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Could there be life that thrives in gamma rays?

  1. May 26, 2017 #1
    I am not sure if this is entirely correct, but first I am going to say that life on earth mostly thrives in the visible range of the electromagnetic spectrum, and perhaps some infrared and ultraviolet (for some creatures), because it is the frequency range that they were the most exposed to throughout the evolutionary timeline.

    In the case that early lifeforms on the earth were given more exposure to highly ionizing radiation such as xrays or gamma rays, could it have been possible to have lifeforms evolve to these frequencies? From a purely probabilistic viewpoint, life would have indeed evolved to adapt to any environmental situations. But from a physics point of view, wouldn't ionizing radiation destroy the genetic makeup of such a species, including the genetic instructions to protect it from the radiation itself?

    On that note, are there any cellular level 'shielding' methods that an organism can make use of when living in such conditions? I was once told about a subterranean bacterium species that lives in areas of high radiation from the ground. And then there are the organisms on the ISS that have evolved to withstand the sun's direct rays....
     
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  3. May 27, 2017 #2

    Baluncore

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    Our organic molecules are held together by electrons with energy levels of the order of one eV. Visible LEDs need electrons with voltages between about 1.6 and 3 volts to operate. So visible light can be used by our biochemistry to convert into usable energy. UV and higher energy photons such as gamma rays will destroy our biochemistry.

    It is possible that there is a higher energy chemistry, maybe something like silicate rocks, that are able to survive in gamma rays. Energy must come from somewhere, so lower energy gamma rays can be used with a mineral equivalent to chlorophyll. But with bonds that strong, things would be slow to happen.

    We have the Earth's atmosphere to protect us from shorter wavelength radiation. There would also be a need for a filter to keep shorter wavelength gamma rays away from a gamma ray fuelled life form.
     
  4. May 27, 2017 #3
    I thought the same! But how about in the case of bacteria like the deinococcus radiodurans? If our atmosphere had gamma ray windows as well, would a larger lifeform be able to adapt this method of DNA regeneration, or are there any limitations?
     
  5. May 27, 2017 #4
    One problem is there is nowhere on or in earth with sufficient natural gamma ray flux to provide significant energy compared to conventional energy sources.

    There is a metabolic cost in preventing/repairing damage caused by ionizing radiation.

    Organisms over time evolve a compromise between the risk of unrepaired damage and the risk of insufficient energy for other activities.
     
  6. May 27, 2017 #5

    jim mcnamara

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    Answer: no.

    This thread is based on a lot of if conditions that are very unlikely. There is also misunderstanding of what is going on.
    To keep it short:
    1. There are several genera of bacteria that are radiation resistant.
    2. Current understanding is the various species evolved resistance to dessication, and as a byproduct resistance (not immunity) to gamma ray exposure came after the ancestors of the bacteria had been around for a long time.
    3. The species lives off byproducts (complex organic molecules) which are by-products of other species life processes. They cannot and do not live off gamma rays. And no carbon-based life forms are going to live off gamma rays because ionizing radiation destroys most of the carbon molecules from which life is built.
    4. From the get-go, an environment with high levels of gamma exposure is not going to evolve life because all of life is based on non-gamma resistant molecules.

    Most important of all: our environment on Earth is the result of billions of years of biological activity.
    see: https://en.wikipedia.org/wiki/Deinococcus_radiodurans

    Please discuss scientific facts as they are known. We love to help, but speculation just causes problems.
     
  7. May 27, 2017 #6

    Baluncore

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    But if there was such a source on Earth or elsewhere, a different chemistry might have evolved.
    You are referring to life as you know it on Earth today. Life on Earth has evolved to use biochemistry that is compatible with the Earth's atmospheric optical window. Without fragile DNA there are other possibilities that cannot be ruled out. Life may develop wherever there are low-pass filters that cut the damaging higher energy radiation.
     
  8. May 27, 2017 #7

    jim mcnamara

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    @Baluncore - do you have some reputable source for the hypothesis? I would like to see something. It is fun to speculate but PF does not do well when people make up stuff ad hoc. I've seen you come down hard on some bad ideas in the EE forum.

    One reason for my position:
    A counterexample of your position from N D Tyson:
    From https://www.nasa.gov/vision/universe/starsgalaxies/search_life_I.html

    Your turn....
     
  9. May 27, 2017 #8
    Gamma rays are ionizing radiation, meaning it will strip electrons from atoms.
    That in turn means that complex chemistry (necessary for life) is inhibited, since any large molecules (like DNA) tend to quickly disintegrate.
    If a form of life could exist in strong gamma rays, it's genetic information would need to encoded in something less vulnerable.
    Some form of encoding genetics into a solid substrate of fairly simple material comes to mind, but of course there is no such form of life known.
     
  10. May 27, 2017 #9

    Ygggdrasil

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    There is precedence for life using the energy from radiation indirectly:
    http://www.sciencemag.org/news/2016/10/alien-life-could-feed-cosmic-rays

    Essentially, the radiation would create high-energy molecules in the environment which life could then feed on and use for fuel and nutrients. Based on these observations, researchers have speculated that life could potentially live off of cosmic rays elsewhere in the universe: http://rsif.royalsocietypublishing.org/content/13/123/20160459
     
  11. May 27, 2017 #10
    I apologize for the number of speculations I have posed. I am new to physicsforums, and just found out that speculations are not entertained here.

    could you please explain this? I don't get how radiation resistance could be a byproduct of dessication resistance.
     
  12. May 27, 2017 #11
    Initially, I had also agreed with this idea that any other sort of chemistry might have cropped up in the case of abundant gamma rays. But now, after having given it some thought, shouldn't any 'life-form' at all be based on molecules capable of forming chains ( such as carbon or silicon)? (Please correct me if I am wrong!) Then the number of possible biochemical configurations would be relatively less, and as far as I know, none of them would be fit to simply shield gamma rays.

    Then, the method of radio resistance can only be attributed to processes of 2 or more stages.
    In the case of D. radiodurans, there are multiple DNA strands created, so that if one is damaged, another still exists.
    And as @Ygggdrasil has mentioned, in D. audaxviator, the gamma ray first breaks a specific molecule, and then the cell uses these byproducts.
     
  13. May 27, 2017 #12

    Ygggdrasil

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    With regard to radiation resistance, here's a good reference on the ability of life to survive and reproduce in extraterrestrial environments: https://academic.oup.com/femsre/article-lookup/doi/10.1093/femsre/fuw015

    Table 1 has a few citations to known examples of radiation-resistant organisms on Earth. It also notes that it is difficult to simulate the complex patterns of radiation on other planets, making it difficult to perform laboratory experiments to test the viability of life under such conditions:
    As noted by others, there is an important difference between the doses of radiation that life is able to survive (e.g. in spore form) and the much lower doses of radiation that organisms are capable of tolerating during active division.

    I also agree with the general point that it would be difficult to imagine chemistries that would render xenobiological molecules resistant to ionizing radiation. Rather, life under these conditions would have to evolve robust repair mechanisms to deal with the damage generated by high levels of ionizing radiation (as is the case for radiation-resistant forms of life on Earth).
     
  14. Aug 13, 2017 #13
    Aside from wearing a heavily-insulated lead snowsuit, the Mars explorer would need a constant DNA repair cocktail. The solar eclipse sunglasses would be another issue that will repel even the most eager space enthusiast who already invested millions for a window seat.

    For our own good, earthlings need to study "preventing" cancer, instead of just "the cure".

    Cheers!
     
  15. Aug 13, 2017 #14
    The op is asking about the possibility of an organism thriving on Gamma radiation in place of visible light. Certainly there are no examples in our biosphere. Of course, we would not expect any. In general, Earth organisms are not exposed to sufficient gamma radiation to be expected to either tolerate its destructive effects or to be able to harvest energy from it.

    The first problem in attacking this question is to settle on what constitutes "gamma radiation". In the not-so-distant past, a simple energy or wave-length threshold was used to determine what was "x-ray" and what was "gamma radiation". But that was when x-ray devices where unable to generate the same energy levels seen in nuclear decay.

    Currently, Gamma rays are defined by their nuclear source. Take this article for example:https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.82.1109.
    It describes "an ultraviolet gamma-ray emission from the metastable 229 thorium daughter" - allowing "gamma radiation" energy levels all the way down to the ultraviolet.

    But I don't thing the OP is concerned with UV energy levels, so let;s stick with 200Kev and higher.

    The problem with such energetic photons is that they have no respect what-so-ever for molecules. When they strike a an atom in a molecule, they thoroughly overwhelm all crystalline and molecular bounds. So if a living organism is to harvest the energy, it's not going to be able to do it directly as with photosynthesis.

    The alternative is to harvest the energy indirectly. Most of the energy becomes available as thermal energy - but the thermal gradient would be very low, so it would be a challenge.
     
  16. Aug 13, 2017 #15
    The thing is that ionizing radiation like gamma rays, does what it says on the tin, it ionizes stuff.
    Electrons become disassociated from atoms, and molecules have a hard time sticking together.
    Visible light doesn't do that, it just energizes electrons, which is the basis of photosynthesis, and hence much of life on Earth.
    It's hard to imagine how life could arise in an environment where complex molecules are unlikely to even occur.
     
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