Posted on 01/24/2002 4:12:22 AM PST by blam
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.
Fiery Crash
This illustration shows an asteroid crashing into Earth at the boundary of the Cretaceous and Tertiary periods in geologic history, about 65 million years ago, which may have caused the extinction of dinosaurs. Although scientists believe they have mapped all of the miles-wide objects that could cross Earth's path and annihilate life here, many research centers are searching the sky for moderate-sized asteroids or comets (about half a mile wide) that might one day collide with Earth and kick up enough dust to cause a "nuclear winter," wiping out crops and creating tsunamis that would swamp coastal areas.
"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.
BULL SNOT!!
It is an exercise for sophomore physics students to see just how futile this "hope" will be. To the futility of lotteries and catching anthrax we can add deflecting asteroids. The numbers are all of the same size. Prayer is equally effective in each case. Money is equally ineffective in each case.
The conspiracy of ignorance masquerades as common sense.
The burst must be in the right direction on a body that will be rotating about all three axes. That is hard to do.
The machinery has to reach the body in a timely manner. That is hard to do.
We aren't even sure of our ability to reliably detect Earth crossers.
The product of all of these uncertainties is HUGE.
The conspiracy of ignorance masquerades as common sense.
If they wait until 3 days before impact, there will barely be time to get the prayer wheels spun up.
If "they" were serious about deflecting asteroids, "they" would have hardware already prepositioned in space.
I seem to remember reading that attaching a solar sail to an asteroid would actually be a more effective means of deflection.
An asymmetric assembly of bovine creatures facing in the same direction should prove adequate to the task.
...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.
BULL SNOT!!
It is an exercise for sophomore physics students to see just how futile this "hope" will be. To the futility of lotteries and catching anthrax we can add deflecting asteroids. The numbers are all of the same size. Prayer is equally effective in each case. Money is equally ineffective in each case.
The conspiracy of ignorance masquerades as common sense.
Wrong. The odds that any given asteroid will actually hit the earth are minute. In order to collide, the orbit of a rock has to cross the orbit of the Earth, and the rock has to cross Earth's orbit at the same time that the Earth crosses the rock's orbit.
Once you find a rock on such a vector, a slight change in speed, or a slight change in the vector, in any direction, will result in a miss.
As Heinlein put it in one of his stories, it's the only case where orbital mechanics is simple.
Finally, a constructive use for DU has been discovered :-).
Breccia, technical term meaning "broken stuff." So they are down 2,800 feet already. The crustal plates around the region are kind of small compared to continental plates, almost as if one or two contintal plates were broken by an impact.
Do you think continental plates are broken by (some) impacts?
Another question is whether they have any tensile strength at all. They might resemble the coating of slag on top of molten metal, a froth initially, a scum, and when they gain some thickness, they might be coherent enough to be fragmented.
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