When NASA’s Cassini dropped into orbit by Saturn it wasn’t just there for the planet. It was there to observe the sixty moons as well. It’s long been speculated but never confirmed that Titan could possibly contain water. The extent of which has never been proven until recently.
Lead study author Luciano Iess, a planetary geodesist (I honestly don’t know what that is and I took astronomy in college) at Università La Sapienza in Rome observed some crazy stuff by examining the gravitational field around the planet. Titan hides water deep in itself as its solid exterior glides and shifts on top of it. And the gravitational forces pull it relentlessly, giving hints to a possible ocean and (extremely theoretically) a place that could eventually sustain life. It could be methane – but that type of ocean can sustain life as well.
As they said on space.com:
To get a glimpse into Titan’s mysterious interior, scientists relied on NASA’s Cassini spacecraft, which has orbited Saturn since 2004. They focused on the extraordinarily powerful tides the planet’s gravitational pull causes its moons to experience — tides ferocious enough to have once ripped apart titanic chunks of ice to produce the world’s rings. Titan itself faces tidal effects up to 400 times greater than our moon’s draw on Earth.
By monitoring how Cassini’s acceleration changed during six close flybys past Titan between 2006 and 2011, the researchers deduced the strength of the moon’s gravity field. Since a body’s gravity stems from its mass, these details helped reveal how matter is distributed within Titan and how this changed depending on how near or far the moon was from Saturn during its oval-shaped 16-day orbit around the planet.