Volume: 02, Issue: 07 04/07/2004 
Saturn as seen from the Cassini-Huygens spacecraft.
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Other Articles in This Issue:
Mars Express Discovers Methane in Martian Atmosphere
Shuttle Technology Gets Hearts Pumping
Most Precise Gyroscopes Ready to Test Einstein Theory
Chat Live about Martian Geology and Rovers

Cassini Reveals New Atmospheric Features on Saturn

As Cassini closes in on Saturn, its view is growing sharper with time and now reveals new atmospheric features in the planet's southern hemisphere.

Atmospheric features such as two small, faint dark spots visible in the planet's southern hemisphere will become clearer in the coming months. The spots are located at 38 degrees south latitude.

The spacecraft's narrow angle camera took several exposures on March 8, 2004, which have been combined to create this natural color image. The image contrast and colors have been slightly enhanced to aid visibility.

Moons visible in the lower half of this image are: Mimas (398 kilometers, or 247 miles across) at left, just below the rings; Dione (1,118 kilometers, or 695 miles across) at left, below Mimas; and Enceladus (499 kilometers, 310 miles across) at right. The moons had their brightness enhanced to aid visibility.

The spacecraft was then 56.4 million kilometers (35 million miles) from Saturn, or slightly more than one-third of the distance from Earth to the Sun. The image scale is approximately 338 kilometers (210 miles) per pixel. The planet is 23 percent larger in this image than it appeared in the preceding color image, taken four weeks earlier.

Wind-blown clouds and haze high in Saturn's atmosphere are captured in a movie made from images taken by the Cassini narrow angle camera between Feb. 15 and Feb. 19, 2004.

The bright areas in these images represent high haze and clouds near the top of Saturn's troposphere. Cassini has three filters designed to sense different heights of clouds and haze in the planet's atmosphere. Any light detected by cameras using the 889-nanometer filter is reflected very high in the atmosphere, before the light is absorbed.

Movie Made of Saturn Wind Patterns

This is the first movie ever made showing Saturn in these near-infrared wavelengths. The images were made using a filter sensitive to a narrow range of wavelengths centered at 889-nanometers, where methane in Saturn's atmosphere absorbs sunlight.

In the movie, atmospheric motions can be seen most clearly in the equatorial region and at other southern latitudes. Saturn's equatorial region seems disturbed in the same way that it has been for the past decade, as revealed by observations from NASA's Hubble Space Telescope. Researchers have speculated that the bright cloud patterns there are associated with water-moist convection arising from a deeper atmospheric level where water condenses on Saturn, and rising to levels at or above the visible cloud tops. Close analysis of future data by scientists on the Cassini-Huygens mission should help determine whether this is the case.

Saturn's rings are extremely overexposed in these images. Because the range of wavelengths for this spectral filter is narrow, and because most of this light is absorbed by Saturn, the disc of Saturn is inherently faint and the exposures required are quite long (22 seconds). The rings do not strongly absorb at these wavelengths, so they reflect more light and are overexposed compared to the atmosphere. Orbiting moons in the images were manually removed during processing. The movie, consisting of 30 stacked images, spans five days and captures five complete but non-consecutive Saturn rotations. The direction of motion is from left to right. Each 10.6-hour Saturn rotation is evenly sampled by six images. After each rotation sequence, the planet can be seen to grow slightly in the field of view. Cassini was 65.6 million kilometers (40.7 million miles) from Saturn when the images, reduced in scale by a factor of two onboard the spacecraft, were taken. The resulting image scale is approximately 786 kilometers (420 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 Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information on the Cassini-Huygens mission, visit:

To view the video of Saturn's clouds, visit:
http://saturn.jpl.nasa.gov/cgibin/gs2.cgi?path=../multimedia/images/saturn/images/PIA05384.gif&type=image. It may take awhile for the full animation to download.

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