The backup to what Allen’s saying is in a paper I’m already familiar with by Michail Petaev of Harvard University’s Department of Earth and Planetary Sciences and his colleagues Shichun Huang, Stein Jacobsen, and Alan Zindler. Published in the Proceedings of the National Academy of Sciences in August 2013, the self-explanatory title of the paper is “Large Pt Anomaly in the Greenland Ice Core Points to a Cataclysm at the Onset of Younger Dryas.”
Platinum is, of course, an element found on earth, but analysis of the platinum in the ice core by Petaev and his colleagues reveals a composition quite unlike terrestrial platinum and leads the scientists to conclude that “an extraterrestrial source,” perhaps “a metal impactor with an unusual composition,” is the most likely explanation.15 They note also that during the 21-year interval—between 12,836 and 12,815 years ago, as indicated by Allen:
The Pt concentrations gradually rise by at least 100-fold over ~14 y and drop back during the subsequent ~7 y. … The observed gradual ingrowth of the Pt concentration in ice over ~14 y may suggest multiple injections of Pt-rich dust into the stratosphere.16
Allen’s reading of what Petaev’s findings point to, shared widely by his colleagues, is that the “impactor” was in fact multiple impactors, all of them fragments of a comet that had wandered in from the outer solar system and taken up a potentially deadly earth-crossing orbit.
Though bound together by ice, comets have rocky cores that are often volatile, and it is in the nature of these cores to undergo fragmentation. Take Comet Shoemaker-Levy 9, for example. It broke apart into twenty-one fragments, all of which smashed into the planet Jupiter over a period of 6 days in July 1994 with spectacular effect, creating huge, fiery explosions and dark scars, in some cases larger than the earth, that persisted on the surface of the gas giant for many months.
Something of the same sort is involved in Allen’s vision, again widely shared by his colleagues, of what happened to the earth at the Younger Dryas Boundary. Drawing also on the work of William Napier, professor of astrobiology at the University of Cardiff, what the Younger Dryas Impact Hypothesis proposes, in brief, is a large parent comet in the range of 100 kilometers in diameter. Plunging in from the outer solar system, it enters an earth-crossing orbit around 30,000 years ago and remains intact for the next 10,000 years. About 20,000 years ago, due to gravitational forces in the inner solar system it undergoes a massive “fragmentation event” that transforms it from a single deadly and potentially world-killing object into multiple objects varying in diameter from the extremely dangerous kilometer-plus range down to a few tens of meters, down to chunks the size of cars, down to boulder-sized pieces, down to fist-sized rubble, and down beyond that to countless billions of smaller fragments and an immense penumbra of dust. As thousands of years pass, the whole turbulent mass of big and little pieces of the comet orbiting at tens of thousands of kilometers per hour begins to separate into multiple filaments each filled with debris, eventually expanding to form a giant tubular “meteor stream” some 30 million kilometers in diameter and extending more than 300 million kilometers across the entire orbit of the earth—which it cuts in two places so that we must pass through the stream twice a year. Traveling 2.5 million kilometers along its orbital path every day, the earth takes 12 days to complete each passage through the stream.17
The Taurid Meteor Stream. Remnant of a giant comet 100+ kilometers in diameter, before undergoing fragmentation. The stream includes three known comets or comet-like objects, namely: Enke, Oljiato, and Rudnicki, and nineteen of the brightest near-earth objects.
