Clovis Comet Lacks Evidence

A group of scientists from archaeology to crystallography and physics are disputing the long-held theory that a comet crashing into the Earth some 13,000 years ago spelled doom to a group of early North American people and ice-age beasts in the region.

The prehistoric Paleo-Indian group known as the Clovis culture suffered its demise at the same time the region underwent significant climate cooling known as the Younger Dryas.

"Despite more than four years of trying by many qualified researchers, no unambiguous evidence has been found [of such an event]," Mark Boslough, a physicist at Sandia National Laboratories in New Mexico, tells LiveScience. "That lack of evidence is therefore evidence of absence."

According to LiveScience:

In 2007, a team of scientists led by Richard Firestone of the Lawrence Berkeley National Laboratory in California suggested these changes were the result of a collision or explosion of an enormous comet or asteroid. 

The theory has remained controversial, with no sign of a crater that would have resulted from such an impact. 

"If a four-kilometer [2.5-mile] comet had broken up over North America only 12.9 thousand years ago, it is certain that it would have left an unambiguous impact crater or craters, as well as unambiguous shocked materials," Boslough said. 

A large rock plunging into the Earth's atmosphere may detonate in the air without coming into contact with the ground. Such an explosion occurred in Siberia in the early 20th century; the explosive energy of the so-called Tunguska event was more than 1,000 times more powerful than the atomic bomb dropped on Hiroshima.

Boslough said the math doesn't add up. The object responsible for the Tunguska event was very small, about 130 to 160 feet (40 to 50 meters) wide. The proposed North American space rock linked with the Clovis demise is estimated to have been closer to 2.5 miles (4 kilometers) across. "The physics doesn't support the idea of something that big exploding in the air," he said.

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