Fresh Craters Research Articles

The Lunar Regolith Thickness and Stratigraphy of the Chang’E-6 Landing Site

The Chang’E-6 (CE-6) mission successfully returned 1935.3 g of lunar soil samples from the Apollo basin within the South Pole–Aitken basin. One of its scientific objectives is to investigate the subsurface structure and regolith thickness at the landing site. Using remote sensing datasets, we estimated the regolith and basalt thicknesses at the landing site by employing the crater morphology method and crater excavation technique. A total of 53 concentric craters and 108 fresh craters with varying excavation depths were identified. Our results indicate that the regolith thickness at the CE-6 landing site ranges from 1.1 to 7.0 m, with an average thickness of 3.5 m. Beneath the regolith, the basalt layer consists of high-Ti basalt overlaying low-Ti basalt, with a total thickness of approximately 64 to 82 m, of which the high-Ti basalt layer accounts for about 22 to 30 m. Based on the local geological history, we proposed a stratigraphy at the CE-6 landing site. These findings provide valuable geological context for interpreting the Lunar Penetrating Radar data and analyzing the returned samples.

Ice degradation and Boulder size frequency distribution analysis of the fresh Martian crater S1094b

S1094b is the largest (155 m-size) and southernmost known ice-exposing fresh crater discovered so far on Mars, revealing a relatively pure and unstable subsurface ice deposit located at the northern Martian mid-latitudes. In this work, we analyze HiRISE images taken on 27 February 2022 and on 5 December 2022 to perform a multi-temporal analysis of its ice-rich ejecta, combining this analysis with geologic mapping, the boulder size frequency distribution (SFD) and thermal modeling. The objective is to provide a multidisciplinary characterization of both the impact and subsequent exposed ice sublimation processes. The boulder SFD of both February and December cases show a power-law best fit with indices −4.68 ± 0.15 and − 3.47 ± 0.10, respectively. In the same timeframe, the density of boulders per km2 ≥ 1.5 m changes from 3908, to 596. This flattening is mainly due to the sublimation and consequent loss of the smaller-size icy boulders. This is confirmed by the ice volume computation performed on the area, which changed from ∼20,274 ± 3997 m3 to ∼7951 ± 1117 m3, i.e. a decrease of ∼60% in 274 Sols. The thermal models showed that the ice in this region is always unstable, leading to a total of 6504.71 sublimation hours from which we estimated a sublimation rate of ∼0.15 ± 0.04 mm/h (i.e. ∼3.60 ± 0.96 mm/Sol). The presence of this amount of accessible ice at such low latitudes could be a valuable resource for potential future human missions.

Multiband Spectropolarimetry of Lunar Maria, Pyroclastics, Fresh Craters, and Swirl Materials

Imaging polarimetry is a well-known method for examining the small-scale structure of the surface regolith of airless celestial bodies. In this study, we examine (for the first time) the wavelength-dependent polarization behavior of selected lunar areas, including maria, highlands, fresh craters, pyroclastic deposits, and the Reiner Gamma swirl, based on telescopic multiband UBVRI imaging polarimetry at phase angles within the range of the positive polarization branch. The terrain-dependent spectropolarimetric behavior is studied for the first time in this work. For each study area, we conduct a mapping of the relative regolith grain size, an analysis of the exponent of the Umov law, and the wavelength dependence of the degree of linear polarization. Furthermore, we perform area-specific principal component analyses of the degree of linear polarization, followed by unsupervised machine learning (clustering) to segment different terrain types. We find that fresh mare craters and high-titanium pyroclastic deposits have an increased regolith grain size, whereas crater ray material, low-titanium pyroclastic material, and the Reiner Gamma swirl are more finely grained than the average regolith. The degree of linear polarization decreases with increasing wavelength-dependent albedo according to a power law whose exponent is itself positively correlated with the albedo. For a constant albedo and grain size, the degree of linear polarization increases linearly with wavelength. The clustering step yields a library of terrain-dependent prototype spectra of the degree and angle of linear polarization.

