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I am currently building a planet that weighs about 4 earth masses and is 2.3 earth radii long. It is an ammonia planet (as the title suggests), and has ammonia oceans with some dissolved water ice, methanol and salts (sodium, chlorides, sulfates, potassium etc.). The average temperature is about 260ºK on the planet and the avg pressure at sea level is about 2.5 atm.

Here is the composition of the atmsophere:

  • Nitrogen: 66%
  • Ammonia: 19.8%
  • Methane: 7%
  • Neon: 5%
  • Argon: 1%
  • Ethylene: 0.9%
  • Propylene: 0.2%
  • Others: 0.1%

In this anoxic environment, I would like to understand how basic microorganisms would produce energy (with some chemical reactions). Some are (most likely) in the ocean, so if they were able to isolate metals or use salts somehow, that can be part of the reaction on how they produce energy. Thanks in advance.

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I see no particular issue why the usual anaerobic metabolic pathways found in extremophiles today wouldn't suffice. You could even potentially have photosynthesis which reduces water and nitrogen into complex oxygen-nitrogen compounds and ammonia. Without more information on the biochemistry of your lifeforms it will be difficult to answer your question.

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    $\begingroup$ I should have clarified. The microorganisms are nitrogen-fixing, obligate or aerotolerant bacteria that are probably similar to real-world anammox bacteria. I don't really have much more info on them because I don't want to delve into the intricacies of bacterial biochemistry. Now that I think of it, I probably could use the same reaction that anammox bacteria use (fixing ammounium and nitrite into nitrogen gas). See this (pubmed.ncbi.nlm.nih.gov/19247843/…) for more. $\endgroup$
    – Neil Iyer
    Commented Mar 21 at 2:32
  • $\begingroup$ And by obligate, I meant obligate anaerobic. $\endgroup$
    – Neil Iyer
    Commented Mar 21 at 13:47
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You need a most basic reaction, which produces energy. In our case, it is the very energetic oxidation of carbon. Clearly your planet can not do that.

There might be other, lesser energetic reactions. Important thing is, that the planet rotates and you have a Sun, which moves chemical balances into a direction (in our case: by driving photosynthetisys, it converts carbon dioxide and water to sugars). Other, lesser energetic reactions revert this (animas eat plants, predators eat animals).

I believe, ammonia and ethylen might produce more complex chemicals whose decay back might serve as the base of a life. Here helps that ethylen happily polymerise, what might be the base of some proteins.

Very likely, this life will be based on much slower and lesser energetic chemical reactions as ours. Where we have humans, they will have at most snails.

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  • $\begingroup$ That gives me an idea for another microorganism that converts ammonia and ethylene in the atmosphere and oceans into ethylamine. Then, the ethylamine breaks apart back into ammonia and ethylene. $\endgroup$
    – Neil Iyer
    Commented Mar 21 at 18:05

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