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Say there would be plants that release a lot of N2O (nitrous oxide or laughing gas). On Earth, N2O is a trace-gas and it is pretty stable. In our atmosphere it has a half-life of > 100 years, and as I understand it, it is destroyed in the stratosphere by ultraviolet with wavelengths of < 230 nm.

Doing a back of the envelope calculation, there would be a strong build-up of N2O in the atmosphere if plants would release half, or even a tenth as much N2O as they release oxygen.

My question: what would happen if there was 10 or even 100 mbar of N2O in an Earth-like atmosphere? More specifically: 2N2O => 2N2 + O2 is an exothermic reaction. I can imagine that at a given threshold the reaction could become self sustaining so that there exists a strict maximum partial pressure of N2O.

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    $\begingroup$ Note that just because a reaction is exothermic doesn't mean it has to be spontaneous (e.g. Diamond -> Carbon is exothermic, but doesn't normally happen at normal Temperatures), I couldn't find any information about the required activation energy for this one though. One interesting thing I found is that N2O is a relatively strong green house gas (298x stronger than CO2), so having it at considerable amounts in the atmossphere may heat things up quite a bit. $\endgroup$ – Nicolai Mar 8 '18 at 13:55
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    $\begingroup$ Greenhouse effect: I think that is a major point. => I am checking a draft of a SF novel; In his story the writer uses a few hundred mbar N2O, produced by engineered plants, to warm up a Mars-like planet. However, I doubt an atmosphere with so much N2O is possible. The writer is trying to get his science right and asked me to help because I am an atmospheric scientist. => I feel very ashamed that I do not know an answer to this one ;-) $\endgroup$ – luim Mar 8 '18 at 14:14
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To summerise the below articles:

Most likely you would get a massive depletion of O3 as an output as well [1] (Constituting a thinner Ozone layer) also a MAJOR soil presence from Nitrosomonas [2], STRONG thunderstorms [3] (High static capacity) Large rainforests [4], and a monstrous rise in temperature [5]

As the Ozone depletes, the reaction will snowball without UV shielding, without measurable data the reaction balance will be far to difficult to pinpoint without access to server time.

Here are some specific data links on the finer points:

[1] http://science.sciencemag.org/content/326/5949/123 [2] https://www.sciencedirect.com/science/article/pii/0032063367900748 [3] https://www.researchgate.net/publication/234484802_Synergy_Effect_in_Electrical_Insulation_Characteristics_of_N2O_Gas_Mixtures [4] http://onlinelibrary.wiley.com/doi/10.1029/GL010i012p01156/full [5]https://journals.ametsoc.org/doi/pdf/10.1175/1520-0469%281980%29037%3C0119%3AMANOTE%3E2.0.CO%3B2

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  • $\begingroup$ Thanks! I'll take a look at the articles, and tell the writer to do the same. $\endgroup$ – luim Mar 13 '18 at 12:27

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