Deadly Voyager

by James Lawrence Powell

  Prediction 3: At least some newly-discovered YDB sites will show peaks in the distinctive event markers.

  We already know this is the case with the sites studied by FEA. But if all YDB layers formed from the same widespread and instantaneous event, then new or newly investigated sites will have the same kinds of event markers as those reported by FEA.

  Prediction 4. Scientists may find a crater or craters of YDB age.

  As with the discovery of the Chicxulub crater, the finding of one of YDB age would strongly corroborate the YDIH. In the case of the KT, the evidence for impact was already so strong that the theory would have survived even if scientists had never found the crater. They well might not have, for 65 million years of erosion could have made the crater hard to recognize. Or, the impactor could have landed on the 70% of the Earth’s surface that the oceans cover, in which case the crater could by now be hidden by seafloor sediment. Or, it could have been subducted and vanished as a result of plate tectonics. The Chicxulub crater was buried under a half-mile of rock, detectable only by geophysical methods. It could very easily have been missed had it not been for the sharp eye of its discoverer, Glen Penfield.

  A putative YD crater is too young to have been lost to erosion, but an impactor could have landed in the ocean and be hidden. Or, given that an ice sheet covered much of northern North America at YD time, the impact could have been onto the Laurentide ice. Would it then have formed a crater? FEA envision the airburst and fragmentation of a comet, which again might not have left a crater as evidence. Thus, the absence of a crater of YDB age would not by itself falsify the YDIH, though without it the theory would require stronger evidence.

  4

  DEAD ON ARRIVAL?

  WILD CLAIMS

  Firestone and colleagues first presented their hypothesis at the spring 2007 meeting of the American Geophysical Union (AGU) in Acapulco. Veteran Science Magazine journalist Richard Kerr was there to describe the reaction of the attending scientists to what he called, “A headline-grabbing proposal that an exploding comet wreaked havoc on man and beast 13,000 years ago.” Many found the idea, “cool,” Kerr wrote, but none were about to rush off to “rewrite the textbooks.”

  Kerr had shown himself to have a good eye for topics in science that were both important and controversial and also to have the skill to explain them to non-experts. He had made impact theories a specialty, providing essential reading for anyone wanting to follow the history of the Alvarez Theory. Kerr had also reported on the giant impact theory for the origin of the Moon, saying it “had breathed new life into a long-stagnant field.” Would anyone be able to say that about the YDIH?

  The PNAS article appeared a few months after the Acapulco meeting. Unlike an oral presentation at a conference, it had passed rigorous peer review. The article reported new findings that replicated the discovery of microspherules and magnetic grains reported in Mammoth Trumpet and in The Cycle. The authors had replicated their own findings by locating the event-marker peaks at ten different YD sites. Collectively, the 26 PNAS authors had published hundreds of articles in peer-reviewed journals. They made their case in the pages of one of the most prestigious. As we saw in the last chapter, the event marker peaks were hard to explain as the result of any conceivable terrestrial process. These facts did not immunize the YDIH against criticism but should have meant that the hypothesis would get a fair hearing and at the very least, not be dismissed out of hand.

  Only three months after the FEA article, the first peer-reviewed response appeared in GSA Today, a magazine from the Geological Society of America whose aim is to keep geologists up-to-date on hot topics. Nicholas Pinter and Scott Ishman titled their article, “Impacts, megatsunami, and other extraordinary claims.” They dismissed the YDIH as a “Frankenstein monster.”

  “Impacts” in their title referred to the YDIH, while “megatsunami” had to do with the giant, possibly impact-generated, tidal waves that some have proposed as the cause of certain enormous, V-shaped sand dunes. The authors said that both hypotheses “engender similar doubts,” but the two have nothing to do with each other except that some have attributed each to impact.