Constraining Formation Hypotheses for Irregular Mare Patches on the Moon With Orbital Reflectance Spectra

AbstractIrregular mare patches (IMPs) are enigmatic volcanic features on the Moon's surface, whose lack of cratering and crisp appearance imply they formed <100 Ma ago, ∼1 Ga after the expected turnoff of lunar volcanism. Multiple contrasting formation hypotheses have been put forth to explain their young appearance, including recent emplacement via eruptions of juvenile volcanic material or outgassing, versus ancient volcanic deposits that were emplaced billions of years ago but only appeared young due to highly porous material. If IMPs formed recently, this would require a reinterpretation of lunar thermal evolution. To help constrain formation hypotheses, we provide a comprehensive mineralogical analysis of IMPs using visible to near infrared hyperspectral data from the Moon Mineralogy Mapper. IMPs appear spectrally dominated by high‐calcium pyroxene and are spectrally similar to their host mare and fresh craters. IMPs do not show clear indications of significant glass, implying that pyroclastic eruption was not significant in IMP formation. Based on spectral comparisons to terrestrial magma foam, we find that this also contradicts the glassiness expected for a magma foam exposed at the surface. Thus, we find it is unlikely that IMPs are composed of recently erupted material and may instead be the result of recent or ongoing surface modification of materials similar in composition and likely contemporaneously emplaced with the mare. We favor previous hypotheses that collapse processes or drainage into subsurface voids or porous materials may have been the major drivers of IMP surface rejuvenation, supported by their proximity to collapse features.

Variation of crater morphological parameters in the landing area of Tianwen-1: relationships with the geological environment and climate change

The Zhurong rover of the Tianwen-1 mission successfully landed in the southern part of the Utopian Planitia and the northern region of the dichotomy boundary. Craters within a ~ 134 km2 region surrounding the Zhurong rover were identified and divided into seven degradation classes based on their preservation states and morphological details. Assessing how craters have degraded over time provides insight into local surface processes and then speculates on the climate evolution of the study area. The small depth/diameter (d/D) of craters in the study area may be caused by the rapid filling of sediments or by impact processes occurring in poorly cohesive weathering layers, and may also be associated with the volatile material alteration. As time went by, the process of crater degradation is nonlinear, and the degradation rate of the fresh crater in the study area at the initial stage of degradation may be as high as 0.2 m/Myr. The calculated surface erosion rate for the study area is ~ 10–2–10–3 m/Myr, indicating that the erosion of the Martian surface since the Middle Amazonian occurred in the dry environment dominated by wind-sand erosion.Graphical

Depth-to-diameter Ratios of Fresh Craters on the Moon and Implications for Surface Age Estimates

The depth-to-diameter (d/D) ratios of small lunar craters (D < 400 m) can be used to determine important properties of the upper regolith, specifically material strength or thickness. The d/D is also an important component of topographic diffusion models that describe how different erosive processes influence and change the topography of a surface over time, and these models have been applied to estimate surface ages. These models must make assumptions regarding rates of erosion and the initial d/D of a crater. Previous works investigating d/D of small craters, which use various methodologies to calculate depth, typically assume that a fresh appearing crater is a young crater. Work presented here provides d/D measurements of known—rather than assumed—young, meter-scale craters to provide better constraints on small crater depths and to help further our understanding of lunar surface ages and upper regolith properties. Given the interest in impact crater modification at small, human scales on the Moon and the wide range of assumptions built into topographic diffusion models and their predictions, understanding whether the results for initial d/D from past work hold up under different analyses is critical. We observed no distinct trends in d/D for small, young craters and report a wide range of d/D from 0.08 to 0.215, in contrast with past work that derived different averages based on crater size. The variation in d/D may correspond to heterogeneous regolith properties or be a result of a data source artifact.

