Splendid Saturn

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The gorgeous moon, Dione, poses for Cassini, with shadowed craters and bright, wispy streaks. The wispy areas will be imaged at higher resolution in mid-December 2004. Subtle variations in brightness across the surface of this moon are visible here as well. Dione’s diameter is 1,118 kilometers, (695 miles). Click image for larger view. Image Credit: NASA/JPL

In a splendid portrait created by light and gravity, Saturn’s lonely moon Mimas is seen against the cool, blue-streaked backdrop of Saturn’s northern hemisphere. Delicate shadows cast by the rings arc gracefully across the planet, fading into darkness on Saturn’s night side.

The part of the atmosphere seen here appears darker and more bluish than the warm brown and gold hues seen in Cassini images of the southern hemisphere, due to preferential scattering of blue wavelengths by the cloud-free upper atmosphere.

The bright blue swath near Mimas (398 kilometers, or 247 miles across) is created by sunlight passing through the Cassini division (4,800 kilometers, or 2,980 miles wide). The rightmost part of this distinctive feature is slightly overexposed and therefore bright white in this image. Shadows of several thin ringlets within the division can be seen here as well. The dark band that stretches across the center of the image is the shadow of Saturn’s B ring, the densest of the main rings. Part of the actual Cassini division appears at the bottom, along with the A ring and the narrow, outer F ring. The A ring is transparent enough that, from this viewing angle, the atmosphere and threadlike shadows cast by the inner C ring are visible through it.

Images taken with red, green and blue filters were combined to create this color view. The images were obtained with the Cassini spacecraft narrow angle camera on Nov. 7, 2004, at a distance of 3.7 million kilometers (2.3 million miles) from Saturn. The image scale is 22 kilometers (14 miles) per pixel.

Titanic Closeup

A mosaic of nine processed images recently acquired during Cassini’s first very close flyby of Saturn’s moon Titan on Oct. 26, 2004, constitutes the most detailed full-disc view of the mysterious moon.

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Scientists puzzle over images from Titan, Saturn’s largest moon, that resemble complex landforms. Click image for larger view. Image Credit: NASA/JPL

The view is centered on 15 degrees south latitude, and 156 degrees west longitude. Brightness variations across the surface and bright clouds near the south pole are easily seen.

The images that comprise the mosaic have been processed to reduce the effects of the atmosphere and to sharpen surface features. The mosaic has been trimmed to show only the illuminated surface and not the atmosphere above the edge of the moon. The Sun was behind Cassini, so nearly the full disc is illuminated. Pixel scales of the composite images vary from 2 to 4 kilometers per pixel (1.2 to 2.5 miles per pixel).

Surface features are best seen near the center of the disc, where the spacecraft is looking directly downwards; the contrast becomes progressively lower and surface features become fuzzier toward the outside, where the spacecraft is peering through haze, which washes out surface features.

The brighter region on the right side and equatorial region is named Xanadu Regio. Scientists are actively debating what processes may have created the bizarre surface brightness patterns seen here. The images hint at a young surface with no obvious craters. However, the exact nature of that activity, whether tectonic, wind-blown, fluvial, marine or volcanic is still to be determined. The images comprising this mosaic were acquired from distances ranging from 650,000 kilometers (400,000 miles) to 300,000 kilometers (200,000 miles).

On January 14, 2005, the Huygens probe will try to descend to the surface of Saturn’s largest moon, Titan–a biochemically rich moon dominated by hydrocarbons like methane and ethane. These building blocks, along with Titan’s dense atmosphere, make the descent one of the milestone events for astrobiology. For the first time, another world presents interesting weather combined with dynamic chemistry that is often compared to a colder version of the primordial Earth.


Related Web Pages

Cassini
Saturn Edition, Astrobiology Magaz.
Saturn’s Rings in UV
Cassini Closes In on Saturn

Saturn– JPL Cassini Main Page
Lord of the Rings
Space Science Institute, Imaging Team Boulder, Colorado
Saturn: The Closest Pass
Prebiotic Laboratory
Planet Wannabe
Where is Cassini Now?