Lunar Reconnaissance Orbiter Research Articles

New insights into the geological evolution history of Mare Fecunditatis

The Luna 16 probe returned 101 g of lunar regolith from the northeast of the Mare Fecunditatis in 1970. Studies on these samples were primarily conducted in the 1970s and 1980s, and limited scientific achievements were obtained due to available technology at that time. China received 1.5 g Luna 16 samples in 2023 and it is expected to conduct in-depth research in the near future. We conducted a thorough investigation on several fundamental issues in this region to provide a refined geological background in the paper. Firstly, a detailed division of the basaltic units within the Mare Fecunditatis was conducted based on the TiO2 content, and impact craters in each geological unit were mapped with the high-resolution Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images. With the method of lunar surface dating from the crater size-frequency distribution, we found that the model ages of these basalt units range from 3.71 Ga to 3.31 Ga. Next, the thickness of the basalt within the Mare Fecunditatis is estimated with different types of craters, and local basalt thickness ranges from 3 m to 304 m from seven rim-completely-exposed craters in the mare. The rim-completely-exposed craters on the mare-highland boundary, the rim-partially-exposed craters in the mare, and rim-completely-buried craters in the maria also provide information on the thickness of local basalt. Finally, numerical simulations of the formation process of the largest young impact crater in this region, Langrenus crater, was conducted. The simulations show that the Langrenus crater could be formed by a 11.2-km-diameter asteroid hitting the lunar surface with a speed of ~10 km/s. The average thickness of the ejecta from the Langrenus crater is ~4.9 m near Luna 16 landing site, indicating that a significant fraction of Luna 16 samples might be the ejecta from the Langrenus crater. The simulations also reveal that the maximum shock pressure on the materials ejected to Luna 16 landing site can reach 92 GPa, and their maximum source depth is approximately 7.1 km. These interpretations can provide valuable information for further study of the Luna 16 samples and inferring the geological history of the Mare Fecunditatis.

Geostratigraphic Mapping of the Intrusive Valentine Domes on the Moon

AbstractLunar intrusive igneous domes have not been the center of much research in the past due to their rare occurrence on the lunar surface, and the difficulty in locating them. Most of the known structures were discovered using images with low illumination angles, including data from the Lunar Orbiter, telescopic images, and photos taken during the Apollo Missions. These intrusive domes are characterized by an oval shape and low slopes. We analyzed one of these systems, the Valentine domes, located near the rim of the western Serenitatis basin, with modern techniques and data sets from the Lunar Reconnaissance Orbiter (LRO) and Chandrayaan‐1 missions. We created a geostratigraphic map of the area, combining geomorphological and spectral classifications. The aspect map (direction of the slope) proved to be the most suitable product to locate and delimit these structures; using it, we identified a new dome southeast of the principal body, suggesting that the intrusive system is larger than previously thought. It was found that the three domes can be classified as laccoliths, and that several derived structures such as rilles, dykes, and secondary domes represent different stages of intrusive activity in the area. Based on crater counting analysis, we determined that the intrusive activity began after 2.98 ± 0.15 Ga and lasted at least until 1.88 ± 0.5 Ga ago.

The LCROSS Impact Crater as Seen by ShadowCam and Mini‐RF: Size, Context, and Excavation of Copernican Volatiles

AbstractThe Lunar CRater Observations and Sensing Satellite (LCROSS) impacted a Centaur rocket stage into a permanently shadowed region (PSR) in Cabeus crater, excavating water ice and other volatiles. We used the Miniature Radio Frequency (Mini‐RF) instrument on the Lunar Reconnaissance Orbiter and the ShadowCam instrument on the Korean Pathfinder Lunar Orbiter to detect the probable 22‐m diameter crater that resulted from the LCROSS impact. The crater formed superposed upon a dense small crater population along a crater ray from a larger pre‐existing crater. From its geologic context, the ice and regolith excavated by LCROSS were likely modified within the last 0.1–0.5 Gyr. An upper limit for the excavated volatiles is ~0.9 Gyr, as the location was not a PSR prior to that time. A young age for the LCROSS‐detected volatiles supports the idea that they were mostly emplaced by an exogenic mechanism, such as from comets or the solar wind.

