These little guys have no conception of light, the sea floor, or the existence of a surface. Any aliens we could cross paths with are probably more relatable.
I assume they have some conception of light, they have eyes[0], and emit bioluminescent mucus. I'm assuming that their conception is "light = danger".
Although I can't find any info if they're one of the blind species of polychaetes. This paper[1] implies they have photoreceptors (I think, I'm a layman who only knows some of the words in it), but more importantly, it just gave me a name for my next synthwave band: Tentacular Cirri.
There seems to be good reason to think that most aliens inhabit eternal darkness in a ocean underneath a global ice cap.
"New research by scientists from NASA and Japan’s Osaka University suggests that rogue planets – worlds that drift through space untethered to a star – far outnumber planets that orbit stars."
GP was precise in their phrasing: "aliens we could cross paths with". It would be much harder to actually meet or communicate with aliens that live in a dark ocean on a rogue planet than it would be for other aliens. ;)
That would limit the available energy inputs though, miniscule solar radiation, miniscule tidal forces, so unless you've got active plate tectonics or radionuclide decay, it's all going to become ice, presumably?
There's some truth to that. Europa, Enceladus, and other places are more than frozen ice balls because they get tidal heating from orbiting a gas giant. Even so, there are probably vast amounts of rogue gas giants between the stars. The very largest of these objects are known as brown dwarfs.
Why? I would imagine life on Jupiter’s moons might be something similar to these creatures, for example.
And our own solar system is the only place where we realistically have the slightest chance of physically crossing paths with aliens for many millennia.