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I remember reading - probably decades ago - that Titan would be the most likely body within out Solar System to contain life.
If memory serves, this was due to methane in the atmosphere and what were thought to be liquid pools on the surface. I believe there was also hope that clouds would help keep the temperature above that which nearly precludes most life.
Do these theories still hold? Is there anywhere "better"?
Given that they are finding water in all sorts of places, my bet is on Enceladus and Mars.
But here's a few interesting quotes I gathered from NASA...
From Water: Life's Elixir in the Solar System:
Liquid water is a necessity for every form of life known, with the possible exception of some plants or fungi that may get by on water vapor. With this in mind, scientists are eagerly searching for liquid water in places other than Earth.
In recent years, NASA spacecraft managed by JPL have found a tantalizing sprinkle of clues supporting both the possibility that liquid water may persist below the dry surface of Mars and the icy surfaces of three large moons circling Jupiter. With NASA's strategy to "follow the water" in the search for life, Mars and Jupiter's moon Europa are priority targets for future robotic missions.
From The Solar System and Beyond is Awash in Water:
There are several worlds thought to possess liquid water beneath their surfaces, and many more that have water in the form of ice or vapor. Water is found in primitive bodies like comets and asteroids, and dwarf planets like Ceres. The atmospheres and interiors of the four giant planets -- Jupiter, Saturn, Uranus and Neptune -- are thought to contain enormous quantities of the wet stuff, and their moons and rings have substantial water ice.
Perhaps the most surprising water worlds are the five icy moons of Jupiter and Saturn that show strong evidence of oceans beneath their surfaces: Ganymede, Europa and Callisto at Jupiter, and Enceladus and Titan at Saturn.
Scientists using NASA's Hubble Space Telescope recently provided powerful evidence that Ganymede has a saltwater, sub-surface ocean, likely sandwiched between two layers of ice.
Europa and Enceladus are thought to have an ocean of liquid water beneath their surface in contact with mineral-rich rock, and may have the three ingredients needed for life as we know it: liquid water, essential chemical elements for biological processes, and sources of energy that could be used by living things. NASA's Cassini mission has revealed Enceladus as an active world of icy geysers. Recent research suggests it may have hydrothermal activity on its ocean floor, an environment potentially suitable for living organisms.
