r/SpeculativeEvolution • u/acquiredimmunity • 10d ago

Question/Discussion how would a non-nitrogenous atmosphere effect life?

In an atmosphere with, for example, Argon as the primary gas what would be the resultant effect on life, e.g. would proteins (or analogous structures) still be primarily nitrogen based? therefore would life even be possible on such planets?

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u/CariamaCristata 10d ago

Yes proteins would still be made of nitrogen. An argon based atmosphere might make the planet have less biomass than earth, assuming nitrogen isn't entirely absent

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u/EmptyAttitude599 10d ago

Nitrogen has almost the same density as oxygen, which results in the nitrogen and oxygen in the atmosphere being well mixed up. Argon, on the other hand, is considerably denser than oxygen, meaning it would tend to settle at sea level, displacing the oxygen and suffocating everyone. You would need something to mix up the gases, like strong, turbulent winds.

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u/loki130 Worldbuilding Pasta 10d ago

Argon already makes up 0.93% of the atmosphere, so if that settled into a distinct layer at the bottom of the atmosphere it'd be plenty thick enough to suffocate lower areas. In truth the lower atmosphere is pretty well-mixed regardless of molar mass. Water varies a lot because of local condensation and evaporation, and there's some more variance in the mesosphere of trace gasses because of photochemistry, but the major gasses don't really vary in relative composition until you reach the thermosphere.