ESA Science & Technology - Publication Archive
Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus could lead to electrodynamic coupling between Enceladus and Saturn like that which links Jupiter with Io, Europa and Ganymede.
Powerful field-aligned electron beams associated with the Io-Jupiter coupling, for example, create an auroral footprint in Jupiter's ionosphere. Auroral ultraviolet emission associated with Enceladus-Saturn coupling is anticipated to be just a few tenths of a kilorayleigh, about an order of magnitude dimmer than Io's footprint and below the observable threshold, consistent with its non-detection.
Here we report the detection of magnetic-field-aligned ion and electron beams (offset several moon radii downstream from Enceladus) with sufficient power to stimulate detectable aurora, and the subsequent discovery of Enceladus-associated aurora in a few per cent of the scans of the moon's footprint. The footprint varies in emission magnitude more than can plausibly be explained by changes in magnetospheric parameters' and as such is probably indicative of variable plume activity.
Saturn's moon Titan has a massive atmosphere laden with layers of photochemical haze. We report a recent dramatic change in the vertical structure of this haze, with a persistent 'detached' layer dropping in altitude from over 500 km to only 380 km between 2007 and 2010. The detached haze layer appears to be a well-defined tracer for Titan's meridional stratospheric circulation, models of which suggest that a pole-to-pole meridional cell weakens during equinox as solar heating becomes more symmetric. These measurements connect the Cassini observations with those made by Voyager almost one seasonal cycle earlier. They place detailed constraints on the seasonal circulation, on the sources of photochemical aerosols, on the microphysical processes and on the complex interplay of these components.