  The word extraordinary in the title is taken from a saying often attributed to Carl Sagan: “Extraordinary claims require extraordinary evidence.” The aphorism goes back much farther than Sagan, to David Hume and to Laplace, who wrote, “The weight of evidence for an extraordinary claim must be proportioned to its strangeness.” The GSA Today authors argued that the YDIH evidence did not meet that standard. But whether or not evidence is extraordinary is a matter of opinion. Seldom do those who demand it spell out exactly what extraordinary evidence would satisfy them. And when such evidence is presented, opponents often raise the goalposts.

  By the time the GSA Today article appeared, some three decades had passed since the introduction of the Alvarez Theory and the criteria for recognizing ET events on Earth had become well defined. They included quartz containing shock effects, glassy impact ejecta, and elevated levels of the rare metal iridium. Though FEA had reported higher than normal amounts of iridium, and though the YD microspherules could have been regarded as impact ejecta, they had not found the diagnostic shocked quartz. Indeed, scientists have yet to find it at any YD boundary site.

  The authors argued that microspherules and magnetic grains were not due to impact but to “the constant rain of sand-sized micrometeorites into Earth’s atmosphere.” Here they referred to the ablation of incoming meteorites, most too small to see, which causes them to shed minute particles of cosmic dust that settle to Earth at random. But by definition a “constant rain” could not produce the event-marker peaks that FEA had reported. The GSA Today authors did not mention those peaks, but in a subsequent article they predicted that such peaks would be found at many geologic horizons. They announced a search for these “ubiquitous” peaks and predicted that they might confront the YDIH with a “wall of contrary data.” But so far, the peaks have not been reported at any other geologic horizons than possible impact boundaries. The GSA Today article ended with this paragraph:

  The 12.9-ka impact theory runs roughshod over a wide range of other evidence. Both the impact and the Holocene megatsunami appear to be spectacular explanations on long fishing expeditions for shreds of support. Both stories have played out primarily in the popular press, highlighting how successful impact events can be in attracting attention. The desire for such attention is understandable in an environment where science and scientific funding are increasingly competitive. The National Science Foundation now emphasizes “transformative” research, and few events are as transformative as an impact. In an era when evolution, geologic deep time, and global warming are under assault, this type of “science by press release” and spectacular stories to explain unspectacular evidence consume the finite commodity of scientific credibility (italics added).

  PNAS covers a wide range of scientific subjects. One might say it is optional reading for busy scientists in a given field, who must first find time to keep up with the literature in their own specialty, an increasingly daunting task. It seems a safe bet that many earth scientists first learned of the YDIH from the GSA Today article. It offered no new data to counter the YDIH and was largely an opinion piece. Nevertheless, few busy scientists, having seen the hypothesis so condemned, would have seen any reason to ever grant it credence. The GSA Today article dug a hole for the YDIH that would grow deeper.

  MAYBE THEY DID, MAYBE THEY DIDN’T

  Kerr followed up with another review article in early March 2008, by which time both the PNAS and GSA Today articles had appeared. His piece focused mainly on the response of the impact specialists and the claim made at the Acapulco meeting that the YDB contains numerous nanometer-sized diamonds. Kerr now found that on the YDIH, “Many [impact specialists] have lately swung from leeriness to thorough disbelief.”

  “The whole thing is contrived,” Kerr quoted one expert saying, “Their data don’t agree with anything we know about impa
cts. It just doesn’t make any sense.” The YDB data do not include “any of the classic evidence of an impact,” said another. The event markers that FEA report “are not diagnostic of impact,” said yet another.

  Yet showing that the hypothesis was still alive, new evidence continued to turn up. By the time of Kerr’s next report in early 2009, Douglas and James Kennett, son and father, and other colleagues, had published an article in Science titled, “Nanodiamonds in the Younger Dryas Boundary Sediment Layer.” They had used a technique called transmission electron spectroscopy (TEM) on YDB sediments at six localities and found two nanodiamond varieties: those with a cubic crystal structure and the “n-diamond” variety that is known to occur in meteorites. These diamonds are absent a few centimeters above and below the YDB, but rise to a peak right at it. Kennett et al. concluded that both types were of cosmic origin. Some nanodiamond specialists were now willing to give the YDIH the benefit of the doubt, but one expert, who would soon report being unable to find any nanodiamonds whatsoever at the YDB, told Kerr, “Maybe they found diamonds, maybe they didn’t.”

