September 19, 2012
Protocols Were Disregarded By Clovis Impact Theory Challengers
April Flowers for redOrbit.com - Your Universe Online
Disregard of three critical protocols, including sorting samples by size, explains why a group challenging the theory of a North American meteor-impact event approximately 12,900 years ago failed to find iron and silica rich magnetic particles in the sites they investigated, says a new study from an interdisciplinary team of scientists.Edward K. Vogel, co-author of the study published in the online Early Edition of Proceedings of the National Academy of Sciences and professor of psychology at the University of Oregon, said that not separating samples of the materials into like-sized grouping made for an unavoidable layer of difficulty.
This new analysis did isolate large quantities of the "microspherules" at the involved sites where the challengers reported finding none. Malcolm A. LeCompte, an astrophysicist at Elizabeth City State University, said the findings support the climate-altering impact, but stopped just short of declaring this as proof positive of the event.
Richard B. Firestone and his team of researchers, which included University of Oregon archaeologists Douglas J. Kennett and Jon M. Erlandson, proposed the Clovis-age cosmic-impact theory in 2007. While some subsequent research groups have found corroborating evidence of a potential cosmic event, other groups reported difficulties doing so.
One such group, led by Todd A. Surovell of the University of Wyoming, did not find any microspherule evidence at five of seven sites they tested, including two previously studied locations where Firestone reported large numbers of microspherules.
"In investigating the two common sites and a third tested only by Surovell's team, we found spherules in equal or greater abundance than did the Firestone team and the reported enhancement was in strata dated to about 13,000 years before the present," LeCompte said. "What we've done is provide evidence that is consistent with an impact, but we don't think it proves the impact. We think there's a mystery contained in the Younger Dryas strata, and that we've provided some validation to the original research by Firestone's group."
As the Firestone group claimed, the particles in question are terrestrial, and not of meteoric origin. Using electron microscopy and spectroscopy, the team determined that the samples are similar to metamorphic materials in the Earth's crust. This is in contrast to the Surovell group's claims that the sampled materials were meteoric.
"These spherules have evidence of very high-temperature melting and very rapid cooling, which is characteristic of debris ejected from an impact," LeCompte said.
Spherules would have melted at temperatures approaching 2,000 degrees Celsius (more than 3,000 degrees Fahrenheit), he added. Cosmic materials, including some microspherules, regularly fall to earth from space due to meteorite ablation, but the spherules found in soils dating to 13,000 years ago are much different, he added. Other researchers had suggested that these spherules were deposited by a cosmic rain or resulted through slow, terrestrial processes occurring under ambient conditions.
When LeCompte and others questioned why Surovell didn't find any spherules, they were lead to Vogel. Many of the spherules investigated were tiny, ranging in size from 20 to 50 micrometers (microns); about the diameter of a human hair.
"The inherent difficulty in finding these small, relatively rare magnetic microspherules suggested there may be inherent limitations in human faculties that needed to be addressed, and that's how and why we sought out UO Professor Ed Vogel. His research into human cognitive capabilities proved so important in understanding both why the search was so difficult and why size-sorting was effective and important in making it easier," LeCompte said.
Vogel specializes in the ability of people to find specific items amid multiple distractions.
"A visual search is a very error-prone process," Vogel said. "This was a case of looking at millions of particles from which you are hoping to find something that might be present much less than 0.1 percent of the time." Size-sorting, he said, is vital because it is easier to find a target item with a characteristic shape and color when all of the many more-distracting objects are very similar. "It is a slow, tedious process to examine such quantities of materials with the human eyes when object sizes are extremely dissimilar."
"Science is only as good as the humans who conduct it, and this study shows how the minds of researchers can operate in some surprising ways," said Kimberly Andrews Espy, UO vice president for research and innovation. "Dr. Vogel's excellent work illustrates the importance of understanding how the human mind processes information and the consequences it can have beyond making everyday computations."
LeCompte described Surovell's study "as possibly the most damning of the reports that had challenged the original theory."
"Todd had worked very hard and couldn't find the spherules, but I think he made some fatal errors that need to be pointed out," LeCompte said. "It is instructive in that we initially made the same mistake and came to the same erroneous conclusion, but then we corrected our mistake. I would say this is a case of a missed opportunity due to their deviations from the protocol."
The current study also discussed two other protocol deviations that were not followed by challengers of the original findings. These involved the amounts of material examined and the use of microscopy techniques specified in Firestone's original research. LeCompte's team identified two other minor protocol aspects that were not repeated.
Using the protocols of Firestone's original group and electron microscopy, LeCompte's team additionally studied a quarry site in Topper, South Carolina, where Clovis-age people had made stone tools. They removed chert debris associated with tool making in soils found at the depth of the Clovis occupation and observed virtually no spherules below it, while in soils just above the chert fragments they found a spike in the number of telltale spherules.
Further above that level, he noted, the soil layers were essentially "a dead zone" somewhat analogous to the K-T boundary, or "tombstone layer," from an extinction event that occurred 65 million years ago. At Topper, the dead zone showed almost no trace of human habitation for perhaps as long a duration as 1,000 years.
"This suggests that something very dramatic happened," LeCompte said.
"The effects of such an impact would have been catastrophic on a global scale," said co-author Barrett Rock, a botanist at the University of New Hampshire. "On the order of 36 ice-age species became extinct, and the Clovis human culture eventually lost. All of this in response to dramatic changes in the vegetation at the base of the faunal food chain."