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Making use of Titan

  1. Mar 29, 2015 #1
    If a methane-filled planet or moon like Titan was pulled toward a star, as the methane warmed and became gaseous, would it be possible to ignite it, converting the methane oceans to H2O with a CO2 atmosphere, which could in turn cause photosynthesis to naturally occur?

    If it's possible, it would be the ultimate battle between good and greed -- would we use our technology to turn methane worlds we discover into living, breathing planets, or would we use it to harvest the fuel for profits and then leave?

    PS My first post here!
     
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  3. Mar 29, 2015 #2

    Bandersnatch

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    Hi bennyschmidt, welcome to PF

    Where would you get the oxygen to burn all that methane from?
     
  4. Mar 29, 2015 #3
    Thanks for the response. As far as I understand, there is already some oxygen on Titan, at least in the form of ice and ammonia under the surface near the poles. If there was enough oxygen to ignite even one small area, the byproduct would be more water and CO2, which makes more oxygen available to fuel more combustion. It's also possible that with a small amount of water, electrolysis from lightning storms in the newly created CO2 atmosphere could release O2 molecules directly from the water, which would quickly turn the planet into a mostly flammable, hellish world.

    But the idea is that for a very long time it burns and burns, producing more and more CO2 and H2O until eventually there is so much more water than methane, and also the methane has become so gaseous from the increased heat that it escapes anyway, leaving only lots and lots of water (oceans) and CO2 (atmosphere) left behind -- the environmental conditions needed for photosynthesis.

    Maybe if it gets too close to the star, like the distance Venus is from the sun, the water too escapes as a gas (evaporates from the heat), and you're left with just a hot CO2 world. But if it gets close enough to the star, but not too close, like in the case of the earth, you end up with oceans, a greenhouse effect, and life.
     
    Last edited: Mar 29, 2015
  5. Mar 30, 2015 #4
    Is bumping threads allowed on this forum? I'm hoping someone can answer the question without relying on "where does the oxygen come from" (because there is oxygen in the form of other chemicals on Titan)?
     
  6. Mar 30, 2015 #5

    Bandersnatch

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    I'm sorry my answer is not to your liking.

    But the fact remains, you still need free oxygen to burn stuff, and there is none on Titan. Neither is there any oxygen ice.
    Water ice and carbon oxides help just as much as they do on Earth - that is, they're fire retardants. Methane won't burn in ammonia either. Unless you've got some process that will first release the oxygen from whatever molecule its bound in, you get no fire.

    I'm not sure what else it is you want to hear. Perhaps restating the question would help.

    You don't need to burn methane to get water on Titan, though. It's got plenty in the ocean/ice layer under its surface.

    Bumping is fine, by the way.
     
  7. Mar 30, 2015 #6

    Nugatory

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    From the forum rules:
    The membership here is spread across all 24 time zones, so if you don't wait at least one full revolution of the planet, you've bumped before everyone has even had a chance to see your post.
     
  8. Mar 30, 2015 #7
    Well, the reason I wasn't happy with your answer is because it's not really accurate. The point of the thought experiment is not to see if it's possible to light water or ammonia on fire... it's to see if it's possible to convert planetary chemicals on Titan into more useful chemicals in order to jumpstart photosynthesis.

    • "Titan also has a presence of organic molecules that contain carbon and hydrogen, and that often include oxygen and other elements similar to what is found in Earth's atmosphere and that are essential for life."

    • "Evidence also indicates the presence of liquid water and ammonia under the surface, which are delivered to the surface by volcanic activity".

    Sources:
    http://www.space.com/15257-titan-saturn-largest-moon-facts-discovery-sdcmp.html
    http://en.wikipedia.org/wiki/Colonization_of_Titan
     
  9. Mar 30, 2015 #8
    The Oxygen existing on Titan is in the form of water ice and CO2.
    These are the products obtained when burning methane.
    In order to set the Oxygen free in order to burn more methane you would have to apply a vast amount of energy,
    and when you do burn it, the same amount of energy you put in gets released again, and you are back with H20 and CO2 again.
    Nothing gained.
     
  10. Mar 30, 2015 #9
    Thanks for the answer; it's a lot different than the previous one of "it's impossible to burn methane on Titan" --@Bandersnatch
     
  11. Mar 30, 2015 #10

    russ_watters

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    I'm sorry, but your speculation that you can somehow convert the water to oxygen (for example) and then use it over and over to burn all the methane is very wrong. You should write some of the chemical formulas for the reactions out - that may help you see that by doing the same steps over and over again, you just run in place and don't burn ANY of the methane in the atmosphere.
     