  As Kerr summed up, “So once again the advocates of a Younger Dryas impact are hearing that they have yet to make their case.” He ended on an encouraging note: “But then, it took the better part of the 1980s for proponents of the dinosaur-killing impact to win that argument.”

  THE LOST DEBATE

  Reading about a controversy in science, one is apt to wonder: “Why don’t both sides just get together and debate until one side wins?” This is how we settle matters in the courtroom, so why doesn’t science use the same method? Perhaps a panel of unbiased senior scientists could serve as jury. The ideal place would be one where scientists are already assembled — say at a large scientific conference like those of the American Geophysical Union.

  But it turns out that scientists seldom confront each other directly. What “debate” there is happens in the pages of scientific journals, or these days, in blogs and on websites. An important exception were the meetings held in the 1980s at the Snowbird ski resort in Utah where scientists on both sides of the Alvarez Theory confronted each other directly, to the great benefit of science.

  Still, a face-to-face debate among scientists remains a tempting idea. Even if no winner could be anointed, at least the two sides could hear each other’s evidence, ask questions, and get ideas for the next stage of their research..

  In that spirit, YDIH proponent Allen West and critic Mark Boslough of Sandia National Laboratory arranged a symposium on the YDIH at the fall 2009 AGU meeting, where speakers from both sides could make their case. They titled the session, “Younger Dryas Boundary: Extraterrestrial Impact or Not?”

  Richard Firestone did not attend, and as reported by David Morrison of NASA, “Ten speakers were squeezed into a single two-hour session.” That works out to only 12 minutes per speaker and scientists are not known for staying within their time limit when summarizing years of research. Not surprisingly, the session ran over and no time was left for questions. As Morrison summarizes, “Even when their conclusions were challenged, most of the scientists in the audience chose not to respond. The result was a lost opportunity for real debate.”

  LAST MAN STANDING

  Richard Kerr was unable to cover that meeting, but in September 2010 he published what would be his last article on the YDIH. The title, “Mammoth Killer Flunks Out,” reflected Kerr’s view that the opponents had won. His subtitle spelled out the reason: “After a new study fails to find nanodiamonds, impact experts are flatly rejecting outsiders’ claims that an impact 12,900 years ago devastated the megafauna.”

  By this time, the impact specialists had grown ever more strident in their rejection. One now told Kerr that the evidence for the YDIH was “not internally consistent, not reproducible, and certainly not consistent with being produced by impact.” Another declared that, “The geochemical story is finished; it’s over,” adding, “There is nothing, no meteoritic signal. No one I know of has come to their defense.” As for the nanodiamonds, “They are the last man standing. Everything else has failed to be corroborated.”

  According to a 2010 review of impact criteria, diamonds showing shock effects occur at many known impact craters and “provide definite evidence of impact.” On the other hand, as noted above, diamond can take different forms, not all of them accepted as evidence of impact. The one structure whose presence is regarded as diagnostic is a rare hexagonal form called lonsdaleite. It is found in meteorite fragments at Meteor Crater, Arizona and is believed to appear in Nature only when meteorites containing graphite (pure carbon) strike the Earth. The great heat and shock pressure transform the graphite into diamond, but do not prevent it from retaining graphite’s hexagonal crystal structure.

  In August 2009, the Kennetts and 15 co-authors reported finding the diagnostic [hexagonal] lonsdaleite at the YDB at Arlington Canyon on Santa Rosa Island in the Santa Barbara Channel. But one doubter told Kerr, “I’m convinced there’s no [hexagonal] diamond present.” The material identified by Kennett et al. “wasn’t diamond,” he said, but other forms of carbon, “a gross misidentification.” As the controversy unfolded, such claims of misidentification and irreproducibility from opponents would stalk the YDIH.

