Researcher Paul Hartogh and colleagues, presenting far-infrared observations from the space telescope Herschel (ESA), report the direct detection of a torus around Saturn consisting of water-dominated gases and ice particles that have escaped from the interior of its moon Enceladus.

Enceladus is famous for its planetary-size geysers. Data from the Cassini spacecraft recently permitted the composition of its plumes to be determined and the discovery of its auroral footprint on Saturn.

The new  finding is important because these gases and particles are typical of those that eventually fall into the atmospheres of Saturn and Titan or coat the surfaces of the satellites and rings, altering their compositions. The inferred flux at Saturn is consistent with that required to explain the planet’s stratospheric composition. However, at Titan this flux is still too weak. Hence, the source of Titan’s atmospheric water remains mysterious.

The paper by P. Hartogh, E. Lellouch, R. Moreno, D. Bockelée-Morvan, N. Biver, et al., has been published on 14 July in Astronomy &  Astrophysics.