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I like Europa for the next most likely place life could exist in the solar system. The necessary parameter for life is water at 0.1 Celsius at 1 atmosphere of pressure (sea level in our gravity well). There may be other stable states of matter at significantly higher temperatures, but the necessary transformation of energies needed for life would involve magnitudes of entropy as well so this is unlikely.
There may be highly specific conditions available in a colder environment, but there isn't enough energy to transform.
There are not three states of matter with water. There are at least five and probably more. Super cold ice is a superconductor. Super hot steam is a universal solvent. Liquid hydrogen hydroxide has specific properties of fluidity, viscosity and conductivity all of which are vital for life as we know it. Nothing else has all these properties, otherwise it would be chemically and physically the same as water, so it's water. This seems like sloppy argument, saying that water has all the properties needed for life, so if it's not in water, it's not life. That's not what I'm saying.
What I'm saying is water provides the best medium for the reactions needed for life to begin autocatalyzing itself, and that Nature, being lazy, will use the best medium and not much else. Still not convinced water is the best medium for life? Ice floats and subsequently insulates. Water vapourizes, concentrating impurities to chemically interesting proportions. It goes on.
So, understanding that liquid water is needed as the medium for life, we can look into the solar system for the likeliest places. For a while, there was a theoretical band around Jupiter where the atmospheric pressure compensated for the wacky temperature and liquid water could possibly form, but this was dismissed. Europa, however, seems to be a ball of water, ice on the outside and probably liquid inside (being subjected to Jupiter's gravity well as a source of movement).
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