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Have been building a game called Rise: The Vieneo Province.

Vieneo is a terrestrial moon (all details can be found here) but we have a Nitrogen (ipp: 2006), Helium (ipp: 578) Oxygen (ipp: 11) and Argon (ipp: 6) composition.

Questions have been raised about the viability of having field crops on the surface since there is no CO2 and lack of animals causing a gap in the carbon cycle, etc. We don't really want to be able to walk around without some kind of biohazard suit and rebreather (level of effort to animate, etc).

The sky is overcast (again so we don't have to render the whole planet from orbit). There is liquid water on the surface (13% coverage). Atmospheric pressure is 2631 mb so if we had to add a little CO2 it would go a long way (assuming plants work with partial pressure like humans do). And maybe the rebreather could catalyze the CO2 to get O2 or something to that effect so we don't have to add O2 to the atmosphere.

Propulsion of the vehicles in the game depends on the mass of air for ejection but the energy does not require combustion.

  1. How can there be field crops - i.e. what is the minimum change to support them?
  2. Is it survivable from a human standpoint with minimal protection (no space suit here... just something to keep air inside separated) and believable that a suit is required at all times.
  3. Is it sustainable? Does it make sense that it is overcast with so little water on the ground? I have temperature ranges too which can be easily adjusted.
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    $\begingroup$ I would advise only asking one question per post. $\endgroup$ – Bellerophon Jul 1 '17 at 20:07
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1) There cannot be field crops, meaning plants similar to those of Earth, without CO₂. At present Earth has an average of 400 parts per million of CO₂ in its atmosphere, and I've read about experiments with plants growing well in double that concentration. For humans, though, CO₂ starts becoming noticeably toxic at concentrations over 1,000 to 2,000 ppm.

Also, if the sky everywhere is always overcast, photons from sunlight will not reach the surface in sufficient amounts for photosynthesis.

2) If you provide humans with a suit that is capable of supplying a reasonable mix of gases they should be fine. The partial pressure of nitrogen in your atmosphere seems a bit high, but (judged from what scuba diving sources tell me) not enough to cause nitrogen narcosis.

The problem is where you'd get your oxygen from. You cannot just take CO₂ and split it into carbon and oxygen. We're exploring technologies to do it using catalyzers and you can safely assume these technologies will become much more efficient in the future. But your present atmosphere has no CO₂, and for O₂ to be produced in sufficient quantities for a rebreather you'd need to have a lot of CO₂ around (meaning a lot more than a few hundred ppm).

3) This atmospheric composition is not sustainable if you throw in Earth-like photosynthetic plants, as you stated you'd like to have. The plants will take CO₂ and produce O₂ and eventually your atmosphere will have a lot of O₂ in it.

You spoke of overcast skies and assumed that this must be caused by clouds of water vapor, which would indeed be asking too much for a planet with so little surface water, but you could have clouds made of other things. If there are plenty of volcanoes they can fill the sky with gases that will react to form smog, as well as particulates.

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  • $\begingroup$ Thank you for the response! 1) So given the composition and the overcast layer the field crops can't exist (or any vegetation for that matter). I forgot to mention we have a texture or two for the surface which implies vegetation. But getting rid of the overcast layer from a "level of effort" standpoint is a lot harder than just getting rid of the field crops. $\endgroup$ – Jason Reskin Jul 1 '17 at 13:37
  • $\begingroup$ 2) So the players would need to bring oxygen with them but otherwise would have good freedom of movement since we aren't talking a big pressure difference, that works well but I forgot to mention somehow 75000 colonists are living on this world. On a larger scale where would they be getting all of this oxygen to survive in buildings ... let alone to bottle oxygen for ventures out into the wild? Plants could exist indoors with artificial light sources and produce enough oxygen? $\endgroup$ – Jason Reskin Jul 1 '17 at 13:39
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    $\begingroup$ @JasonReskin If you want to keep the skies overcast, as I said, just chalk it up to volcanoes, is my advice. As for the oxygen, I suppose you could grow plants indoors (or underground in sealed chambers) and solve two problems at once (O₂ and food). $\endgroup$ – pablodf76 Jul 1 '17 at 13:46
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This should be no problem at all (But your colonists should really try to find out where the O2 comes from).

