Is it the same as the moon?

I've searched Google for a long time and can't find it, or there are so many terms and data I can't understand.

A or B?

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https://preview.redd.it/lfufidcxynec1.png?width=901&format=png&auto=webp&s=8d535d11d164d4fa5ab7d1688a4decd79d9b9a51

I'm working on a story about Europa.

• What print fiction (novels, screenplays, etc) is already out there speculating about life in the oceans of Europa?
• What is the terrain like on the sub-ocean's floor, and for that matter, the ceiling?
• Could the ocean have an active climate like the skies of oxygen on earth? If so, what powers it? Geothermal activity from Europa's eccentric orbit around Jupiter? Energy spawned by Jupiter's massive magnetic field?
• Does it seem reasonable that Europa's global ocean would have different ecosystems based on depth, like one near the water/ice barrier, another in the mid level that feeds off of the upper level and then a more prolific population that hunkers down on the ocean floor and is sustained by geothermal vents and nutrients raining down from above?
• Not specific to Europa, but how does geothermal life work at the bottom of Earth's oceans? Is it fully self-contained or does it rely on food or energy from anything going on above it, like nutrition from dead lifeforms that are higher up, etc.?