere.

Continued on Next Page >>




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