The Aristarchus impact event and the effects of target material

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Abstract
The relatively well preserved, 42 km diameter lunar impact crater Aristarchus was excavated across the boundary between the Aristarchus Plateau and the mare plains. Previous geological mapping of the different ejecta facies associated with Aristarchus has shown that there are distinct morphological differences between ejecta emplaced on either side of the fault scarp that separates the plateau from the mare. One explanation of this observation is that ejecta behaved in different ways on emplacement depending on the original lithology of the excavated material. To test this proposal, we examine the pre-Aristarchus regional stratigraphy and identify the spectral signatures of each of the material's units. By comparing these data with analysis of the geology and spectral characteristics of the ejecta units, we are able to show the provenance of each of the mappable ejecta facies. The conclusions are consistent with the concept of the crater ejecta asymmetry being related to bedrock characteristics. Using geological mapping, spectral interpretation and present understanding of the impact cratering process, we reconstruct the impact event and suggest how such techniques could be used further to interpret the Moon's composition and history.