A Low‐Viscosity Lower Lunar Mantle Implied by Measured Monthly and Yearly Tides

AbstractThe Moon's frequency‐dependent tidal response, expressed as temporal variations in its gravity field through the Love number and as dissipation through the quality factor , provides information about its interior structure. Lunar laser ranging has provided measurements for , but so far no frequency‐dependent values for have been determined. We provide the first spacecraft measurements of and at two frequencies, monthly and yearly, from an analysis of Gravity Recovery and Interior Laboratory and Lunar Reconnaissance Orbiter radio tracking data. Interior modeling indicates that these values can be matched only with a low‐viscosity zone at the base of the lunar mantle, even when using complex rheological laws to model the mantle's response. The existence of this zone has profound implications for the Moon's thermal state and evolution.

The Faustini Permanently Shadowed Region on the Moon

Faustini crater (41 km diameter) hosts a large (664 km2) permanently shadowed region (PSR) with a high potential to harbor water-ice deposits. One of the 13 candidate Artemis III landing areas contains a portion of the crater rim and proximal ejecta. The ShadowCam instrument aboard the Korea Pathfinder Lunar Orbiter provides detailed images of the PSR within Faustini. We characterize the terrain and thermal environment within the Faustini PSR from ShadowCam images, Lunar Reconnaissance Orbiter thermal measurements and laser ranging, and thermal modeling. Our mapping revealed three distinct areas of the floor of Faustini based on elevations, slopes, and surface roughness. These units broadly correlate with temperatures; thus, they may be influenced by variations in volatile sublimation. Crater retention and topographic diffusion rates appear to be asymmetric across the floor, likely due to differences in maximum and average temperatures. Several irregular depressions and a pronounced lobate-rim crater are consistent with subsurface ice. However, differences in the thicknesses of deposited materials on the floor may also explain the asymmetry. Additionally, zones of elevated surface roughness across Faustini appear to result from overprinted crater ray segments, possibly from Tycho and Jackson craters. Mass wasting deposits and pitting on opposite sides of the crater wall may have resulted from the low-angle delivery of material ejected by the Shackleton crater impact event, suggesting that the Artemis III candidate landing region named “Faustini Rim A” will contain material from Shackleton.

SOHO SWAN Lyα Models Supporting LRO LAMP: 2008–2023

The Lunar Reconnaissance Orbiter Lyman-Alpha Mapping Project (LAMP) has been mapping the Moon since its launch in 2009. Faint ultraviolet illumination of the lunar dark side includes light from stars and from hydrogen Lyα emissions, mostly attributed to sunlight scattered by hydrogen atoms near the Sun with a smaller contribution from the whole Galaxy. Models of the lunar illumination by time-dependent Lyα photons have allowed the LAMP team to map polar shadowed craters suspected of harboring water ice and other volatiles. This paper describes the model that provides daily all-sky Lyα maps tuned by comparisons with all-sky Lyα maps from the SOlar and Heliospheric Observatory Solar Wind ANisotropy Experiment stationed at the Sun–Earth L1 point.

Shadow-constrained shape-from-shading for pixel-wise 3D surface reconstruction at the lunar south pole

