The atmosphere have ~1 atm pressure at sea level, It does have water ocean maybe 10-30% of the surface, also it supports tectonic plates so the carbon cycle does work, and the Ocean is made mainly of H2O with traces of H2CO3 since it will absorb some CO2, The day is ~42 hours so will cause a lot of water to evaporate.

So based on that: I thought of this atmosphere: 89.5% N2 1-2% H2O 1-3% CO2 2-5% argon (CO2 and Argon changeable choose any percentage for them) 0.5% other gases

Is it plausible with Earth-like temperature? if no how could a planet lose its CO2 and how could it support an H2O ocean with no problems, and will it be safe for the human skin? so u could walk there with just an Oxygen mask?

  • $\begingroup$ Where did the Carbon chemical compounds containing oxigen come from ? Outer space ? Or did the O2 all vanish into outer space, or was it used up, at some point ? What caused that.. $\endgroup$
    – Goodies
    Aug 13, 2021 at 10:42
  • $\begingroup$ @Goodies Do u mean CO2? by volcanoes, I know that carbon is very abounded in the universe, and Atomic Oxygen is extremely active, it will react with Hydrogen before it leaves the atmosphere, then it will react with Carbon, feel free to change the atmosphere. as long as the H2O or N2 are the dominant gases. $\endgroup$
    – Khalid
    Aug 13, 2021 at 10:58
  • $\begingroup$ I asked because your proposed atmosphere contains about 1000x the amount of CO2 the earth atmosphere has. The atmosphere you propose resembles Earth's atmosphere of 2-3 billion years ago, before the Great Oxidation event, caused by photosynthesis by early cyano lifeforms. When your planet is a very young planet with lots of vulcanism, asteroid impacts and without life, other conditions would probably inhibit walking around there with just a simple mask.. $\endgroup$
    – Goodies
    Aug 13, 2021 at 13:17
  • $\begingroup$ 5% H2O would be steamy. This corresponds to 100% humidity at about 33 C - approximately the conditions of a Turkish bath. $\endgroup$
    – Alexander
    Aug 13, 2021 at 16:52
  • $\begingroup$ @Alexander I made the H2O changeable to 1-2% $\endgroup$
    – Khalid
    Aug 14, 2021 at 6:46

1 Answer 1


Is it plausible? Yes.

Some concerns:

  • If there is Cyanobacteria, it might be anaerobically converting your atmospheric CO2 to O2 over long time scales.

  • Solar wind may be stripping the planets atmosphere and oceans over long time scales

  • I wonder if you can keep the ocean from flipping to carbonic acid.

  • You might possess some kind of cool carbonic acid cycle, where the ocean evaporates and some portion of the humidity is converted by solar radiation and the atmosphere to anhydrous carbonic acid. Then carbonic acid rain falls on the oceans which reduces it back to CO2 and water

  • Keeping with the carbonic acid cycle thought : the carbonic acid, being denser, will sink below the water; leaving a pure water surface exposed for pickup by dry air. The deeper carbonic acid rain would decompose in the presence of water to CO2 and water, causing bubbles, or just a very high concentration of dissolved CO2

  • $\begingroup$ It's a double-planet system so it will have a strong magnetic-filed since both magnetic fields will merge, so I don't think SolarWinds will be able to strip the ocean, thanks for those Ideas. $\endgroup$
    – Khalid
    Aug 14, 2021 at 12:13

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