It's turning out that the outer reaches of the solar system may be more hospitable to life than we ever imagined. Gravity measurements made by Cassini have confirmed that Enceladus, a tiny moon orbiting Saturn, hosts a subsurface ocean in its southern latitudes. Astronomers are now saying it's potentially habitable.
The idea that Enceladus may host a subsurface ocean is nothing new. Back in 2005, NASA's Cassini spacecraft beamed back images showing what appeared to be plumes of water vapor spewing out from fractures, called "tiger stripes," near the icy moon's southern pole (similar to what was recently detected on Europa, another icy moon with a subsurface ocean). By itself, these plumes didn't prove that liquid water existed under the ice. It's conceivable, for example, that massive tectonic forces exerted by Saturn's gravity was creating friction along the plates of ice, resulting in cracks and the jettisoning of liquid water.