We apply machine learning techniques to identify and map resurfacing units in the central South Pole−Aitken (SPA) basin using three Lunar Reconnaissance Orbiter (LRO) mission data sets: 321/415 nm and 566/689 nm band reflectance ratios from Hapke photometrically standardized albedo maps and a Terrain Ruggedness Index map using the Wilson et al. method. Other data were considered, but albedo and topography data were key in distinguishing between maria, cryptomaria, and light plains. A two-step image classification approach was applied to the data sets, an unsupervised K-Means algorithm followed by a supervised Maximum Likelihood Classification (MLC) algorithm. K-Means identified four units, one associated with dark smooth maria, two not associated with any particular features, and a fourth associated with edge effects. To further discriminate between the two nonassociated units, the K-Means unit map and an LRO morphologic basemap were used to select multiple training areas for three defined units in the MLC algorithm: mare, cryptomare, and cryptomare/light plains. From the training area values, the MLC unit map showed a distinction between the two prior indistinguishable K-Means units. Our results show (1) that the cryptomare from the MLC algorithm is in good agreement with cryptomaria mapped by J. L. Whitten & J. W. Head, (2) that the presence of scattered maria within large patches of cryptomaria indicates possible incomplete and/or uneven ejecta deposits or sheet flows covering cryptomare surfaces, and (3) a 79% increase in the total extent of cryptomaria compared to that by J. L. Whitten & J. W. Head for the same given study area in central SPA.

Two fundamental questions face lunar scientists: (1) What is the absolute age of each lunar impact basin and thus the early impact flux curve? (2) To what degree did basin impact melt seas undergo differentiation? We compiled a 1:200,000-scale geological map of the lunar Orientale basin, focusing on identifying the most widespread and accessible occurrences of impact melt deposits from the basin-forming impact to help guide sample-return missions to Orientale and especially to other undated lunar basins using the identification and interpretation strategies for Orientale. We assess the size of craters excavating through basalt cap rock that may have exhumed datable basin impact melt, and we assess the possibility of impact melt sampling and melt differentiation for the large complex crater Maunder. We also provide guidance for distinguishing impact melt produced by larger complex craters from excavated basin melt and determining whether such craters may have also sampled through the entire melt deposit. Our analysis finds six such sites that are predicted to have the same age—that of the Orientale-forming event—and provides guidance for assessing possible melt differentiation. Future missions could collect samples from these sites for in situ age dating and petrologic assessment and/or for return to Earth and subsequent age dating and analysis. By sampling and dating impact melt of known provenance from the Moon’s dozens of large basins, future work can anchor the chronostratigraphy of the Moon’s formative years. Such information could be scaled to infer Earth’s large impactor flux around the time of life’s first emergence.

The lunar south pole is a region of focused scientific and exploration interest, with several crewed and robotic missions to this region planned within the next decade. Understanding the mineralogy of the region is essential to inform landing site characterization and selection and provides the key context for interpreting samples and in situ observations. At high latitudes, extreme illumination conditions (high phase angles) can negatively impact the data quality of orbital instruments. This is especially true for passive near-infrared spectrometers such as the Moon Mineralogy Mapper (M3) and the Kaguya Spectral Profiler, which measure the spectral properties of the surface using reflected sunlight. Using Moon Mineralogy Mapper data, we observed that the south polar region is associated with a detectable mafic signature consistent with the presence of pyroxenes. The strongest mafic signatures are associated with the South Pole-Aitken Basin, suggesting that impact melt and basin ejecta from the lower crust and upper mantle are present within this region. This observation is validated in several ways: (a) comparisons between M3 data acquired during different mission phases, (b) comparisons between multiple spectral parameters sensitive to the presence of mafic minerals, (c) comparisons between the north and south lunar polar regions, and (d) comparisons with publicly available Kaguya polar mineralogy maps and Lunar Prospector elemental abundances. We also investigate the nature of an anomalous high-albedo region within 2-3 degrees of the south pole observed in Lunar Orbiter Laser Altimeter reflectance data exhibiting a spatially conflicting apparent FeO abundance pattern between several data sets. The lunar south pole region is a region of focused scientific and exploration interest, with several crewed and robotic missions to this region currently planned within the next decade and beyond. The rocks and minerals at the lunar south pole are very different from those encountered during the Apollo missions and will provide insight into a wide range of important science questions. It is important to understand the abundance and distribution of these different materials to effectively choose landing sites and plan surface science experiments and sampling targets. We combine several data sets from orbital satellites to determine the types and distribution of rocks across the south polar region. We see evidence for the presence of lower crust and upper mantle materials excavated by a nearby giant impact basin. Moon Mineralogy Mapper data shows that the south polar region exhibits a mafic signature consistent with the presence of pyroxenes Mafic signatures are spatially correlated with ejecta from the South Pole-Aitken Basin, which may be sampled by Artemis astronauts An anomalous high-albedo region within similar to 3 degrees of the south pole exhibits spatially conflicting apparent FeO abundance patterns between several data products

