I got to thinking a simple throwaway thought on this video where this dude flushes mercury in a toilet (in a closed loop)

For one thing, it's easy to think about the properties of mercury (mostly its density) but actually seeing it is really mind blowing. But the imagery of a silver fluid flowing into a toilet bowl instead of something mundane like water gave me that initial thought.

Then it stuck with me. I know it's probably unlikely that it'll be used in a similar function to blood, though given the sheer scale of the universe, you never know, but if elemental mercury were to be in a given alien's physiology, what kind of materials would their bodies be made of to allow for such dense fluid to be able to flow. And would gravity on the planet have to be lower or something?

Would it even be plausible for living creatures or would it be more likely for something artificial?

I'm not even worried about why it'd be used analogously to blood. I'm just wondering what would have to happen for it to be used in the first place.

Although for the artificial argument, there are numerous electrical applications for mercury, though I'm not sure it's for the liquid form.

  • $\begingroup$ Don't feel like writing up an answer but here is where I'd get the base info from. Hope someone expands on this. zmescience.com/science/purple-non-sulfur-bacteria-mercury $\endgroup$
    – Durakken
    Oct 8, 2016 at 0:54
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    $\begingroup$ Mercury is highly toxic; if ingested on small scale it can cause organ damage/failure, blindness and over all death; it's one of the main reasons why thermometers don't contain it any more, so that people don't accidentally die from dropping one. $\endgroup$ Oct 8, 2016 at 0:56
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    $\begingroup$ I think if these magnificent alien creatures do exists their main reason of being(living) is to become a thermometer! $\endgroup$
    – user6760
    Oct 8, 2016 at 4:07
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    $\begingroup$ Mercury would not be highly toxic though to an animal that was built with mercury as one of it's living components. Our blood could be toxic to aliens from other planets (if there are any).You're probably gonna need a real scientist/chemist/biologist to answer this question. I think it would take me weeks to give a proper answer. $\endgroup$
    – X_Wera
    Oct 8, 2016 at 5:14
  • $\begingroup$ its plausible that if you had a planet with large pools of mercury on the surface that extremophile bacteria could survive, but its toxic and not a lot of substances that are useful to organisms can be dissolved in it. but remember the golden rule: if you want to do it for a novel, then do it $\endgroup$ Oct 8, 2016 at 10:20

1 Answer 1


There's a big problem here: The whole point of a circulatory fluid is to transport things around the body. Mercury isn't a very good solvent to use to do such transporting, nor is it exactly friendly to hauling around cells.

Now, if you want circulating mercury in a creature how about a different purpose? Lets look at some sort of space-based life. Spacecraft use reaction wheels to orient themselves, that (the wheel) is a gap that evolution has shown little ability to cross. Instead, lets have three (or perhaps more) vessels in the creature filled with mercury and with a simple pump mechanism. Slow and wasteful compared to a proper reaction wheel but it would get the job done and give a reasonable biological purpose for a mercury-filled tube in the creature.

  • $\begingroup$ This might be the most creative answer I've seen yet on this site. $\endgroup$
    – kingledion
    Oct 9, 2016 at 0:29
  • $\begingroup$ Thank you. That's exactly the kind of possible explanation I was looking for, $\endgroup$ Oct 9, 2016 at 23:13

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