Topographic wavelengths of Ganymede groove lanes from Fourier analysis of Galileo images

Galileo images have shown that grooved terrain on Ganymede consists of perv asive ridges and grooves at a variety of spatial scales, which complicates visual interpretation. We use Fourier analysis to separate complex surface deformation into its component dominant wavelengths (closely correlated to topographic wavelengths) to determine spatial relationships within and amon g grooved terrain units. We analyze groove lanes in four Galileo target sit es (Uruk Sulcus, Byblus Sulcus, Tiamat Sulcus, and Nicholson Regio), spanni ng a range of resolutions and lighting geometries, and we find multiple dom inant wavelengths in each. Fourier analysis of the complexly deformed Uruk Sulcus shows both similarities and differences in wavelength distribution a mong its tectono-stratigraphic subunits (a range of 0.5 to 6 km, with a con centration at 1.2 km); favorable comparison is made to a stereo-derived top ographic model. Of the dominant wavelengths displayed by Byblus Sulcus (sim ilar to 1, 3.3, and 10 km), the longest wavelength is revealed by profiles across both high- and low-resolution images with very different lighting ge ometries. Tiamat Sulcus displays different dominant wavelengths north (5 to 10 km) and south (3 to 5 km) of the orthogonally trending Kishar Sulcus. G roove lanes in Nicholson Regio are significantly different from the other s ites because they are isolated within dark terrain. Fourier analysis of the se dark terrain groove lanes shows dominant wavelengths (similar to 2.1, 3. 2, and 8.0 km) that are similar to those in lanes of more typical grooved t errain. This suggests that the tectonic style and lithospheric characterist ics in this portion of Ganymede's dark terrain were similar to those in bri ght grooved terrain at the time of deformation. Our results support the hyp othesis that longer topographic wavelengths in Ganymede's groove lanes form ed by means of extensional necking of the lithosphere, while multiple short er wavelengths formed by normal faulting of the brittle lithosphere, in bot h bright and dark terrains. The similar wavelengths of deformation seen in several groove lanes in both bright and dark terrain suggest similarity in lithospheric thickness, composition, and mechanical structure at these disp arate sites. A global process (such as differentiation) could be responsibl e for creating a similar planet-wide strain and thermal regime during the t ime of grooved terrain formation.