Recently, I have gained an interest in silicon-based lifeforms. I heard mentions here and there that if they exhaled silicon dioxide, they would exhale a fine dust or solid rather than a gas. Now, the science behind this is beyond me besides silicon dioxide being a solid, and I don't seek to try my hand at silicon lifeforms as of yet. But, it was still an idea that caught my inspiration.

I want to know why a carbon-based lifeform that breathes oxygen and exhales carbon dioxide, such as life on Earth, may exhale dust rather than gas, or at least appear to exhale dust. It doesn't necessarily have to be what it exhales if you have a creative idea, but ideally it should be a substitute for carbon dioxide gas. Bonus for mentioning the ramifications and bonuses of this.

So, in quick summary, why might a carbon-based lifeform breathe dust rather than gas?


2 Answers 2


It lives in the Desert and has a Looped Digestive system:

Organisms have evolved some really extreme adaptations to improve survival in desert conditions. Your organism is a little more extreme than most.

Your organism retains all the moisture it can. Its skin is completely sealed, and it has evolved a digestive system that routes its excrement back to the one open orifice on its body - its mouth. The problem is that this creature still generates solid waste, but it is so dry as to consist of a fine powder by the time the thing is finished extracting the last of the water in the final waste chamber. It also "eats" damp soil into this chamber in the morning, extracting morning dew from the ground.

its lungs discharge into an internal moisture-absorbing chamber to remove any moisture that might be lost breathing. In order to actually excrete their dry, powdery solid waste mixed with sand ans soil, this secondary air drying chamber then blows into the solid waste chamber and is used to blow the solid waste out of the chamber and out the mouth. So your organism is, in fact, expelling dust from its mouth as it exhales.


It's below -78.5 °C. That's the freezing point of CO2. Note that at normal atmospheric pressure CO2 transitions directly from gas to solid. Upon exhalation, the CO2 would probably precipitate as a fine snow.

  • 3
    $\begingroup$ Cold, man. That answer's just cold. $\endgroup$
    – DWKraus
    Oct 15, 2021 at 20:53

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