Ganymede (moon) fits well with Ganymede's tenuous oxygen atmosphere. In the polar cap regions, at latitudes higher than 30°, magnetic field lines are open, connecting Ganymede with Jupiter's ionosphere. In these areas, the energetic (tens and hundreds of kiloelectronvolt) electrons and ions have been detected, which may cause the auroras observed around the Ganymedian poles. In addition, heavy ions precipitate continuously on Ganymede's polar surface, sputtering and darkening the ice. The interaction between the Ganymedian magnetosphere and Jovian plasma is in many respects similar to that of the solar wind and Earth's magnetosphere. The plasma co-rotating with Jupiter impinges on the trailing
Ring Around the Moon (Space: 1999) from the sphere and enveloped the Moon. Tracking sensors reveal the sphere to be stationary but, from their perspective, it is still getting closer to the Moon's surface; John Koenig realises that the Moon has been trapped in an orbit around the sphere. An audio signal is received and a sibilant voice announces that they are prisoners of the planet Triton. The staff reviews the damage caused by the Moon's sudden deceleration. The fact that all but four are non-operational and the main generators show no sign of damage but are only putting out minimum power indicates that the sphere's