ABSTRACT High-resolution digital elevation models (DEMs) of the lunar surface are crucial for lunar exploration missions and scientific research. The emergence of advanced technologies, such as Shape-from-Shading (SfS), has enabled the generation of pixel-wise high-resolution DEMs from monocular images of the lunar surface. However, SfS encounters significant challenges in locations with limited illumination, such as the lunar south pole, where the surface is largely covered by shadows. Therefore, this paper presents a novel shadow-constrained SfS approach for pixel-wise 3D surface reconstruction at the lunar south pole. The proposed approach uses multiple high-resolution images captured under different illumination conditions and an existing low-resolution DEM as the inputs and generates a high-resolution DEM with the same resolution as that of the input image through hierarchical SfS processing incorporating shadow constraints. Experiments were conducted using actual images collected by the Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) at the lunar south pole. Comparisons with respect to photogrammetric DEMs generated from stereo NAC images show that the DEMs generated using the proposed approach exhibit the smallest root mean square error (RMSE). Moreover, shaded relief images rendered from the DEMs generated using the proposed approach demonstrate the highest similarity to the actual NAC images. Detailed profile comparisons further validate the effectiveness of the shadow constraint in optimizing 3D reconstruction in regions in proximity to shadows and within shadowed regions. The proposed shadow-constrained SfS approach can be used to generate high-resolution DEMs to support future missions to explore the lunar south pole, with applications including landing site evaluation and route planning for lunar probes or astronauts.

Crustal origin for olivine in the lunar Shioli crater ejecta boulders: Insights from the geological setting of Theophilus crater and Nectaris basin

On the Moon, impact craters and basins expose a wide range of crustal and mantle rocks that provide excellent opportunity for sampling them, understanding their origins and reconstructing spatial and temporal evolution of lunar interior. The previous studies detected olivine-bearing mantle rocks in and around large impact craters and basins. The Japanese SLIM mission landed on the ejecta of a ∼ 280-m-diameter Shioli crater that was emplaced on the ejecta blanket of ∼ 103-km-diameter Theophilus crater, for characterizing potential mantle-derived olivine in the Shioli crater ejecta boulders. To test this hypothesis, we studied the geological setting of Shioli crater, host Theophilus crater and Nectaris multi-ring basin using the orbiter data from Chandrayaan-1 and 2, Lunar Reconnaissance Orbiter, and Kaguya missions and the earth-based Arecibo radar observation. The asymmetrically distributed secondary craters and impact melt ponds around Theophilus crater suggests that a northeast-directed oblique impact produced this crater. Composition of Theophilus crater and surrounding region indicates that the crater excavated a heterogeneous target composed of a thin layer of high-Al olivine basalt (Mare Nectaris) underlain by anorthositic highland rocks possibly intruded by Mg-suite plutons; layers of Cyrillus crater ejecta blanket and Nectaris basin materials (both ejecta and impact melt sheets) were also present beneath the mare basalt flows. Hence, the Theophilus ejecta blanket is a mixture of all these materials. Our dating of Theophilus crater suggests that it is a ∼ 2 Ga Eratosthenian crater. Shioli is a fresh simple crater that was formed at ∼ 1 Ma on the uprange ejecta blanket of Theophilus, where the Arecibo radar data indicated the presence of abundant buried Theophilus ejecta boulders. An ESE-directed hypervelocity oblique impact event produced the elongated Shioli crater and its asymmetrically distributed bright ejecta. Shioli is a primary impact crater indicating the role of impact spallation processes associated with this hyper-velocity impact in producing thousands of ejecta (or spall) boulders around Shioli crater, displaying their asymmetric dispersal pattern and spatial variation of boulder sizes and shapes. The larger and elongated boulders are concentrated near the crater rim, while their size and axial ratio gradually decreases outward from the crater rim. The SLIM mission landed on a thin downrange ejecta of Shioli crater, where fewer large-size boulders are present. Our compositional study suggests that the Shioli ejecta boulders are composed of olivine basalt (Mare Nectaris) mixed with highland anorthositic fragments, including the reworked Cyrillus ejecta and Nectaris basin materials. The Shioli ejecta boulders were produced by complex impact fragmentation of already existing, buried Theophilus ejecta boulders. The regional crustal structure of Nectaris basin and its petrological composition suggest that both Nectaris basin and Theophilus crater did not excavate the lunar mantle. Therefore, the Shioli ejecta boulders are of crustal origin, including the olivine minerals present in them. Our results have important implications for the origin of olivine in the Shioli crater boulders being investigated by the SLIM mission.

