I have been designing a planet with an atmosphere of about:

  • Nitrogen (N2) - 61.5%
  • Oxygen (O2) - 21%
  • Neon (Ne) - 15.5%
  • Xenon (Xe) - 1%
  • Water Vapor (H2O) - 0.5%
  • Argon (Ar) - 0.479%
  • Carbon Dioxide (CO2) - 0.02%
  • Trace - the rest

The atmospheric pressure is 0.98 atm.

I have quite a high level of xenon in my atmosphere, and it dissolves in blood and can penetrate the blood-brain barrier, so do you have any ways for my lifeforms to not fall asleep on this planet? Would having strong wind currents that distribute and move the xenon be enough?

  • 4
    $\begingroup$ Can you give a source on the harmful effects of Xenon? Afaik, the major danger of breathing xenon would be asphyxiation (or milder hypoxia symptoms) due to oxygen displacement. Otherwise, xenon is chemically inert, and so long as you don't go anywhere low with long periods of no air movement (caves, wells, etc) it shouldn't be an issue or noticeable. $\endgroup$
    – Dragongeek
    Commented Sep 4, 2023 at 14:12
  • 2
    $\begingroup$ pubs.asahq.org/anesthesiology/article/92/3/865/39666/… $\endgroup$
    – Slarty
    Commented Sep 4, 2023 at 15:11
  • 2
    $\begingroup$ To clarify, because I think it's causing confusion: all inert gases act as anaesthetics on humans, as do other soluble unreactive gases (notably nitrogen). AFAIK the mechanism is not fully understood – obviously there's no chemical reaction in the high-school chemistry sense (involving change in oxidation state), but inert gases can still interact sterically and via van der Waals forces etc., so it's not that mysterious. It's nothing to do with hypoxia – you can breathe normally while knocked out by argon or xenon. $\endgroup$
    – bobtato
    Commented Sep 4, 2023 at 18:58
  • 5
    $\begingroup$ Xenon Anesthetic Hazard: great name for a metal band. $\endgroup$
    Commented Sep 4, 2023 at 21:09
  • 6
    $\begingroup$ Note that we're all suffering the effects of nitrogen narcosis all the time when breathing regular atmosphere: pubmed.ncbi.nlm.nih.gov/1130736 $\endgroup$
    – llama
    Commented Sep 4, 2023 at 23:11

2 Answers 2


Xenon is a hazard to terrestrial lifeforms because we do not live in an atmosphere with any appreciable amount of xenon. Any lifeform that evolved with it would have adapted to its presence.

Indeed, it may be dependent on having a certain amount of xenon in its system. For instance, although xenon is chemically inert, it could slow down chemical process by being between two chemicals that would otherwise react. An absence of xenon might increase these reactions by a dangerous fraction.

  • $\begingroup$ So you are saying that if my lifeforms lived on a world with lots of xenon, they would adapt to its presence and may even use it in their body chemistry? $\endgroup$
    – Neil Iyer
    Commented Sep 4, 2023 at 17:16
  • 1
    $\begingroup$ "Slow down chemical process": This what a buffer gas does. On Earth, the buffer gas is nitrogen, which is quite inert chemically. Yes, xenon would work as well. $\endgroup$
    – AlexP
    Commented Sep 4, 2023 at 18:04
  • $\begingroup$ @NeilIyer Yes. Its chemical uses are, of course, very limited, but life is ingenious. $\endgroup$
    – Mary
    Commented Sep 4, 2023 at 20:21
  • $\begingroup$ @AlexP Wouldn't I then have multiple buffer gasses, including argon, neon, xenon, and nitrogen? $\endgroup$
    – Neil Iyer
    Commented Sep 4, 2023 at 20:58
  • 3
    $\begingroup$ Nitrogen is the main buffer gas on Earth and nitrogen, not xenon, would be the main buffer gas in your fictional world, as well. The effects of removing or adding some xenon would be about the same as the effects of removing or adding the same amount of nitrogen. It is not dangerous to remove a few percent of nitrogen from the air a human breathes. (We can breathe pure oxygen if we want, though this does cause some damage.) And so, it would not be dangerous to remove a few percent of xenon from the air on this planet. $\endgroup$
    – causative
    Commented Sep 4, 2023 at 22:45

You do not need an extra explanation at all. A 1% concentration of xenon is not enough for there to be any detectable effects on humans or similar lifeforms, so explaining it away with adaptation would be unnecessary. It's hard to say at what concentration a human would experience noticeable effects, but judging by its potency relative to nitrous oxide the threshold is probably between 10 and 15 percent.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .