Mapping Lineaments on 433eros: Process, Results, Implications

Introduction: The Near-Earth Asteroid Rendezvous NEAR-Shoemaker spacecraft orbited the asteroid 433Eros for a year from 2000-2001. The NEAR Multi-Spectral Imager (MSI) collected tens of thousands of high resolution images and as a result Eros is the most comprehensively studied asteroid in the solar system. Previous mapping of lineaments on Eros has supported the suggestion of planes throughout the asteroid [1,2]. We are creating a global database of all Eros lineaments to better understand the global distribution of these features. Lineament types include shallow and flat-floored troughs, grooves, ridges and pit chains. We identify types of lineaments across the surface using a combination of NEAR Laser Rangefinder (NLR) topog-raphic data and MSI images, and classify them according to region, including areas suggestive of thicker regolith. We compare lineament orientation to impact craters to determine if there is a causal relationship between cratering events and lineament formation. Further lineament/crater interactions are also examined , to determine the effect that lineaments have on crater shape. Mapping Process: It is particularly challenging to map lineament orientations on a non-spherical body (Eros is the shape of a peanut, measuring 34 km on the long axis). To address this issue we are mapping the lineaments directly on the Eros shapefile using POINTS, developed by Jonathan Joseph at Cornell University. POINTS accesses a database of over 140,000 MSI images. Lines can be drawn on each of these images and, since the lines are saved to the shapefile, the lines will appear in the same locations on all other images opened in POINTS. We mapped lines on images with resolutions ranging from approximately 5 to 11 meters per pixel. Mapping on these high resolution images allows the best possible identification of linear features, but their footprints are not large enough to observe regional lineation patterns. When images with lower resolutions (~35 m/p) were opened in POINTS the previously mapped lineations were in their mapped positions and regional patterns emerged. Observations: We have mapped 2153 lineations on 180 high resolution (5-11 m/p) images of Eros, creating a global lineation map of the asteroid. These lineations have been grouped into lineation sets according to location and orientation (Figs. 1,2,3,4). Many different sets of lineations can be identified. Some lineation sets are clearly related to specific impact craters. Other lineation sets have no obvious rela