Deep sea vents were discovered when I was in my 20's before that we used to think abiogenesis had something to do with lightning hitting a mud puddle. The evidence
that life formed around such vets on Earth is strong but inconclusive. Fatty acids from clay in the vent spontaneously form primitive cell membranes (in vents and mud puddles). Sulphur provides chemical energy, porous rock around the vent provides a sponge like scaffold for life to take root and extract passing nutrients. Most importantly the vents are predictable
, the deep, still water stabilizes the temperature gradient. Convection currents cycle the fatty cells through the gradient allowing different chemical reactions within the membrane to synchronize themselves to the thermal cycle (much the same as plants match the cycle of night and day). If that really is how life got started then it's likely that primitive cells are still being spontaneously created near these vents today, the practical problem for scientists researching this idea is finding them before evolved life such as shrimp eat them.
Europa has all these conditions and like Earth it's ocean is also oxygenated at the top. Oxygen is vital for multicellular life on Earth, collagen (the stuff that holds individual cells together as multicellular critters) cannot form in an oxygen poor environment. Oxygen in Europa's ocean is replenished differently than it is on Earth. On Europa's surface strong radiation from Jupiter knocks the H2 off the ice and out into space, the free oxygen is returned to the ocean via plate tectonics. Personally I would think it very odd if we didn't
find single celled life in Europa's ocean, at the very least it would force Science to radically rethink the conditions that lead to abiogenesis on Earth. What I'm interested to find out is whether life on Europa uses the same self-replicating molecules used by life on Earth, but I doubt I will be around to hear the answer..