The key concept of my storybook world is vast and sweeping incompatibility with all things terrestrial. But that is only the backdrop, it is not my question (before we head out on too many tangents).

So I wanted to give my biology a lot of metabolic energy to play with. For our planet, that is mostly adenosine triphosphate (ATP). The first thing that came to mind was, something that oxidizes much more powerfully than oxygen itself, and that is really bad for things with water, beaches, salts, metals, and, well; anything with an ion out of place. So, why not chlorine trifluoride? That checks all my boxes.

Now a metabolism needs to make walls for its stuff, to keep the anabolic stuff away from the catabolic stuff. For us, walls are called cell walls, and they have these crazy amphipathic molecules that can do the sorting out of positive and negative charges. They're called lipids.

That's the gist of what I want to know. Basically, some sort of lipid-like analogue to handle moving a chlorine trifluoride-based energy carrier around. My hunch told me that something in the organolithium inventory could dream up such a workhorse. But I'm at 10,000 feet on this and don't know the math here.

The simplest way to state the question then, can an amphipathic molecule exist to handle my little chlorine trifluoride-blooded critters?

We'll save the discussion of what their bananas are made of for another post.

  • $\begingroup$ So the cool thing about worldbuilding is that you can always just say "X exists in my world". If you want a checks notes amphiphathic molecule that can work with chlorine trifluoride-based critters to exist in your world, then you just say "in my world there exists a amphiphathic molecule that can work with chlorine trifluoride-based critters". Especially if you don't know enough about the subject, it's better to avoid trying to explain it at all, rather than stumble through a poorly thought out explanation. $\endgroup$
    – sphennings
    Mar 3, 2022 at 18:26
  • $\begingroup$ There is that. My doctor said to really watch my handwavium count, so now I read the labels on everything to see if it’s science-based approved first. $\endgroup$
    – Vogon Poet
    Mar 3, 2022 at 18:50
  • $\begingroup$ If you stop the explanation at "life on this planed uses chlorine trifluoride" you will be handwaving less than if you try to explain how it used it. Think of it as reducing the surface area for scrutiny. If you say "It just is" there is only how the thing integrates into the rest of the world to scrutinize. If you explain how something works, then in addition to how the thing relates to the world, there's also your explanation that is open to potential failures. Sort of like how it's easier to just say 1 + 1 = 2 rather than take a massive detour through set theory to prove how 1 + 1 = 2. $\endgroup$
    – sphennings
    Mar 3, 2022 at 18:54
  • $\begingroup$ Oh I completely understand the dangers of over-engineering your world “in canon,” but most of the concepts I pull here will never hit a page. They exist only to help me understand the reader who might say, “What? Not in this universe you didn’t!” Say I want an evacuated airship on, well, Venus, (because they do it on mars, so..) But I don’t know about pressure. The book just gets “And they flew away in their evacuated balloon.” That sort of kills the story. So I ask, and change the balloon, and don’t kill the story. No explanation gets to the reader, but they’re spared a big shock. $\endgroup$
    – Vogon Poet
    Mar 3, 2022 at 21:09

2 Answers 2


It's not as though lipids are the secret sauce for being able to use oxygen; in humans, oxygen is bound to hemoglobin immediately it enters the body, and I would imagine any organism that uses small, toxic molecules would use a similar strategy, rather than having oxygen (or ClF3) just generally dissolved in your tissues.

If you said your organisms had some metalloenzyme that chelates a ClF3 molecule, I would accept that. But if you wanted me to really read this with my chemist hat on, then no, I'm not buying that any kind of Earth-analogous chemical life could exist in a ClF3 atmosphere (or even just a fluorine atmosphere). It's barely less harsh than breathing stellar plasma.

The secret to a convincing lie ("fiction") is the right amount of detail; a sprinkling makes the story feel real, but too much calls attention to how it isn't. So I'd say, by all means mention some science-y stuff in passing, but you don't want to invite a full audit on this one.

(The reason it's hard to see fluorine as a biological energy source is that the elements used by terrestrial life were carefully chosen to be reactive, but not too reactive. Fluorine's reactions tend to be irreversible, when what you need is versatility – it's like, if Lego was based on metal bricks you had to weld together, it wouldn't have lasting play value)

  • $\begingroup$ Granted also, Does raise the question of what’s doing the job of water. $\endgroup$
    – Vogon Poet
    Mar 4, 2022 at 2:42
  • $\begingroup$ OK I think I get what you're saying. ATP breaks down in small increments of energy just right to do whatever folding it needs to do at the time. Say it's building an RNA. Too much energy and you snap the chain; too little, the whole operation fails. Finesse. But that just means it's calibrated to fold terrestrial organics. A ClF$_3$ bond energy with say, hydrogen, is too much energy (welding legoes). No question. But in that environment, you need a receptor with a high Gibbs free energy; the $\Delta$e calibrates like here, just right to fold. OK, high energy proteins? Thermodynamics no likey ? $\endgroup$
    – Vogon Poet
    Mar 4, 2022 at 5:17
  • $\begingroup$ No not likely. It seems there are organic compounds which don't explode on contact or burn vigorously but, RNA, DNA, fats, proteins and carbohydrates are not those sort of compounds. $\endgroup$
    – Slarty
    Mar 4, 2022 at 8:20

You can define whatever you want in fiction, but in reality a chlorine trifluoride life form is not a feasible proposition.

I have just finished reading John D. Clark's book "Ignition" (and informal history of liquid rocket propellants) And the book describes (pages 66-67) attempts at using ClF3 as a rocket oxidizer. Superficially it sounds good - a greenish liquid that boils at 12 degrees C and freezes at a convenient -76 degrees C with a nice fat density of 1.81 at room temperature. But the rest is a disaster.

"it is of course highly toxic, but that's the least of the problem. It is hypergolic with every known fuel and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood and test engineers, not to mention asbestos, sand and water"

It also mentions the destruction of 12 inches of concrete and the gravel below during an accident, the horrors of metal-fluorine fires and a list of other materials destroyed by ClF3 - oil, grease and that no organic material could be restrained from ignition other than Teflon, but even Teflon eroded away like sugar in hot water if ClF3 flowed over it even if it didn't ignite.

Good luck

  • $\begingroup$ This was the intended reaction on earth. Yes, I knew it sets asbestos and water on fire on contact. You have to admit, great molecule to store energy! $\endgroup$
    – Vogon Poet
    Mar 3, 2022 at 22:53

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