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These images shows a rare and powerful storm on the night side of Saturn.
Light from Saturn's rings (called "ringshine") provided the illumination, allowing the storm and other cloud features to be seen.
The storm is a possible source of radio emissions believed to come from electrical discharges (lightning) deep in Saturn's atmosphere. Cassini began detecting the radio emissions, which resemble those from lightning, on January 23. At about the same time, amateur astronomers reported that a storm had appeared in Saturn's southern hemisphere at -35 degrees latitude. Cassini was in the wrong place to take good images of the storm on the day side, since the planet showed only a thin crescent to the spacecraft, but night side imaging was possible using light from the rings.
The top image shows the storm as it appeared to the Cassini imaging system on January 27, 2006. The storm's north-south dimension is about 3,500 kilometers (2,175 miles); it is located at -36 degrees planetocentric latitude and 168 degrees west longitude. This places it on the side of the planet that faces the spacecraft when the radio emissions are detected; the radio emissions shut down for half a Saturnian day when the storm is on the other side.
The second image was derived from the first image by reprojecting it as a cylindrical map and enhancing the contrast to bring out faint features.
No lightning flashes are visible in the images. They would look like medium-sized bright spots, since the light spreads out before it reaches the cloud tops. Non-detection does not mean that the lightning is absent, however. Lightning might be too faint to stand out above background or too deep to be seen through the thick clouds. Bad luck is another possibility: The camera might have missed the strong flashes during the 10 seconds that the shutter was open.
A narrow cloud band crosses the storm from left to right. It is illuminated by the rings from the north and is brighter on that side. Cassini scientists are looking forward to an extensive night side image set, designed to look for lightning, which will be collected during the first half of this year.
The views were obtained in visible light with the Cassini spacecraft narrow-angle camera at a distance of approximately 3.5 million kilometers (2.2 million miles) from Saturn. The image scale is 20 kilometers (12 miles) per pixel.
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. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.