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Cassini Finds Likely Subsurface Ocean on Saturn Moon

Data from NASA’s Cassini spacecraft have revealed Saturn’s moon Titan likely harbors a layer of liquid water under its ice shell.

Researchers saw a large amount of squeezing and stretching as the moon orbited Saturn. They deduced that if Titan were composed entirely of stiff rock, the gravitational attraction of Saturn would cause bulges, or solid “tides,” on the moon only 1 meter in height. Spacecraft data show Saturn creates solid tides approximately 10 meters in height, which suggests Titan is not made entirely of solid rocky material.

An ocean layer does not have to be huge or deep to create these tides. A liquid layer between the external, deformable shell and a solid mantle would enable Titan to bulge and compress as it orbits Saturn ^[Video]. Because Titan’s surface is mostly made of water ice, which is abundant in moons of the outer solar system, scientists infer Titan’s ocean is likely mostly liquid water.

The presence of a subsurface layer of liquid water at Titan is not itself an indicator for life. Scientists think life is more likely to arise when liquid water is in contact with rock, and these measurements cannot tell whether the ocean bottom is made up of rock or ice. The results have a bigger implication for the mystery of methane replenishment on Titan.

Image: This artist’s concept shows a possible scenario for the internal structure of Titan, as suggested by data from NASA’s Cassini spacecraft. Scientists have been trying to determine what is under Titan’s organic-rich atmosphere and icy crust.