Crystallization of a Subsurface Ocean on Triton

Planetary magma oceans are present throughout the Solar System in a variety of forms. Over time, these oceans pass through various evolutionary stages, influencing the dynamics of the planetary body in question. Magma ocean evolution is explored here in greater detail through a case study of a cryomagma ocean beneath the surface of Triton, Neptune's icy satellite. Triton is hypothesized to have experienced extensive tidal dissipation within its interior early during evolution. Given the influence of tidal dissipation, this study evaluates ocean sustainability using a parametrized turbulent convection model and a coupled crust-ocean evolution model. The latter model links the thermal evolution of the crust, solved as a Stefan problem, with the crystallizing multiphase ocean. Due to an evident 'tidal blanketing' effect, these models indicate that an ocean may survive around 1 billion years given Triton's present day orbit, a timescale that increases with increasing dissipation and orbital eccentricity

Powering Triton’s recent geological activity by obliquity tides: Implications for Pluto geology

We investigate the origins of Triton’s deformed and young surface. Assuming Triton was captured early in solar system history, the bulk of the energy released during capture will have been lost, and cannot be responsible for its present-day activity. Radiogenic heating is sufficient to maintain a long-lived ocean beneath a conductive ice shell, but insufficient to cause convective deformation and yielding at the surface. However, Triton’s high inclination likely causes a significant ( 0.7) obliquity, resulting in large heat fluxes due to tidal dissipation in any subsurface ocean. For a 300 km thick ice shell, the estimated ocean heat production rate (0.3 TW) is capable of producing surface yielding and mobile-lid convection. Requiring convection places an upper bound on the ice shell viscosity, while the requirement for yielding imposes a lower bound. Both bounds can be satisfied with an ocean temperature 240 K for our nominal temperature-viscosity relationship, suggesting the presence of an antifreeze such as NH3. In our view, Triton’s geological activity is driven by obliquity tides, which arise because of its inclination. In contrast, Pluto is unlikely to be experiencing significant tidal heating. While Pluto may have experienced ancient tectonic deformation, we do not anticipate seeing the kind of young, deformed surfaces seen at Triton