Geologic Mapping of the Lunar South Pole

The lunar South Pole region (60°-90°S) is being mapped at 1:2.5M scale using spacecraft data (Clementine, Lunar Prospector and Lunar Orbiter) to characterize geologic units, recognize contacts and structures, and identify impact craters (D>2 km) for age-dating. In addition to providing an updated geologic map, the goals of this study are to (1) constrain the geologic history of the lunar South Pole, (2) determine the timing and effects of major basin-forming impacts on crustal structure and stratigraphy, and (3) assess the distribution of units based on composition (e.g., H, Fe, Th).

Most of the map area is located within the South Pole-Aitken Basin, the largest (~2600 km), deepest (~18 km), and oldest basin known on the Moon. The presence of permanently shadowed areas near the pole, that the basin exposes materials derived from the lower crust, and the enrichment in FeO and Th, makes this area geologically unique. Preliminary mapping of the Schrödinger Basin quadrant (70°-90°S, 90-180°E) in the South Pole map area has initially identified three groups of units. Highland Materials form most intercrater highland surfaces, are believed to predate or coincide with the Amundsen-Ganswindt (D=335 km) and Schrödinger (D=312 km) Basin-forming events, and are some of the oldest materials (pre-Nectarian to Nectarian) in this quadrant. Crater Materials, found throughout the quadrant, include materials emplaced by impact events and are Nectarian to Imbrian in age. Schrödinger Materials form some of the youngest deposits (Imbrian to Eratosthenian). Most of Schrödinger's floor deposits exhibit flat expanses with smooth to rough surfaces and lobate edges, are dissected by floor fractures, and are believed to consist of impact melt and/or were emplaced by effusive eruptions. The eastern part of Schrödinger contains a well-preserved ovoidal depression believed to be the source of at least two pyroclastic eruptions.

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