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Science

Extraterrestrial Plutonium Atoms Turn Up on Ocean Bottom (nytimes.com) 68

Posted by msmash from the unraveling-mysteries dept.
Scientists studying a sample of oceanic crust retrieved from the Pacific seabed nearly a mile down have discovered traces of a rare isotope of plutonium, the deadly element that has been central to the atomic age. From a report: They say it was made in colliding stars and later rained down through Earth's atmosphere as cosmic dust millions of years ago. Their analysis opens a new window on the cosmos. "It's amazing that a few atoms on Earth can help us learn about where half of all the heavier elements in our universe are synthesized," said Anton Wallner, the paper's first author and a nuclear physicist. Dr. Wallner works at the Australian National University as well as the Helmholtz Center in Dresden, Germany. Dr. Wallner and his colleagues reported their findings in Science on Thursday. Plutonium has a bad reputation, one that is well-deserved.

The radioactive element fueled the world's first nuclear test explosion as well as the bomb that leveled the Japanese city of Nagasaki during World War II. After the war, scientists found the health repercussions of plutonium to be particularly deadly. If inhaled or ingested in minute quantities, it could result in fatal cancers. Small amounts also pack a bigger punch than other nuclear fuels, a quality that aided the making of compact city busters that nuclear powers put atop their intercontinental missiles. The element is often considered artificial because it is so seldom found outside of human creations. In the periodic table, it is the last of 94 atoms characterized as naturally occurring. Traces of it can be found in uranium ores. Astrophysicists have long known that it's also spontaneously created in the universe. But they've had a hard time pinpointing any exact sites of its origin.
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Extraterrestrial Plutonium Atoms Turn Up on Ocean Bottom More

Extraterrestrial Plutonium Atoms Turn Up on Ocean Bottom

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    • Gravity was too strong and the pirate ships were going to crash into the oceans so they ditched the plutonium because they refused to ditch the gold.

      • they ditched the plutonium because they refused to ditch the gold.

        Those were some dumb pirates. Plutonium is worth 100 times as much as gold.

        The most expensive elements [thoughtco.com]

        • Probably not quite as fungible though

        • Re: (Score:2)

          by e3m4n ( 947977 )
          but not the safest thing to have in your pocket either. its super heavy, and gives off tremendous heat from its alpha decay. Maybe this is the leftovers from Doc Brown's flux capacitor? The damn TFA is paywalled, did they say which isotope? Unlike uranium, where we know how much naturally occurring is u-238 vs u-235. There is no such estimation for plutonium. We mostly come by it by neutron bombardment of U-238 for a n -> p reaction into Pu-239.

          • but not the safest thing to have in your pocket either. its super heavy, and gives off tremendous heat from its alpha decay. Maybe this is the leftovers from Doc Brown's flux capacitor? The damn TFA is paywalled, did they say which isotope?

            The isotope was plutonium 244. As to tremendous heat, the Pu core of the Nagasaki bomb was carried by hand prior to final assembly and was described as a warm metal sphere.

            • Those cores were quite dangerous, but that's because they were designed to go prompt critical at a moment's notice (They're bomb cores, after all)
              A better example would be the plutonium oxide spheres that make up the core of an RTG- perfectly safe to hold, and only moderately warm.

              • Re:I'm not saying it's UFOs, but (Score:4, Informative)

                by ShanghaiBill ( 739463 ) on Thursday May 13, 2021 @08:00PM (#61382542)

                A better example would be the plutonium oxide spheres that make up the core of an RTG- perfectly safe to hold, and only moderately warm.

                The Pu-238 used in RTGs has a half-life of 87 years.

                The Pu-244 described in TFA has a half-life of 80 million years.

                So if Pu-238 is safe to hold, Pu-244 would be even safer by a factor of a million.

                • The half-life isn't relevant to the safety of holding them.
                  All isotopes of Pu are alpha emitters. They aren't capable of penetrating your epidermis.

                  The risk of holding plutonium (in the case of the bomb cores) was, as I said, they are just barely subcritical mass.
                  They're designed to go prompt critical on command, meaning they will fission (and release neutrons) at a rate that will fucking wreck you

                  In comparison to the RTG core components, they're physically incapable of criticality.
                  • Halflife does matter. The shorter the halflife the more reactions per mass. That core on the enola gay burned the copilots hand putting it into the core of the bomb btw. Not sure quite warm is exactly fair. Of course that was the least of his concerns later on. He was too close to the bomb point source to excape a flux of neutrons and gammas.
                    • Half-life only matters with regard to the reactions caused by the alpha emissions- which yes, are heat.
                      alpha emissions are harmless to your skin, but your skin *will* absorb their energy (and heat up)
                      So:

                      The half-life isn't relevant to the safety of holding them.

                      Is a true statement.

                      That core on the enola gay burned the copilots hand putting it into the core of the bomb btw

                      I find that highly unlikely.
                      Pu239 cores were openly handled by Los Alamos scientists. Nobody was burnt.
                      U235 is less energetic than Pu239.

                      He was too close to the bomb point source to excape a flux of neutrons and gammas.

                      I assume you mean... after detonation?
                      Neutron emissions of a subcritical mass of U235 is negligible.

                    • Yes. After detonation. Inverse square laws in play, the crew was too close.
                    • Well, OK...
                      I have no reason to doubt that... But a supercritical exponential fission reaction has nothing to do with half-life.
                      I don't think I ever disagreed that fissile materials are dangerous as fuck... In fact, I'm pretty sure I argued that criticality accidents are the only real risk to handling them.
                      Unless you're ingesting, or breathing them in.. which you also shouldn't do.
                    • There is one alpha emitter that is dangerous as fuck. You know which one that is right?
                    • No, I have no idea what you're talking about.
                      An artificial alpha emitter could certainly be dangerous. It's merely a matter of kinetic energy.
                      alpha decay isn't energetic enough (for the size and charge of the particle) to be dangerous past an inch or so of air, and a couple microns of skin.
                      I imagine with a powerful enough cyclotron, you could get far more than the meager 5MeV an actinide alpha decay gets you.
                    • Yes. Scary as fuck. While it's safe to "handle" a fissile actinide, it's instantly deadly if you cause a criticality event.

                    • Re: (Score:2)

                      by e3m4n ( 947977 )
                      Radon. When I was stationed in Connecticut they said new england was plagued with the stuff. Musta come over on the mayflower ;-) You are right that your epidermis blocks an alpha. But the soft lung tissues is not protected. Radon is a gas heavier than air. When you are around it, it will hang out in the bottom of your lungs and decay. In nuclear power school, in our chem/radcon courses, they listed a pack of cigarettes as being the equivalent to 100 mRem of alpha radiation. I guess thats one of the causes

                  • All isotopes of Pu are alpha emitters. They aren't capable of penetrating your epidermis.

                    The latter is actually not true. Here is a guy who demonstrates the attenuation of alpha radiation by various materials. https://youtu.be/C7TwBUxxIC0?t... [youtu.be]

                    The former is sort of true, but the decay products include beta emitters. The first few steps are Pu244 (alpha) - U240 (beta) - Np240 (beta) - Pu240 (alpha) - U236 (beta). Since Np240 and U240 have vastly shorter half lifes than Pu244, you get two betas for every alpha. If the plutonium has been around for millions of years, you also have enough U240 to se

                    • The latter is actually not true.

                      Then you know something the rest of science does not.

                      Here is a guy who demonstrates the attenuation of alpha radiation by various materials. https://youtu.be/C7TwBUxxIC0?t [youtu.be]... [youtu.be]

                      Oh, this should be interesting.
                      here's [harvard.edu] some [nrc.gov] more [cdc.gov] credible [arpansa.gov.au] sources. [nih.gov]

                      Now, what's more likely? That the entire scientific community is wrong, or YouTube guy is wrong?

                      The former is sort of true

                      No, the former, like the latter, is entirely true.
                      Whatever caveat you're about to say does not change the fact that every Pu isotope is an alpha emitter.

                      but the decay products include beta emitters.

                      Ah, of course.
                      U240 has a very short half-life.
                      A very small portion of Pu244 is going to be in the U240 state of its decay chain at any poi

            • That was pu-239, it doesnt alpha decay and has an insane halflife.

          • its super heavy, and gives off tremendous heat from its alpha decay.

            You're correct- it does give off a tremendous amount of heat.
            However, that does not imply that it has a high temperature.

            It's safe to hold plutonium, as long as it's a subcritical mass.
            Get it too close to a neutron reflector, and you're flat out fucked.

        • Re:I'm not saying it's UFOs, but (Score:4, Funny)

          by DamnOregonian ( 963763 ) on Thursday May 13, 2021 @06:52PM (#61382344)

          Those were some dumb pirates. Plutonium is worth 100 times as much as gold.

          Right now, maybe.
          I'm sure in 2051, plutonium is available at every corner drugstore, but in 2021 it's a little hard to come by.

    • Evidence of Xenu's genocide!

    • "it's UFOs!"

      It's obviously Cthulhu.

  • the most punch? (Score:3)

    by iggymanz ( 596061 ) on Thursday May 13, 2021 @04:15PM (#61381744)

    Am-242m is also a contender, might even have smaller spherical critical configuration

    • californium-251 would have a a diameter without a neutron reflector of 8.5cm vs AM-242 of 12cm. The smallest critical mass would be californium-252 at under 7cm and less than 2.8kg but it has a half life of under 3 years so you would have to use it fast. With a reflector, casing etc. you might be able to make a device smaller than a tennis ball (6.8cm) but it would cost on the order of 100 Billion USD.

  • Most logical explanation (Score:3)

    by backslashdot ( 95548 ) on Thursday May 13, 2021 @04:32PM (#61381834)

    Aliens wanted to exterminate us In a galaxy cleansing operation but then realized we could provide them with comedic entertainment for some time.

  • We are talking about the tiniest of trace amounts of a heavy element, the presence of which doesn't harm anybody but instead informs astro-physicists about star formation or some such thing.

    Who writes " the deadly element that has been central to the atomic age"

    Someone who didn't even get admitted to a Journalism major in college?

    • Oh, I don't know.
      Or someone who was well educated and knows that Pu, like many other elements that exist in nature (extraterrestrial or not), is quite fucking deadly.
      Of course Pu has quite a bit of caveats to how deadly it is, but it cannot be argued that it isn't deadly in the unqualified form.
      The holding of a subcritical mass of plutonium is about the only safe way it can be interacted with.
      Inside of your body, it's highly toxic, and of course with enough mass, it's highly radioactive.

      If the article

      • Having too much of any element is deadly.

        Hydrogen, the deadly element, responsible for the fire on the Hindenberg.

        • Hydrogen, the deadly element, responsible for the fire on the Hindenberg.

          Stupid analogy.
          Ingest 1g of hydrogen, and then ingest 1g of plutonium.
          Hydrogen is entirely non-toxic.

          Plutonium is a toxic heavy metal. Think of it like lead, but radioactive.

          As I said: The holding of a subcritical mass of plutonium is about the only safe way it can be interacted with.
          Compare this with hydrogen, where it's entirely undangerous in any direct capacity.

          • The investigators in TFA handled a countable number of atoms quantities of plutonium from their samples in a mass spectrometer.

            I seriously doubt they were in much risk of plutonium exposure.

            You are also telling us that hydrogen is not dangerous in macroscopic quantities?

            • The investigators in TFA handled a countable number of atoms quantities of plutonium from their samples in a mass spectrometer.

              Please, do learn to read:

              As I said: The holding of a subcritical mass of plutonium is about the only safe way it can be interacted with.

              You are also telling us that hydrogen is not dangerous in macroscopic quantities?

              Hydrogen itself is not dangerous.
              Hydrogen mixed with oxygen can be dangerous, of course.
              If you've got enough hydrogen to displace enough oxygen that your lungs can't absorb the partial pressure of O2 that you need to survive? Ya, that can be dangerous.
              But neither of those things are qualities of hydrogen.
              Hydrogen is non-toxic. Plutonium is not.

              I seriously doubt you've got 2 brain cells to rub together if you're trying to continue to push this analogy.

              • Of the 93 elements below Plutonium most of them are toxic and/or explosive in their pure form.

                The article is needlessly hyperbolic, stop making excuses for bad journalism and fearmongering.

                • Of the 93 elements below Plutonium most of them are toxic and/or explosive in their pure form.

                  Ah, yes. You're right. Health effects of naturally occurring elements is boolean.

                  The article is needlessly hyperbolic, stop making excuses for bad journalism and fearmongering.

                  Let's say you're right. That it's bad journalism and fearmongering.
                  What do we call you, the one trying to equate plutonium, a highly toxic element (in every known chemical form) with hydrogen, a biologically inert element, in almost every known chemical form?

                  Frankly, their use of the word "deadly" is a lot more intellectually honest than the horse shit you're engaging in.

    • Yep. It was here before any of us. Shitheads. +1

  • Arenâ(TM)t they all? (Score:4, Interesting)

    by fermion ( 181285 ) on Thursday May 13, 2021 @04:33PM (#61381844) Homepage Journal
    In fact everything heavier than oxygen is extrasolar. Anything heavier that lead will decay. Plutonium is dangerous, and relatively abundant, because some isotopes have extreme long half life. Like any heavy metal it will stay in you. However, unlike lead, it will radiate and damage your cells, so you have cancer as well as mental health problems. This is somewhat interesting because it had to be a significant mass created and deposited on earth within a few million years for any to be left, more that a fraction of a percent.

  • Reputation (Score:1)

    by Anonymous Coward

    Plutonium has a bad reputation, one that is well-deserved.

    Err... what? Why the moralizing language about plutonium? So what if it was used in bombs. So is hydrogen, and carbon.
    Like always, """Science""" """Journalism."""

    • Hear, hear. Everything can be dangerous and everything can be innocuous. Heavy metal's reputation (especially the fissionable/fertile ones) came from the Greenies demonizing it decades ago for their political purposes. Practically any HM is dangerous simply because it is intensely poisonous. Think arsenic. Pu, U, etc. are similarly poisonous, regardless of their radioactivity. In fact, if I recall my nuclear chemistry correctly, if you ingest enough Pu to possibly cause cancer you should not worry as

  • The TFA calls it "extraterrestrial" because it came from a stellar collision. By that definition, every atom on Earth that isn't Hydrogen or Helium is extraterrerstrial. Plutonium, along with every other atom in the universe heavier than Helium comes from either stellar nucleosynthesis or stellar cataclysm. There is no such thing "terrestrical" Plutonium.

    • By that definition, every atom on Earth that isn't Hydrogen or Helium is extraterrerstrial.

      Pu-244 has a half-life of 80M years. No primordial Pu-244 is left from the formation of the earth.

      The Pu-244 found in the sediment came much more recently. So it is "extraterrestrial" in a different way than the dirt in your backyard.

      • Actually it is easy to demonstrate that if Pu-244 was originally as abundant as U-238 (believed to be the case) that there must still be atoms of it left from the Earth's formation. It is just so scarce that it has been impossible to detect from that source.

        Demonstration 4.5 billion divided by 80 million is 56.3 and 0.5^56.3=1.1e-17. U content of the mantle (which is most of the Earth) is 0.021 ppm, or 6e24 kg * 0.021e-6 = 1.26e17 kg. So 1.26e17 * 1.1e-17 = about a kilogram left, scattered through the Earth

        • LOL.
          +5 can't argue with the math... but uhhh, ya.

        • According to TFA, were that 1 kilogram concentrated from all of the bulk of the Earth, it would be pretty darned dangerous.

          Of course the entire Earth would be turned to rubble extracting it, which isn't exactly a safe operation.

          • The amount of natural Pu-239 on Earth is going to be way bigger. It is hard to estimate in a simple fashion since it depends on how often a spontaneous fission neutron gets captured by another U-238 atom. But about a million tons of U-238 undergoes spontaneous fission each year in the Earth, so if the probability is significantly higher than one in a billion it will exceed the Pu-244 content.

            • Or rather its annual production will exceed the Pu-244 content. It will build up to somewhat more than is produced in its half-life of 24,400 years. So 100,000-to-1 or, more likely,better.

    • Yes, but a majority of the atoms on Earth have been sitting on this chunk of rock for billions of years while the plutonium was having its own adventures.

    • Re: (Score:3)

      by Strider- ( 39683 )

      There is no such thing "terrestrical" Plutonium.

      Uh, yes there is (despite your misspelling). All the plutonium used since the dawn of the atomic age has been synthesized from Uranium in nuclear reactors, with only a tiny amount created in particle accelerators.

      • trace amounts are also created in uranium when U-238 captures a neutron from other decaying U-238. Also, there have been natural nuclear reactors on Earth in the past.

        • U-238 undergoes alpha decay.

          If U-238 captures a neutron, it ends up as plutonium.

          The natural nuclear reactors fissioned U-235, which was more abundant natural uranium in an earlier geological epoch, and they did this because they were moderated by ground water flow,

          • It also decays by spontaneous fission, releasing neutrons, though the rate is one-two millionth of the alpha decay rate. Pu-239 from this source has been detected in uranium ores.

          • So you only learned the Freshman 101 decay modes... in the 201 class you'd learn U-238 does indeed sometimes decay and release neutron, and made plutonium of a neighboring U-238.

  • That being a sunken soviet sub..?
  • Besides rocket ships, isn't it possible that extra terrestrials have submarines?

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