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Fragility of the Uranian satellite system during the epoch of giant planet migration

Presentation #203.04 in the session Planets and Satellites Dynamics (Oral Presentation)

Published onOct 23, 2023
Fragility of the Uranian satellite system during the epoch of giant planet migration

The four satellite systems in the outer solar system are scientifically lucrative targets for exploration and theoretical investigation as they not only provide numerous constraints on solar system formation hypotheses, but are also themselves the end-state of a miniaturized version of a solar system-scale planet accretion process. Compared to the other giant planets’ satellite systems, the Uranian system appears exceptionally dynamically pristine; having only been affected by tidal migration since its formation. Because the satellites possess equatorially prograde orbits relative to the planets’ tilted spin axis, it has been argued that they formed in the aftermath of a giant impact that generated Uranus’ extreme obliquity. While past studies presumed this event occurred prior to nebular gas dissipation, our analyses of a suite of instability models indicate that the Uranian system is unlikely to have survived the solar system’s subsequent epoch of dynamical instability. In the majority of cases the regular moons are stripped or overly-excited as Uranus experiences multiple encounters with Neptune or other ice giants within, or just outside of Oberon’s modern orbit. While this problem is most pronounced at Uranus, we find that similarly frequent ice giant flybys of Jupiter can be problematic for the Galilean moons as well. Our results suggests that either planetary encounters during the instability were weaker and rarer than previously assumed, or the Uranus-tilting impact that possibly birthed its moons occurred much later than proposed in the current literature. While the former possibility might not support the capture of a sufficient number of irregular moons at each giant planet, the latter is potentially consistent with models arguing for prolonged ice giant formation via late giant impacts.

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