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NASA’s Cassini spacecraft’s Grand Finale orbits found a powerful interaction of plasma waves moving from Saturn to its rings and its moon Enceladus. Photo: NASA/JPL-Caltech

The dynamic plasma energy between Saturn and its second-smallest moon is made up of electromagnetic waves in the audio frequency range.

Now we can hear them.

Before its fatal plunge into the planet last November, the probe Cassini recorded the hissing, whistling and gradual fadeaway for 16 minutes. Now NASA has compressed the audio time to 28.5 seconds, and decreased the wave frequency by a factor of 5, and you can conveniently tune in on your computer.

The “circuitry” between the planet and its moon is the subject of two recent papers in the journal Geophysical Research Letters.

“Here we present evidence of communication between Saturn’s ionosphere and Enceladus during (Cassini’s) Grand Finale orbits, revealing the vast spatial extent of their coupling via plasma waves,” the scientists write. “These results underline Saturn’s system as one of the most diverse and dynamic in the solar system.”

Enceladus, long considered one of the most interesting bodies in our solar system, orbits the ringed planet at a relatively close distance, just over 237,000 kilometers. By comparison, the moon orbits Earth at a radius of 384,400 km.

The latest audio was recoded Sept. 2, 2017, just two weeks before Cassini began its final plunge into Saturn’s atmosphere. The recording was converted by a NASA Radio Plasma Wave Science team at the University of Iowa.

“Enceladus is this little generator going around Saturn, and we know it is a continuous source of energy,” Ali Sulaiman, one of the University of Iowa authors, said. “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.” 

Previous studies by Cassini have determined that the tiny moon emits a plume of hydrogen from its surface. The plumes from Enceladus indicate the microbes could mix hydrogen with carbon dioxide within the water to undergo methanogenesis to produce energy and a methane byproduct.

The Cassini mission’s deepest dive into the plume took place on Oct. 28, 2015, and found its composition to be 98 percent water, one percent hydrogen, and a mixture of other molecules including carbon dioxide, methane and ammonia. 

“Although we can’t detect life, we’ve found that there’s a food source there for it,” Hunter Waite, lead author of the Cassini study from April 2017, said. “It would be like a candy store for microbes.”

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