[PaulHoule]

It’s thought that the most common habitable environment in the universe is in underground oceans which are generic in outer solar system and probably interstellar bodies.

https://en.wikipedia.org/wiki/Planetary_oceanography

It’s easy to believe you could get bacteria in that kind of place with an ecosystem like

https://en.wikipedia.org/wiki/Hydrothermal_vent

but without energy input from sunlight it is hard to believe you could get more complex organisms or ecosystems, but if you had some oxygen from chemistry that might make a difference.

[wongarsu]

Earth is a glowing ball of magma and semi-liquid stone, with a tiny solid crust where it has cooled off. There is plenty of energy there in heat, nuclear decay, elements that could chemically react and release energy, etc.

On this sun-blasted surface life that uses sunlight can outcompete anything that doesn't use it. But that doesn't mean those other energy sources aren't viable on their own

[knowitnone]

"but without energy input from sunlight it is hard to believe you could get more complex organisms or ecosystems" Where did you pull this from? Why couldn't complex organisms form without sunlight?