Study rebuts hypothesis that comet attacks ended 9,000-year-old Clovis culture

Jan 30, 2013
Sandia National Laboratories' Mark Boslough rebuts a speculative hypothesis about comets leading to the end of the Clovis culture in North America. Credit: Randy Montoya

(Phys.org)—Rebutting a speculative hypothesis that comet explosions changed Earth's climate sufficiently to end the Clovis culture in North America about 13,000 years ago, Sandia lead author Mark Boslough and researchers from 14 academic institutions assert that other 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 is, unfortunately, bogus."

In a December 2012 American Geophysical Union monograph, first available in January, the researchers point out that no appropriately sized 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 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 hypothesizers.

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

The Boslough trail

Boslough has a decades-long history of successfully interpreting the effects of comet and asteroid collisions.

His credibility was on the line on in July 1994 when Eos, the widely read newsletter of the , ran a front-page prediction by a Sandia National Laboratories team, led by Boslough, that under certain conditions plumes from the collision of with the planet Jupiter would be visible from Earth.

The Sandia team—Boslough, Dave Crawford, Allen Robinson and Tim Trucano — were alone among the world's scientists in offering that possibility.

"It was a gamble and could have been embarrassing if we were wrong," said Boslough. "But I had been watching while Shoemaker-Levy 9 made its way across the heavens and realized it would be close enough to the horizon of Jupiter that the plumes would show." His reasoning was backed by simulations from the world's first massively parallel processing supercomputer, Sandia's Intel Paragon.

On the one hand, it was a chance to check the new Paragon's logic against real events, a shakedown run for the defense-oriented machine. On the other, it was a hold-your-breath prediction, a kind of Babe Ruth moment when the Babe is reputed to have pointed to the spot in the center field bleachers he intended to hit the next ball. No other scientists were willing to point the same way, partly due to previous failures in predicting the behavior of comets Kohoutek and Halley, and partly because most astronomers believed the plumes would be hidden behind Jupiter's bulk.

That the plumes indeed proved visible started Boslough on his own trajectory as a media touchstone for things asteroidal and meteoritic.

It didn't hurt that, when he stands before television cameras to discuss celestial impacts, his earnest manner, expressive gestures and extraterrestrial subject matter make him seem a combination of Carl Sagan and Luke Skywalker, or perhaps Tom Sawyer and Indiana Jones.

Standing in jeans, work shirt and hiking boots for the Discovery Channel at the site in Siberia where a mysterious explosion occurred 105 years ago, or discussing it at Sandia with his supercomputer simulations in bold colors on a big screen behind him, the rangy, 6-foot-3 Sandia researcher vividly and accurately explained why the mysterious explosion at Tunguska that decimated hundreds of square miles of trees and whose ejected debris was seen as far away as London most probably was caused neither by flying saucers drunkenly ramming a hillside (a proposed hypothesis) nor by an asteroid striking the Earth's surface, but rather by the fireball of an asteroid airburst—an asteroid exploding high above ground, like a nuclear bomb, compressed to implosion as it plunged deeper into Earth's thickening, increasingly resistive atmosphere. The governing physics, he said, was precisely the same as for the airburst on Jupiter.

Among later triumphs, Boslough was the Sandia component of a National Geographic team flown to the Libyan Desert to make sense of strange yellow-green glass worn as jewelry by pharaohs in days past. Boslough's take: It was the result of heat on desert sands from a hypervelocity impact caused by an even bigger asteroid burst.

In the present case

In the Clovis case, Boslough felt that his ideas were taken further than he could accept when other researchers claimed that the purported demise of Clovis civilization in North America was the result of produced by a cluster of comet fragments striking Earth.

In a widely reported press conference announcing the Clovis comet hypothesis in 2007, proponents showed a National Geographic animation based on one of Boslough's simulations as inspiration for their idea.

Indiana Jones-style, Boslough responded. Confronted by apparently hard asteroid evidence, as well as a Nova documentary and an article in the journal Science, all purportedly showing his error in rebutting the comet hypothesis, Boslough ordered carbon dating of the major evidence provided by the opposition: nanodiamond-bearing carbon spherules associated with the shock of an asteroid's impact. The tests found the alleged 13,000-year-old carbon to be of very recent formation.

While this raised red flags to those already critical of the impact hypothesis, "I never said the samples were salted," Boslough said carefully. "I said they were contaminated."

That find, along with irregularities reported in the background of one member of the opposing team, was enough for Nova to remove the entire episode from its list of science shows available for streaming, Boslough said.

"Just because a culture changed from Clovis to Folsom spear points didn't mean their civilization collapsed," he said. "They probably just used another technology. It's like saying the phonograph culture collapsed and was replaced by the iPod culture."

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HannesAlfven
1 / 5 (7) Jan 30, 2013
Re: "There's no plausible mechanism to get airbursts over an entire continent," said Boslough, a physicist."

Of course there isn't. By ruling out the competing worldview -- that electromagnetism might be at play in comet science -- you rule out the very mechanism which would be needed to make it plausible. We *can* build these models, but only if we desire it. The historical lesson for catastrophism has consistently been less about finding arguments to support it, but instead that people are naturally disinclined to pursue models which position our existence on Earth as subject to forces which we cannot control. At the current trajectory, scientists will simply refuse to entertain that class of ideas, until they no longer can.

Re: "It didn't hurt that ... Carl Sagan"

Yes, indeed. Just as they did when Carl Sagan waged and arguably "won" his war on catastrophism, looks oftentimes matter more than arguments.
dschlink
3.7 / 5 (3) Jan 30, 2013
None the less, a very odd climate event occurred in that time frame. The cycle of glaciation broke and we have had very stable temperatures (compared to the prior 660,000 years) for the last 13,000 years.
Maggnus
4.4 / 5 (7) Jan 30, 2013
Of course there isn't. By ruling out the competing worldview -- that electromagnetism might be at play in comet science -- you rule out the very mechanism which would be needed to make it plausible


Bull puckkey! Even if electromagnetism played a role in comet science, which it doesn't, there is no mechanism which could make it plausible and not leave traces.

We can make up models of anything, given the desire to do so. The reason there are no models of electrical phenomenae such as proposed by the increasingly isolated and out of touch proponants of the EU universe is because IT DOES NOT WORK in the way they propose! The moving goalposts set out by the remnants of the EU crowd no longer have relevence to actual scientific study. They moved the posts past the point of absurdity.

If you have any real contribution hannesalfven, then stop posting to a science site and put out a bloody paper. Otherwise just keep your nonsense to the Thunderbolts site for the faithful.
Tektrix
3.3 / 5 (4) Jan 30, 2013
I think that a real comet attack would be . . . magnificent. For a few seconds.
StarGazer2011
2.8 / 5 (4) Jan 30, 2013
The point here is the 'dissapearance' of the Clovis doesnt actually need any explaination; they didnt dissapear they just used better technology.
yep
2.3 / 5 (3) Jan 31, 2013
If a 330 ft comet flattened 770 miles of Siberia why would a much larger one not possibly create a continental sized airburst. Not to say that is what happened in this case as I like Stargazer's point.
yep
1 / 5 (5) Jan 31, 2013
Magnus, have you read anything about comets in the last twenty years? Hell, these comets have magnetospheres and the tails that follow the magnetic field lines. We are still in the dark ages with them as far as thinking of what the tails are composed of including the antitail. The whole idea of dust and out-gasing from ice hiding under the rocks and solar heating that is where the Bull pukkey lies. It is easy to see it is the comets path in and out of the heliosphere, that gives it the different charge resulting in the coma and tail. Like lightning they give off x-rays. With all our equipment in space you better start getting used to the Electric Universe Theory, because it is laboratory testable, scalable and makes much more sense than that Big Bang Black Hole reality you old dinosaurs cling to.
Maggnus
4 / 5 (4) Jan 31, 2013
@ yep - Laughable! As in wow, how can you be so gullible?

Do you know about the Rosetta mission? How about Stardust? Ice? Giotto? Deep Space 1? Deep Impact? Have you read about any of these?

How about you do this; take a couple of days and read up on the missions I've just mentioned. Read about their findings as to the composition of comets, especially as it relates to the sample return missions. Take a look at what the instruments used discovered about their magnetic fields. Learn!

EU is not science any more. It stopped being science by about 1996.
ryggesogn2
2.4 / 5 (5) Jan 31, 2013
One theory is a meteor hit a North American glacier.
Maggnus
1 / 5 (1) Feb 01, 2013
True Ry, however that theory runs into the same problem; that is, the lack of shocked materials and the lack of an appropriately sized crater. Even taking into account the thickness of the ice sheet, an impact large enough to have affected the whole of North America should have left some clear signs.
ryggesogn2
1.7 / 5 (6) Feb 01, 2013
Left a clear sign?
Again, it is asserted the meteor hit an ice sheet hundreds of meters thick covering what is now Canada.
As for shocked material,

"A 17-member team has found what may be the smoking gun of a much-debated proposal that a cosmic impact about 12,900 years ago ripped through North America and drove multiple species into extinction. "
http://uonews.uor...e-comets
Maggnus
3 / 5 (2) Feb 01, 2013
Ry - think about what you post. The shocked material they are talking about in that news article from 2009 is among the material that has been brought into question. The material, it is claimed, was "contaminated".

Did you not read where I said "even taking into account..."? A meteor hitting the earth anywhere in Canada during the iceage, that was large enough and/or had enough energy to affect the whole of the North American continent, should have left clear signs of its impact.

Should have Ry. Not would have. But if one hit, and if it didn't leave such clear evidence, there has to be a reason.
MandoZink
5 / 5 (1) Feb 02, 2013
The headlines weren't specific enough. Were we supposedly attacked with comets by superior extraterrestrial beings, or were we attacked by the comets themselves?

I would think just getting hit by a statistically random comet would be bad enough. An attack would be awful.
Paradox
1 / 5 (1) Feb 03, 2013