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I am trying to create an organism that can survive in space for short periods, but I realized that I can't have its eyes be similar to those of most animals and humans because they would boil in space.

Is there some sort of alternative for eyes that do not boil in space?

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    $\begingroup$ What makes sth boil in space is a combination of high temperature (if exposed to the star's radaition) and low pressure. If membranes are strong enough, everything inside that membrane could be kept presurized liquid. $\endgroup$ – Rafael Jun 5 at 20:16
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    $\begingroup$ That is an idea, but would it mess with the optics? $\endgroup$ – Efialtes Jun 5 at 20:17
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    $\begingroup$ Without an atmosphere to offer counter pressure, the eye would probably become more spherical which would mess with the optics if the eye had a raised cornea like people do. However, if the alien's eyes start off spherical, the distortion should be minimal. $\endgroup$ – Nosajimiki Jun 5 at 20:34
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    $\begingroup$ @Rafael: Insect eyes do not have liquid surfaces exposed to the exterior, and they don't have large-ish liquid-filled cavities either. $\endgroup$ – AlexP Jun 5 at 21:33
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    $\begingroup$ Are you only looking for vacuum-resistant eyes? Or must we design eyes that can handle unbuffered sunlight and other radiation? $\endgroup$ – JBH Jun 6 at 15:36

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Grow you some extra-tough nictitating membranes... eyelids you can see through! You'll probably have to deploy them with a bit more ceremony than merely a sideways-blink... you might have to secrete some gloop around the edges to form a seal, wipe them dry with your paws to prevent any frost forming and interfering with your vision, that sort of thing, but there's no reason that with enough effort they couldn't be made to work.

The eye won't suffer any serious ill effects if it remains well protected behind a membrane which won't itself boil or freeze-dry. Your vision will be distorted, sure, but it beats the alternative and you'll be able to operate with some minimal level of functionality. Think about how well your eyes work underwater without the aid of goggles or a mask, for example.

nictitating membrane

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    $\begingroup$ Not even any need for the vision to be distorted if the membrane is more of a rigid plate. $\endgroup$ – Joe Bloggs Jun 6 at 5:59
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    $\begingroup$ @JoeBloggs rigid plates need room to move in. But a thin spherical layer should work just as well without lensing significantly. $\endgroup$ – John Dvorak Jun 6 at 9:48
  • $\begingroup$ @JohnDvorak: Yeah, I was envisioning having a cavity in the skull into which the plates could slide. Or maybe even just being a fixture. :D $\endgroup$ – Joe Bloggs Jun 6 at 10:33
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    $\begingroup$ Note many animals have nictitating membranes that are quite transparent and won't affect vision a noticeable amount. $\endgroup$ – John Jun 7 at 0:12
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Barreleyes, a.k.a. spook fish, have their eyes well inside their heads. They can see just fine, because their heads are transparent.

Their eyes are the green structures you can see below:

Barreleyes A.k.a. spook fish

Such a configuration might be helpful in a hard vacuum.

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    $\begingroup$ Fits the space theme with the cute astronaut helmet $\endgroup$ – XenoDwarf Jun 5 at 20:44
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    $\begingroup$ boredpanda.com/… $\endgroup$ – Sobrique Jun 6 at 9:05
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    $\begingroup$ Please reference images you are using/ $\endgroup$ – Mołot Jun 6 at 11:50
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    $\begingroup$ That is the coolest thing I've seen in a while. How on earth did such a creature evolve? $\endgroup$ – JBH Jun 6 at 15:34
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    $\begingroup$ @Mołot I found these images are under copyright by The Monterey Bay Aquarium Research Institute (MBARI). See Researchers solve mystery of deep-sea fish with tubular eyes and transparent head. $\endgroup$ – Theraot Jun 7 at 21:13
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The extinct organisms known as Trilobites had compound eyes which had lenses made of calcite crystal.

This hard mineral layer would protect the sensory cells underneath from exposure to space.

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    $\begingroup$ Ok, calcite crystal eyes. That's awesome. $\endgroup$ – Draco18s Jun 6 at 21:19
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I can't have its eyes be similar to those of most animals and humans because they would boil in space

That's not true. Regular eyes don't boil in space (vacuum). The whole boiling/blowing up thing is mostly Hollywood imagination. Humans and other animals can survive unprotected exposure to vacuum for minutes unharmed even though none evolved to this environment. https://www.scientificamerican.com/article/survival-in-space-unprotected-possible/ Your requirements can be fulfilled with only minor adaptations.

The biggest problem with eyeballs is not the water contained inside, but the tear film on the outside - this would boil leaving eyes dry. As every liquid boils in vacuum, you need eyes that can work when dry, externally. So, snake eyes. Their transparent lids are always closed, protecting the layer of liquid an eyeball can slide on.

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  • $\begingroup$ +1 for the snake eye idea, but do notice that eyes can tear and pop im a vacuum. In some places of the world sick dogs are disposed of not through lethal injection, but in a vacuum chamber. Their eyes puff and tear. $\endgroup$ – Renan Jun 8 at 3:57
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Eyes work in space. If they didn't, astronauts couldn't see. Seems kind of what you're looking for is a strong transparent layers that can insulate the eyes. Which leads me to a question - what's the rest of the alien made out of? I assume this animal has got some sort of non-living organic shell, similar to crustaceans. In which case all this animal needs is the transparent variety.

