Uranus moons Titania, Oberon may host subsurface oceans
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Thermal models suggest that Titania and Oberon, the two largest moons of Uranus, could harbor liquid water oceans beneath icy crusts kept warm by radioactive decay. If confirmed, they would join Enceladus and Europa as ocean worlds, expanding the known habitable zone to the ice giant system.
Thermal Modeling
A 2022 modeling study that excluded tidal heating found Titania and Oberon could retain subsurface oceans if heat escaped slowly through their ice shells. Smaller Uranian moons did not preserve long-lived oceans under the same assumptions. The result shows present oceans are physically plausible even at Uranus's distance from the Sun.
Internal Heating
Rock within the moons contains radioactive isotopes like uranium, thorium, and potassium-40, whose decay generates heat. A thick ice shell slows heat loss, while ammonia and salts lower water's freezing point. A 2023 reconstruction suggested possible oceans tens of kilometers thick in the two largest moons, though the answer depends on uncertain composition and thermal history.
Voyager 2 Observations
Nearly all direct knowledge of these moons comes from Voyager 2's flyby in January 1986. The spacecraft observed only part of each world and returned images far less detailed than those later obtained at Jupiter and Saturn. No spacecraft has measured the moons' gravity fields or searched for electromagnetic signatures of salty water.
What's Next
NASA's Uranus Orbiter and Probe, a priority for the next decade, could confirm or rule out subsurface oceans when it arrives in the 2040s. Until then, the existence of liquid water on Titania and Oberon remains a plausible but unverified hypothesis.
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Uranus moons Titania, Oberon may host subsurface oceans
