I have been working on a game called Rise: The Vieneo Province.

Vieneo is a terrestrial moon (all details can be found here) but we have an atmospheric composition we arrived on from another question:

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

We have a perpetually overcast sky and a lot of rain in the game (like tropical environments on Earth) ... I am being told that we need more water vapor in the air because of the small hydrosphere of 13%. But with an average global temperature of 7.7 Celsius we are too cold.

The middle of the cloud layer averages about 9.25 km above sea level and are about 2.5 km thick on average.


What is the minimum increase in water vapor percentage and global temperature that will make the the described cloud layer and tropical precipitation work? I would like to remove the SO2 altogether in favor of the water vapor explaining the persistent cloud layer.

Thanks in advance!


1 Answer 1


I'm not sure that you can have both a lower average temperature than Earth and a more active hydro-logical cycle.

Perhaps you could have low lying volcanic regions that locally emit lots of water vapor (and dust for your condensation nuclei - does not have to be SO2). These clouds would then spread out and give you plenty of rain, so you would be all of cold, overcast and raining lots. How you get these features is another matter, some sort of volcanic calderas might be a solution - these could be your 'oceans'.

So.. your moon has several water bodies, all sat in volcanic calderas and heated up by the magma therein - no genuine earth-like oceans. Water vapor evaporating from these caldera give you a permanent cloud layer at it hits the cold atmosphere.

(Sorry if this is all a bit hand-wavy)

  • $\begingroup$ I am totally willing to increase global average temperature... how much are we talking? $\endgroup$ Commented Jul 25, 2017 at 3:20
  • $\begingroup$ I updated the question... sorry for any confusion. The expectation is that we would increase the global average temperature and increase the water vapor percentage and get rid of the SO2 altogether. $\endgroup$ Commented Jul 31, 2017 at 15:28
  • $\begingroup$ Haven't received any more feedback on this question and can't accept the answer that was provided. Posted as a new question: worldbuilding.stackexchange.com/questions/88263/… $\endgroup$ Commented Aug 7, 2017 at 16:20
  • $\begingroup$ @JasonReskin If you feel that the answers provided aren't sufficient and want more attention on your question you should issue a bounty not re-ask the exact same question. $\endgroup$
    – sphennings
    Commented Aug 9, 2017 at 17:52
  • $\begingroup$ @sphennings Sorry, I don't have enough reputation to do the bounty ... so I am kind of stuck. Thanks for the help! $\endgroup$ Commented Aug 10, 2017 at 1:55

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