I'm making a Region of a planet with very high humidity, mostly covered in fog at ground level. I am open to having seasonal changes and would like there to be a few sunny days lets say 1 out of 15, that figure is completely changeable. I need the fog to be pretty thick, thick enough to use Electroperseption for sight and have hydrolysis be used for breathing and getting hydrogen to float. How would I make this work without the planet being entirely underwater? Thanks.

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    $\begingroup$ You're asking a few questions here. Please try to chop it down to one. $\endgroup$
    – kleer001
    Sep 24, 2019 at 20:33
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    $\begingroup$ Having a climate that's uniform enough across an entire planetary surface to produce fog everywhere seems tricky, to say the least. $\endgroup$ Sep 24, 2019 at 20:37
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    $\begingroup$ It should also be noted (by the OP and otherwise) that outside of an actual aquatic environment, electroreception is only useful to the order of centimetres, and would make a poor mechanism for sight. $\endgroup$
    – jdunlop
    Sep 24, 2019 at 20:41
  • $\begingroup$ How Earth-like do you need this planet to be? $\endgroup$ Sep 24, 2019 at 22:43
  • $\begingroup$ The Planet needs to support life, and I would like the human explorers not to be Hazmat suits all the time but if they have to they have to. $\endgroup$
    – WindWelder
    Sep 24, 2019 at 22:55

1 Answer 1



image from Gibbous-Venus-from-Akatsuki
(source: pcdn.co)

Should FOG1 look like Venus, it is because it will in some aspects be similar to it and because this is an image of Venus. :)

FOG1 is a predomenetly metallic (read 90%+) super-earth orbiting a long lived, dim K-Type star. Its planetary attributes are:

$$M = 7,5 Me$$ $$R = 1,3871 Re$$ $$gravity = 3,898 G (38,228 m/s^2)$$ $$Vescape = 26 km/s$$

Its average surface temperature is 320 K (47 °C), just shy of the dreaded runaway greenhouse effect. This is why it's parent star has to be so dim and small, because it will live longer and get brighter slower. Using an M-type star would be even better, but would mean that the planet is tidally locked and I wasn't sure if OP would like that. The low mass of its parent star is also the reason why FOG1 lacks an hydrogen+helium atmosphere. While it should have one due to its temperature and escape velocity making the atmospheric escape of these gases implausible, there was little of these gases around when the solar system formed and the parent star was a flare star in its youth and stripped most of the atmosphere away.

Now how do I create the fog? Firstly FOG1 is an ocean planet with less than ten percent land cover. Most of this landmass are low island continents near the equator. Surprisingly FOGG1 has significantly less water than Earth, but because its gravity is almost four times stronger its profile is flatter than Earth's. The highest mountain is only 2.5 kilometers high due to the higher stresses the rock will be under and the stronger erosion. The surface mostly consisting of water and the high temperatures will make sure that there is a lot of water in the atmosphere, because I optimized the setup to get the optimal vapor pressure out of it. This is why there will be a global cloud cover, resulting in a Venus-like appearance. The equatorial landmasses will be in a zone of maximum evaporation, creating an extremely wet version of tropical climate. Torrential rain, extremely humid air and fog whenever it isn't raining will be the result.

A bonus is that the clouds will and extremely low in FOG1 as the scale hight of its atmosphere will be only 2.35 km instead of Earths 8.5 km. Assuming that the hight of Cumulonimbus clouds can be found at scales with the scale hight, we can find these on FOG1 at min: 128m, avg: 2128m and max: 3410 m. This will give you a continuous oppressive cloud cover which could plausibly envelop all land above 100 m all the time under the right (story appropriate) circumstances.

EDIT1: One could of cause do something similar with a planet of lower mass, trading the low cloud layer for higher mountains. However, I thought that a super-earth would be more interesting to explore. Additionally, this planet might very well be superhabitable. The island continents and shallow oceans will create a lot of room for very biodiverse kelp- and land forests and the oceans might be filled with mighty sea monsters feeding of these very rich marine ecosystems. Incidentally these kelp forests could justify the electroperception you want. Your species lives a semi-aquatic lifestyle. They spend a lot of time in the water of the kelp forests where their electroperception is really useful as the environment makes vision somewhat impractical. However, they rest and live on the shoreline as the dangerous and numerous sea-borne predetors can't reach them there. Their electroperception is useless there and limited to a range if centi or decimeters, but they can rely on other senses.

  • $\begingroup$ Thank you for this, this helps a lot. did you use a program which one? if not id like to pick your brain a little bit about FOG1. Can Humans breath on it? would there be any Sunny days? what would the Seasons look like? Email in Bio for more questions. $\endgroup$
    – WindWelder
    Sep 28, 2019 at 16:07
  • $\begingroup$ I didn't use a program, though I used the notes on the matter I've collected in order to write such a program in the future. Go ahead, ask your questions. Do you prefer to do this via Email or here in a chatroom? $\endgroup$ Sep 28, 2019 at 20:03
  • $\begingroup$ let's do it here, help people out. fire away. $\endgroup$
    – WindWelder
    Sep 28, 2019 at 20:06
  • $\begingroup$ The seasons will depend on the axial tilt and, if high enough, the eccentricity. My answer here goes into some detail about seasons. I would recommend sticking with a low axial tilt for this planet, as seasonal variation would mess up the fog generation. $\endgroup$ Sep 28, 2019 at 20:27
  • $\begingroup$ This answer of mine here gives you the limits of gasses in the atmosphere a human can breathe. For FOG1 I think a thick atmosphere of 5 to 15 atm is very appropriate. Most of it will be nitrogen, thus nitrogen will be the limiting factor. Humans may stay on planets for several days, but will act like drunk idiots due to nitrogen narcosis. Oxygen is probably at the wildfire limit, water vapor will be high and volcanic gasses like CO2 and SO2 as well, as the planet will have a lot of vulcanism due to its immense internal heat budget. $\endgroup$ Sep 28, 2019 at 20:47

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