Does Titan host an underground ocean? Recent measurements by the Cassini spacecraft suggests that this may be the case, making Titan an even more attractive candidate in searching for life or thinking about future space colonization.
The evidence for an ocean on Titan comes from observations of the moon “bulging” due to gravitational influences with Saturn. The Cassini spacecraft captured precise measurements of the gravitational field surrounding Titan in an effort to tell what materials might be under the planet’s icy surface. These new measurements seem to indicate that the subsurface of Titan features a liquid water ocean, rather than a layer of solid rock.
Tidal forces on Titan are similar to tidal forces experienced on Earth. Oceanic tides occur on Earth due to the gravitational influence of the Moon (and the sun to a lesser extent), which causes a “bulging” of Earth’s oceans that we experience as periods of high tide. Although we typically associate tidal forces with these waves of water, tidal forces also occur on land-dominated planets and lead to similar bulging effects. In the case of Titan, it is the planet Saturn that exerts tidal forces to cause the bulges that have been interpreted as evidence of oceans.
The resulting picture of Titan’s structure seem to suggest that beneath the thick atmosphere, organic-rich surface, and icy shell is a subsurface ocean--with a high pressure ice surface likely beneath, and probably a silicate core toward the center. The presence of this ocean may help to understand other features of Titan, such as how methane is cycled through Titan’s atmosphere. Future observations and follow-up missions will ultimately be needed to confirm this inference of an underground ocean and further explore its astrobiological potential. Whether or not these oceans harbor indigenous life, they will nevertheless provide clues as to the abundance or rarity of life in the galaxy.
The possibility of an underground ocean on Titan raises the possibility that primitive forms of life might lurk beneath the surface. While this seems unlikely, perhaps forms of prebiotic chemistry will be discovered in Titan's oceans, as precursors to living systems. As for prospects of space colonization, the presence of an underground ocean might make it that much easier for human explorers to find the basic resources needed to establish temporary or permanent colonies away from Earth.