Because the meteor stream produces showers of “shooting stars” that look to observers on the ground as though they originate in the region of the sky occupied by the constellation Taurus, it’s called the Taurid meteor stream. Our planet still passes through it twice a year, negotiating its dangerous inner filaments in late June and early July (when shooting stars are not visible because they are encountered in daylight) and again from late October into November, when a spectacular “Halloween fireworks” display is put on.18
On most of these biannual encounters with the Taurids we just get the pretty fireworks, but occasionally we get more. On June 30, 1908, for example, an object thought to have fallen out of the Taurid meteor stream,19 and estimated to be somewhere between 60 and 190 meters in diameter, penetrated earth’s atmosphere. It exploded in the air—fortunately above an uninhabited region of Siberia—flattening 80 million trees across an area of 2,000 square kilometers. To put this in context, Greater London has an area of 1,582 square kilometers and a population of more than 7 million people. “If transferred to London,” Professor Napier calculates, the Tunguska airburst:
would have been heard throughout the UK, north to Denmark and across Europe as far as Switzerland. Topsoil would have been stripped from fields in the north of England, people in Oxford would have been thrown through the air and severely burned, an incandescent column of matter would have been thrown 20 km in the air over London, and the city itself would have been destroyed about as far out as the present-day ring road. Impact energy estimates range from 3 to 12.5 Mt (megatons TNT equivalent).20
The consequences if an object of similar size were to explode over a major city today would, in other words, be utterly catastrophic, but because the Tunguska event took place in a remote region before the era of modern mass communications, very few people are aware of how deadly even relatively small chunks of space rock can be.
Professor Napier and his colleague Victor Clube, formerly dean of the Astrophysics Department at Oxford University, go so far as to describe the “unique complex of debris” within the Taurid stream as “the greatest collision hazard facing the earth at the present time.”21 Coordination of their findings with those of Allen West, Jim Kennett, and Richard Firestone, has led both teams—the geophysicists and the astronomers—to conclude that it was very likely objects from the then much younger Taurid meteor stream that hit the earth around 12,800 years ago and caused the onset of the Younger Dryas. These objects, orders of magnitude larger than the one that exploded over Tunguska, contained extraterrestrial platinum, and what the evidence from the Greenland ice cores seems to indicate is an epoch of 21 years in which the earth was hit every year, with the bombardments increasing annually in intensity until the fourteenth year, when they peaked and then began to decline before ceasing in the twenty-first year.
Tunguska—an airburst at an altitude of 5–6 kilometers. The object was estimated to have had a diameter of between 60 and 190 meters. It flattened 80 million trees across an area of more than 2,000 square kilometers. This is an area larger than London. Had the event occurred over a major city, rather than over an uninhabited area, the loss of life would have been horrendous. PHOTOS: LEONID KULIK.
“It’s as though after dodging the bullet for thousands of years,” I say to Allen as we walk back along the baking floor of the arroyo, “the earth finally intersects a particularly lumpy and rocky filament of debris and we get hit really hard, over and over again, year after year, until we’ve passed through it.”
“Petaev himself says ‘multiple injections of platinum,’” Allen reminds me. “I think those were pretty much his exact words in the paper, so that’s an independent assessment of the idea. There’s something else, too, from new research we’ve been working on. In the ice core, at the exact same moment we see this big onset of platinum at the beginning of the 21 years, we also see a sudden rise in dust.”
The Younger Dryas Boundary strewn field. The area enclosed by the dotted line defines the current known limits of the YDB field of cosmic impact proxies spanning more than 50 million square kilometers.
“Which tells you what?”
“Which tells us that along with everything else that was going on at the time there were also very high winds blowing. There are certain proxies of that windiness that end up in the ice sheet. When it’s windier the winds will pick up continental dust, and, number one, it’s colder so there’s less plant cover
, so when it gets windier and there are less plants to hold the sediment down, you get huge dust storms. We can see that buildup in the Greenland ice sheet. We see magnesium and calcium, a huge increase in them, and those are indicative of terrigenous dust, continental dust, and we see an increase in sodium and chlorine which are from sea salt—so the winds are so strong they pick up more sea salt and deposit it in Greenland. The levels of these windiness proxies continue to climb for nearly 100 years. At the same time we see one of the biggest peaks in the entire ice core in all the biomass-burning proxies, and those occur within less than a 10-year window of the start of that 21-year interval—so you look at that and the best explanation is the impact occurred, that it triggered immense biomass burning, and that it changed the climate radically, resulting in high winds and immense dust storms.”
“So it was a combination of really horrible things?”
“A cascade of bad things. It must have felt like the end of the world for those who lived through it.”
“And particularly bad here in North America—the epicenter of the disaster?”
“Much worse here than anywhere else! A true calamity. But it wasn’t only North America. We’ve traced evidence of further impacts from the same swarm in the exact same period in Europe and as far east as Syria and even into South America. The strewn field extends across more than 50 million square kilometers of the earth’s surface.”
NEW EVIDENCE
I HAVE WRITTEN EXTENSIVELY ABOUT the Younger Dryas Impact Hypothesis in Magicians of the Gods. There I present evidence that the impacts changed the world completely and wiped from the record almost all traces not only of the Clovis people but also of an advanced civilization of the Ice Age.
The fact that North America was the epicenter of the cataclysm, though acknowledged, has profound implications for our understanding of the human past that archaeologists have never thought through—in part because the scale of the cataclysm is only now beginning to be fully mapped out.
After completing Magicians, therefore, I made sure I stayed up to date with the steady stream of new evidence released by Allen and his group in the scientific journals. There was a visible quickening in the pace of the research, and in 2017 and 2018 two major studies revealed how truly devastating the cataclysm at the onset of the Younger Dryas really was.
If there was ever a time when a significant chapter in the story of human civilization could have been lost, this, surely, was it.
FIRE AND ICE
ALLEN WEST AND THE TEAM of scientists working on the Younger Dryas Impact Hypothesis established themselves as a formal research organization, the Comet Research Group, in 2015.1 The group (hereafter CRG) presently numbers sixty-three leading scientists from fifty-five universities in sixteen countries.2 Many other scientists are also directly and indirectly associated as coauthors of papers written by CRG members.
This is the case with a paper, published in Nature’s sister journal Scientific Reports on March 9, 2017, titled “Widespread Platinum Anomaly Documented at the Younger Dryas Onset in North American Sedimentary Sequences.”3
The lead author is geoarchaeologist and CRG member Dr. Christopher Moore of the University of South Carolina. His coauthors and fellow CRG members are geophysicist Allen West, whom we met in the last chapter, anthropologist Randolph Daniel of East Carolina University, archaeologist Albert Goodyear, whom we met in chapter 6, earth scientist James P. Kennett of the University of California, geologist Kenneth B. Tankersley of the University of Cincinnati, and geologist Ted Bunch of Northern Arizona University. The non-CRG coauthors are planetary and atmospheric scientist Malcolm LeCompte of the University of South Carolina, geomorphologist Mark J. Brooks, also of the University of South Carolina, environmental scientist Terry A. Ferguson of Wofford College, South Carolina, geoscientist Andrew H. Ivester of the University of West Georgia, luminescence-dating expert James K. Feathers of the University of Washington, and physicist Victor Adedji of Elizabeth City State University.4
All in all, therefore, a very distinguished assembly of scientists—and the task that they set themselves was also in the finest tradition of good science, namely, to test an important prediction made by other scientists. From the previous chapter, the reader will recall the research by Michail Petaev and his colleagues showing elevated levels of platinum in the Greenland ice cores over a 21-year period between 12,836 and 12,815 years ago. Petaev reports what appear to have been “multiple injections” of platinum-rich dust into the stratosphere over this period and predicts that if the source of the dust was cometary, asteroidal, or meteoroidal, then the fallout should have extended far beyond Greenland and would be “expected to result in a global Pt anomaly.”5
The coauthors of the 2017 platinum paper chose North America, the suspected epicenter of the Younger Dryas cataclysm—and also their home turf—to test this prediction by establishing “whether or not a Pt anomaly exists in terrestrial sediments of YD age that is similar to that reported from the GISP2 ice core.”6
It sounds low-key, but much was at stake. If soil samples showed platinum to be at normal background levels in the YDB layer across North America, then Petaev’s prediction would be false and the Younger Dryas Impact Hypothesis would suffer serious collateral damage. On the other hand, if elevated levels of platinum were found, it would vindicate Petaev and give further strong support to the hypothesis that cosmic impacts caused the Younger Dryas cataclysm.
