Saturn's system continues to surprise and delight us. Researchers analyzing data from the final days of the Cassini mission have discovered an intense interaction between Saturn, its rings, and its icy moon, Enceladus. NASA scientists discovered that waves of plasma travel on magnetic field lines that connect the planet and the moon. And now they have turned their motion into sounds we can hear by shrinking 16.5 minutes of recording into 28 seconds.
These sounds are generally referred to as auroral (or electromagnetic) hiss because when played through an audio system they can sound like white noise. But don't be fooled, a lot of information is hidden within this data. The team is now getting a much clearer picture of the interaction of Enceladus and the rings within Saturn’s magnetic field. The analysis is reported in two papers published in Geophysical Research Letters (here and here).
Although covered in ice, Enceladus is an active world; below its surface, there’s a liquid ocean and recorded geological activity. It emits plumes of water vapor, which lose electrons as they go up into space and end up forming Saturn’s E ring. This electrically charged material is sloshed about by the incoming plasma waves from Saturn.
"Enceladus is this little generator going around Saturn, and we know it is a continuous source of energy," lead author of both papers, Ali Sulaiman, a planetary scientist at the University of Iowa, said in a statement. "Now we find that Saturn responds by launching signals in the form of plasma waves, through the circuit of magnetic field lines connecting it to Enceladus hundreds of thousands of miles away."
And this didn't appear to be exclusive to Enceladus. The team was also able to detect currents connecting the planet to the rings too. In fact, the whole environment is extremely dynamic.
Plasma is the fourth state of matter, and it can have mechanical waves moving through it just like air or water, which were recorded here using the Radio Plasma Wave Instrument on board Cassini.
These observations were only possible because Cassini was preparing to end itself by deliberately plunging into the gas giant, so it was decided that in its Grand Finale, the spacecraft would orbit closer to Saturn than ever before. This allowed the probe to directly measure the magnetic field and the plasma waves from the inside. The recording was taken on September 2, 2017, just two weeks before its swan dive into Saturn.