Geologic setting of Boulder 1, Station 2, Apollo 17 landing site

Boulder 1 at Station 2 is one of three boulders sampled by Apollo 17 at the base of the South Massif, which rises 2.3 km above the floor of a linear valley interpreted as a graben formed by deformation related to the southern Serenitatis impact. The boulders probably rolled from the upper part of the massif after emplacement of the light mantle. Orbital gravity data and photogeologic reinterpretation suggest that the Apollo 17 area is located approximately on the third ring of the southern Serenitatis basin, approximately 1.25 times larger than the analogous but fresher Orientale basin structure. The massif exposures are interpreted to represent the upper part of thick ejecta deposited by the southern Serenitatis impact near the rim of the transient cavity. Basin ring structure and the radial grabens that give the massifs definition were imposed on this ejecta at a slightly later stage in the basin-forming process. There is no clear-cut compositional, textural, or photogeologic evidence that Imbrium ejecta was collected at the Apollo 17 site.