Saturn's moon Titan could harbor life, but only a tiny amount

I'm interested that their conclusion -- that Saturn could only support tiny life forms such as bacteria -- is not dependent in any way on the distance from Titan to the Sun.

Am I wrong in thinking that any life must require a steady input of energy, and that this must come from either solar energy or geothermal energy? Quick Googling says that Titan's core isn't known for sure, but probably isn't very hot.

If Titan's life were dependent of solar energy, wouldn't it's distance from the Sun imply very little energy to go around, and so very unlikely to have large organisms?

Solar energy can be captured only by living beings that have reached a relatively high complexity after a long evolution.

In places with so little solar energy, living beings might never develop means for capturing it.

For the appearance of life, a source of internal heat for the planet or satellite is a necessary condition.

As another poster has mentioned, in the big satellites of the giant planets such a source of internal heat exists, because of the tidal forces which cause internal friction.

For the internal heat to be able to provide energy for life forms, there must exist some kind of volcanism that cycles matter between the interior and the exterior of the satellite or planet, so that substances that were in chemical equilibrium at higher temperatures are brought to lower temperatures, where they are no longer in chemical equilibrium, which can provide the energy for the synthesis of complex organic molecules.

(On Earth, the principal source of energy for the bacteria that do not depend on solar energy has its origin in the iron(II) ions from the mantle and lower crust of the Earth, which are brought by volcanism at the surface, where they are no longer in chemical equilibrium with water, so they are oxidized by water to Fe(III) ions, i.e. rust, liberating elemental hydrogen from the water, which can be consumed by bacteria and combined with carbon dioxide into organic substances, without needing any other source of energy. When rocks are recycled by subduction into the mantle, because of the high temperatures the iron ions are reduced again to Fe(II) ions, completing the cycle by consuming a certain amount of internal heat.)

Sure, but that's basically my point, or at least the point I thought I was making. Chemosynthesis can provide enough energy for bacteria, but to have anything much larger than bacteria you'd need a bigger source of energy, such as high solar radiation, right?