In the last leg of its more than 13 years journey, which ended in September 2017, Cassini spacecraft was put on a particularly daring orbit passing between Saturn and its rings.
This brought Cassini closer to Saturn than ever before. For the first time scientists allowed to obtain images of Saturn’s ultraviolet auroras in unprecedented resolution.
Saturn’s auroras are located in the planet’s polar regions and known to be highly dynamic. They generated by the interaction of the solar wind, a stream of energetic particles emitted by the Sun, together with Saturn’s rapidly rotating magnetic field. They often pulsating and flashing as different dynamic processes occur in the planet’s plasma environment.
“Surprisingly many questions revolving around Saturn’s auroras remain unanswered, even after the outstanding success of the Cassini mission,” said Lancaster University PhD. student and lead author of the research Alexander Bader.
“This last set of close-up images gives us unique highly detailed views of the small-scale structures which couldn’t be discerned in previous observations by Cassini or the Hubble Space Telescope. We have some ideas about what their origin could be, but there is still a lot of analysis to be done.”
Satellite imagery alone will hardly be enough to unravel the aurora’s mysteries – the energetic particles causing the bright lightshows around Saturn’s poles originate far away from the planet’s surface where magnetic field lines twist and clouds of plasma interact with one another.
When located in the right region, Cassini was sometimes embedded in the particle stream connecting the auroras to the magnetosphere.
The first analysis of the spacecraft’s particle measurements recorded during these times showed that Saturn’s auroras, like Jupiter’s, are generated by much more energetic particles than Earth’s. However, the underlying physical mechanisms appear to show similarities between all three.
The new observations are detailed in two new studies published in Geophysical Research Letters and JGR: Space Physics.