The best thing I would suggest is a layer of clear fat cells (for insulation), followed than by a formerly organic layer of clear shell.

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    $\begingroup$ This should be a comment, not an answer $\endgroup$ – infinitezero Jun 6 at 12:17
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    $\begingroup$ Actually, with a bit of fleshing out this is an answer. My cat has an inner eye lid. Halfthawed is simply proposing a transparent, protective eyelid that could protect from the vacuum of space. Clever idea, but it does need further explanation with examples of transparent secondary lids in nature. $\endgroup$ – JBH Jun 6 at 15:33
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Nautilus is an ocean-based macroorganism (mollusc) which has pinhole eyes. This means they function without any liquid water inside, and can survive some time in space. They're not very good as eyes go, but then again many mammals don't rely on eyes that much.

Nautilus

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    $\begingroup$ I feel like this works but a space fairing creature would probably need massive, sensitive eyes. $\endgroup$ – XenoDwarf Jun 5 at 20:48
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    $\begingroup$ @XenoDwarf the only requirement here is to "survive in space for short periods". That doesn't necessarily need vision at all, just the ability to turn around and cycle the airlock you just got flung out of, which could be done with touch alone. $\endgroup$ – Starfish Prime Jun 5 at 20:50
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Go with gecko eyes, they have eyes like any other vertebrae, better than humans, except they have a solid transparent scale (literally called spectacles or eyecaps) that grows over it. So there is no exposed fluids. That is why they occasionally have to clean it by licking, no external fluids. Snakes and a few other reptiles have a similar scales but gecko have both eye caps and eyelids.

this will give you all the same functionality of a human eye without the exposed fluids.

enter image description here

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Ever heard of tardigrades (water bear)? They're a microanimal known to survive exposure in space (extreme temperature, pressures, and radiation. I don't know if it can be scaled up, but they have sensory bristles and rhabdomeric pigment-cup eyes.

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    $\begingroup$ Sensory bristles would be useless in a vacuum $\endgroup$ – XenoDwarf Jun 5 at 20:43
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    $\begingroup$ @XenoDwarf you could still touch stuff. So long as you were in contact with a solid object, either directly or via a tether, you could navigate around it "blind", so you're not entirely helpless. Remember also that the bristles woudl work regardless of ambient light, unlight eyes. $\endgroup$ – Starfish Prime Jun 5 at 21:12
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    $\begingroup$ @Xenodwarf: Some spiders have sensory bristles theoretically sensitive enough to detect the force applied by light. Cool fact about spiders number 1057. $\endgroup$ – Joe Bloggs Jun 6 at 6:02
  • $\begingroup$ Tardigrades can survive anything...except everything they're actually likely to encounter in their short, 1-year, lifespans. Its kind of hilarious. TierZoo on the subject. $\endgroup$ – Draco18s Jun 6 at 21:21
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    $\begingroup$ the writers of Star Trek: Discovery think that tardigrades could be scaled up: memory-alpha.fandom.com/wiki/Tardigrade_(alien) $\endgroup$ – dlatikay Jun 7 at 16:24
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You might consider diatoms https://en.wikipedia.org/wiki/Diatom which have the ability to deposit silicon dioxide in their cell walls. They can be transparent, or have structural coloration due to refraction of light. Extend that ability to deposit SiO2 to multi-cellular creatures, and you can have them evolve quartz lenses, prisms, and perhaps even mirrors, all of which form the basis of human optics.

So your SiO2-depositing* creature can capture and focus light. Now all you need is some sort of sensor that works in vacuum. Now since your organism already manipulates SiO2, it isn't stretching credibility to imaging that it could evolve something like a CCD or CMOS sensor, as used in digital cameras.

*Note that I'm not suggesting silicon-based life here, just ordinary carbon-based life that can also manipulate SiO2 at the nanoscale.

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I feel like boiling isn’t the main problem, especially since others here have mentioned physical layers. Keep in mind that this physical barrier would probably require pigment to absorb UV radiation so it doesn’t burn out the retinas/corneas depending on visual spectrum.

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    $\begingroup$ In a pinch, you could always go for the "don't stare directly into the naked fusion reactor" approach, and you'll probably get away with a bit of photokeratitis from reflections (which, incidentally, is a sunburnt cornea, not retina, because the front bits of your eye are already quite UV opaque). A personal magnetic field will not save you from UV, and it won't do much good against cosmic radiation either. Probably not worth it. $\endgroup$ – Starfish Prime Jun 5 at 21:02
  • $\begingroup$ Fair point @Starfish Prime $\endgroup$ – XenoDwarf Jun 5 at 21:06
  • $\begingroup$ That said, this being a xenobiology question and all, it probably doesn't do to make assumptions about whether the species in question sees into the UV spectrum. If they did, they would have to worry about burnt retinas and that's potentially a lot more serious than burnt corneas. $\endgroup$ – Starfish Prime Jun 5 at 21:10

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