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Thread: How would a methane-oxygen atmosphere work?

  1. #1 How would a methane-oxygen atmosphere work? 
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    I'm working on a SF story I I want to create a methane breathing species. The problem is I don't know how an atmosphere that is rich in methane and also has some Oxygen would work. I get that it would be highly flammable but I don't know how this will manifest more exactly.

    I thought about having them use sulfur as on oxidant instead of oxygen but they would still need water and that implies oxygen. I also thought about having them use liquid hydrocarbons instead of water as a biological solvent since we're already talking about a methane rich planet. The problem with that is hydrocarbon isn't a polar solvent so I'm not sure it's even possible for complex life to evolve using liquid hydrocarbons as a solvent. Even if it were possible it would need to be very different from what we know and I'm not good enough at biology to predict how such lifeforms might look.

    So, oxygen seems inevitable. The problem is I only have a rudimentary knowledge of chemistry so I have no idea how such a highly flammable atmosphere act. Could it just catch fire and burn away? Would intelligent life even be possible under this conditions? For example, what would happen if they would try to start a fire in that atmosphere?


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  3. #2  
    Forum Cosmic Wizard
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    Flammability limit - Wikipedia, the free encyclopedia

    You should find just about everything you need in that Wiki page.
    The main problem I think you would have is having enough oxygen to breath in a methane rich atmosphere. Many cases of people dying from gases are from asphyxiation because the oxygen levels fell below 17%.



    Edit:
    I am assuming you would need humans interacting with the aliens so I made the comment about breathable air.
    However if you don't need oxygen for breathing you could bind most of your oxygen into water.
    Most methane producers here are anaerobic bacteria anyhow.


    Last edited by dan hunter; July 23rd, 2014 at 10:37 AM.
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  4. #3  
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    Quote Originally Posted by dan hunter View Post
    Flammability limit - Wikipedia, the free encyclopedia

    You should find just about everything you need in that Wiki page.
    The main problem I think you would have is having enough oxygen to breath in a methane rich atmosphere. Many cases of people dying from gases are from asphyxiation because the oxygen levels fell below 17%.
    This is great, thanks a lot. It's exactly what I needed. I can't believe I didn't think of simply increasing the atmospheric pressure and decreasing the temperature!

    I am assuming you would need humans interacting with the aliens so I made the comment about breathable air.
    The planet would most definitely not be inhabitable by humans, so that is not a problem. The only reason I mention oxygen is because the planet needs water. If I can have water but no oxygen in the atmosphere, then that is perfect.

    However if you don't need oxygen for breathing you could bind most of your oxygen into water.
    That would be ideal. Is it possible though? What would need to happen for a planet to have liquid water in sufficient quantities for life to develop but no oxygen in the atmosphere?

    Most methane producers here are anaerobic bacteria anyhow.
    In fact the methane would be in the atmosphere before life develops. The idea is to have a carbon planet (I can't post links since I'm a new user but wikipedia has a good article on them). The atmosphere would consist mainly of carbon monoxide and methane. The "plants" in ecosystem would produce sulfates as a waste byproduct of photosynthesis if they have enough light. In the absence of abundant oxygen the animals would depend on eating these plants to use the sulfates for oxidation in some kind of anaerobic oxidation of methane. It all works out except that they need water.

    Which is a problem because:

    Quote Originally Posted by Wikipedia
    However, carbon planets will probably be devoid of water, which cannot form since any oxygen delivered by comets or asteroids will react with the massive amounts of carbon on the surface.
    I'm starting to think life on a carbon planet is impossible which is a pity, because it would have made for a very interesting environment.
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  5. #4  
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    Quote Originally Posted by Re.V View Post
    Quote Originally Posted by dan hunter View Post
    Flammability limit - Wikipedia, the free encyclopedia

    You should find just about everything you need in that Wiki page.
    The main problem I think you would have is having enough oxygen to breath in a methane rich atmosphere. Many cases of people dying from gases are from asphyxiation because the oxygen levels fell below 17%.
    This is great, thanks a lot. It's exactly what I needed. I can't believe I didn't think of simply increasing the atmospheric pressure and decreasing the temperature!

    I am assuming you would need humans interacting with the aliens so I made the comment about breathable air.
    The planet would most definitely not be inhabitable by humans, so that is not a problem. The only reason I mention oxygen is because the planet needs water. If I can have water but no oxygen in the atmosphere, then that is perfect.

    However if you don't need oxygen for breathing you could bind most of your oxygen into water.
    That would be ideal. Is it possible though? What would need to happen for a planet to have liquid water in sufficient quantities for life to develop but no oxygen in the atmosphere?

    Most methane producers here are anaerobic bacteria anyhow.
    In fact the methane would be in the atmosphere before life develops. The idea is to have a carbon planet (I can't post links since I'm a new user but wikipedia has a good article on them). The atmosphere would consist mainly of carbon monoxide and methane. The "plants" in ecosystem would produce sulfates as a waste byproduct of photosynthesis if they have enough light. In the absence of abundant oxygen the animals would depend on eating these plants to use the sulfates for oxidation in some kind of anaerobic oxidation of methane. It all works out except that they need water.

    Which is a problem because:

    Quote Originally Posted by Wikipedia
    However, carbon planets will probably be devoid of water, which cannot form since any oxygen delivered by comets or asteroids will react with the massive amounts of carbon on the surface.
    I'm starting to think life on a carbon planet is impossible which is a pity, because it would have made for a very interesting environment.
    There are other metabolic pathways. Like I mentioned, most of our methane producers here are anaerobic. You have bacteria that eat H2S.
    from Chemosynthesis - Wikipedia, the free encyclopedia
    12H2S + 6CO2 → C6H12O6 (=carbohydrate) + 6H2O + 12S

    If you look into life on earth you can likely find good models for your exoplanet life to copy.
    Try some of the things that live near deep sea vents.


    http://ocean.si.edu/ocean-videos/hyd...vent-creatures
    Last edited by dan hunter; July 23rd, 2014 at 08:29 PM. Reason: corrections
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