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The Cassini narrow angle camera took this image of Saturn in blue light on Feb. 29, 2004 showing several bands and spots in Saturn's atmosphere, including a dark band south of equator with a scalloped southern border. The distance to Saturn was 59.9 million kilometers (37.2 million miles); the image scale is 359 kilometers (223 miles) per pixel.
The BL1 broadband spectral filter (centered at 451 nanometers) allows Cassini to "see" light in a part of the spectrum visible as the color blue to human eyes. Images made using this filter can be combined with those taken with red and green filters to create full-color composites.
In this image, everything on the planet is a cloud, and the contrast between bright and dark features is determined by the different blue-light absorbing properties of the particles that comprise the clouds. White regions contain material reflecting in the blue; dark regions contain material absorbing in the blue. This reflecting/absorbing behavior is controlled by the composition of the cloud's colored material, which is still a mystery and one which may be answered by Cassini. The differing concentrations of this material across the planet is responsible for its banded appearance in the visible region of the electromagnetic spectrum.
Three of Saturn's moons can be seen in the image: Enceladus (504 kilometers, 313 miles across) at left; Mimas (396 kilometers, or 246 miles across) left of Saturn's south pole; and Rhea (1,528 kilometers, or 949 miles across) at lower right. The brightnesses of the moons have been enhanced to aid visibility.
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 Office of Space Science, 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.