Faustini And Slater Craters: Psrs Containing Geologically Young Craters
Two areas within the lunar south polar Permanently Shaded Regions (PSRs) of Faustini and Slater craters have significantly brighter Lyman-α albedo as measured by the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP; shown in Fig. 1). These areas correlate with the ejecta blankets of two small craters (<2 km diameter) that also have much higher Circular Polarization Ratios (CPR), as measured by LRO Mini-RF (shown in Fig. 2d). The higher albedo is likely due to significantly lower surface porosity in the regolith covering the ejecta blankets compared to the surrounding PSRs, while high CPR indicates increased surface roughness. These combined observations suggest that the two craters are very young on geologic timescales: 75-450 million years (Myr) for crater A and ~16 Myr for crater B. Missions to one or both of these craters would have high value. While both PSRs contain volatiles, Faustini has a region inside an inner crater that is constantly very cold and has higher normal albedo at 1064 nm, as observed by the Lunar Orbiter Laser Altimeter (LOLA) and shown in Fig. 3. This area may have more complex volatile composition than other PSRs. However, the geologically young crater in Slater is much younger than the one in Faustini and would be of high value for sampling materials from a young crater. In order to properly explore either of these sites, mobility is highly desired. Given the appropriate suite of instruments sample return may not be necessary. Science objectives identified by NAC (2007) that could be addressed at one or both of these sites include: 1. Determine the compositional state (elemental, isotopic, mineralogic) and compositional distribution (lateral and depth) of the volatile component in lunar polar regions (4a). 2. Determine the source(s) for lunar polar volatiles (4b). 3. Understand the transport, retention, alteration, and loss processes that operate on volatile materials at permanently shaded lunar regions (4c). 4. Understand the physical properties of the extremely cold (and possibly volatile rich) polar regolith (4d). 5. Determine what the cold polar regolith reveals about the ancient solar environment (4e). 6. Quantify the effects of planetary characteristics (composition, density, impact velocities) on crater formation and morphology (6c). 7. Measure the extent of lateral and vertical mixing of local and ejecta material (6d). 8. Search for and characterize ancient regolith (7a). 9. Determine physical properties of the regolith at diverse locations of expected human activity (7b). 10. Understand regolith modification processes (including space weathering), particularly deposition of volatile materials (7c). REFERENCES: Mandt et al. (2016), LRO-LAMP detection of geologically young craters within lunar permanently shaded regions, Icarus, 273, 114-120. National Research Council, 2007. The Scientific Context for Exploration of the Moon, The National Academies Press, Washington, D.C., National Academy of Sciences. FIGURE CAPTIONS: Fig. 1: LAMP Lyman-α albedo overlaid on a LOLA shaded relief map of the two PSRs of interest. The Lyman-α albedo in the PSRs is lower than areas that are exposed to sunlight, the exception being the ejecta blankets of two small craters, designated A & B. The circles surrounding the craters have a radius of 3 km and are centered on the crater (inset). LOLA shaded relief map of the lunar south polar region (area south of 80o S latitude) produced using the JMoon beta tool (http://jmars.asu.edu/node/2055). Lines of latitude and longitude are shown for every 10o (right hand panel). The box indicates the region of focus for this study. Fig. 2: LROC, Diviner and Mini-RF observations of the PSRs of interest. As in Fig. 1, craters A & B are identified with circles drawn to have a radius of 3 km and centered on the craters: (a) LROC composite image of the interior of Faustini taken with an 24.23 ms exposure time with an image resolution is 20 m/pixel. (b) LROC composite image of the interior of Slater crater taken with an 24.23 ms exposure time with an image resolution of 20 m/pixel. (c) Annual average temperature measured by Diviner (d) Mini-RF CPR of the two PSRs and the surrounding area. Fig. 3: LOLA 1064 nm normal albedo of the two PSRs (shaded) covered in this study. As in Fig. 1, craters A & B are identified with circles drawn to have a radius of 3 km and centered on the crater.