Saturn’s shocking moon
Stories from Physics for 11-14 14-16
The Cassini spacecraft received a 200 V shock from the surface of one of Saturn’s moons. As Cassini made a flypast of Hyperion, approximately six minutes before its closest approach, instruments detected a flow of electrons coming from the moon. It is thought that the surface of Hyperion becomes charged both by the absorption of ultraviolet radiation and through exposure to charged particles that become trapped in Saturn’s magnetic field. The build-up of charge resulted in a potential difference between the probe and moon, driving a beam of electrons over a distance of 2,000 km. There is no evidence that Cassini was damaged by the discharge but spacecraft designers have noted the effect as a potential hazard to future missions.