Did Comet attacks end 9,000-year-old Clovis culture?

Sandia National Laboratories' Mark Boslough rebuts a speculative hypothesis about comets leading to the end of the Clovis culture in North America. Photo by Randy Montoya.

Sandia lead author Mark Boslough rebuts a speculative hypothesis that comet explosions changed Earth's climate sufficiently to end the Clovis culture in North America about 13,000 years ago.

He and other researchers from 14 academic institutions assert that some other, more plausible, explanations must be found for the apparent disappearance.

"There's no plausible mechanism to get airbursts over an entire continent," said Boslough, a physicist. "For this and other reasons, we conclude that the impact hypothesis is, unfortunately, bogus."

In a December 2012 American Geophysical Union (AGU) monograph, first available in January, the researchers point out that no appropriately sized impact craters from that time period have been discovered, nor have any unambiguously "shocked" materials been found.

In addition, proposed fragmentation and explosion mechanisms "do not conserve energy or momentum," a basic law of physics that must be satisfied for impact-caused climate change to have validity, the authors write.

Also absent are physics-based models that support the impact hypothesis. Models that do exist, write the authors, contradict the asteroid-impact hypothesis.

The authors also charge that "several independent researchers have been unable to reproduce reported results" and that samples presented in support of the asteroid impact hypothesis were later discovered by carbon dating to be contaminated with modern material.

NB: Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration.