Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Life Outside Our Planet Without Oxygen and Water

  1. Feb 16, 2018 #1
    Hello everyone :)

    I have a question.Is it possible for life to exist in other planets without oxygen and water?

    I mean just because we need it to survive here on Earth.It doesn’t mean all planets need it to support life as well.
     
    Last edited by a moderator: Mar 1, 2018
  2. jcsd
  3. Feb 16, 2018 #2
    Do you mean intelligent life or something more simple like bacteria?
     
  4. Feb 16, 2018 #3
    Yes Intelligent life
     
  5. Feb 16, 2018 #4
  6. Feb 16, 2018 #5

    BillTre

    User Avatar
    Science Advisor

    Since we only know of life on earth (n=1), there is no certain answer.

    Not all life on earth does requires oxygen.
    Active life on earth does require water though.
    Dehydrated tardigrades for example are in "suspended animation".

    Water is important because much (all?) of the chemistry of underlying life occurs in solution.
    This allows molecules to move around and interact more quickly and freely. Guess the same could happen in a gas, but (of course) its never been seen.
     
  7. Feb 16, 2018 #6
    I wonder if some planets doesn’t need water to support life just cuz we do here on Earth. Maybe they survive on sources not know to us yet :) just an thought
     
  8. Feb 25, 2018 #7
    I’d say yes because life as we know so far is all carbon based from what I know and we all need water. The fact that we don’t know of species that aren’t carbon based or that don’t need water doesn’t mean every other species needs it. It’s not impossible so I reckon it’s possible...
     
  9. Feb 27, 2018 #8
    It might be impossible. Life may only exist under conditions very similar to our own, and may be very recognizable to us. From a chemistry standpoint, carbon appears to be the most viable element that can support life, and it doesn't really have any legitimate competitors.

    But since we just don't know, there's always a slim chance it's possible I suppose. But my gut feeling(which is worthless), is that we won't find life elsehwere that isn't carbon based.
     
  10. Mar 1, 2018 #9
    Being carbon-based is not related to breathing oxygen though. Anaerobic bacteria are also carbon-based. The problem is oxygen is good at, well, oxidation. All complex life forms use oxygen, because complex life is power-hungry, just as complex machines. So one needs to find alternative easily available oxidant as a replacement. Not impossible, but oxygen is common and good at what it does, hence more probable. One may argue that free oxygen is not that common, but complex life on Earth didn't evolve until simpler life forms freed some oxygen.

    The solvent is another problem. Water also has the advantage of being common molecule in the Universe. It's made of the most abundant element (hydrogen) and end-product of nuclear synthesis in very common stars (oxygen). It is unique among simple molecules in that it could be liquid in fairly large range of conditions (pressure, temperature). There are competitors like methane and ammonia, but they have less favorable thermodynamic properties. Methane is not polar, so it requires completely different biochemistry (possible on cold Titan-like worlds). One can imagine life emerging in a water-ammonia solution, which could be liquid in much lower temperatures than pure water, but if it is so cold, then you probably have a problem with the energy source anyway.
     
  11. Mar 2, 2018 #10

    stefan r

    User Avatar
    Gold Member

    Does the Boltzmann brain count?

     
  12. Mar 2, 2018 #11

    BWV

    User Avatar

    Reminds me of the Stanislaw Lem story

    That evening, something emerged at the edge of the dump, not
    far from the puddle which had by now dried up, and this something,
    a creature of pure accident, was Mymosh the Selfbegotten, who had
    neither mother nor father, but was son unto himself, for his
    father was Coincidence, and his Mother --Entropy. And Mymosh
    rose up from the garbage dump, totally oblivious of the fact that
    he had about one chance in a hundred billion jillion raised to
    the zillionth power of ever existing, and he took a step, and
    walked until he came to the next puddle, which had not as yet
    dried up, so that, kneeling over it, he could easily see himself.
    And he saw, in the surface of the water, his purely accidental
    head, with ears like muffins, the left one crushed and the right
    a trifle underdone, and he saw his purely accidental body...

    --Truly, I am beautiful, nay, perfect, which clearly implies the
    Perfection of All Created Things!! Ah, and how good must be the
    One Who fashioned me!



    http://psychadelicbus.tripod.com/mymosh.txt
     
  13. Mar 6, 2018 #12

    JMz

    User Avatar

    Back to the OP: Have you not seen Cosmos, at least? This is well trodden ground!
     
  14. Mar 10, 2018 #13

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    For life of any form to exist, it would have to reproduce and react to its surroundings. Of the elements that are available to any other system of life, there are very few (or none) that have the flexibility of Carbon as a basis. The valency of Carbon allows a massive range of different molecules to be formed. In the popular Science press there are suggestions about Silicon based life but I don't know of any viable suggestions.
    There are a number of extremophiles and anaerobic organisms on Earth so why not imagine carbon based life on planets with very different levels of oxygen and water.
     
  15. Mar 10, 2018 #14
    There has been consideration that there are other temperature ranges, such as on Titan, where the temperature is essentially contolled by the evaporation point of Ethane and Butane at the pressures it is under. There is chemical action there, we know, but water there would be as rock is here, if used it may be the form of Bones or Teeth, perhaps scales etc. Possible carbon life, with a different type of cellular structure, perhaps more crystalline and dependent on microchannels for ethane type blood, and being around us would be like standing right next to pool of lava.

    That is the other possibility, creatures living in lava, thinking it fine as any seawater we know. Living on growing crystals, perhaps heated by internal nuclear reaction, as long as one eats the right balance of elements, stays within the right temperature zones, and avoids predation, may well survive to replicate, possibly by fission. We now know water exists down at those depths, and there are plenty of liquids and semiliquids, as well as the metals and perovskites to make it possible. The slow conveyor of subduction zones would provide a nice and varied meal to such critters, and their lives and thus movement would likely be that of tens of thousands of years in scale. Who knows, as several authors have pointed out the Universe is stranger than we Can imagine.

    Not that this is highly likely, but it is within the realm of possible until it is completely disproven, and there is a LOT of Universe out there for Nature to try it in.
     
  16. Mar 10, 2018 #15
    While it's true that Silicon can form complex molecules in a similar way to Carbon, unfortunately most of them are solids which cannot dissolve in water.
    Stretching the imagination a bit though, I guess Silicon life is a possibility if it evolves in hot magma instead of water.
     
    Last edited: Mar 10, 2018
  17. Mar 10, 2018 #16

    stefan r

    User Avatar
    Gold Member

    Silane is very much a gas at standard earth temperatures and pressure. Trisilane boils at 53C and melts and -117C.
    Diamond, graphite and fullerrenes are not used in earth biology equally useless crystaline silicon.

    In silicone you have lots of flexibility. Carbon chemistry uses very small building blocks like a sugar ring, amino acid, or lipid chain. Silicone particles can suspend in water The base units can be hundreds or thousands of atoms. Complex process can be executed using arrays of suspended silicone. It can form rings and chain. You can add reactive surfaces to parts.
     
  18. Mar 10, 2018 #17

    JMz

    User Avatar

    Assuming we are dealing with a chemical basis for life, then there are couple of fundamental limits (absent technological creation of life): (1) Life seems to require complex chemicals, like RNA, in order to reproduce and diversify. That means you can't overheat them: Every bond in your hypothetical complex molecule has to be strong enough to withstand the heat of the environment long enough to reproduce. I suspect you will find that you need many atoms whose bonds are weaker than silicates to build up a sufficiently complex molecule, so you can't take silicates to be representative of high-temperature biochemistry. (This is not my area of expertise, though, so perhaps someone with a high-temp chem background can weight in.)

    (2) There has to be enough time to evolve those complex chemicals. Substantial levels of carbon and other non-hydrogen atoms have only existed for a few billion years longer than on Earth. (And the entire universe less than 10 GY longer.) Not a short time, to be sure, but if you wait for (e.g.) ethane-based chemistry on a cold world like Titan, you may have to wait far longer than that to produce complex chemistry, because the reactions slow down so dramatically as the temperature falls.
     
  19. Mar 12, 2018 #18

    stefan r

    User Avatar
    Gold Member

    Check colloidal silicates. The SiO2 balls are highly resistant to heat and the bond is too strong. However, the spheres form lots of hydrogen bonds and will react with some chemicals. Silica balls that have strong reactants on the surface are still spheres and they tend to have new properties introduced by the reactant.. A chain of silica balls could, for example, have stretches of hydrophilic spheres and stretches of hydrophobic spheres. That gives the chain the ability to fold up in an organized way where the hydrophilic surfaces face the water. Similar to the organization of protein chains. Also consider amorphous silica alumina. It is used in catalysts. Organic chemistry can take place on and between the particles.
     
  20. Mar 12, 2018 #19

    JMz

    User Avatar

    I can believe that there are such compounds, and perhaps they can function in Earth-like environments. My only point about silicates is that, unless every bond in a complex molecule is strong, then the molecule cannot survive high heat, such as lava (as someone suggested) -- even if a silicon "core" could survive it. Hydrogen bonds are particularly weak, in all the examples that I know. (But again, I'm not a chemist.)

    Specifically, if liquid water is involved (as the words hydrophobic and hydrophilic indicate), then we are evidently dealing with less extreme temperatures, which might not be too high for such Si-based spheres.
     
  21. Mar 12, 2018 #20

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    The time factor is very relevant when discussing possible alternative life chemistries. There are windows in the development of star systems which may allow life forms to start and then to develop before the star ceases to be suitable. Bigger stars than the Sun evolve much quicker and there may not be time before they become hostile. So, before getting too excited about an alternative chemical basis for a life form, that time constraint must be considered. It's all too tempting to be more and more vague about where appropriate conditions could exist and it's easy to stray into the SciFi way of thinking.
    Here's another thing to think about. Would we actually recognise the existence of some of those suggested lifeforms? If their timescale were just a bit slower than ours, would we even notice them growing or reacting to an environment that we happen to be sharing? Messages, sent at 0.01 bits per second would probably not be recognised by any of our monitoring systems and it would be the same with bursts of data with THz rates. How wide could we justify a search range to be? It could like Bit Coin Mining; most attempts give a null result.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted