Touchdown!: YDB team publishes best paper yet in PNAS

Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world’s premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event…..

……..The geographical extent of the YD impact is limited by the range of sites available for study to date and is presumably much larger, because we have found consistent, supporting evidence over an increasingly wide area. The nature of the impactor remains unclear, although we suggest that the most likely hypothesis is that of multiple airbursts/impacts by a large comet or asteroid that fragmented in solar orbit, as is common for nearly all comets. The YD impact at 12.8 ka is coincidental with major environmental events, including abrupt cooling at the YD onset, major extinction of some end-Pleistocene megafauna, disappearance of Clovis cultural traditions, widespread biomass burning, and often, the deposition of dark, carbon-rich sediments (black mat). It is reasonable to hypothesize a relationship between these events and the YDB impact, although much work remains to understand the causal mechanisms.  

Link to paper at PNAS

Wittke 2013 PNAS Clovis Comet Younger Dryas Impact Spherules Found on Four Continents by George Howard


James H. Wittke (Northern Arizona University)

James C. Weaver (Harvard University)

Ted E. Bunch (Northern Arizona University, NASA)

James P. Kennett (University of California, Santa Barbara, CA)

Douglas J. Kennett (The Pennsylvania State University)

Andrew MT Moore (Rochester Institute of Technology)

Gordon C Hillman (University College London)

Kenneth B. Tankersley (University of Cincinnati)

Albert C. Goodyear (University of South Carolina)

Christopher R. Moore (University of South Carolina)

I. Randolph Daniel, Jr. (East Carolina University)

Jack H. Ray (Missouri State University)

Neal H Lopinot (Missouri State University)

David Ferraro (Viejo California Associates)

Isabel Israde-Alcántara (Universidad Michoacana de San Nicólas de Hidalgo)

James L Bischoff (US Geological Survey)

Paul S. DeCarli (SRI International)

Robert E Hermes (Los Alamos National Laboratory (retired)

Johan B. Kloosterman (Amsterdam)

Zsolt Revay (Institute for Isotope and Surface Chemistry)

George A. Howard (Restoration Systems, Raleigh, NC)

David R. Kimbel (Kimstar Research)

Gunther Kletetschka (Charles University)

Ladislav Nabelek (Institute of Geology, Czech Academy of Science of the Czech Republic)

Carl P. Lipo (California State University)

Sachiko Sakai (California State University)

Allen West (GeoScience Consulting)

Richard B. Firestone (Lawrence Berkeley National Laboratory)


  • Steve Garcia

    And BTW, when money is tight all people operate out of committees, and all committees are by their nature scares of their shadows, even in times of plenty.

    “Committees of ten
    Accomplish now and again,
    And committees of two
    Once in a while do,
    But most things are done
    By committees of one.”

  • Ed,

    I finally finished your book. My head is reeling from the density of it. You commentary on the state of American urban centers and the US highway system were an especially refreshing summation at the end. Very impressive work.

    Please contact me offline if I can be of any assistance in the HSIE documentary process in the form of moving imagery. Think single operator camera crane, documenting both the site collection and sample analysis efforts in order to memorialize the entire process and spread the word in subsequent TV/Movie production.


  • More recent stuff of interest, including a few useful articles posted at Space Daily:

    “Is Arctic Permafrost the “Sleeping Giant” of Climate Change?”

    “FEMA, Russian Ministry to Join Forces Against Space Threat”

    The above article is the best news I’ve heard all week, even though it is essentially void of any useful details and completely lacking in any mention of the schedule of proposed joint efforts between FEMA and Russia.

    Which brings me to the third article –

    Space junk shielding..

    This brings up a good point. Currently directed energy technology has the best demonstrated capacity for applications such as reduction of space-borne threats at a distance. Boeing’s AirBorne Laser (ABL) comes to mind. It hasn’t actually intercepted orbital stuff yet, but it is a reusable technology and doesn’t require a dedicated launch vehicle for every target. It can also work incrementally on a single target, either by vaporizing portions of a given target at a time, or by reducing orbital mechanical energy to induce earlier reentry of that debris.