The National Aeronautics and Space Administration (NASA) has defined a functionally based Moon to Mars (M2M) architecture consisting initially of four key human exploration segments: human lunar return (HLR), foundational exploration (FE), sustained lunar evolution (SLE), and humans to Mars (H2M) [1]. These segments are portions of the architecture which represent a stepwise increase in complexity and achievement of M2M objectives. As systems are deployed during the FE segment, it may be desired or even necessary to relocate these elements on the lunar surface. While some Artemis elements under development, such as rovers, are being designed for mobility during both crewed and uncrewed/dormant periods, other element concepts do not currently carry a mobility capability. A team was assembled to establish a methodology for assessing the feasibility of relocating normally stationary elements. Such a capability could be applied locally or regionally, and might allow for re-purposing previously occupied terrain, expansion of exploration range, aggregation of habitation elements, or retiring systems at the end of their useful service life.The NASA team investigated the relocation trade space through defining a representative concept of operations and assessing possible system impacts. The team focused predominately on the relocation of medium and large surface habitat architectural concepts through surface-based traverses utilizing separable mobility platforms. A representative mobility platform model was placed through simulation to analyze the possible energy requirements and dynamic illumination impacts. Preliminary assessment indicated that element relocation might be achievable, however significant system and architectural-level risks still need to be quantified to properly evaluate the methodology. Future analysis will assist in determining what degree of element relocation provides the greatest benefit to achieving a sustained lunar presence.

The Moon Mineralogy Mapper (M-3) on the Chandrayaan-1 spacecraft provided nearly global 0.5-3 mu m imaging-spectroscopy data at 140 m pixel-1 in 85 spectral bands. Targeted locations were imaged at 70 m pixel-1 and higher spectral resolution. These data enable a detailed look at the mineralogy, hydroxyl, and water signatures exposed on the lunar surface. We find evidence for multiple processes, including probable solar wind implantation, excavation of hydroxyl-poor and water-poor material in cratering events, excavation of hydroxyl and water-rich materials from depth and global trends with rock type and latitude. Some water-rich areas display sharp boundaries with water-poor rocks but have a diffuse halo of hydroxyl surrounding the water-rich rocks indicating a weathering process of destruction of water, probably due to a regolith gardening process. Mapping for specific mineralogy shows evidence for absorptions near 2.2 mu m, probably associated with smectites, and near 1.9 mu m due to water. Lunar swirls are confirmed to be OH-poor, but we also find evidence that swirls are water-poor based on a weak 1.9 mu m water band. Some swirls show enhanced pyroxene absorption. "Diurnal" signatures are found with stable minerals. Pyroxene is shown to exhibit strong band depth changes with the diurnal cycle, which directly tracks the solar incidence angle and is consistent with changing composition and/or grain size with depth. Mapping of M-3 data for the presence of iron oxides (e.g., hematite and goethite) is found to be a false signature in the M-3 data due to scattered light in the instrument.

