Illustration showing a glowing patch of ultraviolet light near Saturn's north pole that occurs at the "footprint" of the magnetic connection between Saturn and Enceladus, its moon. The footprint, which is invisible to the naked eye, marks the presence of an electrical circuit that connects Saturn with Enceladus and accelerates electrons and ions along the magnetic field lines. In this image, the footprint is in the white box marked on Saturn, with the magnetic field lines in white and purple. A larger white square above Enceladus shows a cross-section of the magnetic field line between the moon and the planet.