Icy moons around the ice giant planets may contain subsurface oceans.
Their oceans could be detected and characterized using measurements of
magnetic fields induced by the host planet’s time-varying magnetospheric
field. We explore the possibility of detecting and characterizing
subsurface oceans among the five major moons of Uranus—with a
particular focus on Ariel—using spacecraft magnetometry measurements.
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 (>~6-100 km)
and conductivities (>2 S m-1), the
induced surface fields should have amplitudes exceeding the typical
~1 nT sensitivity of spacecraft magnetometry
investigations. Furthermore, the magnetic field at the moons spans
periods ranging from 1 to 103 h. This could enable
long-term measurements to separately constrain ocean and ice thicknesses
and ocean salinity.