Where Is That Crater? Best Practices for Obtaining Accurate Coordinates from LROC NAC Data

The Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images and their derived products make up one of the highest-resolution and most spatially accurate data sets available for the Moon, making them a crucial resource for planners of landed lunar missions. However, it is essential to understand the best uses for each data type and the limits on the accuracy and resolution of the data sets available. With this understanding, users can better interpret and communicate their results. In this paper, we describe what assumptions may be made about the accuracy of LROC NAC images and the various derived products created by the LROC team. NAC digital terrain models and their corresponding orthophotos have the best accuracy of all NAC products, usually better than 10 m horizontally, and should be used where available. Other controlled NAC products usually have accuracies better than 30 m. For areas without controlled products, we describe how to process NAC images to obtain coordinates with the highest possible accuracy. We also recommend best practices for data users interacting with LROC data through online map servers, such as QuickMap or Lunaserv, and for processing LROC data locally using the US Geological Survey Integrated Software for Imagers and Spectrometers.

Topography‐Enhanced Ultra‐Cold Trapping at the LCROSS Impact Site

AbstractSmall topographic features below the resolution of existing orbital data sets may create “micro ultra‐cold traps” within the larger permanently shadowed regions that are present at the lunar poles. These ultra‐cold traps are protected from the major primary and secondary illumination sources, and thus would create surfaces that are much colder than lower‐resolution temperature maps would indicate. We examine this effect by creating a high resolution (1 m pix−1) terrain map based on upscaled data from the Lunar Orbiter Laser Altimeter. This map is illuminated by scattered sunlight and infrared emissions from sunlit terrain, which are then run through a thermal model to determine temperatures. We find that while most of the terrain experiences maximum temperatures around 50 K, there are a number of 1–30 m‐scale ultra‐cold traps with maximum temperatures as low as 20–30 K. By comparing our modeled ultra‐cold trapping area to volatile abundances measured by Lunar Crater Observation and Sensing Satellite (LCROSS), we reveal a diverse environment where the surficial abundances necessary to explain the LCROSS results are strongly dependent on precisely where the impact occurred.

The Generation of High-Resolution Mapping Products for the Lunar South Pole Using Photogrammetry and Photoclinometry

High-resolution and high-accuracy mapping products of the Lunar South Pole (LSP) will play a vital role in future lunar exploration missions. Existing lunar global mapping products cannot meet the needs of engineering tasks, such as landing site selection and rover trajectory planning, at the LSP. The Lunar Reconnaissance Orbiter (LRO)’s narrow-angle camera (NAC) can acquire submeter images and has returned a large amount of data covering the LSP. In this study, we combine stereo-photogrammetry and photoclinometry to generate high-resolution digital orthophoto maps (DOMs) and digital elevation models (DEMs) using LRO NAC images for a candidate landing site at the LSP. The special illumination and landscape characteristics of the LSP make the derivation of high-accuracy mapping products from orbiter images extremely difficult. We proposed an easy-to-implement shadow recognition and contrast stretching method based on the histograms of the LRO NAC images, which is beneficial for photogrammetric and photoclinometry processing. In order to automatically generate tie points, we designed an image matching method considering LRO NAC images’ features of long strips and large data volumes. The terrain and smoothness constraints were introduced into the cost function of photoclinometry adjustment, excluding pixels in shadow areas. We used 61 LRO NAC images to generate mapping products covering an area of 400 km2. The spatial resolution of the generated DOMs was 1 m/pixel, and the grid spacing of the derived DEMs was 1 m (close to the spatial resolution of the original images). The generated DOMs achieved a relative accuracy of better than 1 pixel. The geometric accuracy of the DEM derived from photoclinometry was consistent with the lunar orbiter laser altimeter (LOLA) DEM with a root mean square error of 0.97 m and an average error of 0.17 m.

