The Cassini mission came to an end in 2017 with an orchestrated swan dive into Saturn, but data and images from its final few months, the mission’s “Grand Finale”, are still being analyzed and continue to reveal new insights into the ringed planet.
Now new images of Saturn’s aurorae have been released revealing both major differences as well as similarities to our Earthly northern lights. The new observations are reported in two papers published in Geophysical Research Letters and JGR: Space Physics.
The aurorae on Saturn, like on Earth and Jupiter, are generated by the interaction between the strong and rotating magnetic field of the planet and the solar wind, the stream of particles emitted by the Sun.
The aurorae on Saturn, which are only visible in ultraviolet light, pulsate and change as the underlying process varies. They form in the polar regions, high above the planet’s atmosphere where the magnetic field lines twist and the interplanetary plasma is caught in them.
Cassini flew through these clouds of plasma and the first analysis of this shows that aurorae on Saturn are caused by heavier particles than on Earth. In that respect, the planet’s aurorae are similar to Jupiter’s ones. That said, the team stresses that the underlying mechanism is the same among the three planets. Despite this, there are still many mysteries left to uncover.
“Surprisingly many questions revolving around Saturn's auroras remain unanswered, even after the outstanding success of the Cassini mission,” lead author Alexander Bader, a graduate researcher at Lancaster University said in a statement.
"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."
Cassini was a cooperative mission between NASA, the European Space Agency, and the Italian Space Agency. Over the 13 years in which it orbited Saturn, it provided us with incredible observations, expanding our understanding of the ringed planet and its moons, and leading to important discoveries such as the seasonal changes of Titan and the geothermal activity on Enceladus. It's still not finished revealing Saturn's secrets.