This lifeform is a carbon based humanoid that uses ammonia instead of water, breathes chlorine gas, and its body uses the mineral olivine to toughen its skin. Its blood is blue; apparently an ammonia-copper mix would be that color. The temperature is colder than the earth average, and there is enough atmospheric pressure to allow the mineral olivine to form on the surface. I know the boiling point of things is dependent on pressure levels. These creatures are good swimmers in the ammonia seas and semi-aquatic. I asked about this creature in another question about why it might have olivine in its skin.

Would these elements work well together? If not, which ones should be changed and which elements would be better to use under the conditions that this creature is a good swimmer and has olivine in it's skin and the pressure is strong enough for olivine to form on the surface?

How would that much pressure effect its body structure?

  • $\begingroup$ @Bitter dreggs thanks I'm not really that knowledgeable about what tags apply to different questions. $\endgroup$ Jan 29, 2020 at 21:42

1 Answer 1


Sinks Like a Stone

There are a lot of potential issues here, but the first one I can see is the discrepancy between a carbon-based lifeform with olivine skin and "good swimmer in the ammonia seas".

Ammonia, even under low pressure (and extremely low temperatures) has a density at best three-quarters that of water. Though using ammonia in their bodies in place of water will reduce the density of your creatures to an extent, carbon constructs and olivine will result in a creature that cannot swim, unless they have specific adaptations (rigid voids, given the pressures required) to allow them to do so.

It's also worth noting that chlorine gas is very reactive, and reacts vigorously with ammonia, so while the reaction may be dampened by very cold temperatures, it's hard to imagine much free chlorine in the air of a planet with ammonia seas.

Oxygen is nonreactive with water, which is why it can be used as an oxygen-carrying medium for water-breathing creatures, and serves fine as the primary component of blood plasma. I can't see how it would work in your creature if they're breathing chlorine gas and have liquid anhydrous ammonia in their veins.

Edit for clarification: as indicated on the linked charts, anyhydrous liquid ammonia is less dense at greater pressures, because of the corresponding higher temperature at which it can be liquid. Yet another place where the weird properties of water make it somewhat unique as the fluid of life.

  • $\begingroup$ then what elements would allow for a swimming rock armored creature with pressure that would allow olivine to form at the surface? $\endgroup$ Jan 30, 2020 at 1:03
  • $\begingroup$ Depends on what you're willing to give up. You'd have to give up the chlorine atmosphere, for a start, since olivine needs oxygen in its molecular structure, but free oxygen would result in the formation of hydrochloric acid (hydrogen isn't going to be missing, and aqueous HCl would then form), which degrades olivine. If you're willing to let the olivine be a later addition (rather than something in the creature's skin), it could reasonably be something much more earthlike. $\endgroup$
    – jdunlop
    Jan 30, 2020 at 1:17
  • $\begingroup$ (Also, if water is present, the anhydrous ammonia would become aqueous ammonia in at least some cases, prompting a different reaction with free chlorine that would result in dense clouds of white vapour... and also the consumption of one or the other reagent.) $\endgroup$
    – jdunlop
    Jan 30, 2020 at 1:21
  • $\begingroup$ So oxygen atmosphere okay. Instead of ammonia instead of water, what's a denser liquid to allow olivine armored creature to swim that is liquid at olivine forming pressures? $\endgroup$ Jan 30, 2020 at 1:22
  • $\begingroup$ What are those pressures? I've been unable to find any description of olivine forming anywhere but the upper mantle, which is not a place known for having pressures readily duplicated by anything resembling a terrestrial atmosphere - particularly if it has to make up for lower temperatures! $\endgroup$
    – jdunlop
    Jan 30, 2020 at 1:29

You must log in to answer this question.

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