    It seems to me that along with characterization of the ET threat of Earth crossing bolides, we should be putting money into useful systems of mitigation. As an orbits and astro guy, I realize that multiple laser shots at an orbiting golf ball are not the same problem as diverting the orbit of an asteroid or comet fragment away from Earth crossing. But directed energy is the best bet in terms of cost effectively diverting such orbits, since anything else places all eggs in a single, expensive launch vehicle basket. On the other hand, if the laser pulses don’t give the desired effect, you haven’t wasted time getting to the bolide with an expensive rocket that can never be reused.

    Anyway, I guess its just crazy enough to be attractive; Russia and the USA cosponsoring a directed energy system that can pick off orbital debris. That tech basis could then be expanded in scale and energy to counter whatever Earth crossing threats are discovered. If both countries have skin in the game, then its less likely to be used by one against the other (biggest threat of all given human history of man’s inhumanity to man, and we can share the expense in the development and operation. We already have a current need for close range mitigation (space junk), and any astro person will tell you that a ground based or airborne platform is more economical in the long run than flying extra mass on EVERY SPACECRAFT launched as we move forward into our own contaminated near Earth environment (sadly).

    If you look at the trade-off in useful payload mass to carry shielding instead of payload, as a function of the extremely high cost per pound to launch and operate spacecraft, it would be much more sensible to have launch and ops entities pay a “clean space” fee (per launch, or as some function of usage requirement) to support directed energy development and operations. That way the tech basis and aerospace manufacturing complex are in place to scale up the threat mitigation to interplanetary scales as required.

    This is the reality that we should be considering and funding before squandering limited resources to send humans to Mars. And I say that as a pro space exploration person. Robotics is much more cost effective for exploration in the near term, and the near term already contains space-borne hazards that need mitigation. Clearly. Think it through. The path should becomes clear with proper consideration of combined existing threats (space junk) and unquantified threats (cold dark bolides) which we know exit but don’t know the quantity of. The impact of such bolides is not an acceptable risk, no matter what the politicians tell you.


  • Robert Grant

    TH, you are spot on.

  • My group (The Archimedes Group) is just about to publish a paper on this. We were thinking of just putting the one side into the geometric caustic of a large nearby parabolic mirror, which avoids a whole lot of intervening hardware between the energy and the beam. Our primary technique though is asteroid lasso with a lightly set and tightened circumference cable in order to detumble it and derotate it for future diversion and exploitation. The orbital debris will need directed energy, though, and active rendezvous, collection and removal. The trick with all of these operations is not to create even more debris in the form of ejecta and dust and stuff. It won’t take long to cover this problem once we have good detection assets in place.

  • E.P. Grondine

    Hi TH –

    Thanks for your kind words.

    While Kennett et al will own the Holocene Start Impact Event in the mainstream, I will continue to own it among te First Peoples. (I do wish the team would get the name right – it’s Holocene Start Impact Event.)

    And of course I coninue to own and will always own zll of the other impacts in the America, with the exception of Schultx’s team’s work on Rio Cuarto. And I will continue to own all of those impacts I recovered during my years of reporting for the Cambridge Conference as well.

    My current needs are a macxed out dual G4 MacPro, and a macxed out dual G5 tower.

    Aside from that, I need around $10,000 to document a likely crater from the Holocene Start Impact Event. That should bring Morrison, Boslough, et al’s nonsense to an abrupt screeching halt. If all of the people who Boslough et al burned were simply to pass the hat among themseles and split up that $10,000…

    There are a couple of small video projects I will contact uopi privately about.

  • E.P. Grondine

    Hi TH 2 –

    Good cath.

    That is very good news about the emergency management agencies agreement.

  • Careful Ed,
    They may start listening to you after all…!

  • Trent Telenko

    This is a article link from Instapundit —

    Meteoroid, Not Comet, Explains the 1908 Tunguska Fireball

  • Trent Telenko

    The closing text from the link —

    “A 1978 expedition came closer when it uncovered minuscule mineral samples embedded in peat at the epicenter of the blast. Researchers determined the samples to be 99.5 percent carbon with inclusions of other trace elements such as troilite and iridium. The amount of pressure required to form such samples suggested that the minerals were contained in a meteorite that smacked into the Earth. But these samples could also have formed when the heat and pressure of the space blast encountered rocks right here on our home planet, so the results were deemed inconclusive.

    Armed with new and improved scanning technology, a group of geologists from Europe and North America decided to resurrect these mineral samples from their archive in the Ukrainian Academy of Sciences. They analyzed the samples with traditional microscopy techniques, mass spectrometry and high-powered X-rays—techniques that have been developed and refined in the past few decades—to give a much more detailed view, and published their findings in Planetary and Space Science in May.

    While the carbon components of the samples weren’t necessarily from out of this world, the iridium concentration was ten times higher than in Earth rocks. The researchers were able to look at the surface structure and chemical composition of the samples in detail to determine that the mineral samples gathered at Tunguska most likely represent tiny bits of an iron meteorite. They suggest that the structure is the result of rapid cooling after an impact, and report that the mix of minerals matched those of other confirmed iron meteorites, like the one found in Arizona.

    So it looks like the case is closed, just in time for Tunguska to blow out the candles on its 105th carbon-studded birthday cake. Let’s just try to keep the fire under control this time.”

  • Steve Garcia

    Trent –

    I gotta ask…

    “Researchers determined the samples to be 99.5 percent carbon with inclusions of other trace elements such as troilite and iridium. The amount of pressure required to form such samples suggested that the minerals were contained in a meteorite that smacked into the Earth.”

    “The researchers were able to look at the surface structure and chemical composition of the samples in detail to determine that the mineral samples gathered at Tunguska most likely represent tiny bits of an iron meteorite.”

    Am I the only one who sees a discrepency here? 99.5% carbon or is it an iron meteor? I can see if the researchers ONLY asserted the carbon was from target material, but the “suggest” otherwise.


  • Steve Garcia

    Oops! “… but they suggest otherwise.”

  • Steve Garcia

    Trent –

    I’d suggest myself that the Tunguska object was a meteor, based on the Chelyabinsk air burst. That much is pretty much a no-brainer.

    But then they talk about “smacked into the Earth.” Wha?????

    I have done extensive reading about Tunguska going back over 30 years, and NO ONE has ever found supporting evidence for a ground impact meteor. That is a dead horse. The lack of meteoric ground impact evidence is why Tunguska has been a mystery all these 105 years. Finding Iridium itself is not evidence that it hit the ground.

    A fireball/airburst, yes (and much closer to the ground than Chelyabinsk). A ground impact, no.

  • E.P. Grondine

    Hello –

    Wr all remember Morrison’s good friend Boslough. self proclaimed impct mechanics specialist, showing up at Chelyabinsk on someone’s dime.

    Well, He’s now going to tell us what the current impact threat level is:

    Perhaps someone should give this busy fellow some time off to do some reading and write a retraction.

  • It’s downright ludicrous to hear a self convinced amateur with no academic standing or degrees whatsoever, yet who’s convinced he is the world’s foremost expert on the subject of impact science, but whose only publication is a single poorly edited, self published, paperback book, describe a PhD level physicist who is a leading member of the technical staff at Sandia National Laboratory, and adjunct professor at The University of New Mexico as a “self proclaimed impact mechanics specialist”. When In fact, according to his curriculum vitae his command of the subject of impact mechanics has been verified, and proclaimed, by some pretty major academic institutions. He has a B.S. in Physics from Colorado State University, and an MS and PhD in Applied Physics from Caltech, where his research focused on geophysics.

    I guess since you have no real academic standing of your own, and are incapable of intelligently parsing and reviewing the data they will present on the 8th anyway, I suppose the best you will ever be able to come up with when you disagree with the work and/or opinions, of real honest to PhD scientists you disagree with are cheap shots and personal ad hominem insults. The most ridiculous part of it though is that the panel described in that link won’t convene for another four days, yet you’re already spouting your excremental ad hominem tripe, and calling for a retraction without even really having a clue what they are going to say when it does.

  • E.P. Grondine

    Hi Dennis –

    All the theories in the world added together do not make one fact.

    Here’s a fact, Dennis.

    Bolough’s model handles heat very poorly.

    That is probably related to anoher fact, which is that Boslough is at Sandia instead of Los Alamos or Berkeley.

    Another fact. We know Boslough’s angling to get the data processing for the ground based Atlas system. One problem with that: the MPC at Harvard is the recognized and used US international clearing house. Another problem: finding these things with adequate warning times will require space based systems.

    Since you’re such good friends with Morrison as well, you can tell him that his impact hazard estimate based on data from the Moon is off, in comparison with impact hazard estimates based on data from the Earth.

    Another fact. Before my stroke I collected far more data on impacts than what is in my book, and it is published.

    Final fact: Your attempts to find data validating Boslough’s model have produced nothing.

    I need %10,000 to document a crater likely to be from the Holocene Start Impact Event.

    Aside from that, there is a need for an online research clearing house where only real impact researchers are allowed to post.

    That will include research on impacts other than the Holocene Start Impact Event, and exclude delusional ramblings from Dennis Cox and Chicken Little.

  • Steve Garcia please shoot me an email – I’ve got the mobile device coordinating w/ home computer email now (finally!) and I need an email from u to get your e-dress on the mobile while I’m on vacation…

    Ed and Dennis
    Remember if Einstein had stuck to his job as a

  • E.P. Grondine

    Oh yeah.

    Boslough was an author on a paper which denied the Holocene Start Impact Event, and saw it through to publication even after data czme in proving he was wrong.

    That by itself pretty well proves that he does not know what he is proclaiming himself an expert in. Just like you, Dennis.

  • Trent Telenko

    Steve G,

    Discover has increasingly become like Science Daily in it’s tech writing.

    If they get spelling right, they call it good.

  • ….had stuck to his job as a Patent clerk where would we be?

    Without any interdisciplinary pollination among technical disciplines, the advances to human knowlege come more slowly. For that reason we should embrace diversity, not reject it. That is what this forum is about, remember? To do any less is to simply be ruled by our own insecurities.


  • Myself I can’t spell worth a darn. Dyslexia makes the letters swim around in all different order. That’s why I prefer the universal language of math.


  • Robert Grant

    Yeah, who paid for Boslough to go to Russia? Why did he have trouble finding a fragment? Seems as though Russians and Native Americans have better luck finding things. For all the lack of formal education, they seem to have a good idea of what they have found.

  • Steve Garcia

    Trent –

    I won’t disagree. The day Discover published an article about the Oceanic Conveyor Shutdown, I knew they had no idea about physical properties and physics.

  • Steve Garcia

    TH –

    Dyslexia doesn’t affect your math? You don’t get terms on the wrong side of the equation?. . . LOL

  • Steve Garcia

    Einstein. . .

    If he’d stayed at the Patent Office, we wouldn’t have Quantum Physics or String Theory. And the world might be better off.

  • E.P. Grondine

    Has anyone contacted the NOVA managers yet and dragged Boslough over the rocks with them?

  • Paul Repstock

    Congrats Tuskers; YDB has hit the mainstream media. BBC

  • Steve Garcia

    Yeah, but this hypothesis has all been shown to be insect poop, misidentified.

  • Pingback: But seriously, folks: Harvard bangs a big fat Platinum nail in YDB critic coffin « The Cosmic Tusk()

  • I read with interest (only the brief summary so far). That some of the less than enthused impact scientists – specifically Dr. Mark Boslough sp?) are now admitting the that the recent Russian bolide is up to seven time more likely to affect earth than though before the Russian object. Does this nay sayers like him are now willing to at least consider the possibility of the Younger Dryas as caused by cosmic showers, as Dr. Napier suggests? I hope so, finally!!!!!! Rod Chilton.

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