Lunar High Alumina Basalts in Mare Imbrium

High-alumina (HA) mare basalts play a critical role in lunar mantle differentiation. Although remote sensing methods have speculated their potential presence regions based on sample FeO and TiO2 compositions, the location and distribution characteristics of HA basalts have not been provided. In this study, the compositions of exposed rocks in Mare Imbrium were determined using Lunar Reconnaissance Orbiter (LRO) Diviner oxides and Lunar Prospector Gamma-Ray Spectrometer (LP-GRS) Thorium (Th) products. The exposed HA basalts were identified based on laboratory lithology classification criteria and Al2O3 abundance. The HA basalt units were mapped based on lunar topographic data, and their morphological geological characteristics were calculated based on elevation data. The results show that there are 8406 HA basalt pixels and 17 original units formed by volcanic eruptions in Mare Imbrium. The statistics of their morphology characteristics show that the HA basalts are widely distributed in the northern part of Mare Imbrium, and their compositions have a large range of variation. These units have different area and volume, and the layers formed were discontinuous. The characteristic analysis shows that the aluminum-bearing volcanic activities in Mare Imbrium were irregular. The eruptions of four different source regions occurred in three phases, and the scale and extent of the eruptions were different. The results in this study provide reliable evidence for the heterogeneity of the lunar mantle and contribute valuable information to the formation process of early lunar mantle materials.

A Catalogue of Impact Craters and Surface Age Analysis in the Chang’e-6 Landing Area

Chang’e-6 (CE-6) is the first sample-return mission from the lunar farside and will be launched in May of 2024. The landing area is in the south of the Apollo basin inside the South Pole Aitken basin. Statistics and analyses of impact craters in the landing area are essential to support safe landing and geologic studies. In particular, the crater size–frequency distribution information of the landing area is critical to understanding the provenance of the CE-6 lunar samples to be returned and can be used to verify and refine the lunar chronology model by combining with the radioisotope ages of the relevant samples. In this research, a digital orthophoto map (DOM) mosaic with resolution of 3 m/pixel of the CE-6 landing area was generated from the 743 Narrow Angle Camera of the Lunar Reconnaissance Orbiter Camera. Based on the DOM, craters were extracted by an automated method and checked manually. A total of 770,731 craters were extracted in the whole area of 246 km × 135 km, 511,484 craters of which were within the mare area. Systematic analyses of the crater distribution, completeness, spatial density, and depth-to-diameter ratio were conducted. Geologic model age estimation was carried out in the mare area that was divided into three geologic units according to the TiO2 abundance. The result showed that the east part of the mare had the oldest model age of μ3.27−0.045+0.036 Ga, and the middle part of the mare had the youngest model age of μ2.49−0.073+0.072 Ga. The crater catalogue and the surface model age analysis results were used to support topographic and geologic analyses of the pre-selected landing area of the CE-6 mission before the launch and will contribute to further scientific researches after the lunar samples are returned to Earth.

Analysis of the temporal and spatial characteristics of lunar reconnaissance orbiter’s orbit error based on multi-coverage narrow angle camera images

ABSTRACT Photogrammetric mapping of large area of the lunar surface using high-resolution orbiter images is very challenging due to increasing spatial resolution and lack of a comprehensive understanding of orbit error characteristics. The Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) images are currently one of the highest-resolution images of the Moon available. The study of LRO orbit errors from the perspective of mapping applications is important for high accuracy mapping of large areas using NAC images. This paper proposes a method for orbit error estimation using multi-coverage NAC images. First, available NAC images covering the study regions are orthorectified using ISIS. Then, the impact crater feature matching algorithm is used to match the multi-coverage images. Finally, estimation of the orbit error is achieved through statistical analysis of a large number of homologous points obtained from the matching. The orbit error analyses of nine representative regions on the Moon show that in most cases the refined ephemeris provided by the LOLA/GRAIL team can significantly reduce the orbit error. The orbit errors show a sawtooth variation with a period of about one year, which have been stable for a long time and tend to increase slightly in recent years. There is a slight variation of the orbit error in space, which is even less obvious when using the refined ephemeris. The general tendency is for the far side to be larger than the near side at the same latitude, and for the higher latitudes to be larger than the lower latitudes. The proposed method and analysis results provide a reference for selection and processing of multi-coverage LROC NAC images for high-resolution large-area mapping.

