Identifying the geologic context of Apollo 17 impact melt breccias

The origin of the boulders sampled during the Apollo 17 mission to the Taurus-Littrow Valley has been debated since the completion of the mission four decades ago. No consensus has yet been reached whether the sampled boulders originated in material emplaced as a result of the Serenitatis impact (i.e., massifs), the Imbrium impact (i.e., Sculptured Hills), a combination of both impact events, or as a result of another pre- or post-Serenitatis impact event (i.e., massifs or superposed deposits on valley floor). These on-going debates demonstrate the importance of identifying the geologic context of samples collected during the Apollo missions. Using high-resolution imagery and topography data, we identify boulder tracks that connect sampled boulders with source outcrops. These observations verify astronauts' impressions that boulders originated in outcrops within massif walls and that they remain uncontaminated by nearby Sculptured Hills materials. This finding can be used with updated Ar-Ar and U-Pb ages of analyzed samples to constrain the timing and intensity of the lunar cataclysm epoch. (C) 2016 Elsevier B.V. All rights reserved.