Computer Assisted Time Sequence Sorting of Grooves in Eastern Mysia

Introduction: Two thirds of the surface of Ganymede is covered by grooved terrain, suggesting an active history of extensional tectonics. One important piece of Ganymede geological history is to determine the order in which groove-forming events happened. Separating grooves into a time sequence will help to constrain the geological events that formed the grooves. Previous investigations into the time sequence of grooved terrain formation have been made in the Uruk Sulcus and Nippur Sulcus regions [1], the Nun Sulci region [2], and the leading hemisphere and Sippar Sulcus regions [3]. These studies came to the conclusion that the orientation and morphology of the grooves changed over time. Ultimately we hope to link this investigation with previous regional investigations to form a global picture of the sequence of grooved terrain formation. Target Area: The target area is located in eastern Mysia Sulci, 20°N to 10°S, 305° to 355°W. This area includes both dark and bright terrain, with the central region composed of a complex network of crisscrossing grooves. Most grooves in this area trend in the E-W to NE-SW direction and are interspersed with small polygons of dark terrain (Figure 1). There are few large craters in this region, providing a relatively clear view of the relationships within the grooved terrain. Past analyses of grooved terrain time sequences required sorting by hand, which was time consuming due to the number of grooves, and the difficulty of tracking the relationships between them. These difficulties inspired the development of a computer-assisted technique. This technique has recently been developed and applied to the complex overlapping ridges on the surface of Europa [4]. This is our first attempt to adapt the technique to the grooved terrain of Ganymede. We began our investigation with the global geological base map being developed by Patterson et al. [5], which separates the grooved terrain into polygons of similar morphology and orientation. We modified the base map to