Surface morphology at the Pathfinder landing site

Abstract

The morphology of the Pathfinder landing site shows small elongated ridges. These ridges extend to the horizon. Within a radius of app. 100 m the Imager for Pathfinder (IMP) camera provided stereoscopic information. Photogrammetric analysis of images were carried out to obtain a digital terrain model and to map ridges and throughs within this radius. Panoramic images were inspected on stereoscopic screens to help in indentificiation of ridge crests by the human eye. Coordinates have been measured for about 2000 ridge crest points. Ridges were found to have wavelengths of about 10-20 m and elevations of 1-3 m on average. Maps of the ridge crest points show that ridges and troughs are generally oriented from SW to NE, with minor lineaments oriented from S to N and SE to NW. The dominant SW to NE, with minor lineaments oriented from S to N and NW to SE directions fit with main orientations of Ares Vallis. These three directions of material transportation at the end of Ares and Tiu Valles can be identified in Viking Orbiter images by those streamlined islands which have been eroded by both channels. Crater counts show Ares Vallis to be older than Tiu Vallis. Tiu Vallis material has to some extent modified the pre-existing Ares Vallis materials but the last deposition was the major geological process in this area.