The lunar south pole is a region of focused scientific and exploration interest, with several crewed and robotic missions to this region planned within the next decade. Understanding the mineralogy of the region is essential to inform landing site characterization and selection and provides key context for interpreting samples and in situ observations.The Artemis exploration zone (areas poleward of 84° latitude) is also relevant to geological investigations providing new insight into fundamental planetary processes. Specifically, Artemis Science Objective 1 from the Artemis III Science Definition Team Report is to understand a wide range of planetary processes including formation and differentiation of the Moon into a core, mantle, and crust, in addition to subsequent processes such as volcanism, tectonism, impacts, and regolith development. Artemis astronauts will address these objectives in several ways, guided by compositional remote sensing analyses of the region. Here, we present local mineralogical and compositional analyses of candidate high-priority science targets drawing upon several remote sensing datasets including Moon Mineralogy Mapper data. Moon Mineralogy Mapper (M3) data provide the highest spatial - and spectral-resolution mineralogical data for the lunar surface and are therefore ideally suited for characterizing compositional diversity at ~100 m spatial scale. Mineralogical diversity across the lunar surface is dominated by variations in the abundance and composition of a handful of common lunar minerals and oxides, including plagioclase, pyroxene, olivine, spinel, and ilmenite. This diversity is reflected in overall albedo and differing strengths and relative positions of spectral absorption bands at 1 and 2 μm. M3 achieved near-complete coverage of the south polar region. Due to the pole-crossing orbit of Chandraayan-1, areas close to the pole were imaged numerous times across the lifetime of the M3 mission, with different lighting conditions and orbital altitudes. This is helpful, as lighting conditions at high latitudes involve extreme solar incident angles and large shadows, affecting data quality (signal-to-noise ratio) and availability. The number of M3 observations available for each candidate Artemis III region is given in Table 1. In this work, we examine the character and mineralogical diversity reflected full-resolution M3 data for the candidate Artemis III landing regions.Fig. 1: M3 1 μm Integrated Band Depth across the Artemis Exploration Zone. Areas lacking well-illuminated M3 pixels (in global mosaics) are shaded light grey. Note: these areas may be illuminated in individual M3 images.

As a first step in preparing for the return of samples from the Moon by the Artemis Program, NASA initiated the Apollo Next Generation Sample Analysis Program (ANGSA). ANGSA was designed to function as a low-cost sample return mission and involved the curation and analysis of samples previously returned by the Apollo 17 mission that remained unopened or stored under unique conditions for 50 years. These samples include the lower portion of a double drive tube previously sealed on the lunar surface, the upper portion of that drive tube that had remained unopened, and a variety of Apollo 17 samples that had remained stored at −27 °C for approximately 50 years. ANGSA constitutes the first preliminary examination phase of a lunar “sample return mission” in over 50 years. It also mimics that same phase of an Artemis surface exploration mission, its design included placing samples within the context of local and regional geology through new orbital observations collected since Apollo and additional new “boots-on-the-ground” observations, data synthesis, and interpretations provided by Apollo 17 astronaut Harrison Schmitt. ANGSA used new curation techniques to prepare, document, and allocate these new lunar samples, developed new tools to open and extract gases from their containers, and applied new analytical instrumentation previously unavailable during the Apollo Program to reveal new information about these samples. Most of the 90 scientists, engineers, and curators involved in this mission were not alive during the Apollo Program, and it had been 30 years since the last Apollo core sample was processed in the Apollo curation facility at NASA JSC. There are many firsts associated with ANGSA that have direct relevance to Artemis. ANGSA is the first to open a core sample previously sealed on the surface of the Moon, the first to extract and analyze lunar gases collected in situ, the first to examine a core that penetrated a lunar landslide deposit, and the first to process pristine Apollo samples in a glovebox at −20 °C. All the ANGSA activities have helped to prepare the Artemis generation for what is to come. The timing of this program, the composition of the team, and the preservation of unopened Apollo samples facilitated this generational handoff from Apollo to Artemis that sets up Artemis and the lunar sample science community for additional successes.

Spinels represent a small fraction of lunar surface materials but provide important insights into the petrological evolution of the lunar crust and mantle. Previous remote sensing analyses of highlands spinel‐bearing lithologies have focused on pure Mg‐Al spinels, which are rare in the lunar sample collection. Using Moon Mineralogy Mapper data, we develop and test an approach for detecting spectral signatures of spinel across a wider range of Mg, Al, Fe, Cr, Ti‐bearing compositions than have been addressed in previous studies, including within mafic‐bearing assemblages. This approach is validated through integration with laboratory‐measured spinel spectra and petrographic observations of samples returned by the Luna 20 mission from the Hilly and Furrowed Terrain surrounding the Crisium Basin. Applying this approach to data from the Crisium region, small abundances of spinel (<∼5 vol%) with a range of Mg, Al, Fe, Cr, and Ti content and petrologic origin (inferred from Luna 20 samples) were found to be widespread within highlands soils across the Crisium region. This result diverges from previous remote sensing analyses, which only reported small, isolated exposures of pure Mg‐Al spinel (as well as a possible detection of Fe, Cr‐bearing spinels localized within pyroclastic materials at Sinus Aestuum). Geologic associations of candidate spinel detections across this region are consistent with a shallow crustal origin rather than excavation from depth during the Crisium‐forming impact. These spinels are detectible in near‐infrared spectroscopic data, particularly in areas of low optical maturity and may influence the spectral continuum of highlands soils.

