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P.M. Schenk (Lunar and PLanetary Institute)
Each of the 4 Galilean satellites has distinct regional topographic properties related to their divergent geologic histories. Currently available data are limited to Galileo derived stereogrammetry and photoclinometry. Locally dominated by smooth dark plains and steep-sided bright promontories, Callisto is regionally divided into irregularly shaped bright and dark patches several hundreds of kilometers across. These patches may be related to Callisto's ancient history but regional elevation characteristics are currently unconstrained. Ganymede's bright terrains are subdivided structurally into smaller polygons 10's to a few hundred km across. Again, regional data are scarce but in at least one location they suggest varying degrees of tectonic defomation may correlate with elevation and possibly age. On Europa, regional geology varies from ridged plains to highly disrupted mottled terrains. Each is very different topographically, forming distinct provinces, although these do not always correspond directly to albedo regions. Only 20% of the surface can be so mapped, however. Europa also has numerous oblong plateaus several 10's of km across and up to 1 km high. These bear a superficial resemblance to some of Io's large mountains but at somewhat reduced scales. Regional mapping of Io is in progress but geologic units near the subjovian point have different elevations. The origin of these variations is poorly understood as these units were images at only 500-1000 m resolutions and their formation is not well understood. For each satellite, acquisition of regional topographic mapping data is thus as equally important as high resolution local topographic mapping in any future Jovian Moon mission.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.