Returning Treasure From The Moon: Fundamental Importance Of Planetary Sample Return (Sr) And Fulfilling The Scem Goals
Introduction: Samples returned from the lunar surface are critical to validate both orbital and in situ observations and provide a unique perspective for understanding the nature and evolution of the Moon. This unique perspective is based on the scale the sample is viewed (mm-Å), the ability to manipulate the sample, the capability to analyze the sample at high precision and accuracy, and the ability to significantly modify experiments and measurements as logic and technology dictate over an extended period of time (decades). Multiple SR missions to the Moon are increasingly more scientifically and economically feasible. With the acquisition and development of significant global lunar data sets, SR targets to fulfill science goals have become much more refined, sample data can be better placed within a global (surface and interior) context, and landing site safety can be comprehensively assessed. The return of small sample masses by scientifically targeted robotic missions are becoming increasingly more valuable as advances in analytical technology enable extraction of important data from smaller sample masses. Such efforts support concepts developed in the SCEM report  and LEAG efforts to evaluate the advances since the SCEM report . Within this context, SR should be viewed as an integral exploration step with many degrees of complexity. SR Target Selection within the Context of SCEM Report and Recent LEAG Appraisals: Here, we highlight examples of potential SR targets that will fulfill science linked to SCEM and LEAG report concepts . CONCEPT 1: The bombardment history of the inner Solar System is uniquely revealed on the Moon. Scientific rationale: Determine the age of the South Pole-Aitken basin (SPA) to constrain models for the impact bombardment of the Moon and inner Solar System and dynamics of the outer Solar System. Sample Material: Impact melt produced by the SPA event. Characteristics of Target: Relatively smooth plains in the central part of SPA basin. CONCEPT 2: The structure and composition of the lunar interior provide fundamental information on the evolution of a differentiated planetary body. Scientific rationale: Determine the composition of the upper lunar mantle to constrain chemical/stratigraphy of the lunar interior and aid the interpretation of current and future geophysical data. Sample Material: Mantle assemblages excavated during basin formation. Characteristics of Target: Basin interiors with (a) thin or absent lunar crust as interpreted by GRAIL, (b) limited mare deposits, and (c) mafic central peaks. CONCEPT 3: Key planetary processes are reflected in the diversity of lunar rocks. Scientific rationale: Determine the nature and timing of primordial lunar differentiation. Sample Material: Ferron anorthosite and related lithologies. Target: The feldspathic far side highlands. CONCEPT 5: Lunar volcanism provides a window into the thermal and compositional evolution of the Moon. Scientific rationale: Determine differences among basalts associated with different crustal terrains (e.g. PKT versus lunar highlands) and different ages to test models for planetary differentiation and lunar mantle evolution. Sample Material: Mare basalts from the lunar far side and young basalts. Target: Relatively smooth plains in SPA and Mos-coviense basins; farside cryptomaria (e.g., Dewar); youngest basalts in southwest Aristarchus plateau. CONCEPT 7: The Moon is a natural laboratory for regolith processes and weathering on airless bodies. Scientific rationale: Determine the influence of lunar surface environment (e.g., plasma, magmatism) on regolith evolution. Sample Material: Bulk regolith samples. Target: Samples collected from well-defined surface environments. LEAG ASM-SAT identified new lunar concepts: The “water” cycle, origin of the Earth-Moon system, and lunar tectonics. The water cycle can be studied by sample return Scientific rationale: Determine the interaction and evolution among different volatile reservoirs (e.g., interior, surface) on the Moon. Sample Material: Polar regolith, pyroclastic deposits, and recent degassing deposits (e.g., Ina). Target: Samples collected from surface environments well-defined by in situ measurements.