Erosion rate of lunar soil under a landing rocket, part 2: Benchmarking and predictions

In the companion paper (“Erosion rate of lunar soil under a landing rocket, part 1: identifying the rate-limiting physics”, this issue) an equation was developed for the rate that lunar soil erodes under the exhaust of a landing rocket. That equation has only one parameter that is not calibrated from first principles, so here it is calibrated by the blowing soil's optical density curve during an Apollo landing. An excellent fit is obtained, helping validate the equation. However, when extrapolating the erosion rate all the way to touchdown on the lunar surface, a soil model is needed to handle the increased resistance to erosion as the deeper, more compacted soil is exposed. Relying on models derived from Apollo measurements and from Lunar Reconnaissance Orbiter (LRO) Diviner thermal inertia measurements, only one additional soil parameter is unknown: the scale of increasing cohesive energy with soil compaction. Treating this as an additional fitting parameter results in some degeneracy in the solutions, but the depth of erosion scour in the post-landing imagery provides an additional constraint on the solution. The results show that about 4 to 10 times more soil was blown in each Apollo landing than previously believed, so the potential for sandblasting damage is worse than prior estimates. This also shows that, with further development, instruments to measure the soil erosion during lunar landings can constrain the soil column's density profile complementary to the thermal inertia measurements, providing insight into the landing site's geology.

Near-infrared Photometry of the Moon’s Surface with Passive Radiometry from the Lunar Orbiter Laser Altimeter (LOLA)

Examining the reflectance of the Moon’s surface across a broad range of viewing geometries through photometric analysis can reveal physical and geological properties of its regolith. Since 2013 December, the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO) has been operating as a near-infrared (1064 nm) passive radiometer when its laser is turned off. We present a new analysis of this data set spanning roughly 8 yr and covering the surface up to high latitudes in both hemispheres. We apply semiempirical phase functions to find a lower photometric slope and a narrower opposition effect for the highlands than the maria, consistent with theoretical expectations given the higher albedo of the highlands. Examining various geological properties at global scales shows that, in the highlands, iron abundance (FeO) and optical maturity (OMAT) are the dominant factors affecting the phase function, with a smaller influence from surface slope. In the maria, FeO is the dominant factor, with smaller influences from OMAT, surface slope, and TiO2. Submicroscopic iron abundance (SMFe) has a similar effect to OMAT in both highlands and maria. Analysis at specific sites, including the Reiner Gamma swirl and several silicic anomalies, indicates that the phase functions are consistent with the global data for similar FeO and OMAT. Thermophysical properties inferred from surface temperature observations by the Diviner Lunar Radiometer Experiment on board LRO do not affect the 1064 nm phase function, possibly due to a difference between their depth scale and LOLA’s sensing depth.

Shape-from-shading Refinement of LOLA and LROC NAC Digital Elevation Models: Applications to Upcoming Human and Robotic Exploration of the Moon

The Lunar Reconnaissance Orbiter (LRO) has returned a wealth of remotely sensed data of the Moon over the past 15 years. As preparations are under way to return humans to the lunar surface with the Artemis campaign, LRO data have become a cornerstone for the characterization of potential sites of scientific and exploration interest on the Moon's surface. One critical aspect of landing site selection is knowledge of topography, slope, and surface hazards. Digital elevation models derived from the Lunar Orbiter Laser Altimeter (LOLA) and Lunar Reconnaissance Orbiter Camera (LROC) instruments can provide this information at scales of meters to decameters. Shape-from-shading (SfS), or photoclinometry, is a technique for independently deriving surface height information by correlating surface reflectance with incidence angle and can theoretically approach an effective resolution equivalent to the input images themselves, typically better than 1 m per pixel with the LROC Narrow Angle Camera (NAC). We present a high-level, semiautomated pipeline that utilizes preexisting Ames Stereo Pipeline tools along with image alignment and parallel processing routines to generate SfS-refined digital elevation models using LRO data. In addition to the present focus on the lunar south pole with Artemis, we also demonstrate the usefulness of SfS for characterizing meter-scale lunar topography at lower equatorial latitudes.

