Volume: 02, Issue: 20 12/01/2004 
A mosaic of nine processed images recently acquired during Cassini's flyby of Saturn's moon Titan on Oct. 26, 2004 constitutes the most detailed full-disc view to date of the mysterious moon.  Image courtesy NASA/JPL/Space Science Institute.
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Having passed closer to Tethys than the Voyager 2 spacecraft, Cassini has returned the best-ever natural color view of this icy Saturnian moon. Image courtesy NASA/JPL/Space Science Institute.
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Artistís rendering of Huygens probe orbiting Saturn.  Image courtesy NASA/ESA.
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Scramjet Shatters Speed Record
Swift Satellite Soars into Space
Space Shuttle Flight Assembly Begins
Chat Live with NASA Astronaut

A Tale of Two Moons

New views of Titan and Tethys, two of Saturn's moons, show sharp contrasts between them: one is foggy and one is cratered; one appears young, the other old. These new images represent the most intricate documentation to date of the contrasting moons.

Scientists recently pieced together a full-disc of the mysterious Titan using images from Cassiniís Oct. 26, 2004 flyby of the moon. The mosaic comprises nine images taken at distances ranging from 650,000 kilometers (400,000 miles) to 300,000 kilometers (200,000 miles). The images that make up the mosaic were processed to reduce effects of the atmosphere and to sharpen surface features. The mosaic of images has been trimmed to show only the illuminated surface and not the atmosphere around the edge of the moon. The Sun was behind Cassini, so nearly the full disc was illuminated.

Titan's lack of obvious craters is a hint of a young surface, but scientists are still investigating the surface features seen in the image. Surface features become fuzzier toward the outside of the mosaic, where the spacecraft is peering through more haze. South polar clouds are seen at the bottom. A brighter region dubbed Xanadu Regio can be seen on the right side near the equator. Scientists are debating what processes may have created the bizarre surface brightness patterns seen there, but the exact nature of that activity, whether tectonic, wind-blown, river-related, marine, or volcanic, is still unknown.

Two days after the close encounter with icy Titan, Cassini captured the images used in a mosaic of the battered and cratered moon Tethys. The images were taken at a distance of about 256,000 kilometers (159,000 miles) from Tethys. This view shows the trailing hemisphere of Tethys, which is the side opposite the moon's direction of motion in its orbit.

Upon observation of the mosaic, the surface of Tethys has a neutral hue. The mosaic reveals a world nearly saturated with craters: many small craters lie on top of older, larger ones, suggesting an ancient surface. Grooves can be seen at the top and along the boundary between day and night.

Tethys is known to have a density very close to that of water, indicating that it is likely composed mainly of water ice. Its frozen mysteries await Cassini's planned close flyby in September 2005.

While scientists were examining these new images, the European Space Agencyís (ESA) Huygens probe, now orbiting Saturn aboard Cassini, successfully passed its 16th in-flight inspection. This procedure was the last checkup planned before the separation of the Huygens probe from Cassini in December. The preliminary analysis of the real-time data received showed all events in the check-out procedure occurred as, and when, expected.

The Cassini-Huygens mission is a cooperative project of NASA, ESA, 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.

For images and more information about the Cassini-Huygens mission, visit the following websites:

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