Remote sensing observations have been interpreted to indicate that the Crisium basin‐forming event excavated deep crust and upper mantle. Samples from the highlands adjacent to the Crisium basin returned by Luna 20 (L‐20) bring a unique perspective for evaluating this concept. The magmatic lithologies returned from the noritic Hilly and Furrowed Terrain (nHFT) by L‐20 are coarse‐grained feldspar (>300 μm) with inclusions of pyroxene, and finer‐grained norites, troctolites, spinel troctolites, and gabbros (<100 μm). These two suites represent ferroan anorthosites (FANs) and the Mg‐suite, respectively. There is limited evidence for mantle or deep crustal material within the nHFT samples. Ultramafic rocks such as dunites and orthopyroxenites are absent, and Mg‐rich olivine‐ and orthopyroxene‐bearing‐assemblages are derived from magmatic rocks emplaced in the shallow crust. These lithic fragments represent pre‐Crisium episodes of magmatism (Mg‐suite) and lunar magma ocean products (FANs). The lack of deep lithologies at the L‐20 site seems contradictory to excavation models for Crisium. Mineralogical‐chemical differences suggest a higher FAN component in the rim and that this represents FANs excavated from the deep lunar crust. If it exists, the Mg‐rich olivine previously identified within the Crisium rim is most likely related to deep, complementary versions of the Mg‐suite rocks from L‐20. The material associated with the Crisium basin is not derived from the lunar mantle but represents crustal lithologies from the shallow to deep crust, a substantial mantle component may have been incorporated into the Crisium basin impact melt sheet, or that our “Earth‐analog” for the lunar upper mantle is incorrect.

LUNAR SOUTH POLE-AITKEN BASIN. Frank C. Chuang, Jennifer L. Whitten, Deborah L. Domingue, Ryan N. Watkins, Bradley L. Jolliff, Sarah N. Valencia, and Daniel P. Moriarty, Planetary Science Institute, 1700 E. Ft. Lowell Road, Suite 106, Tucson, AZ 85719 USA (chuang@psi.edu); Tulane University, New Orleans, LA 70118; Arctic Slope Regional Corporation Federal, Beltsville, MD 20705; Washington University in St. Louis, St. Louis, MO 63130; NASA Goddard Space Flight Center, Greenbelt, MD 20771; University of Maryland, College Park, MD 20742.

The Luna 20 mission returned samples from the Hilly and Furrowed Terrain of the Moon that is associated with the impact event that formed the Crisium Basin. This event potentially excavated deep crustal and upper mantle lithologies. Spinel is commonly considered to be a mineralogical indicator of rocks of high‐pressure origin, and orbital data indicate the presence of spinel‐bearing lithologies exterior to the basin. We have examined 166 Luna 20 particles in the 250–500 μm size range and found 31 spinel‐bearing fragments. Of these 10 are igneous plutonic Mg‐suite rocks, most of which are troctolitic, and 16 are impact melt rocks. The other five are fused soil or devitrified glass fragments. The spinel‐bearing lithic fragments are plagioclase‐rich and do not have the high modal abundances of Mg‐Al spinel previously identified in the region through remote sensing analyses. The textures, compositions, and inferred crystallization sequences of the present magmatic spinel‐bearing samples are most consistent with a relatively shallow crustal (rather than a deep crustal) origin, with a petrogenesis involving assimilation of ferroan anorthosite crust by Mg‐rich, mantle‐derived magmas. Both relict and newly formed spinels are found in impact melt rocks and are also inferred to have formed at relatively low pressures. Thus, the presence of spinel is not an unambiguous indicator of mantle or deep crustal material. The insights gained from this study show that studies of a small, robotically collected sample can improve our understanding of regional lithologies and petrologic processes.

