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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’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. (See
accompanying release below.)
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.
