Some studies, like this one for Titan, consider that the external activity on Jupiter's Moon hosting oceans (Io, Titan or Enceladus, Gaynimede, Callisto and Europa)* due to comets or cosmic events is not sufficient, thus definitely excluding the possibility of life. We assert that on a physical aspect the internal gravitational effects are absolutely sufficient to maintain the hypothesis that there's life on theses planetoïds (Moons).
In opposition with recent arguments which scientifically shows that the external cosmic activity on Jupiter's Moons, especially Titan, is not sufficient to produce exospermia into its internal ocean we would like to express another way for life to have emerged in theses planetoïds' oceans :
Jupiter is a huge gravitational object.
Its Moons hosting internal liquid oceans covered by layers of ice do orbit around this huge gravitational object (Jupiter).
Depending on their orbits (equatorial or not) we do maintain that revolving around such a massive object do produce internal dynamics on the really core of theses Moons ;
Hence, certainly producing frictions and internal tectonics dynamics — such as magmatic activity, core compression and extension, thus producing activity in magmatic chambers and magmatic chimney.
This would mean that we could find deep sea volcanoes at the really bottom of theses Moons' ice covered oceans.
Using the anthropomorphic** argument, we do maintain that in such conditions with active volcanoes due to a active core we could find — at least — microbes colonies and, or, extremophiles organisms for conditions of heat, flux movement (water) and pressure might be ideal for theses (micro)organisms to evolve.
With the above arguments, we maintain our assertion that the hypothesis of finding life on Jupiter's Moons' oceans is still valid.
* Extrapolating this paper words, having six Moons with oceans around Jupiter does also significantly increase the statistical chances of finding life elsewhere, even simple, in our Solar System.
** Reminder of the Anthropological argument firstly expressed in Two Body Problem : Special Set (see here), III. About Dark Mater :
Derived from anthropological principle stating that : "If it is as such on Earth, from a physical and biophysical perspective, then it surely may as such elsewhere in the Universe" — for example : "If carbonated lifeforms are permitted by physics here on Earth, then it may surely be the case elsewhere in the Universe".
Hence the Anthropological argument is there evoked to state that "If we there is Dark Matter elsewhere in the Universe, observable through State-Of-The-Art (SOTA) instruments, then there surely may be Dark Matter also here on Earth, and thus within ourselves".