&lt;p&gt;Within the next decade, humans are slated to return to the Moon via NASA&amp;#8217;s Artemis Program.&amp;#160; A driving goal of this program is to establish a sustained presence at one or more sites near the lunar south pole.&amp;#160; Artemis astronauts are expected to participate in a diverse suite of scientific investigations, many of which leverage the extreme illumination and thermal environment at the lunar poles [1].&lt;/p&gt; &lt;p&gt;The lunar south pole is also relevant to geological investigations providing new insight into fundamental planetary processes.&amp;#160; Specifically, Goal 1b of the Artemis III Science Definition Team Report [1] is to probe planetary differentiation and evolution processes including formation of a magma ocean, crust, mantle, and core.&lt;/p&gt; &lt;p&gt;The Artemis program will address this goal in several ways.&amp;#160; The lunar south pole is set within highlands crustal terrane far-removed from previous lunar sample return missions (&lt;em&gt;e.g., &lt;/em&gt;the Apollo and Luna programs).&amp;#160; Sampling local crustal material will provide important insight into ancient crust-building processes (&lt;em&gt;i.e., &lt;/em&gt;differentiation of the lunar magma ocean).&amp;#160;&lt;/p&gt; &lt;p&gt;Ejecta from nearby impact basins will provide further insight into a wider range of planetary processes.&amp;#160; Specifically, the lunar south pole is in the vicinity of the ~2000 km South Pole &amp;#8211; Aitken Basin (SPA), the oldest and largest impact structure preserved on the Moon. Due to its size, age, and unique geophysical properties, SPA impact melt and ejecta samples are critical to unraveling lunar differentiation, the interior structure of the lower crust and upper mantle, and lunar chronology. Unusual volcanic resurfacing across SPA reveal complexities in the Moon&amp;#8217;s thermal evolution [2]&amp;#8211;[4]&lt;/p&gt; &lt;p&gt;SPA ejecta is associated with pronounced geochemical and mineralogical signatures, including Th, Fe, Ti, KREEP, and high-Ca pyroxene elevated relative to the surrounding highlands [5].&amp;#160; These compositional properties are consistent with exposure of late-stage lunar magma ocean cumulates[6].&amp;#160;&lt;/p&gt; &lt;p&gt;These ancient mantle materials excavated by SPA are concentrated in the NW quadrant of the basin, presumably downrange from the impact[5], [7].&amp;#160; However, the relevant compositional signatures are also observed across the southern region of the basin, encompassing the lunar south pole (Figures 1+2).&amp;#160; Using these compositional properties as a guide, Artemis astronauts will be able to identify and return candidate lunar mantle materials for detailed analyses in terrestrial laboratories.&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Figure 1:&lt;/strong&gt;&amp;#160; The expected distribution of mantle materials ejected by SPA and modified by subsequent impact events (right) closely matches the distribution of thorium, a possible marker of late-stage lunar magma ocean cumulates (left) [5].&amp;#160; Small elevations in thorium persist across the south polar region.&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Figure 2:&lt;/strong&gt;&amp;#160; 1 micron Integrated Band Depth maps constructed from Moon Mineralogy Mapper data reveal an elevated pyroxene abundance across the south polar region associated with SPA [8].&amp;#160;&lt;/p&gt; &lt;p&gt;While fragments of SPA material are likely to be sampled at the Artemis site(s), the most recent planetary science decadal survey [9] strongly recommends a more direct approach to maximize the sample return of the Artemis program.&amp;#160; Endurance-A [10], a mission concept study performed at the Jet Propulsion Laboratory and released with the Decadal survey, is a long-range robotic rover that would collect samples from multiple points of interest along a traverse beginning in central SPA and ending at a rendezvous with Artemis astronauts (Figure 3). As currently planned, the rover would collect and deliver up to ~100 kg of samples from ~12 sites, providing a diverse overview of the basin addressing numerous high-priority lunar science questions relevant to solar system chronology and lunar evolution.&amp;#160; The rover is outfitted with a suite of instruments providing sampling context and &lt;em&gt;in situ &lt;/em&gt;science measurements.&lt;/p&gt; &lt;p&gt;&lt;img src=&quot;&quot; alt=&quot;&quot; /&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Figure 3:&lt;/strong&gt;&amp;#160; An example traverse for Endurance-A (purple) beginning in at Mons Marguerite (an unusual volcanic construct) and sampling SPA impact melt (SW Bhabha, Bose), mare basalts (Haret C mare), high-Th mantle ejecta (Abbe M), subsequent impact melt (Poincare, Schrodinger peak ring, Lyman), and pyroclastic materials (Schrodinger pyroclastics) &lt;em&gt;en route&lt;/em&gt; to the Artemis base camp [10].&amp;#160;&lt;/p&gt; &lt;p&gt;[1]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Weber &lt;em&gt;et al.&lt;/em&gt;, in &lt;em&gt;Lunar and Planetary Science Conference&lt;/em&gt;, 2021, no. 2548.&lt;/p&gt; &lt;p&gt;[2]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; James and Kiefer, in &lt;em&gt;AGU Fall Meeting Abstracts&lt;/em&gt;, 2017, vol. 2017.&lt;/p&gt; &lt;p&gt;[3]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Moriarty and Pieters, (2015), &lt;em&gt;Geophys. Res. Lett.&lt;/em&gt;, vol. 42, no. 19,&lt;/p&gt; &lt;p&gt;[4]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Moriarty and Pieters, (2018), &lt;em&gt;J. Geophys. Res. Planets&lt;/em&gt;, vol. 123, no. 3,&lt;/p&gt; &lt;p&gt;[5]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Moriarty &lt;em&gt;et al.&lt;/em&gt;, (2021), &lt;em&gt;J. Geophys. Res. Planets&lt;/em&gt;, vol. 126, no. 1,&lt;/p&gt; &lt;p&gt;[6]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Moriarty &lt;em&gt;et al.&lt;/em&gt;, (2021), &lt;em&gt;Nat. Commun.&lt;/em&gt;, vol. 12, no. 1,&lt;/p&gt; &lt;p&gt;[7]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Melosh &lt;em&gt;et al.&lt;/em&gt;, (2017), &lt;em&gt;Geology&lt;/em&gt;, vol. 45, no. 12,&lt;/p&gt; &lt;p&gt;[8]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; Moriarty and Petro, in &lt;em&gt;Lunar and Planetary Science Conference&lt;/em&gt;, Mar. 2020.&lt;/p&gt; &lt;p&gt;[9]&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; National Academies of Sciences &lt;em&gt;et al.&lt;/em&gt;, (2022).&lt;/p&gt; &lt;p&gt;[10] Keane et al., (2022).&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;

At c. 820 km in diameter, the Smythii impact basin is one of the large lunar basins (>200 km diameter) thought to have formed during the pre-Nectarian period. We combine Lunar Reconnaissance Orbiter imagery, topography, and Moon Mineralogy Mapper compositional data to interpret the surface and subsurface geology of the Smythii basin with the goal of identifying datable impact melt for investigation by a future lunar lander. Surface outcrops exposed on the central peak of the Schubert C crater are identified as uplifted deposits of Smythii impact melt, and a mission concept is presented for sampling these exposures in order to establish the absolute age of the Smythii basin using radioisotopic geochronology. This mission concept is in line with one of the current top-tier priorities for lunar science: determining the age of large basins and thus constraining the impact flux during the Moon's first billion years, which is a proxy record for the role of impacts on the surface environment and habitability of early Earth and the inner solar system during this interval.

MAGMATISM FROM LITHIC FRAGMENTS FROM DOUBLE DRIVE TUBE 73001/73002. C.K. Shearer, S.B. Simon, B.L. Jolliff, F.M. McCubbin, R.A. Ziegler, J. Gross, C. J.-K. Yen, K.H. Joy, S.K. Bell, M. Cato, S. Eckley, L. Borg, N. Marks, B. Jacobsen, C.R. Neal, J.L. Valenciano, J.I. Simon, N. Petro, H.H. Schmitt, D. Moriarty, R. Tartese, M. Anand, and the ANGSA science team. Dept. of Earth and Planetary Science, Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico 87131; Lunar and Planetary Institute, Houston TX 77058; 3 Washington University in St. Louis, St. Louis, Mo 63130; ARES, NASA Johnson Space Center, Houston TX 77058-3696; University of Manchester, Manchester, UK ; Lawrence Livermore National Laboratory, Livermore, CA 94550; 7 University of Notre Dame, Notre Dame IN 46556, NASA Goddard Space Flight Center, Greenbelt, MD 20771; 9 University of Wisconsin-Madison, P.O. Box 90730, Albuquerque, NM 87199; 10 University of Maryland, College Park, Md 20742, The Open University, Milton Keynes, UK, the list of co-authors includes all members of the ANGSA Science Team (https://www.lpi.usra.edu/ ANGSA /teams/) (cshearer@unm.edu).

