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This is a continuation of a question I made earlier!

The atmosphere consists of 80% N2, 17% O2, 1% CO2, 1% NH3. I am not extremely familiar with the chemistry of ammonia, but I do know that it behaves as a weak base and can dissolve in water to form ammonium and hydroxide.

I am already certain on how the ammonia will be replenished in the atmosphere and etc. but I am very curious on what effects ammonia will have on the properties of the planet. Will the rain be more basic than Earth's rain? Will this prompt more plant growth with the more available nitrogen? What might happen to the evolution of life/technology with the higher level of ammonia?

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    $\begingroup$ It would be better if you narrow down the scope of your question. Life alone is already too broad, topping with technology, rain and plant growth doesn't help. $\endgroup$
    – L.Dutch ♦
    Commented Aug 20, 2019 at 2:35
  • $\begingroup$ Worth noting, the planet's oceans would have a certain concentration of ammonia in them. $\endgroup$
    – Arkenstein XII
    Commented Aug 20, 2019 at 3:20

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Well, it'll react with CO2 to form ammonium carbamate, which is highly water soluble. That will help neutralize the oceans (which would otherwise be acidified by the high CO2 levels--good news for carbonate shell forming creatures), and increase bioavailability of carbon and nitrogen for aquatic autotrophs, but it also means you need an explanation for what is replenishing all that CO2 right along with the ammonia.

It may prompt more plant growth; at least, symbiotic nitrogen-fixing microbes will not be as important.

Rain may be slightly more basic, but the high CO2 levels may very well balance that out.

Ammonia is a very good solvent for metal ions, so you may see more extensive usage of chelated metal complexes than in Earthling biology, which could simplify a lot of enzymes. That's annoying for technology, though--protecting refined metals from corrosion will be slightly trickier than ot is for us.

Ammonia is a strong greenhouse gas, so adjust stellar illumination accordingly.

It will also depress the freezing point of water; at that low concentration, ice should still float, though, if your world is cold enough to have any.

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  • $\begingroup$ Plants will grow much faster when so much nitrogen is available, producing more biomass, which will then burn (or eaten by animals) which replenishes the CO2. $\endgroup$
    – Juraj
    Commented Aug 20, 2019 at 10:58
  • $\begingroup$ @Juraj Only if nitrogen is the limiting nutrient. And that would tend to pull down the CO2 level; the fact that plants are growing faster does not automatically imply that animals will eat & metabolize faster to make up for it. $\endgroup$
    – Logan R. Kearsley
    Commented Aug 20, 2019 at 16:11
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The oxygen in your atmosphere will convert the ammonia to nitrogen and water.

4NH3(g) +3O2 (g) → 2N2(g) +6H2O(g) source

This is like the fate of methane in our atmosphere of oxygen excess. Oxygen strips away the hydrogens to be its little pets and then double teams the carbon. I think with NH4 there may be nitrogen oxide intermediates for a while but eventually those settle into stable nitrogen and oxygen.

But there are traces of methane in the environment - it just must be repleted and it is. If your ammonia is repleted you could keep the stable 1%. Reduced nitrogen (like ammonia) in necessary for life, and everything alive on earth depends on the few critters able to fix atmospheric nitrogen into biologically available forms. The history of life on earth would be very different with available reduced nitrogen in the atmosphere - after the Great Oxidation, soluble nitrogen was in short supply and some people think this is what stalled evolution for about a billion years.

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