Image depicting radio emissions at Saturn.
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July 25, 2005
Saturn's radio emissions could be mistaken for a Halloween
sound track.
That's how two researchers describe their recent findings,
published in the July 23 issue of the Geophysical Research Letters.
Their paper is based on data from the Cassini spacecraft radio and
plasma wave science instrument. The study investigates sounds that
are not just eerie, but also descriptive of a phenomenon similar to
Earth's northern lights.
"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," said Dr. Bill Kurth, deputy
principal investigator for the instrument. He is with the University
of Iowa, Iowa City. Kurth made the discovery along with Principal Investigator
Don Gurnett, a professor at the University. "We believe that the changing
frequencies are related to tiny radio sources moving up and down along
Saturn's magnetic field lines."
Samples of the resulting sounds can be heard at http://www.nasa.gov/cassini ,
http://saturn.jpl.nasa.gov and http://www-pw.physics.uiowa.edu/cassini/ .
The radio emissions, called Saturn kilometric radiation, are generated
along with Saturn's auroras, or northern and southern lights. Because
the Cassini instrument has higher resolution compared to a similar instrument
on NASA's Voyager spacecraft, it has provided more detailed information on the
spectrum and the variability of radio emissions. The 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 on the International Sun-Earth Explorer
spacecraft in Earth orbit. Kurth said that despite their best efforts, scientists
still haven't agreed on a theory to fully explain the phenomenon.
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. Gurnett said, “It is amazing that the radio emissions
from Earth and Saturn sound so similar.”
Other contributors to the paper include University of Iowa scientists George
Hospodarsky and Baptiste Cecconi; Mike Kaiser (currently at Goddard Space
Flight Center, Greenbelt, Md.); French scientists Philippe Louarn, Philippe
Zarka and Alain Lecacheux; and Austrian scientists Helmut Rucker and Mohammed Boudjada.
Cassini, carrying 12 scientific instruments, on June 30, 2004, became the
first spacecraft to orbit Saturn. It is conducting a four-year study of the
planet, its rings and many moons. The spacecraft carried the Huygens probe,
a six-instrument European Space Agency probe that landed on Titan, Saturn's
largest moon, in January 2005.
The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory,
a division of the California Institute of Technology in Pasadena, manages
the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington.
JPL designed, developed and assembled the Cassini orbiter. The radio and plasma
wave science team is based at the University of Iowa, Iowa City.
For information on the Cassini mission visit http://saturn.jpl.nasa.gov and
http://www.nasa.gov/cassini
Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
Gary Galluzzo (319) 384-0009
University of Iowa, Iowa City
2005-119
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