Geochronology, or determination of absolute ages for geologic events, underpins many inquiries into the formation and evolution of planets and our Solar System. Absolute ages of ancient and recent magmatic products provide strong constraints on the dynamics of magma oceans and crustal formation, as well as the longevity and evolution of interior heat engines and distinct mantle/crustal source regions. Absolute dating also relates habitability markers to the timescale of evolution of life on Earth. However, the number of geochronologically-significant terrains across the inner Solar System far exceeds our ability to conduct sample return from all of them. In preparation for the upcoming Decadal Survey, our team formulated a set of medium-class (New Frontiers) mission concepts to three different locations (the Moon, Mars, and Vesta) where sites that record Solar System bombardment, magmatism, and/or habitability are uniquely preserved and accessible. We developed a notional payload to directly date planetary surfaces, consisting of two instruments capable of measuring radiometric ages in situ, an imaging spectrometer, optical cameras to provide site geologic context and sample characterization, a trace element analyzer to augment sample contextualization, and a sample acquisition and handling system. Landers carrying this payload to the Moon, Mars, and Vesta would likely fit into the New Frontiers cost cap in our study ( 1B). A mission of this type would provide crucial constraints on planetary history while also enabling a broad suite of investigations such as basic geologic characterization, geomorphologic analysis, ground truth for remote sensing analyses, analyses of major, minor, trace, and volatile elements, atmospheric and other long-lived monitoring, organic molecule analyses, and soil and geotechnical properties.

The evolution and compositional structure of the lunar mantle has been extensively modeled but insufficiently constrained by observations. Here, we identify and characterize mantle materials exposed by the Moon's largest impact basin to better understand the composition, stratigraphy, and evolution of the upper mantle. The vast South Pole‐Aitken Basin (SPA) exhibits a broad, crescent‐shaped thorium and potassium distribution. These incompatible elements are predicted to be concentrated in the dregs of the lunar magma ocean during end‐stage crystallization. Through consideration of basin formation models convolved with subsequent geologic evolution, we demonstrate that the distribution and implied stratigraphy of Th‐ and K‐bearing materials across SPA are consistent with an upper mantle ejecta origin. The most pristine exposures of these materials are confined to northwest SPA and also exhibit elevated Ti and Fe (relative to the farside highlands) in association with a gabbronoritic mineralogy. This is consistent with late‐stage magma ocean assemblages predicted by petrologic models. In contrast, SPA impact melt derived from greater depths is associated with a low‐Ca pyroxene‐dominated assemblage. Together, these compositional patterns are evidence for a stratified ancient upper mantle. Importantly, the incompatible‐element‐enriched, ilmenite‐bearing ferroan gabbronoritic cumulates evidently had not participated in gravitational overturn at the time of SPA formation. Contrary to recent hypotheses invoking nearside sequestration of incompatible elements to explain hemispherical differences in crustal building and volcanic resurfacing, it follows that incompatible elements were globally distributed in the magma ocean at the time of SPA formation.

UNDERSTANDING THE ORIGIN OF FAN AND MG-SUITE LITHOLOGIES AT THE LUNA 20 LANDING SITE. C. K. Shearer, S.B. Simon, N. Petro , D. Moriarty, J.J. Papike, and F.S. Joyce. Institute of Meteoritics, USA. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, Lunar and Planetary Institute, Houston TX 77058; NASA Goddard Space Flight Center, Greenbelt, MD 20771; 5 University of Maryland, College Park, MD. cshearer@unm.edu

Introduction: The Apollo 17 mission collected a diversity of materials from across the Taurus-Littrow Valley, much of which have been studied in detail for nearly five decades [1-3]. Recently a number of orbital missions have mapped the Moon in unprecedented detail, generating an enormous volume of data and derived products including mineralogy [4]. With these new datasets we have an opportunity to revisit interpretations of the geology of the Apollo 17 site [3] as well as use the remotely sensed data to support the analysis of “new” lunar samples. A set of samples was set aside for future study enabling modern analytical techniques to examine “pristine” samples, including the double core tube collected at Station 3 (73001/73002) [5]. The ~70 cm deep core sample was collected within a landslide deposit (the “light mantle”) near the surface exposure of a lobate scarp [1, 6, 7]. These new samples afford a unique opportunity to use remotely sensed data and an understanding of geologic processes to predict what could have been sampled in the core. Here we focus on estimated abundance of olivine across the valley floor [4] to characterize basaltic stratigraphy of the landing site, similar to the sample analysis for the Apollo 11 and 12 sites [8]. Prior analyses of the composition of the valley utilized Clementine UVVIS and Moon Mineralogy Mapper (M3) data to characterize compositional variability in the valley [3, 9,