Forni, O. P. | Search NASA

NASA NTRS1985

Global Tectonics on Ganymede

Three large basin surroundings on Ganymede located on grooved terrains, which are supposed to be intensely tectonized areas were studied. All rectilinear morphological elements such as ridges, block edges; and parts of scarps were mapped. The geometric properties (grid pattern) characteristics were determined and a history for the formation of the Ganymede basins studied is proposed. Results indicate that the grooved terrains are very surficial layers, and that their formation does not significantly affect, disturb or rotate the basement. This is in agreement with the conclusion obtained from completely different data (crosscutting relationships between groove sets and their basements).

Thomas, P. G.↗

NASA NTRS1985

Importance of the Tectonic Motions on Ganymede

Voyager close up views of Ganymede reveal some provinces of old, cratered, dark terrains that are broken into polygons and cut through by light stripes of grooved terrains. The groove terrain unit and its relationships with the other units was studied at various scales because these features seem to relate at least to two main scales of processes. Minor displacements concerning only local features, i.e., large scale processes and major displacements concerning usually the major evolution of the surface, i.e., small scale processes. It appears that tectonic processes, at least in the studied areas, if playing a role in the formation of local or regional features, are very limited. The conclusions reached agree with those of Thomas et al. who show that post grooves basins reveal the presence of a primitive grid that is not disturbed by the grooved terrains.

Forni, O. P.↗