Cassini reveals Saturn’s eerie-sounding radio emissions

Saturn’s radio emissions could be mistaken for a Halloween sound track.

That is how University of Iowa researchers Bill Kurth and Don Gurnett describe their recent findings, published 23 July in the journal Geophysical Research Letters. Their research investigated sounds that are not just eerie, but also descriptive of a phenomenon similar to Earth’s northern lights. The study was based on data from the Cassini spacecraft’s radio and plasma wave science instrument, which was built at the University of Iowa under Gurnett’s direction.

“All of the structures we observe in Saturn’s radio spectrum are giving us clues about what might be going on in the source of the radio emissions above Saturn’s auroras,” says Kurth. “We believe that the changing frequencies are related to tiny radio sources moving up and down along Saturn’s magnetic field lines.”

The radio emissions, called Saturn kilometric radiation, are generated along with Saturn’s auroras, or northern and southern lights. The Cassini instrument has provided new information on the spectrum and the variability of the radio emissions, thanks to the higher resolution of the instrument, as compared to that on the earlier Voyager spacecraft. These high-resolution measurements allow scientists to convert the radio waves into audio recordings by shifting the frequencies down into the audio frequency range.

The terrestrial cousins of Saturn’s radio emissions were first reported in 1979 by Gurnett, who used an instrument onboard the International Sun-Earth Explorer spacecraft in Earth orbit. Kurth says that despite their best efforts, scientists still have not agreed on a theory to fully explain the phenomenon. He adds that they will get another chance to solve the radio emission puzzle beginning in mid-2008, when Cassini will fly close to, or possibly even through, the source region at Saturn.

Commenting on the new observations, Gurnett says, “It is amazing that the radio emissions from Earth and Saturn sound so similar.”