The Cassini spacecraft, which began its tour of the Saturn system just over a month ago, has detected lightning and a new radiation belt at Saturn, and a glow around the planet’s largest moon, Titan. The spacecraft’s radio and plasma wave science instrument detected radio waves generated by lightning. Cassini finds radio bursts from this lightning are highly episodic. There are large variations in the occurrence of lightning from day to day, sometimes with little or no lightning, suggesting a number of different, possibly short-lived storms at middle to high latitudes. A major finding of the imaging instrument for the magnetosphere is the discovery of a new radiation belt just above Saturn’s cloud tops, up to the inner edge of the D-ring. This is the first time that a new radiation belt has been discovered above Saturn with remote sensing.
This new radiation belt extends around the planet. It was detected by the emission of fast neutral atoms created as its magnetically trapped ions interact with gas clouds located planetward of the D-ring, the innermost of Saturn’s rings. With this discovery, the radiation belts are shown to extend far closer to the planet than previously known. Cassini’s visual and infrared mapping spectrometer also captured Saturn’s largest moon Titan glowing both day and night, powered by emissions from methane and carbon monoxide gases in the moon’s extensive, thick atmosphere. The sun illuminated fluorescent glow of methane throughout Titan’s upper atmosphere – revealing the atmosphere’s immense thickness and extending more than 700 kilometers (435 miles) above the surface, was expected. However, the nighttime glow, persistently shining over the night side of Titan, initially surprised scientists.
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, D.C. JPL designed, developed and assembled the Cassini orbiter.