Field crops

Todays solution: algae farms, supported by parabol mirrors. CO2 Input from human output and from underground (e.g. limestone, not yet explainable where that might come from) Tomorrows solution: use plants which are able to grow in darkness and with very low or no CO2 levels (engineered to be edible or engineered to use less light or other wavelengths or use chemical energy and maybe some sort of CO2 fertilizer).

Depending on your other settings the cloud cover may be very thin, so that it is not very dark on your planet. The wavelength emissions from your sun (B9V) seems to be (much) more to the higher, blue wavelengths, so you might get in fact problems with too much light, not only in the UV part for your plants (and humans), but plants should be able to overcome this problem by engineering or evolution. The high radiation levels might explain the oxygen.

Surviving of humans

Use a lot of sunblocker and o2 enhancer with oxygen flasks on your back. No suit needed, maybe a hat. Oxygen is part of water and a lot of minerals. If you have free O2 in your atmosphere, then you must have a lot of oxidized rocks laying around. Concentrate the O2 from the atmosphere with a portable machine or use oxygen flask filled with electrolysis or atomize some silicate or iron oxide.

Sustainability of the atmosphere

The cloud cover should be calculatable (Moon of a Planet around a B2V sun, 0.984 AU). I will not try it, because since there is oxygen in the athomsphere there are some unexplained processes going on which might do anything to stabilize or destabilize the athomsphere. Perhaps some undiscovered life, machine or "recent event" (recent in the past thousand years) or constant replenishment from the planet around your world moves or some of it's rings. The temperature seems to be very low for it beeing so near it's star, but this depends again on the thickness and composition of your cloud or a (volcano, impact or industrial induced) dust layer high up. You might explain anything here or just say that it is until now not known what caused it to be like this and how long (years, millenials, or much longer) it will last. Every new atmosphere humanity discovered yet hat some unpredictable features, and most of them are not fully explainable yet, too, except perhaps mercury.

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Side note: On the atmospheric composition, it is unlikely helium would be sustainable under these conditions. Terrestrial planets can't hold helium unless they are extremely cold, otherwise only ice and gas giants have the mass to keep helium in their atmosheres.

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  • $\begingroup$ Okay I would like to propose an alternative composition: N, O, and trace CH4, NH3, H2O, Ne, N2, CO... Nitrogen 99.4% 2613.7 mb Oxygen 0.6% 16.4 mb $\endgroup$ – Jason Reskin Jul 1 '17 at 16:24
  • $\begingroup$ What is the actual component(s) that gets suspended in the atmosphere to create perpetual volcanic cloud justification? Sulfur Dioxide? Does that need to be included in the composition or is it a trace amount that does the trick? $\endgroup$ – Jason Reskin Jul 1 '17 at 16:52
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    $\begingroup$ That would work for the new composition, I would include SO2 but it does not take much, even 1% would be more than enough to create a permanent cloud cover. $\endgroup$ – Brooks Nelson Jul 1 '17 at 18:21
  • $\begingroup$ Ok we landed on this N, SO2, O, and trace CH4, NH3, H2O, Ne, N2, CO... Nitrogen 98.4% 2589 mb Sulfur Dioxide 1.0% 26 mb and Oxygen 0.6% 16 mb $\endgroup$ – Jason Reskin Jul 2 '17 at 2:29
  • $\begingroup$ I forgot to mention that we have a lot of rain (like subtropical environment on Earth) ... does that work with this new composition? Or do we need more water vapor in the air instead of SO2? Keep in mind the small hydrosphere of 13%. Thanks! $\endgroup$ – Jason Reskin Jul 6 '17 at 1:58

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