Noah E. Petro

During their orbits of the Moon in 1972, Apollo astronauts reported three impact flashes, associated with meteoroids striking the surface and vaporizing. We examined data from the Apollo seismic network to investigate whether these flashes produced detectable moonquakes whose locations and timing could be independently validated. No candidate matches were found, though stream modeling indicates a high probability that both Apollo 17 impacts were Geminids from parent body 3200 Phaethon. Our analysis pipeline is likely instructive for coordinating observations made by future Artemis astronauts from orbit with seismic data from upcoming geophysical missions to the lunar surface.

Most lunar surface conditions are incredibly harsh for microbial survival. High ultraviolet radiation, temperatures, and energetic particle radiation limit survival over most unprotected lunar surfaces, particularly in equatorial regions where all previous crewed exploration occurred. However, whether these harsh conditions are widespread at lunar poles has not been examined considering topographical effects. Here, we show that recent microorganism survivability data and lunar surface remote sensing reveal likely survivable niches in lunar polar regions. Analysis of topography and latitude-driven surface conditions using remote sensing data and high-resolution illumination models indicates the lunar south pole has substantial regions with persistent low temperatures and ultraviolet flux. Comparing these conditions to survivability data of specific microorganisms, we find that significant lunar polar areas likely have surface conditions amenable to microbial survival. Our findings suggest that lunar polar regions may be less hostile to microbial survival than previously assumed. This does not encompass growth likelihood, but survival in a cryptobiotic state where growth would be possible if habitable conditions were present. Potential microbial survivability at lunar poles is particularly significant given many examined microbes will likely be transported to the Moon during crewed lunar south pole exploration planned in numerous near-term missions. Thoughtfully planning exploration and tracking its impact is key to limiting and understanding potential unintended life transfer to the Moon.

Several national space agencies and commercial entities are currently targeting the Moon's south polar region for human and robotic exploration. Of particular interest are materials excavated and ejected from the Moon's largest and oldest impact structure, the South Pole‐Aitken Basin (SPA), as these ancient materials are a window into the early history of the Moon. SPA ejecta and impact melt are associated with the presence of Fe, Th, and pyroxene minerals. Mons Kocher, within the NASA Artemis exploration zone, exhibits elevated Fe, Th, and pyroxene abundance and presents a viable opportunity for Artemis astronauts to sample SPA material. Using orbital hyperspectral data from the Moon Mineralogy Mapper, we investigated the distribution of mafic minerals across the Mons Kocher region. We identified two types of mafic‐bearing units: small (∼300 m) craters and sun‐facing slopes. Spectral properties of the small craters (as well as the nearby ∼21 km Kocher crater) are consistent with low‐Ca pyroxene, whereas the illuminated slopes exhibit similar pyroxenes with possible signatures of hematite‐driven space weathering. Using least cost path models, we generate optimized traverse paths to the mafic craters through integration of topographic slope, average Earth visibility, and average solar illumination data.

High-resolution digital elevation models (DEMs) are an important resource both for lunar science and for human and robotic exploration. Photoclinometry, or Shape-from-Shading (SfS), is particularly well adapted to producing highly resolved DEMs even under the extreme illumination conditions typical of the lunar polar regions. The resulting DEMs can achieve pixel scales up to the native resolution of the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images, which is 0.7–1.5 m pix ⁻¹ at south polar latitudes. Here we present 5 m pix ⁻¹ SfS DEMs (SDEMs) for the list of 13 Artemis III candidate landing regions released in 2022. While our SDEMs match the resolution of the recently updated polar DEMs (or LDEMs) from the Lunar Orbiter Laser Altimeter, we use SfS to enhance them by introducing details from the LROC NAC images. The result is a complementary product which leverages the geodetic control of the LDEMs while also providing a more uniform effective resolution. To deal with the cumbersome preparation of properly selecting and coregistering NAC images, necessary to produce the SDEMs of such large regions, we developed a semi-automated SfS pipeline leveraging widely used open-source tools. We show that our accurate models are a powerful resource to quantify surface characteristics (e.g., slope, roughness, Sun and Earth illumination), to assess the viability of potential landing sites, and to plan surface activities.

The “light mantle” deposit at the base of South Massif in the Moon's Taurus‐Littrow Valley was a primary science target for the Apollo 17 exploration. The possibility that it was a landslide triggered by ejecta from Tycho Crater is critical for establishing the age of Tycho and constraining recent lunar impact chronology; however, the mechanism of emplacement of the deposit has recently been questioned. The newly opened 73001/73002 double drive tube from Station 3 sampled 70.6 cm deep into the regolith and represents the first stratigraphic section of an extraterrestrial landslide deposit returned to Earth. Here we provide an overview of the stratigraphy of the 73001/73002 core based on top to bottom variations revealed by coordinated laboratory analyses and explore constraints on the emplacement of the light mantle deposit. Briefly, the upper ∼10 cm of 73002 contains a disturbed zone from space weathering and emplacement of ejecta from a nearby crater that excavated and ejected basaltic material. Below 10 cm is a nearly uniform unit of immature regolith. These data support a single event for the emplacement of the deposit at this location, followed by weathering and mixing of materials from nearby crater ejecta in the upper 10 cm. Slight variations in chemistry and clast components may reflect the relative stratigraphy of the South Massif slope, with material toward the bottom of 73001 originating from lower slopes and material from higher up in the core representing regolith from higher up the South Massif slopes.

During the six Apollo missions, astronauts collected 2196 lunar samples, nearly all of which have been studied over the past five decades. Six Apollo samples remained unexamined until 2019 and were saved to be analyzed by the next generation of lunar scientists using advanced modern laboratory facilities. Now more than 50 years after Apollo, NASA is returning to the Moon with Artemis and will return geologic samples from a different region of the lunar surface than Apollo. Curation will play an instrumental role in helping to prepare for the safe return of these valuable samples, ensuring their integrity during all stages of the missions, and thus maximizing their scientific return. To prepare for the return of these samples, NASA initiated the Apollo Next Generation Sample Analysis (ANGSA) Program to open previously unstudied samples including unopened double drive tube 73002 and 73001 (also vacuum‐sealed) from the Apollo 17 mission to the Taurus‐Littrow Valley. The ANGSA program was designed to function as a low‐cost analog sample return mission and served as a testing ground to understand processes, update techniques, and prepare for the preliminary examination (PE) of the to‐be‐returned lunar samples with Artemis. New and advanced curation techniques were developed and applied to support the analyses of 73002/73001 during the PE. Furthermore, cutting‐edge analytical instruments such as X‐ray Computed Tomography were utilized to aid in PE that were unavailable during Apollo. These efforts are equipping the Artemis generation for future lunar missions and lessons learned from the PE of ANGSA samples will be directly applied to Artemis.

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° of the south pole observed in Lunar Orbiter Laser Altimeter reflectance data exhibiting a spatially conflicting apparent FeO abundance pattern between several data sets.

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.