9 July 2018

Listen: The sound of electromagnetic energy moving between Saturn, Enceladus

Posted by Nanci Bompey

By Gretchen McCartney

New research from Cassini’s up-close Grand Finale orbits shows a surprisingly powerful and dynamic interaction of plasma waves moving from Saturn to its moon Enceladus and its rings. The observations show for the first time that the waves travel on magnetic field lines connecting Saturn directly to Enceladus. The field lines are like an electrical circuit between the two bodies, with energy flowing back and forth.

Researchers converted the recording of plasma waves into a “whooshing” audio file that we can hear — in the same way a radio translates electromagnetic waves into music. In other words, Cassini detected electromagnetic waves with antennas in the audio frequency range — and on the ground, we can amplify and play those signals through a speaker. The recording time was compressed from 16 minutes to 28.5 seconds.


Much like air or water, plasma (the fourth state of matter, made of positive and negative particles) generates waves to carry energy. The Radio Plasma Wave Science (RPWS) instrument onboard NASA’s Cassini spacecraft recorded intense plasma waves during one of its closest encounters to Saturn.

“Enceladus is this little generator going around Saturn, and we know it is a continuous source of energy,” said Ali Sulaiman, planetary scientist at the University of Iowa and a member of the RPWS team. “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.”

Sulaiman is lead author of a pair of papers published recently in Geophysical Research Letters, a journal of the American Geophysical Union. The papers are available here and here

The interaction of Saturn and Enceladus is different from the relationship of Earth to its Moon. Enceladus is immersed in Saturn’s magnetic field and is geologically active, emitting plumes of water vapor that become ionized and fill the environment around Saturn. Our own Moon does not interact in the same way with Earth. Similar interactions take place between Saturn and its rings, as they are also very dynamic.

The recording was captured Sept. 2, 2017, two weeks before Cassini deliberately plunged into the atmosphere of Saturn. It was converted by the RPWS team at the University of Iowa, led by physicist and RPWS Principal Investigator Bill Kurth.

— Gretchen McCartney is a science writer at NASA’s Jet Propulsion Laboratory. This post originally appeared on the NASA JPL website.