New data from the Cassini spacecraft (the one responsible for almost all of the beautiful Saturn photographs on the internet) has revealed that Titan, supersized moon of Saturn has an entire subterranean (Subtitanean?) ocean lurking deep beneath its surface. Scientists first noticed that something unusual was going on when they noticed that Titan was flexing more under tidal stresses than had previously been expected.
Titan was already known to have large masses of water, and a climate very much like Earth’s, complete with lakes, rain and clouds. The only difference is that titan is so cold that the weather is formed from liquid methane, while the water is frozen into a solid outer layer over a rocky core. As solid as this sounds, the massive tidal forces of an entire planet are still enough to flex and deform the planet-sized moon, and scientists expected to observe Titan’s shape deforming by as much as a meter. Instead, the Cassino mission reported flexure of more than ten meters – Titan was obviously a great deal softer than expected!
Considering the icy outer layer, the most reasonable explanation seemed to be that all that flexing raised the temperature of the moon’s interior by enough to melt the lower levels of ice. Result: one planet-sized ocean deep beneath the surface. Current data suggest that it could be as much as 50km deep, and lie some 250km below the surface.