The theoretical world of Hēdran is the 2nd planet of a 7 planet system. It lies within its star' s (a G1.4) habitable zone, but with a hot jupiter gas giant only ~1 AU away it experiences heavy gravitational flux (this will be important later).

Hēdran is the remnants of a carbon planet and as such it is already rich in hydrocarbons, but for the majority of its life is has been an oxygenless barren world. Until planetary drift occurred bringing one of he gas giants to the innermost orbit. Hēdran was spared annihilation but was instead seeded with liquid water and other chemicals necessary for life.

Now eons later it maintains an atmosphere slightly different to our own

  • N2 68.8%
  • O2 24.8%
  • CO2 3.23%
  • Neon 1.02%
  • Argon .94%
  • N2O .17%
  • Trace gasses consisting of SO2, CH4, water vapor, ect...

As mentioned before the planet receives more than the usual amount of gravitational flux due to the close gas giant. This has caused an increase in volcanism and geological activity. This is how I explain the replenishment of gasses such as SO2 and N2O, also a unique property of the planet is that it is inherently high in metals.

How these conditions might affect life will come in another, later, question.

Atmospheric Content Physical Characteristics

Main question at hand

I am aware of the acidification effects of CO2, N2O, and SO2 would have on my world's oceans. From my limited chemistry knowledge this would not prevent life from happening. Is this a correct assumption?

Thank you to any and all who reply as I'm slowly refining my idea into something that feels real.

  • $\begingroup$ Hi, it's clear that you've put in significant effort. However, this post violates the site rule of strictly one question per post and will get closed in short order. I don't think any of the three individual questions at the end would be a problem, far from it. May I suggest you break them out into three posts? You could even duplicate most of the text. $\endgroup$
    – user86462
    Aug 25, 2022 at 10:05
  • $\begingroup$ Re: CO2, it's hard to imagine almost any amount of CO2 rendering life impossible at earthlike temperatures and pressures. As a weak acid, it just doesn't push pH down that far. $\endgroup$
    – user86462
    Aug 25, 2022 at 10:07
  • 1
    $\begingroup$ @SeanOConnor thank you, I will edit accordingly and make separate posts. Apologies for rule breaking $\endgroup$ Aug 25, 2022 at 10:17

2 Answers 2


No, re: CO2 you'll be fine. CO2 is a weak acid. The pKa of CO2 is 6.35; you'll never go much lower than that in pH without other acids pulling it down. If anything, plants will love it.

The only thing is to make sure your planet's temperature remains amenable to life; there are lots of calculators out there that you could plug 3% and a given pressure into. Pretty sure it's not a huge problem though.

All this assumes Earthlike atmospheric pressure. As a commenter has pointed out, with high enough pressure, you'll start to get quite low pH.

  • $\begingroup$ At high pressures, CO2 depresses the pH of water as low as 3. Probably not relevant here, but there's a strong drop that occurs right around 1 bar of CO2. $\endgroup$ Aug 25, 2022 at 15:56
  • $\begingroup$ @LoganR.Kearsley Interesting, I'll edit to mention I assume earthlike pressures. $\endgroup$
    – user86462
    Aug 25, 2022 at 19:19
  • $\begingroup$ @SeanOConnor Appreciate the input, I've added more information for reference to my planet. $\endgroup$ Aug 25, 2022 at 23:49

Acidity is not inherently inimical to life, no. It does, however, change the details of exactly which macromolecules are more or less stable than others. This leads to two different adaptation strategies for Earthling acidophiles: most use proton pumps to maintain a neutral interior environment despite living in acidic conditions, but some (such as acetobacter) have modified proteins that operate in an acidic intracellular environment. The fact that that is possible indicates that life should have no problem developing in acidic conditions to start with.

Of particular interest is that RNA is more stable against hydrolysis in acidic conditions. (Its maximum stability occurs between pH 4 and 5 at 90C.) A biosphere that developed in an acidic ocean might thus end up using RNA rather than bothering to develop DNA, or at least make greater use of ribozymes and less use of protein enzymes than we do.

  • $\begingroup$ Thank you, this will be useful in the biology development stage. I've added more info for reference to my planet. $\endgroup$ Aug 25, 2022 at 23:51

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