Morphological analysis of polar landing regions for a solar powered ice drilling mission

Planning of mission toward the lunar polar region is supported here by the analysis and better understanding of the most frequent landforms: craters on the Moon in the polar region between 79.30 and 84.35 southern latitude. This work surveys impact crater morphologies and spatial density based age estimation and slopes for eight earlier selected, large candidate landing regions of the Luna-27 solar powered ice drilling mission at the southern lunar polar region. The morphological, morphometrical, slope and dating analysis provided the following results: The d/D values of craters follow the earlier found d/D trend for larger craters, but there is a scatter in depth values related to the ageing of craters. The occurrence of shallow craters looks to be somewhat more abundant here than at lower lunar latitudes, in agreement with Mahanti et al. (2015). Beside fresh craters, rock boulders also occur at some km sized local topographic elevations, indicating erosion of ∼1 m thick regolith layer by micro-scale impacts roughly on the scale of 100 Ma.Characteristic temporal sequence of change in the morphology of about 100 m-sized craters confirmed earlier results. The sequence starts from the freshest craters, with mass wasting produced stripes in the interior slope, later diminish of high-reflectance proximal ejecta happens, then boulders, and even later elevated rims diminish. The surveyed large terrains showed crater statistics-derived model ages ranged between 3.9 and 4.2 Ga, indicating below a thin pulverised surface regolith layer, the topography of the poorly fragmented bedrock below it still holds the Late Heavy Bombardment aged basement. The equilibrium crater population was possibly identified below the 100–200 m diameter range. Surveying crater retention at >30° slopes indicates exposure of 78–140 Ma for steep terrains, and 330–150 Ma for flat <5° slope surfaces considering the size domain below 100 m diameter. This observation indicates rejuvenation of the top few m thin layer of slopes produces faster mixing than on plains.The surveyed kilometre sized craters formed about 1–2 Ga ago, and show correlation between formation age and depth, indicating an infilling rate around 100 m thickness in 1 Ga duration. This is 2 orders of magnitude larger than the 1–2 m impact driven regolith mixing depth during the same period. Thus, while impact mixing desiccates the shallow top regolith layer, inside km scale craters earlier accumulated ice might still be there shielded by faster rock debris accumulation.The surveyed candidate landing regions were evaluated according to general landing safety, lower temperature (to support ice preservation), and solar illumination (for energy supply). Comparing the eight regions, altogether 5.1% of their total area was found to meet with the threshold values of slope angle below 8°, modelled 1 m deep subsurface temperature below 125 K and at least 20% of time available solar illumination and Earth visibility. The largest continuous area that fulfil the used constraints are present in the candidate LS8 area at −82.70°, −82.72°.

Lunar Impact Craters: New Perspectives From Full‐Polarimetric Analysis of Chandrayaan‐2 Dual‐Frequency SAR Data

AbstractWith the availability of the full‐polarimetry data from Chandrayaan‐2 Dual‐frequency Synthetic Aperture Radar (DFSAR) for the first time, the lunar impact craters are studied for comprehensive characterization, which was earlier limited due to hybrid‐polarimetry based observations. In conjunction with the conventional Circular Polarization Ratio (CPR), we explore the unique full‐polarimetric parameters such as Single‐bounce Eigenvalue Relative Difference and T‐Ratio which are sensitive to surface roughness and dielectric constant, respectively. We studied the polarimetric behavior of a total of 115 nos. of impact craters within a specific size range (∼1–25 km diameter) belonging to different categories viz. fresh, degraded, polar and non‐polar anomalous craters. Our results confirm that both kinds of non‐polar and polar anomalous craters overall hold centimeter‐decimeter scale surface roughness similar to the exterior of the fresh craters, which mainly leads to the anomalous nature of the craters. Our analysis indicates possible control of the crater degradation process on the change in the radar scattering behavior of the studied lunar craters. The crater degradation causes a reduction in the surface roughness and dielectric property (density) of the scatterers present in various craters leading to a change in the radar scattering behavior. Alongside, water ice, if at all present admixed into the regolith in the polar anomalous craters, is not in the form of dominant scatterers that can influence the radar signature. However, the occurrence of relatively higher CPR values in smooth low dielectric crater interiors supports the possibility of the presence of water ice in some of the studied polar anomalous craters belonging to Pre‐Imbrian to Imbrian lunar geological periods.

