Advancing Science Of The Moon: Progress Toward Achieving The Goals Of The Scientific Context For Exploration Of The Moon Report
Introduction: In 2007, The National Academy of Science published The Scientific Context for Exploration of the Moon (SCEM) , a report that detailed the case for the Solar-System-wide importance of lunar science, described eight prioritized Science Concepts and associated Key Science Goals, and discussed implementation options for each. NASA’s Planetary Science Division recently tasked the Lunar Exploration and Analysis Group with convening the Advancing Science of the Moon Specific Action Team (ASM SAT). The ASM SAT met in August, 2017 and following the charter, assessed progress on the goals described in the SCEM report, science implementation, and new concepts that have become apparent in the decade since its publication. Here we present findings from the ASM SAT and highlight the continued relevance of the SCEM report for prioritized progress in lunar science in general, and future landed missions in particular. Progress made, progress still needed: The eight SCEM report Science Concepts span 1) the bombardment history of the inner Solar System; 2) the structure and composition of the interior; 3) the diversity of crustal rocks; 4) volatiles at the poles; 5) volcanism; 6) impact processes; 7) regolith processes and weathering; and 8) the atmosphere and dust environment. A common theme in evaluating progress toward achieving the Goals of each Concept was the substantial progress made either by mining existing data and samples or from the analysis of new orbital measurements, while also acknowledging that in many cases true advances will require landed missions for in situ measurements, deployment of instrumentation, or sample return. For example, the Goal ranked highest in priority in the SCEM report was to “Test the cataclysm hypothesis by determining the spacing in time of the lunar basins.” Analysis of returned samples and meteorites has provided new information about the history of lunar impact events, and analysis of new orbital data has provided a better understanding of the geologic context of some returned samples, new hypotheses for the relative ages of some basins, and has identified probable deposits of basin melt for future in situ analysis and/or sample return. However, without geochemical and geochronological analyses of key melt deposits, the timing of lunar basins remains unknown. Similar conclusions can be made for nearly all of the highest priority Goals: we have refined our knowledge such that we know where to go and how to find the answer; now progress requires that we go and seek it out. New concepts in lunar science: New data and analyses have resulted in new concepts in lunar science as well as new ways of thinking about old problems. While not comprehensive, we note several high-priority topics that have emerged or increased in importance in the last ten years, and merit further attention. 1) Work from the last decade has pointed to a lunar ‘water’ cycle with three principal components: primordial (interior) water, surficial water (linked to solar wind), and polar (sequestered) water. Identifying and characterizing these lunar volatile reservoirs and evaluating their interrelations is of high priority. 2) The origin of the Earth-Moon system and the geologic processes that operate during high-temperature planetary accretion are recorded within the lunar rock record. Studies of lunar samples can provide constraints on, among other things, the timing of the giant impact, the physicochemical conditions and processes in the protolunar disk, and isotopic contrasts between the Earth and Moon. 3) High-resolution imagery has also revealed lunar tectonic features that need further evaluation in terms of age and, if currently active, correlation with moonquakes. Conclusions: The SCEM report highlights the importance of lunar science to questions ranging from the evolution of the Solar System to the origin of life on Earth. A decade of intensive lunar science research has led to substantial progress in many areas, but the concepts, goals, and priorities remain relevant today. Together with new concepts that have emerged in the past ten years, the SCEM report provides context and a framework for how lunar surface exploration missions can advance lunar geology and Solar System science, particularly in an era of renewed interest in the Moon and its environs as a target for human exploration. Reference:  National Research Council (2007) The Scientific Context for Exploration of the Moon, National Academies Press, Washington.