Jupiter casts a baleful eye on wayward Ganymede in this frame, color-composited from narrow angle images taken on November 18 and high-pass filtered and contrast-enhanced to bring out details not readily seen otherwise. The smallest features in this image are 240 km across.

Jupiter and Ganymede as seen by Cassini. Photo: NASA/JPL/University of Arizona. SEE THE FULL SCREEN VERSION

Jupiter's "eye", the Great Red Spot, was captured just before disappearing over the eastern limb of the planet. The furrowed eyebrow above and to the left of the Spot is a turbulent wake region caused by westward flow deflected to the north and around the Red Spot. (An animation of ISS images from early October, beautifully illustrating this flow, was released on November 20 and can be viewed below.) Within the band south of the Red Spot are seen a trio of white ovals, small high pressure counter-clockwise rotating regions that are dynamically similar to the Red Spot. The dark filamentary features interspersed between the white ovals are probably cyclonic circulations, similar to those seen by Galileo, and, unlike the ovals, are rotating clockwise.

Jupiter's Equatorial Zone stretching across the planet to the north of the Spot appears bright white, with gigantic plume clouds spreading out from the equator both to the northeast and to the southest. in a chevron pattern. This zone looks distinctly different than it did during the Voyager flyby 21 years ago when its color was predominantly brown, and only SW/NE-trending white plumes north of the equator were conspicous against the darker material beneath. The bluish gray regions near the equator, noted in earlier releases, are regions where the clouds have cleared and, except for partial obscuration by thin upper level hazes, we can see to great depth. The darker, brownish North Equatorial belt north of the Equatorial Zone is also quite turbulent.

Ganymede is Jupiter's largest moon, about 50% larger than our own Moon and larger than the planet Mercury. Like the Moon and Mercury, Ganymede has no atmosphere; the visible details seen in this image are different geological terrains on the satellite's surface. Dark areas tend to be older and heavily cratered; the brighter locales are younger and more sparsely cratered. The latter are the famed grooved terrains first seen by Voyager and imaged at high resolution by Galileo. Cassini images of Ganymede and the other Galilean satellites taken near closest approach on December 30 will have resolutions of ~60 km/pixel, four times better than that seen here.