Cassini Sees Saturn Electric Link With Enceladus
NASA is releasing the first images and sounds of an electrical connection between Saturn and one of its moons, Enceladus.
PASADENA,  Calif. -- NASA is releasing the first images and sounds of an electrical connection  between Saturn and one of its moons, Enceladus. The data collected by the  agency's Cassini spacecraft enable scientists to improve their understanding of  the complex web of interaction between the planet and its numerous moons. The results of the data analysis  are published in the journals NatureScientists  previously theorized an electrical circuit should exist at Saturn. After  analyzing data that Cassini collected in 2008, scientists saw a glowing patch  of ultraviolet light emissions near Saturn's north pole that marked the  presence of a circuit, even though the moon is 240,000 kilometers (150,000  miles) away from the planet.The  patch occurs at the end of a magnetic field line connecting Saturn and its moon  Enceladus. The area, known as an auroral footprint, is the spot where energetic  electrons dive into the planet's atmosphere, following magnetic field lines  that arc between the planet's north and south polar regions."The  footprint discovery at Saturn is one of the most important fields and particle  revelations from Cassini and ultimately may help us understand Saturn's strange  magnetic field," said Marcia Burton, a Cassini fields and particles  scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It  gives us the first visual connection between Saturn and one of its moons."The  auroral footprint measures approximately 1,200 kilometers (750 miles) by less  than 400 kilometers (250 miles), covering an area comparable to California or  Sweden. At its brightest, the footprint shone with an ultraviolet light  intensity far less than Saturn's polar auroral rings, but comparable to the  faintest aurora visible at Earth without a telescope in the visible light  spectrum. Scientists have not found a matching footprint at the southern end of  the magnetic field line.Jupiter's  active moon Io creates glowing footprints near Jupiter's north and south poles,  so scientists suspected there was an analogous electrical connection between  Saturn and Enceladus. It is the only known active moon in the Saturn system  with jets spraying water vapor and organic particles into space. For years,  scientists used space telescopes to search Saturn's poles for footprints, but  they found none."Cassini  fields and particles instruments found particle beams aligned with Saturn's  magnetic field near Enceladus, and scientists started asking if we could see an  expected ultraviolet spot at the end of the magnetic field line on Saturn,"  said Wayne Pryor, a lead author of the Nature study released today, and Cassini  co-investigator at Central Arizona College in Coolidge, Ariz. "We were  delighted to find the glow close to the 'bulls-eye' at the center of our target."In 2008,  Cassini detected a beam of energetic protons near Enceladus aligned with the  magnetic field and field-aligned electron beams. A team of scientists analyzed  the data and concluded the electron beams had sufficient energy flux to  generate a detectable level of auroral emission at Saturn. A few weeks later,  Cassini captured images of an auroral footprint in Saturn's northern hemisphere.  In 2009, a group of Cassini scientists led by Donald Gurnett at the University  of Iowa in Iowa City, detected more complementary signals  near Enceladus consistent with currents that travel from the moon to the top of  Saturn's atmosphere, including a hiss-like sound from the magnetic connection.  That paper was published in March in Geophysical Research Letters.The  water cloud above the Enceladus jets produces a massive, ionized "plasma"  cloud through its interactions with the magnetic bubble around Saturn. This  cloud disturbs the magnetic field lines. The footprint appears to flicker in  these new data, so the rate at which Enceladus is spewing particles may vary."The  new data are adding fuel to the fire of some long-standing debates about this  active little moon," said Abigail Rymer, the other lead author of the Nature  study and a Cassini team scientist based at the Johns Hopkins University Applied  Physics Laboratory in Laurel, Md. "Scientists have been wondering whether  the venting rate is variable, and these new data suggest that it is."The  Cassini-Huygens mission is a cooperative project of NASA, the European Space  Agency and the Italian Space Agency. JPL, a division of the California  Institute of Technology in Pasadena, manages the mission for NASA's Science  Mission Directorate in Washington. The Cassini orbiter and several of  its instruments were designed, developed and assembled at JPL.To  see a video and hear the sounds of the electrical connection, and to get more  information about the Cassini mission, visit:http://www.nasa.gov/cassiniandhttp://saturn.jpl.nasa.gov.