Possible Anthropogenic Contributions to the LAMP-observed Surficial Icy Regolith within Lunar Polar Craters: A Comparison of Apollo and Starship Landings

This work assesses the potential of midsized and large human landing systems to deliver water from their exhaust plumes to cold traps within lunar polar craters. It has been estimated that a total of between 2 and 60 T of surficial water was sensed by the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project on the floors of the larger permanently shadowed south polar craters. This intrinsic surficial water sensed in the far-ultraviolet is thought to be in the form of a 0.3%–2% icy regolith in the top few hundred nanometers of the surface. We find that the six past Apollo Lunar Module midlatitude landings could contribute no more than 0.36 T of water mass to this existing, intrinsic surficial water in permanently shadowed regions (PSRs). However, we find that the Starship landing plume has the potential, in some cases, to deliver over 10 T of water to the PSRs, which is a substantial fraction (possibly >20%) of the existing intrinsic surficial water mass. This anthropogenic contribution could possibly overlay and mix with the naturally occurring icy regolith at the uppermost surface. A possible consequence is that the origin of the intrinsic surficial icy regolith, which is still undetermined, could be lost as it mixes with the extrinsic anthropogenic contribution. We suggest that existing and future orbital and landed assets be used to examine the effect of polar landers on the cold traps within PSRs.

On the reachability and genesis of water ice on the Moon

Understanding the reachability of water ice by future in-situ experiments near the lunar poles is crucial for supporting growing exploration plans and constraining the uncertainties on its genesis and distribution. To achieve this objective, we perform a thorough three-dimensional mapping of the distribution of water ice in the lunar polar regions (70° onward), integrating radar, optical, and neutron detector observations from the Lunar Reconnaissance Orbiter mission (LRO). Our analysis reveals ∼5-to-8-fold larger expanse of subsurface water ice (∼1-3 m depth) compared to surface water ice (up to 1 m depth) for the north and south poles, respectively. Our investigation cannot rule out the possibility of deep-seated water ice deposits in the lunar poles that remains beyond the detection capabilities of existing instruments on LRO. Moreover, we find that the extent of water ice in the northern polar region (∼1100 ± 74 km2) is twice that in the southern polar region (∼562 ± 54 km2). Our mapping also suggests that the dichotomous latitudinal distribution and the antipodal longitudinal distribution of water ice are likely driven by Mare volcanism and preferential cratering. We provide additional evidence that outgassing during Imbrian volcanism was probably the primary source of subsurface water ice in the lunar poles, which favors larger expanse over meteoritic sources.

The Population of Young Craters on the Moon: New Catalog and Spatial and Temporal Analysis

We present a new catalog of the Moon’s rayed and rocky craters from 5 to 130 km in diameter. Using data from the Lunar Reconnaissance Orbiter and the JAXA Kaguya/Selene missions, we identify 571 unique craters with albedo, maturity, and/or thermophysical rays, or rocky ejecta, or all of these, located between 70° S and 70° N at all longitudes. We analyze the cumulative size–frequency distribution (CSFD) and spatial distribution of these craters and find that in general the albedo-rayed population and the rocky population are consistent with an aggregate age of ∼1.2 Gyr, and both groups show deviations from the CSFD predicted by canonical production and chronology functions at diameters >30 km. Strikingly, we also find that although the rocky craters and craters with thermophysical rays show uniform spatial distributions with both longitude and latitude, the albedo-rayed craters show a strong equatorial concentration that deviates significantly from uniform and that is too large to be explained by analytical models of orbital motion.