wylde_writer (wylde_writer) wrote in little_details,

Science question: atmospheric gases on alien planet

Setting: alien planet with very dense, hothouse atmosphere. How dense? Probably 3 to 5 times earth normal. Avg temp around 140 deg F.  (~60 C.)  Diameter, 9500 km. Gravity: assume earth normal, unless higher g is absolutely essential to achieve that degree of density. Planet is riddled with volcanic rifts that pump out a lot of sulphur dioxide and carbon dioxide gases and other common volcanic gases as well. Dense jungle vegetation abounds (adapted to this gas mix, obviously).

Two additional considerations: 1) these basic parameters have already been infered (but not closely detailed) in previous writing in this setting. 2) Core requirement is that I have an atmosphere with sufficient oxygen in it (preferably oxy/nitro mix) that an unprotected human can survive in it, even if in great discomfort, for some period of time (at least in more temperate locations on the globe).

Question: I need pockets of toxic gases that are trapped in lowland areas, ground-hugging like fog. I presume held down by combo of atmospheric pressure and their own molecular weight. The q is, what kinds of gases should these be? Obviously this ought to be some kind/s of volcanic gases, but which ones in particular? I don't know what a volcano emits that lends itself to this behavior in these conditions, as opposed to blending harmlessly with the dominant atmosphere.

Research done: I've read up on basic atmospheric science (with textbooks) but it is earth-normative of course, and I don't know enough atmospheric science and/or gas physics to extrapolate soundly into this kind of setting. Hence my question to the group mind.

Bonus questions:  given parameters above and whatever variables you advise be added, what color will the sky be?  Musings about color/temp of primary star and necessary orbital distance from same also welcome.
Tags: ~climate/weather, ~science: astronomy

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