December 16, 2004

Dione and Titan: Zooming Into View

The close approach of the Cassini probe, now flying by Saturn's moons, Dione and Titan, reveals a complex atmosphere with clouds hovering over what may prove next month to be continents and even oil-rich oceans.

Astrobiology Magazine -- The map of Saturn's moon Dione, generated from Cassini images taken during the spacecraft's first two orbits of Saturn, illustrates in the banner image, the imaging coverage planned during Cassini's first Dione flyby on Dec. 14, 2004.

Colored lines enclose regions that will be covered at different imaging scales as Cassini approaches Dione.

Cassini will zoom past Dione at a distance of approximately 81,400 kilometers (50,600 miles) during this flyby. An even closer encounter with Dione is in store for Cassini in October 2005, when the spacecraft is slated to fly past the icy moon at a mere 500 kilometers (311 miles).

Images from this week's flyby will be superior in resolution to those obtained by NASA's Voyager 1 in November 1980. Voyager 1 passed Dione at a distance of 161,520 kilometers (100,364 miles) at closest approach, yielding a best resolution of approximately 1 kilometer per pixel.

The area to be imaged at highest resolution by Cassini during this upcoming flyby will be centered on the bright, wispy terrain on Dione's trailing hemisphere, marked by the red outline on this map. The resolution of Cassini images in this region will be 500 meters per pixel and better.

The flyby map of Titan (inset left) was created by images acquired in visible light using the Cassini narrow angle camera. The highest southern latitudes on Dione have not yet been seen by Cassini, resulting in the map's lower limit of approximately 80 degrees south latitude.

This view from Cassini's second close flyby of Titan on Dec. 13, 2004 shows bright material within the large dark region west of Xanadu. The area in this image is a region that has not previously been seen by Cassini at this high resolution.

The image was taken with the Cassini spacecraft narrow angle camera at a distance of approximately 125,900 kilometers (78,200 miles) from Titan, using a filter centered at 938 nanometers that emphasizes the moon's surface and clouds. The image scale is 735 meters (2,400 feet) per pixel.

In the global view (inset, upper right) right streaks of cloud in Titan's southern hemisphere are visible. Linear clouds such as these have appeared intermittently in this region of Titan.


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