Searching for Subsurface Oceans on the Moons of Uranus Using Magnetic Induction

Abstract

The icy moons of Uranus may contain subsurface oceans. Such oceans could be detected and characterized using measurements of magnetic fields induced by Uranus' time-varying magnetospheric field. Here we explore this possibility for Uranus's five major moons, with a focus on Ariel. We find that the magnetic field at each moon is dominated by the synodic frequency with amplitudes ranging from ∼4 nT at Oberon up to ∼300 nT at Miranda. If these bodies contain oceans with sufficient thicknesses (>∼3–40 km) and conductivities (>2 S m−1) even underlying relatively thick (∼50 km) ice shells, the induced surface fields should have amplitudes exceeding the typical ∼1 nT sensitivity of spacecraft magnetometry investigations. Furthermore, the magnetic field variations at the moons span periods ranging from 1 to 103 h. These could enable long-term measurements to separately constrain ocean and ice thicknesses and ocean salinity.