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What would animal life on a methane world look like and how would it evolve?

What would the conditions on a methane world be like?

How would an intelligent race on a methane world achieve a fire equivalent?

Question:

I have asked how an animal species evolved to live on a methane world would look like and how it would evolve and I realize that the presence of plants of some kind of flora is required for animal life to form.

Therefore, how would the flora on a methane world (like Titan) look? How could they evolve and what chemical process could take the place of photosynthesis on such a world? I would prefer that this process is close to or an equivalent (energy production-wise) of Earth-based photosynthesis producing any other byproduct than oxygen.

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  • $\begingroup$ You seem to enjoy methane a lot. :) Methane-based life is something we're still working out. You might use this as another starting point, though it is infuriatingly spare with details. $\endgroup$ – Frostfyre Apr 15 '15 at 16:55
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If you look at photosyntesis the plant uses carbon dioxide (CO2) and water (H2O) to create carbohydrate and oxygen. The formula:

CO2 + H2O → CH2O + O2

If you replace carbon dioxide with methane the formula would look something like this:

CH4 + H2O → CH2O + 2 H2

So instead of releasing oxygen the plants would release hydrogen. So having a lot of plants would mean that a whole lot of hydrogen would be released into the atmospere.

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The daylight on Titan is very dim: half way (log scale) between our daylight and moonlight. However, the light that does get through is heavily filtered. It is essentially monochromatic with most wavelenths blocked. You don't have energy for photosynthesis, unless it is indirect via chemosynthesis: life eats the mana produced by the action of uv on the cloud tops; or the bottom of the food chain lives at the cloud tops rather than the surface. The orange clouds are like our ocean with plankton at the top and a sparsely populated abyssal plain below.

See wikipedia for the answer to this question in lowest terms.

As for your hypothesis that plants are necessary for animals, you are being more terracentric then you realize! Why would the same strong divisions exist in an alien biology? There might not be the same concept of plants and animals at all. In fact, they are a small part of Earth life.

Follow the Energy. What is the power source? If not the sun, what else? If sunlight, where is it available (as noted above) and how does that relate to distribution of physical resources?

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what chemical process would take the place of photosynthesis?

On a methane world, plants would produce long chain alkanes.

The plant equivalent in this scenario would be an organism that captured ambient energy and converted it into stored chemical energy. In an oxidizing environment (like ours), oxidizing things is the easy way to release energy. Reducing things would be a way to store energy, to be released with later oxidation. On earth, plants start with oxidized carbon (CO2), capture solar radiation and convert the energy into reduced carbon (sugars).

The plants then oxidize the reduced carbon later to release the energy as they need it. Freeloader animals eat the plants and steal the reduced carbon, then themselves oxidize it back to CO2 using ample atmospheric O2.


Methane would not exist in any quantity in an oxidizing environment I do not think. On earth it gets oxidized by free O2 fairly quick. So it is safe to deduce that an environment with loads of methane would be a reducing environment. The situation there is then reversed from ours: storing energy would be via oxidation, and the release later would be via reduction.

Oxidation sounds like oxygen is involved but not necessarily.
I propose that "plants" in a methane rich environment would store nonchemical energy (you pick - solar, radiant etc) by oxidizing methane to ethane. There may be advantages to continuing this process: oxidizing further by adding additional methanes and growing a long chain alkane. This would release hydrogen (the reducer doppleganger of oxygen) and produce long chain alkanes.

The release of this energy would be via reduction: hydrogenating the alkane with H2 and releasing its constituent carbons back to methane.

Maybe methane metabolism like this occurs on earth. I have long been intrigued by the prospect that microbial action on primordial methane might be responsible for terrestrial petrochemicals - long chain alkanes. This was Thomas Gold's proposition in Deep Hot Earth. The deep earth is a methane world. There are not fossils in crude oil.


"how would they look". I have described only their metabolism. The macroscopic structure of plants has to do with energy capture (leaves), reproduction (flowers / seeds / spores) and defense against herbivory (thorns, toxins). Your methane world plants will be evolved to maximize energy capture (whatever energy they are capturing), defend against herbivores (whatever those may be) and reproduce themselves.

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