Saturn and Enceladus produce the same amount of plasma

The first evidence that Saturn's upper atmosphere may, when buffeted by the solar wind, emit the same total amount of mass per second into its magnetosphere as its moon, Enceladus, has been found by UCL scientists working on the Cassini mission. Magnetospheres are regions of space that are heavily influenced by the magnetic field of a nearby planet and can contain charged particles in the form of plasma from both external and internal sources. In the case of Saturn, its moon Enceladus ejects water from its icy plumes which is ionised into H2O⁺, O⁺, OH⁺ and then transported throughout the magnetosphere. For Jupiter, its moon Io provides plasma from its sulphurous volcanoes whereas Earth's magnetosphere is strongly driven by the solar wind but fed by a polar wind from the ionosphere - the atmospheric layer ionised by solar and cosmic radiation. The Cassini mission previously established the importance of Enceladus as the dominant mass source for Saturn's magnetosphere but this is the first time that Saturn's ionosphere has been seen providing, at times, a similar plasma production rate. The study, published in the Journal of Geophysical Research , reports on an event measured by the Cassini spacecraft on 21 August 2006 while it was traversing Saturn's magnetotail - the part of the magnetosphere compressed and confined by the solar wind. This compression causes quite dynamic, large changes to take place resulting in auroras containing energised ions and electrons.