Dino-Era Crater Probed for Clues to Mass Extinction

Robert S. Boyd
The Record (Bergen County, New Jersey)

January 23, 2002

Scientists have begun drilling a mile-deep hole into a huge underground crater that was left by a mountain-sized asteroid or comet that slammed into Earth 65 million years ago. According to a widely accepted theory, the cataclysmic event wiped out the dinosaurs.

This month, the scientists reached the uppermost layer of broken rocks buried beneath Mexico's Yucatán Peninsula that were smashed, twisted, and hurled about by the tremendous force of the collision.

The researchers hope to learn exactly what the space invader did when it penetrated Earth's crust in a fiery ball of unimaginable violence. The goal is to better understand how the impact devastated the global environment, clearing the way for the rise of mammals, including humans.

"Since we can't go back 65 million years in a time machine, drilling down to the 65-million-year level is the best we can do," said James Powell, the executive director of the National Physical Science Consortium at the University of Southern California in Los Angeles.

Time of Transition

The ancient catastrophe marked "the transition between the Age of Reptiles and the Age of Mammals," said David Kring, a planetary scientist at the University of Arizona in Tucson and a leader of the drilling team from Mexico and the United States.

"Mammals were able to develop because the impact caused a complete change in the biological landscape of Earth," he added. "Then evolution took advantage of the change."

The smashed rubble, technically known as breccia, was found 2,800 feet (853 meters) below ground, about 25 miles (40 kilometers) southwest of the Yucatán city of Merida. The crater is called Chicxulub (pronounced cheek-shoo-loob) for the village located over its center.

Kring, a principal investigator in the Chicxulub Scientific Drilling Project, said the drilling would bring up rocky cores about as thick as a baseball bat that would reveal the complete history of the ancient disaster.

"For the first time, we will be able to see the entire geology of the structure, all the way down to the bedrock of the continental crust," he said.

Between the breccia and the bedrock, researchers expect to find a thick stony sheet that was melted by the intense heat of the long-ago crash. The volume of the molten material could have been as much as 24,000 cubic miles (100,000 cubic kilometers), enough to fill Hudson's Bay or the Gulf of California with lava.

"People have a hard time understanding the scale of this impact," Kring said. "It moved millions of tons of rock, some of it more than 60 miles (97 kilometers)."

Material 20 miles (32 kilometers) beneath the surface was affected by the shock wave. A large part of Earth's crust was uplifted and folded by the blast.

Poisonous gases, dust, smoke, and fire from the impact blotted out the sun, lowered temperatures, and contaminated the air for months or years, killing more than 75 percent of the plant and animal species in existence.

Closer Monitoring

Wary of another such calamity, astronomers have begun a search for all large "Near Earth Objects" that might be on a collision course with our planet.

On January 7, for example, they spotted an asteroid the size of three football fields that streaked within 500,000 miles (804,672 kilometers), twice the distance to the moon.

If a space rock is detected early enough, scientists hope they will be able to deflect it with a nuclear-armed missile. Even a slight change of course could be enough for a far-off object to miss Earth.

According to Powell, who is not a member of the Chicxulub project, the drilling may clear up some mysteries, such as whether the space intruder was a comet or an asteroid.

Asteroids are rocky objects orbiting between Earth and Jupiter. Comets are balls of ice and frozen gas from beyond Pluto that periodically swoop through the solar system. Comets are considered more dangerous than asteroids because their enormous speed multiplies their power.

In addition, Powell said the drillers might find traces of sulfur-rich rocks in the crater that could help explain why the atmosphere poisoned so many living creatures.

Copyright 2002, The Record (Bergen County, New Jersey)