GEOLOGIC MAPPING OF WESTERN SOUTH POLE-AITKEN USING DATA FROM LRO

In comparison to previous lunar datasets, the large quantity and improved spatial scale of data from the Lunar Reconnaissance Orbiter (LRO) now permits highly detailed studies of the lunar surface, particularly well-suited for geologic mapping. Using a 100 m/pixel global mosaic from the LRO wide-angle camera for surface morphology and Clementine UVVIS 415-750 nm band-ratio data for soil maturity, we have mapped a portion of Lunar Quadrangle 29 (LQ29, Planck). The LQ29 area (30°-60° S, 120°-180° E) covers the western portion of South Pole-Aitken Basin (SPA), which contains diverse volcanic materials and has excavated deep into the lower crust, providing the greatest stratigraphic cross-section on the Moon. Preliminary mapping of the eastern half of the quadrangle was recently completed using ArcGIS for Desktop Advanced (ver. 10.x), a software package that permits user display, querying, mapping, and analysis of raster and vector datasets.

For the eastern half of Planck, 18 geologic units were identified along with structural features and 750 primary craters for crater count age estimates. Units include: Mare Ingenii rim materials; Mare Ingenii floor materials; Leibnitz rim materials; Leibnitz floor materials; Poincare rim materials; Von Karman rim materials; Von Karman rim and Leibnitz rim materials; sharp-rimmed, bowl craters; sharp-to-round rimmed craters; complex craters with central peak; crater and ejecta; ejecta; mare materials (1 and 2); cratered plains; plains with Leibnitz ejecta materials; and surficial materials (1 and 2). Several craters (D= ~30-60 km) have well-developed sinuous channels along portions of their interior walls. Wrinkle ridges are apparent near the center of crater Poincare. Individual to branching systems of linear to arcuate rilles (1-100 km) occur mainly on the floors of craters Poincare, Garavito, and Jules Verne. Impact craters larger than 1 km in diameter were counted on all mapped units as a first step in relative age dating of geologic units. Areas with secondaries, secondary chains or clusters were avoided. The N(20) values, combined with the mapped geology, shows that Mare Ingenii and Poincare, have some of the oldest geologic surfaces in the region. This result is reasonable considering that the eastern half of the quad is within SPA, one of the oldest features on the Moon.