Energetic ion sputtering effects at Ganymede

The energy spectra of magnetospheric ion measurements from the Energetic Particle Detectors (EPD) experiment on Galileo during the G2 encounter with Ganymede were used to estimate the ion sputtering rate from the surface of this largest Galilean moon. A combination of the ion composition and the mass-dependent sputtering yield shows that a total production rate of about 10²⁶ -4.6 × 10²⁶ H₂O molecules/s can be expected from the precipitation of the energetic ions at the polar region. The emission of the sputtered neutral particles will contribute to the formation of an extended exosphere as well as a distributed gas cloud in the Jovian system. Additional sputtering might be possible if an electrostatic potential drop of a few kV forms leading to the acceleration of ionospheric (oxygen) ions towards Ganymede's surface.