  12. Mar 30, 2015 #11

    russ_watters

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    Actually, no, it was the same answer. "Nothing gained" means you aren't burning any of the existing methane.
     
  13. Mar 30, 2015 #12
    The fuel used by people to warm up their houses during the winter. A really evil action. :)
    We should freeze in the winter so that the gas company does not make any profits. The ultimate battle, yes.
     
  14. Mar 30, 2015 #13
    You miss the point.

    Why is it wrong? It seems to me that as long as you have methane (the fuel), you can certainly burn it over and over -- until the fuel is depleted. That's how burning fuel works.
     
    Last edited by a moderator: Mar 30, 2015
  15. Mar 30, 2015 #14
    There is no point. You just imagine that there is one.
     
  16. Mar 30, 2015 #15

    Bandersnatch

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    Burning requires fuel and oxidiser.

    Look at this reaction:
    $$CH_4+2O_2 ->2H_2O+CO_2 + Energy$$
    it takes the methane, burns it with oxygen to release energy and produce water and carbon dioxide.
    Methane is freely available, but you need oxygen (four atoms per reaction). Where to get if from? Well, you could get water ice and melt it, or maybe even drill deep for some liquid water, and run an electrolysis to get
    $$4H_2O + Energy -> 8H + 4O$$
    So to be able to burn a molecule of methane, which nets you two molecules of water, you need to destroy four molecules of water. The end result is, you're converting water and methane into carbon dioxide and hydrogen (which then either bonds with something else or escapes into space). While I don't know the exact energy balance (somebody calculate it please?), it's also unlikely to be positive - especially once you take into account inefficiencies. Which is to say, even if you ran an engine powered by the methane burning to output electricity for electrolysis, you'd end up with a negative balance (you'd have to import energy or oxygen from elsewhere).

    So once again, the proposed reaction is not going to happen. One way of seeing it is, all the methane that could ever burn on Titan had already burned.

    But, since the idea was to take the moon closer to the Sun*, you could circumvent the problem of water dissociation by the simple fact that UV radiation can do it for you. You just need to get the moon close enough for the water to remain liquid on the surface.
    Then you leave the moon for some millions of years, and you may very well eventually end up with all methane transformed into water and CO2 (still no global conflagration, though).
    But then a lot of other things can happen in that time, including complete stripping of the atmosphere by increased solar flux due to the low gravity and lack of magnetic field.


    *this is by the way an idea so far out there, as far as energy requirements go, that worrying about methane being used as a fuel source is a bit silly; it's like flying rockets to Alpha Centauri to collect wood for your stove.
     
  17. Mar 30, 2015 #16

    Drakkith

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    As has been explained already, converting water to oxygen and hydrogen requires energy. 572,000 joules per mole of water actually. Burning one mole of methane with oxygen to produce CO2 and water nets you 802,000 joules, but since each reaction requires four oxygen atoms, you need to produce 4 moles of oxygen atoms, which requires 4 moles of water and 4x572 kJ, or about 2,228,000 joules. So, to get enough oxygen atoms to burn with methane, you need 2.85 times the energy that the combustion process even produces. In other words, you're losing energy. A lot of energy.
     
  18. Mar 30, 2015 #17

    russ_watters

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    Its not the methane you want to use over and over, it is the oxygen. In order to use it again, you have to "unburn" it, which just leaves you back where you started. You can, for example, do this:
    Step 1: Convert water and carbon dioxide to methane and oxygen.

    Step 2: Burn the oxygen and methane you just created, yielding water and carbon dioxide.

    Repeat forever, with the same small group of molecules, never touching the rest of the planet.
     
  19. Mar 30, 2015 #18

    russ_watters

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    IMO, the energy considerations are secondary to the problem with the required chemicals not even existing on Titan to do what he wants (or, rather, reactions not being able to use the same three oxygen molecules over and over to consume the whole atmosphere). A hydrogen economy on earth would be a net energy loser too, but it at least can be done.
     
  20. Mar 30, 2015 #19
    Benny, more than once you have mentioned your end goal is to "jump start photosynthesis". What life forms are you planning to seed Titan with to initiate and maintain this photosynthesis?
     
  21. Mar 30, 2015 #20
    Losing energy has nothing to do with the thought experiment. I imagine that essentially terraforming a moon would have a high energy cost. I'm wondering if it's possible to do it though, not wondering if I can gain energy from it. The question is whether it's possible or not to change the chemical state of Titan by converting its methane into other chemicals.
     
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