Titan has clouds, rain and lakes, like Earth, but these are composed of methane rather than water. However, methane lakes were seen only at Titan's poles until now — its tropics around the equator were apparently home to dune fields instead.
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The question of how a subterranean aquifer might form on Titan is still unclear. "Titan's orbit about Saturn might give us a clue. It is not circular," Griffith said. Some scientists suggest that Titan's noncircular orbit was once even more elliptical and only recently decayed to its current slightly noncircular orbit. During this possible orbital decay, the gravitational pull of Saturn on Titan would have led to powerful tides, releasing heat that could have caused subsurface reservoirs of methane to form and outgas.
Giant Tropical Lake Found on Saturn Moon Titan