Eleven archaeological sites—see map below—all with good stratification and well-established YD-age sediments were selected as the focus of the study: 1. Arlington Canyon, Santa Rosa Island, California; 2. Murray Springs, Arizona; 3. Blackwater Draw, New Mexico; 4. Sheriden Cave, Ohio; 5. Squires Ridge, North Carolina; 6. Barber Creek, North Carolina; 7. Kolb, South Carolina; 8. Flamingo Bay, South Carolina; 9. Pen Point, South Carolina; 10 Topper, South Carolina; and 11. Johns Bay, South Carolina.
The project began by testing soil samples from Arlington Canyon, Murray Springs, Blackwater Draw, and Sheriden Cave, four sites with particularly “well-defined and well-dated YDB age sediments containing peaks in YDB impact-related proxies.”7 What the tests revealed was:
a large above-background Pt anomaly at each site in the identical sample previously identified as the YD boundary layer containing abundance peaks in YDB proxies, including micro-spherules, meltglass, and nanodiamonds.8
The team then extended the Pt analysis to soil samples from the seven other sites. In summary, across all eleven sites, they conclude that their results
provide strong evidence for above-background enrichment in Pt within sediments that date to the onset of YD climate change at ~12,800 Cal B.P. Pt abundances from our study sites averaged 6.0 parts per billion (ppb) … compared to background abundances above and below the YDB layer averaging 0.3 ppb. Average background Pt concentrations are all lower than crustal abundance of 0.5 ppb, whereas average YDB concentrations are 12× higher. These concentrations are also higher than the peak Pt concentration (~80 parts per trillion [ppt] or 0.1 ppb) reported at high chronological resolution from the GISP2 ice-core in Greenland by Petaev et al. All study sites contain significant Pt peaks that are ~3 to 66× higher than in Greenland.9
The technical language and abbreviations make it difficult to stay focused on the grave implications of all this. In a layer in the earth that already contains abundant evidence of a cataclysmic cosmic impact around 12,800 years ago, a mass of new corroborative evidence has now been discovered. In parallel, the much greater strength of the Pt signal in the United States than in Greenland joins multiple other indicators pointing to North America as the most severely affected locus of the cataclysm. If this were a homicide investigation in which the prosecution were hesitating to charge the suspect, new evidence of this quality would be decisive, and a winnable case could be brought to court. Moore and his colleagues are cautious and modest, however, claiming only that:
the consistent presence of anomalous Pt concentrations within sediments from multiple
archaeological sites across North America that date to the onset of the YD Chronozone is compelling. … This study finds no evidence to contradict the conclusions of Petaev et al. that the Greenland Pt enrichment most likely resulted from an extraterrestrial source. … In addition, our findings show no contradiction with the Younger Dryas impact hypothesis.10
After completing their own investigation, Moore et al. combed the scientific literature for indications of how far beyond North America and Greenland the YDB platinum anomaly extends. Though not central to any investigation prior to Petaev’s, they found that platinum group elements had been discovered and mentioned in passing in other earlier studies of the Younger Dryas Boundary at locations as far afield as Belgium, the central Pacific, Venezuela, the southwest of England, and the Netherlands—“important information,” hinting at a truly global picture, that they hope “may encourage further research.”11
In the Supplementary Information to their main paper, Moore and his colleagues also provide detailed evidence ruling out either volcanic activity or processes in the mantle of the earth as the sources for the enriched platinum at the YDB.12 By contrast, after compiling geochemical data for 167 meteorites, including chondrites, achondrites, irons, and ureilites, they found very high average Pt abundances, “making all four classes of meteorites possible sources of YDB Pt enrichment.”13
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