What are the natural life sustaining resources available in the Jovian moon system? Hard science fiction writing question.  Premise: what natural resources are present in the Jovian system that would be necessary and desireable to an autonomous, self-sustaining human community?  Water on Europa, for example.  What else? Would like to keep this plausible without a lot of speculation.  Thank you.
The moons Europa, Ganymede, and Callisto all have substantial amounts of water ice on their surfaces, and for the latter two, also silicate rocks. There is also some CO2 in the ice as well as ammonia and methane. These give potential sources of carbon and nitrogen, and with enough energy you could make glucose and amino acids - Food.

Io is a crazy place, with lava flows, and sulphur covering the surface. Its not an easy place to mine

One potential source of energy is ${}^3\mathrm{He}$ This is a potentially useful fuel for a fusion reactor. It is found (in very low concentrations) in shaded parts of the moon. It may also be found on Jupiter's moons.

The minor moon Carme may have originated in the Kuiper belt (long ago) and have an interesting combination of carbon based substances. Amalthea has an interesting red colour - maybe carbon compounds again. There are quite a few moons that began as captured asteroids, but none seem to have been metallic.

There are lots of problems with life on Jupiter's moons: Cold - No air - radiation - etc