If alien life exists on Europa, we may find it in hydrothermal vents

They get interesting results also for Earth, since thermal systems are still relatively long lived:
The team was particularly excited about one result from the computer simulations featured in the new paper showing that, under very low gravity—like that found on the seafloor of Enceladus—circulation can continue with low to moderate temperatures for millions or billions of years. This could help to explain how small ocean worlds can have long-lived fluid-circulation systems below their seafloors, even though heating is limited: The low efficiency of heat extraction could lead to considerable longevity—essentially, throughout the life of the solar system.
https://news.ucsc.edu/2024/06/ocean-worlds.html
Under g_Ea conditions, siphon discharge rates for simulations in the present study extrapolate to Earth ocean residence times of t_circ ≈ 1–10 My. These values are somewhat greater than those inferred for Earth's ocean fromthe catalog of heat‐flux observations, as the systems simulated are modest in both fluid flow and advective heatoutput. But even for these relatively long residence times, given the median age of Earth's seafloor (∼60–70 My),there is ample time for the ocean to circulate in and out of the seafloor repeatedly between seafloor creation and subduction.