  DIAMONDS AND ICE

  On March 31, 2009, nearly six months before the Kerr report declaring nanodiamonds the cause of death of the YDIH, the PBS television show NOVA aired an episode originally titled “The Last Extinction,” later changed to Megabeasts’ Sudden Death: Scientists propose a radical new idea of what killed off mammoths and other large animals at the end of the Ice Age. The program is available on YouTube and is essential viewing for any reader of this book. The PBS website includes a complete transcript.

  The focus of the nearly hour-long program is the attempt of three scientists to locate and investigate the YD boundary in the ice of Greenland. Not in an ice core mind you, but exposed at or near the surface, which is still possible with an event only 13,000 years old. Paul Mayewski of the University of Maine is a specialist on modern glaciers; his university colleague Andrei Kurbatov analyzes ice for microscopic particles like the ones found at the YDB. Joining them as a guide is J. P. Steffensen, a Danish scientist and expert on the stratigraphy of the Greenland ice sheet.

  The video shows the scientists in Mayewski’s laboratory using oxygen isotope ratios and their established profile across the YDB to pin down the boundary in the Greenland ice. They find it and a modest iridium elevation, but their real focus is on nanodiamonds. For that, the scene moves to U. C. Santa Barbara and the transmission electron microscope laboratory of materials scientist Chris Mercer. Now we are about to see what we almost never do: a scientific discovery as it happens. In a remarkable piece of television journalism, we see James Kennett seated in front of the screen of the TEM as the first images come through from the Greenland ice. As the screen fills with images of minuscule diamonds, Mayewski says, “There’s tons of them all over.” Kennett follows up: “There’s no way you are going to get these kinds of particles in the ice sheet unless they are raining out of the atmosphere.”

  Mercer conducts a test to be sure the micro-particles are diamonds — and they are, different types including the unmistakable pattern of the hexagonal lonsdaleite. Then, in an even more dramatic scene, we see tears well up in the eyes of James Kennett as his emotions nearly overcome him at this finding of a long and distinguished scientific career.

  In August 2010 in the Journal of Glaciology, the four scientists and co-authors published, “Discovery of a nanodiamond-rich layer in the Greenland ice sheet.” They confirm the presence of lonsdaleite among the nanodiamonds in the Greenland ice at the YDB, noting that is, “the first highly enriched, discrete layer of [nanodiamonds] observed in glacial ice anywhere, and its presence indicates that ice caps are important archives of ET events.” They could not date the ice layer precisely, but believed that it dated to the YDB.

  FIGURE 3:

  James Kennett (L) and son D
ouglas Kennett on Greenland

  As James Kennett said, the diamonds and other markers found in the pristine Greenland ice could only have gotten there by being airborne and settling from the atmosphere. Some event 12,900 years ago had injected billions of nanodiamonds into the atmosphere from where they traveled for hundreds or thousands of miles before sifting down to Earth. To explain that by any known terrestrial process is virtually impossible. But this positive evidence of nanodiamonds was checked if not outweighed by the reports of others who said they could not find them. Absence of evidence trumped the existence of evidence. But note that even if the nanodiamond evidence was disregarded, at least the proponents of the YDIH had the microspherule peaks on their side. Or did they?

  5

  AN INDEPENDENT EVALUATION

  Let us move back in time to October 2009, when anthropologist Todd Surovell of the University of Wyoming and eight co-authors [henceforth SEA] published, “An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis.” Six, including Vance Haynes, were from university anthropology departments, the first response from members of this specialty.

  This was the first peer-reviewed article to report a failure to replicate the key microspherule evidence reported by FEA. It set the stage for much that was to follow. For that reason, the article stands with FEA as among the most important in the large literature on the YDIH. We will examine it here and again in Chapter 8.

  REPRODUCIBILITY

  An assumption implicit in any scientific finding is that other scientists following the same procedures will get the same results. In the earth and historical sciences, not only is the effort to replicate a finding apt to take a lot longer than in the lab sciences like chemistry and physics, the nature of the evidence differs. To try to replicate FEA’s findings, a scientist would first have to locate the YDB, best done by finding the black mat, but it is not always present. In that case, to pin down the YDB might require time-consuming radiocarbon dating.