Exploding stars may have caused mass extinction on Earth, study shows

UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN, NEWS BUREAU

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IMAGE: A TEAM OF RESEARCHERS LED BY PROFESSOR BRIAN FIELDS HYPOTHESIZES THAT A SUPERNOVA ABOUT 65 LIGHT-YEARS AWAY MAY HAVE CONTRIBUTED TO THE OZONE DEPLETION AND SUBSEQUENT MASS EXTINCTION OF THE… view more CREDIT: GRAPHIC COURTESY JESSE MILLER

CHAMPAIGN, Ill. — Imagine reading by the light of an exploded star, brighter than a full moon – it might be fun to think about, but this scene is the prelude to a disaster when the radiation devastates life as we know it. Killer cosmic rays from nearby supernovae could be the culprit behind at least one mass extinction event, researchers said, and finding certain radioactive isotopes in Earth’s rock record could confirm this scenario.

A new study led by University of Illinois, Urbana-Champaign astronomy and physics professor Brian Fields explores the possibility that astronomical events were responsible for an extinction event 359 million years ago, at the boundary between the Devonian and Carboniferous periods.

The paper is published in the Proceedings of the National Academy of Sciences.

The team concentrated on the Devonian-Carboniferous boundary because those rocks contain hundreds of thousands of generations of plant spores that appear to be sunburnt by ultraviolet light – evidence of a long-lasting ozone-depletion event.

“Earth-based catastrophes such as large-scale volcanism and global warming can destroy the ozone layer, too, but evidence for those is inconclusive for the time interval in question,” Fields said. “Instead, we propose that one or more supernova explosions, about 65 light-years away from Earth, could have been responsible for the protracted loss of ozone.”

“To put this into perspective, one of the closest supernova threats today is from the star Betelgeuse, which is over 600 light-years away and well outside of the kill distance of 25 light-years,” said graduate student and study co-author Adrienne Ertel.

The team explored other astrophysical causes for ozone depletion, such as meteorite impacts, solar eruptions and gamma-ray bursts. “But these events end quickly and are unlikely to cause the long-lasting ozone depletion that happened at the end of the Devonian period,” said graduate student and study co-author Jesse Miller.

A supernova, on the other hand, delivers a one-two punch, the researchers said. The explosion immediately bathes Earth with damaging UV, X-rays and gamma rays. Later, the blast of supernova debris slams into the solar system, subjecting the planet to long-lived irradiation from cosmic rays accelerated by the supernova. The damage to Earth and its ozone layer can last for up to 100,000 years.

However, fossil evidence indicates a 300,000-year decline in biodiversity leading up to the Devonian-Carboniferous mass extinction, suggesting the possibility of multiple catastrophes, maybe even multiple supernovae explosions. “This is entirely possible,” Miller said. “Massive stars usually occur in clusters with other massive stars, and other supernovae are likely to occur soon after the first explosion.”

The team said the key to proving that a supernova occurred would be to find the radioactive isotopes plutonium-244 and samarium-146 in the rocks and fossils deposited at the time of extinction. “Neither of these isotopes occurs naturally on Earth today, and the only way they can get here is via cosmic explosions,” said undergraduate student and co-author Zhenghai Liu.

The radioactive species born in the supernova are like green bananas, Fields said. “When you see green bananas in Illinois, you know they are fresh, and you know they did not grow here. Like bananas, Pu-244 and Sm-146 decay over time. So if we find these radioisotopes on Earth today, we know they are fresh and not from here – the green bananas of the isotope world – and thus the smoking guns of a nearby supernova.”

Researchers have yet to search for Pu-244 or Sm-146 in rocks from the Devonian-Carboniferous boundary. Fields’ team said its study aims to define the patterns of evidence in the geological record that would point to supernova explosions.

“The overarching message of our study is that life on Earth does not exist in isolation,” Fields said. “We are citizens of a larger cosmos, and the cosmos intervenes in our lives – often imperceptibly, but sometimes ferociously.”

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Also participating in the study were scientists from the University of Kansas; Kings College, UK; the European Organization for Nuclear Research, Switzerland; the National Institute of Chemical Physics and Biophysics, Estonia; the United States Air Force Academy; and Washburn University.

The Science and Technology Facilities Council and the Estonian Research Council supported this study.

From EurekAlert!

116 thoughts on “Exploding stars may have caused mass extinction on Earth, study shows

  1. Regardless of any extinction event speculations, it is clear Earth and our solar system is clearly blessed. We have a well-behaved Mother Sun, as far as G1-4 stars go, and also lucky to have been in a quiet neighborhood in a back-water cul-de-sac off-shoot of a main arm of the large galaxy whereby there have clearly been no nearby sterilizing Gamma-ray bursts for hundreds of millions of years.

    A part of the Rare Earth hypothesis.

    • Yep. Additionally, our magnetic field, and the Sun’s, protect us from the cosmic rays that seem always to be present. Would life be impossible without the magnetic field?

      In addition to the danger of being nuked by the cosmic rays themselves, Svensmark has the theory that cosmic rays modulate cloud cover and are therefore responsible for ice ages and interglacials like the one in which we’re now living. link Say what you will, it’s more credible than the theory that CO2 is some kind of pollution.

      • Or just lucky to be, out of the hundreds of billions of planets and moons in the galaxy, among the few particularly hospitable to the evolution of complex lifeforms.

        • Actually considring all dwarf planets, moons and even asteroids potentially capable of supporting life. we’re talking trillions of worlds in the Milky Way.

    • I look at the map of the galaxy … how could life develop in the inner area. I see constant bombardment of energy from neighboring systems.

      • There’s a life form there that thinks it’s impossible to have life here because there isn’t enough energy. They have an equation that proves it beyond any doubt.

    • Well portrayed in The Privileged Planet video at: https://www.youtube.com/watch?v=F9SEUtPEGAM . But how else are otherwise permanent grad students going to attain their astronomy/physics PhD.s without such novel ‘mays’, ‘coulds’, and ‘exploring the possibility ofs’ giving both the appearance of advancing the field and demonstrating their candidacy through mastery of now standard ingredients in the process (short of actually finding the supporting smoking gun, of course)?

    • Actually, you are the result of it. All elements heavier than Helium came about through fusion reactions in star cores and blown away into space in explosions like a SN or colliding neutron stars.

      • And elements heavier than iron, that can’t be formed by fusion, are almost exclusively formed in supenovae.

        • Burbidge, Burbidge, Fowler and Hoyle used the P-process, R-process and S-process to predict the abundance of nucleotides. Their predictions match well with abundances measured in the sun. At least that was what Geoffrey Burbidge was saying back in the 70’s. Supernovae alone cannot produce many of the nucleotides we see today. They are however very good at dispersing the material into the interstellar medium.

          • A nucleotide is one of the building blocks of nucleic acids, such as DNA and RNA. A nucleotide consists of a base (adenine, thymine or uracil, guanine, cytosine). plus a molecule of sugar and one of phosphoric acid.

            You’ve mixed up “nucleotide” with nucleosynthesis, ie the formation of the nuclei of atoms (elements) heavier than H and He in stars or supernovae.

  2. “Far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy lies a small unregarded yellow sun. Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue green planet whose ape-descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea.”
    ― Douglas Adams, The Hitchhiker’s Guide to the Galaxy

  3. “The overarching message of our study is that life on Earth does not exist in isolation,” Fields said. “We are citizens of a larger cosmos, and the cosmos intervenes in our lives – often imperceptibly, but sometimes ferociously.”

    I would guess that Henrik Svensmark might agree.

  4. “When you eliminate the impossible, what remains, however improbable, must be the truth.” Sherlock Holmes. Problem is, you can never eliminate all the impossible because of “unknown unknowns” (Donald Rumsfelt).

    • Vincent,
      I have never worried too much about the “unknown unknowns” they will always be there. It is the cult of certainty with its forgotten “unknown knowns” that bothers me.

      • I believe the point regarding the unknown unknowns was that one should never get cocky, convinced that you have everything figured out. I’m looking at you, climate alarmists.

  5. Quote”The explosion immediately bathes Earth with damaging UV, X-rays and gamma rays.”

    How, surely they will take 65 years to get here.

    Quote”Later, the blast of supernova debris slams into the solar system, subjecting the planet to long-lived irradiation from cosmic rays accelerated by the supernova”

    What is this ‘later’
    Don’t cosmic rays travel at (as close as makes no difference) Light Speed?

    How does this loss of Ozone create a problem, especially, how does this loss of Ozone even happen?
    Stratospheric Ozone is created by UV impacting upon ordinary O2 oxygen. If a blast of UV arrives it will create a corresponding ‘blast’ of Ozone. Assuming there’s oxygen in the atmosphere.

    How did science become such a train-wreck?

    Answer my own question, maybe Griff could enlighten us further….
    https://www.theguardian.com/books/2020/aug/21/nick-cave-says-political-correctness-has-run-amok-is-that-the-right-word-for-it

    Notice how the Grauniad takes issue with whether mr Cave has used/spelled the Right Word – they go for the Ad Hom. (As is the way with Mr Trump)
    Very neatly confirming what people (those with a Real Life to live) *know* to be the message

    Who’s paying for these muppets?

    • Quote ”The explosion immediately bathes Earth with damaging UV, X-rays and gamma rays.”

      With such a barrage of UV, X-rays and gamma rays, ….. forget about the loss of O3, …. it would have been then loss of O2 that caused the mass extinction.

        • “DUH”, …. O2 + UV = O3 (ozone)

          inhaled, ozone can damage the lungs. Relatively low amounts can cause chest pain, coughing, shortness of breath and throat irritation. Ozone may also worsen chronic respiratory diseases such as asthma and

          • Formation of O3 in the stratosphere protects O2 in the troposphere, where aerobic organisms can make use of it. Without ozone high in the atmosphere, high energy UV light would reach the lower atmosphere, making O3 there.

            In the stratosphere, there’s an O2-O3 cycle.

          • You all forgot about this, to wit:

            Excerpt from article:

            The team concentrated on the Devonian-Carboniferous boundary because those rocks contain hundreds of thousands of generations of plant spores that appear to be sunburnt by ultraviolet light – evidence of a long-lasting ozone-depletion event.

            Wouldn’t it also mean a “long-lasting oxygen-depletion event”?

          • Samuel,

            No.

            There can be O3 in the stratosphere, with virtually no O2 close to the surface, as was the case before the Great Oxygen Catastrophe, because sunlight can also break water molecules apart high in the atmosphere. The H2 escapes, while the oxygen ions combine to form O2 and O3.

          • hundreds of thousands of generations of plant spores that appear to be sunburnt by ultraviolet light

            But, but, but, …. John Tillman, …. the O2 breathing biomass lives on the surface, not high in the stratosphere.

            And iffen thousands of generations of plant spores were sunburnt by a long-lasting ultraviolet “oxygen (O2)” depletion event, ….. which surely also resulted in scads of “ozone (O3)” at the surface, … then the O2 breathing animals would have had a tuff time surviving.

            RIGHT?

          • There just were not any land breathing animals apart from lungfish and insects.

            But Philip M,

            there were huge amounts of land situate O2 breathing biomass that couldn’t subsist on the O3 being created by the UV barrage, …… now could they.

          • Samuel,
            The plants by photosynthesis are the source of all the oxygen in the air, they make enough for everything (all of biology as well as all of geochemistry).
            However the primary source of all of this oxygen by far is the life in the sea (even today).
            This must be so because we know that the atmosphere contained oxygen in the Proterozoic long before any land plants ever existed. https://en.wikipedia.org/wiki/Proterozoic#The_accumulation_of_oxygen

          • Philip,

            Me thinks you are not seeing the forest because of all the trees, …. or something like that.

            Reread this statement:

            Excerpted statement:

            The team concentrated on the Devonian-Carboniferous boundary because those rocks contain hundreds of thousands of generations of plant spores that appear to be sunburnt by ultraviolet light – evidence of a long-lasting ozone-depletion event.

            Philip, UV creates atmospheric O3, …… it doesn’t deplete it.

            And there is presently enough UV that reaches the surface to cause skin cancers on humans even though O2 is at 20%.

            But, long term “Killer cosmic rays from nearby supernovae” could create massive amounts of ozone all the way to the surface, …. not just in the per se ozone layer. Thus, atmospheric O2 is depleted clear to the surface where the “sunburnt plant spores were found”.

          • Samuel
            First you were worried by lung damage when there were no air breathing land animals in the Devonian.
            Now you are worried about skin cancer on humans?
            Sorry, but Placet is a Crazy Place so, Ike Witt.

          • Samuel,

            There were very few land animals in the Devonian. Only some arthropods, whose O2 requirements were limited.

            Only in the Late Devonian did vertebrates start to move onto land, in the form of our tetrapod ancestors.

            The Late Devonian mass extinctions were primarily of marine organisms. So how does less O3 affect sea creatures?

            Anoxia did play a big role in the Late Devonian extinctions, but not by any mechanism you’ve suggested.

          • Philip, …. John, …. it appears you both “pick n’ choose” different parts of my previous comments to respond to in your most recent posts … which results in “out-of-context” tripe and piffle.

            So, from now on act professional, …… quote the part or portion of my commentary that you are responding to.

            Sam C

          • Philip Mulholland – August 23, 2020 at 2:19 pm

            Samuel,
            We seem to have moved from
            “inhaled, ozone can damage the lungs.”

            Philip, therein is explicitly defines your reading comprehension problem,

            You are citing “quoted text” that I posted in response to tty’s question of August 21, 2020 at 7:17 am ….. that was excerpted from the following:

            How is Ozone Harmful?
            The same chemical properties that allow high concentrations of ozone to react with organic material outside the body give it the ability to react with similar organic material that makes up the body, and potentially cause harmful health consequences. When “inhaled, ozone can damage the lungs. Relatively low amounts can cause chest pain, coughing, shortness of breath and throat irritation. Ozone may also worsen chronic respiratory diseases such as asthma and

            https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners#:~:text=When%20inhaled%2C%20ozone%20can%20damage,body%20to%20fight%20respiratory%20infections.

            Philip, you should QUIT posting until you learn to “keep track” of the discussion …. and to specifically reference comments of others that you critiquing.

        • OOPS, forgot to include this in above post …..

          By the Late Devonian, the land had been colonized by plants and insects.

          The biota was also very different. Plants, which had been on land in forms similar to mosses, liverworts, and lichens since the Ordovician, had just developed roots, seeds, and water transport systems that allowed them to survive away from places that were constantly wet—and so grew huge forests on the highlands.
          https://en.wikipedia.org/wiki/Late_Devonian_extinction

    • “Don’t cosmic rays travel at (as close as makes no difference) Light Speed?”

      Even if they travel at 99% of the speed of light, at a distance of 65 light years, they would still arrive 0.65 of a year later, almost 8 months.

      • Um, what? 65 light years means light takes 65 years to get here. How could something traveling at 99% light speed get here in 8 months? Wdm? (What da math)

        • 8 months later than the light that would have arrived 65 years later. In other words, 99% of the speed of light for cosmic rays means they arrive 65 years 8 months later. 8 months later than the light photons. Simple arithmetic.

        • You can’t even have a “speed” defined before light arrives, because the past isn’t there. When we observe deep space, we don’t see “the past”; we see the remote present, which is still just after the Big Bang: far way, the universe is still primitive for us. And vice versa for possible remote civilizations that will exist in the “future” and may will/have existed sonner after the Big Bang than ours.

    • “How, surely they will take 65 years to get here.” Yes that true yet we would not know it coming since most would be traveling at or near the speed of light. That a problem I have with Star Trek how on earth do you know a energy weapon is fired ahead of time. If they travel at the speed of light(which energy weapons would not) you will never see them coming.

  6. Hm. A SN brighter than the full moon. The full moon is 400000 less (apparently) luminous than the sun, so a SN of similar apparent brightness is still tens- or hundreds thousand times less luminous than the sun. The typical lifetime of the SN phase is 100 days, most luminosity produced in the first month. Therefore the totally received UV flux on Earth is still much less than the daily dose of UV dumped into the atmosphere during daytime. Doesn’t appear to be that destructive to me. Apart from that, Ozone is caused by absorption of UV in the upper atmosphere converting O2 into O3. Just light an UV light in your closed garage and smell the stuff. So a big influx of UV will counteract itself as long as there is enough oxygen. (The Ozone scare was and is based on the hypothesis that that reaction is inhibited by CFCs).
    The cosmic rays may be a different matter, after passage of the shockwave which would come several thousand years after the event. But also here, the effect would primarily be increased cloudiness, possibly for quite a long time and it is questionable if the flux at sea level would increase to damaging levels. The atmosphere acts as a pretty good protecting shield.

    • Ed,
      You and your oppressive patriarchal racist logic!

      Let me break it down for you.

      1) There was a mass extinction event a long time ago, (like before Reagan and Thatcher). This was bad.

      2) Scientists say: (blah blah woof woof don’t bother to listen, something about the ozone hole)

      3)

      “ Earth-based catastrophes such as …global warming can destroy the ozone layer, too, …,” Fields said.

      Ergo: Extinction Rebellion is right! Global warming is a global extinction event.

      So simple that a middle school dropout can grasp it. What’s your excuse?

      Need I point out, that this comes to us from the good propagandists of EurekAlert!?

      • Your reference is paywalled. So you’re suggesting that an event lasting for 100 days or so, from 65 ly away, resulted in 300 millennia of depleted ozone? How does that work exactly?

        • From what I’ve read, a nearby SN’s “wind” can blow the sun’s magnetic field leeward like a flag in a wind, and greatly reduce the solar system’s protection from cosmic rays coming from the windward side — including the rays from the SN itself.

      • Just from Wikipedia (so use caution), a Type 1a supernova’s electromagnetic energy output is ~0.01 E44 Joules. While that’s tremendous, at 65 light-years its concentration is 2.65 E6 J/m^2. If most of that radiation arrived in one pulse, the luminosity could be anywhere from bright to incendiary (a 1 second pulse would be almost 2,000 times the solar flux).

        Spread out over 100 days, however, it amounts to only 0.306 W/m^2. That would make it quite bright, especially compared to the Moon (~0.0006 W/m^2), about 500 times as bright. But I can’t see it doing damage lasting 300,000 years.

  7. It’s unlikely they will find traces of Pu244 or Sm146. If any of either isotope was present, its likely to have decayed. Half life for Pu244 is 80 million years and it’s 68 million for Sm146

    • “It’s unlikely they will find traces of Pu244 or Sm146.”

      There would be about 4% of the original Pu244 and 2% of the original Sm146. Might be detectable? Depends on how much there was originally?

      • Most of us were taught that no elements heavier than uranium exist in nature. The article implies that this was always imprecise thinking, possibly based on the assumption that none of the matter that formed the earth has been in a supernova for probably well over 6 billion years. At an 80-million year half-life, only 2.65e-25 % (1/2^75) of the original Pu244 would remain after 75 half-lives. So it would be undetectable if there had been any in the matter that formed the earth around 4.5 billion years ago. But if new plutonium rained down from a nearby supernova, then it might be a bad assumption. I suspect that the amount of plutonium arriving by that route would be vanishingly small though. A lot less than the plutonium we have put into the environment through nuclear weapons production and testing. How could we be sure that any Pu244 that we think we’re finding in a sediment is not just contamination?

        • Rich,

          I would imagine that they will sample by taking a core through several meters of hypothetically impermeable sediment. If the Pu-244/SM-146 levels jump abruptly at some level it’s probably (not certainly, but probably) not contamination.

          • Except that the quantities involved are likely so low that we’re talking about stray atoms that can’t be detected anyway. How would they drill the core without bring surface materials in contact with the core? Likewise how to prepare the samples and perform testing? If our biosphere has more contamination than the pristine samples, how can a signal be detected?

        • Rich, Elements heavier than uranium were found to exist in a natural fission reaction. In Oklo, Gabon evidence was found of a natural nuclear reaction that occurred about 1.7 million years ago and ran for a few hundred thousand years being moderated supposdely be ground water. It was discovered by the French in 1972. Plenty of information about this is around if it is of interest.

      • The total amount of naturally occurring Pu244 on earth is estimated to be about 9 grams and, that’s the high estimate. SM146 is even less. Not much Pu244 would be produced in the super nova and it would have been distributed by an explosion 65 light years away. So, my thought, is it possible they could detect either element, sure, is it likely, not even remotely.

        • Nowadays it is quite possible by gamma spectrometry to identify single decaying atoms of Pu244 or Sm146.

          • I was going to say, read somewhere that a few atoms of Pu are occasionally detectable in deposits that are high in uranium & rare-earths.

          • Would it be practical to assay by gamma spectrometry mass samples of Late Devonian rocks from around the world for surviving isotopes of Pu and Sm?

  8. I wish there was a greater focus on the Younger Dryas. It was an extinction event that was only 12k years ago. The fact that we are fumbling around with hypotheses and yet have no theory shows how poorly we understand catastrophic climate change. The rapidly declining magnetic field of the earth isn’t getting the attention I think it deserves.

    • I totally agree. Not only is the Earth’s magnetic field’s strength declining but the poles are shifting at a pretty good clip. There are a lot of theories (and credible evidence) that a weaker field coupled with increased cosmic ray activity impact the magma under us all setting off periods of volcanic activity.

      Icelandic volcanoes can wreak havoc in Europe and the big explosive ones can impact global temperatures. Additionally our solar system passes through dust as it rotates around the Milky Way which also changes the magnetic environment around the Sun. Some theories on this have it impacting CME generation which also could have major impacts. The good news these events are relatively rare so the probability of it happening tomorrow is very low.. but it could happen.

    • The YD was not a mass extinction event. It was an interval in the Late Pleistocene megafaunal extinctions, which occurred over at least tens of thousands of years, and extended in places into the Holocene. The extinctions were barely above background, but noticeable because concentrated in large, dramatic animals.

      • The megafaunal extinctions were actually quite dramatic because they virtually removed all really large animals from most of the Earth, with considerable ecological side effects. It is hard to find something similar during the last 65 million years.

        • ecological side effects = there was a lot less manure around for fertilization. It also had a very detrimental effect on all the mucking jobs out there which led to an economic downturn that we are just now slowly climbing out of…

          • It also caused the extinctions of a lot of species dependant on the megafauna and had a very large effect on vegetation both through loss of grazing/browsing pressure and on plants that were dependent on the megafauna for see d dispersal (e. g. Osage Orange).

            Have a look at african bush where there are elephants and/or hippopotami and where there isn’t and you will get an idea.

          • tty says:
            dependent on the megafauna for seed dispersal (e. g. Osage Orange).

            Kentucky coffeetree (Gymnocladus dioicus) too, which later got some help from indigenous people carrying the big, shiny seeds around.

        • The Pleistocene extinctions were spotty. Few if any large land animals went extinct in Africa and India, for instance. They were largely wiped out in areas where modern humans were a new invasive species or subspecies.

        • IMO, the Eocene–Oligocene extinction event isn’t just similar, but arguably more extensive, as including flora as well as fauna, and being largely marine, where most life on Earth resides.

          Among the megafauna wiped out by modern humans during the Late Pleistocene and Holocene extinctions were our closest kin, other members of genus Homo, who just make the mass cut of greater than 44 kg. Of course we didn’t just drive them to extinction, but absorbed some of their genetic sequences.

      • The evidence is striking and observable.

        Uniformitarianism is increasingly untenable as a guiding idea in geology.

        Regarding the Younger/Dryas, it’s not just the megafauna, but the evidence of geological upheaval.

        Great extinction events mark the geologic record.

        Failure to observe, study, and understand catastrophism in the geologic record is a massive blind spot and for those determined to maintain the status quo.

        They will be consigned to the dust bin of failed scientific ideas.

        • Uniformatarianism is alive and well. Indeed, it’s an indisputable fact, ie repeated observation of nature, that the processes seen today occurred in the past. It appears that you don’t understand what the term means. You seem to think it refers only to gradual processes rather than including sudden changes.

          Catastrophic events are fully part and parcel of uniformitarianism, since they’re observed all the time today and in the geologic record.

          What evidence of geological upheaval do you see at the onset of or during the YD, other than the naturally ongoing melting of ice sheets and consequent sea level rise?

          • Mr. Tillman wrote:

            “Catastrophic events are fully part and parcel of uniformitarianism, since they’re observed all the time today and in the geologic record.”

            Catastrophic events stand on their own.

            As I wrote: “Failure to observe, study, and understand catastrophism in the geologic record is a massive blind spot…”

            Well, Mr. Tillman, I’m glad you state:

            “Catastrophic events are…[…] observed all the time today and in the geologic record.”

            Now, we can have an intelligent discussion & conversation about the most current evidence available.

            Your definition of Uniformitarianism is adapted to recognize what can’t be avoided:

            Catastrophic events (Catastrophism) are part of the geologic record.

            In fact, the study of Catastrophism as it relates to substantial geologic changes, thus, different environments might lead to greater understanding of the causes of great extinction events in the biological history of Earth.

          • Catastrophic events don’t stand on their own. They have happened throughout the history of our planet.

            Uniformitarianism arose in opposition to fundamentalist catastrophism, which argued that the geologic record was formed by one flood in particular. That view is now universally recognized as delusional among geologists.

            OTOH, uniformitarianism from the outset recognized that “catastrophes” are observed today, so were from the beginning considered uniformitarian. It’s just that it wasn’t a single global flood, but included earthquakes, volcanic eruptions and regional floods. The only kinds of catastrophes not envisioned by Hutton and Lyell were ET impacts.

            My definition isn’t adapted. It’s the same as Lyell’s original definition. Please read Hutton and Lyell before presuming to comment on the history of geology. In the beginning, they saw that Earth history was background gradualist, punctuated by sudden events, rather than resulting from a single flood.

            Walter Alvarez, originator of the Cretaceous impact hypothesis, as himself a geologist, teaches that uniformitarianism is both uniformitarian and “catastrophist”. That has been true since 1785. He just updated the theory to include ET catastrophes.

            I wonder what “most current evidence available” you imagine challenges the theory, indeed fact, of uniformitarianism, ie that processes visible today shaped Earth in the past.

        • There were some pretty big volcanic eruptions around the YD, perhaps related to the weight of ice being lifted off the continents, but they didn’t cause the megafaunal extinctions which occurred during it.

        • Uniformitarianism just means that whatever processes operate now, operated in the past.
          In other words, there’s nothing new under the sun.

          It has never meant that change occurred slowly and at a constant pace.

          • Wikipedia: “In geology, uniformitarianism has included the gradualistic concept that “the present is the key to the past” and that geological events occur at the same rate now as they have always done, though many modern geologists no longer hold to a strict gradualism.”

            MarkW: “It has never meant that change occurred slowly and at a constant pace.”

            Wrong.

            And, perhaps, this provides an idea to motivation of it’s proponents:

            Sikipedia:”Coined by William Whewell, it was originally proposed in contrast to catastrophism.”

            The idea and study of Catastrophism was already scientific discussion, but Charles Lyell and others rejected it in favor of their own ideas that they could control in their peer groups.

            An early example of academic dogma building up to the detriment of scientific knowledge.

          • James,

            You have that backwards.

            While Cuvier, Father of Catastrophism, tried to avoid the biblical implications of his geological theory, he was nevertheless a Protestant. He tried to explain the succession of fossils in rocks of different ages by hypothesizing periodic floods, which wiped out the older forms, then replaced with new ones, by separate, sequential creations. This fit with his discovery of the fact of extinction. He did however argue that Earth must be at least millions of years old.

            British catastrophists, like the famously eccentric Rev. Buckland, did however associate the last such catastrophic extinction with Noah’s Flood. It was this kind of catastrophism which Lyell showed false. But neither Lyell nor other uniformitarians ever denied the reality of catastrophes and their impact on Earth history. The fact that gradual geologic processes proceeded between catastrophes meant that Earth must be at least hundreds of millions of years old.

            I’m still interested in what evidence you find for catastrophism, whether classical Cuvierism or some modern variation, as opposed to the everywhere observed fact of uniformitarian geology, ie that processes seen at work today proceeded in the past as well.

  9. If the kill zone is 25 light years, how do stars that exploded 65 light years away contribute to the problem?

    If I’m standing safely outside the blast zone of a grenade by a factor of ~3, it doesn’t matter how many grenades go off, I’m still safe.

    • You may not be killed by the grenade, but the odds are that you will still be hit by fragments from the grenade. Just not enough to kill you.

      If the grenades keep going off, eventually you will get enough wounds, or a wound in a critical enough spot to kill you.

  10. “ Researchers have yet to search for Pu-244 or Sm-146 ”, so basically it’s just simple speculation on a possible science fiction short story plot line…..

    • My thoughts too. I couldn’t help but notice the word “could” all over the place. I think they are so in love with their theory that they couldn’t wait until they had any actual evidence before trying to establish it as credible in the public eye (if you’re going to make your fortune in science, you must capture the public eye).

      Too bad Popper and Feinman aren’t buried together so they could roll over in a synchronized flop…

  11. If too little Pu244 remain to be detectable, then this is an infalsificable conjecture, not a scientific hypothesis.

    The authors try to account for the long duration of the Late Devonian extinctions by proposing a prompt EM pulse, followed by a later particle bombardment (cosmic “rays”). The first I suppose is meant to explain the Kellwasser Event, and the latter the Hangenberg Event some 14 million years later. Students of the extinctions have found that these two apparent peaks actually consist of one or two series of extinction waves over 25 million years.

    The Kellwasser series were entirely marine, while the Hangenberg were mainly marine, but also with some on land. This pattern doesn’t comport well with the speculation of a supernova-caused ozone depletion. A better supported and falsifiable hypothesis is changes in sea level and anoxia.

    • Changes in sea-level and large scale anoxia don’t just happen. They have causes. And that has proven hard to find for the Hangenberg and Kellwasser events.

  12. PASADENA, Calif. — Astronomers, including a NASA-funded team member, have discovered a new class of Jupiter-sized planets floating alone in the dark of space, away from the light of a star. The team believes these lone worlds were probably ejected from developing planetary systems. ….
    Our results suggest that planetary systems often become unstable, with planets being kicked out from their places of birth

  13. Hmmm. The Sirius system is only about 8.6 light years away, but it is expected to evolve into a white dwarf.

  14. The star that exploded was our very own sun going micronova. There isn’t any way certain isotopes would still exist on earth from distant novas.

  15. Very, very Off Topic, but too incredible to pass up. Here is a video put out by Viper TV which is a true mind blower. History as we were taught is now credibly shredded by the details in this video. The basis of the story line in this video is based on information from the cuneiform tablets from ancient Sumeria. The explanation of how and why all of this took place is beyond compelling. Ancient history, and the history of mankind needs to be rewritten. … https://www.youtube.com/watch?v=Dgfs1yrcm4U

    • Here is a brief outline of what this video presents. The main point is that ancient Sumerians traveled to South America in search of new tin deposits, and other precious metal deposits. There is evidence in Bolivia around Lake Titicaca of bronze tools being found. Bronze tool manufacturing was never developed in South America, but the Sumerians had such technology. Tin was essential for bronze, and bronze at one point in time was essential for Sumerian art and cultural needs, plus weaponry and tool making.

      The sites of Tiwanaku and Pumu Punku bear strong resemblances to the handiwork of stone masons from Sumeria. After watching a video from one Praveen Mohan on a site called Warangai Fort in southern India in where he posits that the Warangai site was not a fort, but was a manufacturing site for stone works for Hindu temples the thought then struck me that this could well be the answer for describing Tiwanaku/Pumu Punku sites. These two Bolivian sites were manufacturing sites for tools and mining equipment for the mineral rich areas around Lake Titicaca. The large stone platforms which dot the terrain would make sense if viewed in that light, as manufacturing plants require sturdy bases for operation.

      Watch the video and decide for yourself if this makes sense.

    • It makes absolutely no sense.

      Both South and North America were enjoying their Bronze Age when the Europeans arrived. Just as dearly in the Old World Bronze Age, high status and ceremonial weapons were bronze.

      Please look up Aztec and Inca bronze before falling for such obvious total twaddle.

      • https://en.wikipedia.org/wiki/Tlaximaltepoztli

        Cottie Arthur Burland (1968). Peru Under the Incas. Putnam. p. 101. “The sling was the most deadly projectile weapon. Spear, long-handled axe and bronze-headed mace were the effective weapons. Protection was afforded by a wooden helmet covered with bronze, long quilted tunic and flexible quilted shield.”

        I’ve seen Inca bronze star-shaped mace heads in museums in Lima and Cuzco.

        • This page suggests otherwise “What little I can read online of The Metal Industry of the Aztecs, by George Brinton Phillips appears to be saying that the indigenous Mexicans had access to copper, but not enough to make everyday use of. However, when the Spaniards came, they found enough tin deposits around to start making their own bronze (for cannons), so it’s not like the supplies weren’t there for those who knew how to use them.

          In South America the Moche actually did use some bronze, but not for common tools or weaponry. The Inca later started to adapt bronze to such mundane uses, but it was still an expensive material for them. Perhaps they would have soon developed their own proper bronze age, had Pizarro not intervened.”. … https://history.stackexchange.com/questions/2519/was-there-a-bronze-age-in-the-americas

          I would think that the information contained in those Sumerian cuneiform tablets and cylinders is pretty strong evidence. Here is an interesting story about mysterious bronze artifacts which are thought to precede the Incas by several thousand years, “The ‘Bronze Gears of Ancient Peru’, or ‘Gears of Ancient Peru’ are considered by many as one of the most mysterious artifacts discovered in South America. While not much is known about the enigmatic ‘gears,’ they are considered by many as the ultimate evidence that thousands of years before the Inca, an advanced civilization flourished in South America. Today, when you talk about the ‘Bronze Gears of Peru’ most people will agree they are ‘out-of-place-artifacts,’ while skeptics remain confident they are nothing more but mere decorative items used by ancient people who worshiped the sun.” … https://www.ancient-code.com/the-mechanical-gears-of-ancient-peru-keys-to-the-gate-of-the-gods/

          Or how about this “The Fuenta Magna is a large stone vessel, resembling a libation bowl, that was found in 1958 near Lake Titicaca in Bolivia. It features beautifully engraved anthropomorphic characters, zoological motifs characteristic of the local culture, and, more surprisingly, two types of scripts —a proto-Sumerian ancient alphabet and a local language of the ancient Pukara, forerunner of the Tiahuanaco civilization. Often referred to as “the Rosetta Stone of the Americas,” the stone vessel is one of the most controversial artifacts in South America as it raises questions about whether there may have been a connection between the Sumerians and the ancient inhabitants of the Andes, located thousands of miles away.” … https://www.ancient-origins.net/artifacts-ancient-writings/fuente-magna-controversial-rosetta-stone-americas-003660

          • There is more ““The ruins of Tiahuanuco have been regarded by all students of American antiquities as in many respects the most interesting and important, and at the same time most enigmatical, of any on the continent. They have excited the admiration and wonder alike of the earliest and latest travelers, most of whom, vanquished in their attempts to penetrate the mystery of their origin, have been content to assign them an antiquity beyond that of the other monuments of America, and to regard them as the solitary remains of a civilization that disappeared before that of the Incas began, and contemporaneous with that of Egypt and the East.

            Unique, yet perfect in type and harmonious in style, they appear to be the work of a people who were thorough masters of an architecture which had no infancy, passed through no period of growth, and of which we find no other examples. Tradition, which mumbles more or less intelligibly of the origin of many other American monuments, is dumb concerning these. The wondering Indians told the first Spaniards that “they existed before the sun shone in the heavens,” that they were raised by giants, or that they were the remains of an impious people whom an angry Deity had converted into stone because they had refused hospitality to his viceregent and messenger. “
            From here, … https://blog.world-mysteries.com/mystic-places/ancient-ruins-of-tiwanacu-and-pumapunku/

            One thing is clear that the ruins at Lake Titicaca can not be explained in any other fashion. Once again I would have to say that I will side with the written history described on the Sumerian tablets/cylinders as narrated in the video I linked to. The one main clue which can not be disputed is the megalithic stone work which can be found in many countries around the globe, and which all bear similar tool markings. These are monuments built to last through time which even the greatest quakes though out history could barely shift from their foundations. Some culture with advanced understandings of stone work built those structures. We would be hard pressed to duplicate them today with our best technology.

          • There is zero evidence that Sumerians sailed to South America.

            Aztecs had copper and made bronze with it.

          • There are extensive copper mines in Michigan thousands of years old. Yet very few Native American copper artifacts let alone bronze.

  16. Since they haven’t actually looked to see if the isotopes are there, this is an interesting but completely unsupported hypothesis. At least it is somewhat test-able. Astronomers have a decent idea of the general motion of the stars, especially those near us. 359 million years is a couple of rotations of the galaxy but could they roll back the clock and see if any supernova remnants would be a possible candidate?

  17. DJ Johan Gielen presents A Special Person*

    “We look, but we don’t see.
    We touch, but we don’t feel.
    We search, but won’t reveal.
    And we move.
    Like shadows.”

    – B. Kuyten*, J. Gielen*, M. Verkuylen*

    https://www.youtube.com/watch?v=p8WTyOo25Lk
    (K90 Remix – released in the year 2000)

    … in song and balladry the truth is often writ large but goes by unnoticed by the “scientist”. The lyrics written are not mere rhymes to fit in with the times, but in mine own humble opinion are indeed windows into the sole of the ghosts in the machine, that are the artifacts of conciousness, in this self reproducing biological computer lifeforms we call ourselves, Human Beings.

  18. For years, the Ordovician-silurian Extinction: 440 million years ago was thought to have an astronomical component, perhaps a local GRB. This paper is applying that to the Devonian Extinction: 365 million years ago. Did they get confused? Or am I?

    You don’t need to be in close proximity to a supernova for bad things to happen. All you have to do is be in line with whatever jets are produced. And a lot of things produce jets.

    There is a guy named James Marusek who claims to be a nuke physicist / engineer that runs something called the Impact Blog.

    http://www.breadandbutterscience.com/

    He applies the Svensmark theory on incoming cosmic rays to close proximity to supernovae. He is of the opinion that the solar system is crossing a galactic arm, relatively close to a number of stars in pre-supernova state. It is multiple close supernovae over the course of the last 2 Ma that caused the recent ice age cycle by jacking up the cosmic ray flux. After a few more Ma, we clear this space and temps return back to normal. Hopefully there will be enough CO2 in the atmosphere to allow that journey. Cheers –

    • “Hopefully there will be enough CO2 in the atmosphere to allow that journey”

      A few more Ma to go?
      No problem agimarc.
      There is plenty of limestone stored in the bunkers.
      Just keep making the cement and we’ll do fine.

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