A Tectonic Origin for the Largest Marsquake Observed by InSight

AbstractThe S1222a marsquake detected by InSight on 4 May 2022 was the largest of the mission, at 4.7. Given its resemblance to two other large seismic events (S1000a and S1094b), which were associated with the formation of fresh craters, we undertook a search for a fresh crater associated with S1222a. Such a crater would be expected to be ∼300 m in diameter and have a blast zone on the order of 180 km across. Orbital images were targeted and searched as part of an international, multi‐mission effort. Comprehensive analysis of the area using low‐ and medium‐resolution images reveals no relevant transient atmospheric phenomena and no fresh blast zone. High‐resolution coverage of the epicentral area from most spacecraft are more limited, but no fresh crater or other evidence of a new impact have been identified in those images either. We thus conclude that the S1222a event was highly likely of tectonic origin.

Boulder distribution, circular polarization, and optical maturity: A survey of example lunar polar terrains for future landing sites

Boulder occurrence at the southern polar regions of the Moon was analysed to see connections between optical, radio, spectral, and topography-related roughness datasets. On optical images, boulders tend to concentrate in groups (the groups are 0.9–1.8 km diameter and cover about 9% of the surveyed regions; while boulders inside these groups have up to 6 boulder/100 m2, e.g., 60,000 boulder/km2 (54% of areal coverage), while outside these groups around 7 boulder/km2 (0.06% areal coverage). The correlation between optical boulder density and Circular Polarization Ratio: CPR (0.26) and Optical Maturity: OMAT (0.38) values are weak, while CPR and OMAT distribution patterns are elevated around fresh craters with elevated boulder density. While fresh craters with boulders coincide with elevated CPR values, but in some cases, elevated CPR is without elevated surface boulder occurrence, indicating shallow subsurface boulders. A good correlation between CPR values and surface roughness (0.68) indicates boulder exhumation at topographic differences of craters. OMAT and CPR values of fresh craters (with elevated and sharp rims) show elevated values above the adjacent regions. OMAT is elevated up to 1–3 times the crater diameter, while CPR is elevated at a smaller area than OMAT values. The CPR might partly come from boulders that could not be ejected as far as smaller regolith grains indicated by OMAT-related freshness. Boulder occurrence at fresh impact craters indicates a thickness of the loose top porous regolith layer of 6–11 m, not far from those gained by another author (5–18 m) for terrain areas.

“The spatial distributions of degraded craters and valley networks on Mars as a function of elevation: Their implications for Noachian climate”

Cold and dry models of Noachian Mars postulate that the Noachian epoch characterized a hyperarid and frigid world dominated by low-latitude cold-locked icefields. This ice caps supposedly protected underlying substrates and topography of the Southern Highlands from erosional degradation. I test the Late Noachian Icy Highlands (LNIH) hypothesis by mapping small distribution of both degraded and fresh [2–4] km diameter craters, crater depth and infilling of the smallest [2–5] km craters, valley network (VN) and inverted channels within an area of interest (AOI) representing over 1.1 × 107 km2 of the Noachian Southern Highlands utilizing Environmental Systems Research Institute (ESRI) ArcMap, clipped exclusively to Noachian terrain. Crater degradation results from this study do not show preferential preservation of fresh craters at elevation. Also, crater rim – crater floor (km) depth values show greatest erosion at elevations >1 km purported LNIH Equilibrium Line Altitude (ELA). VN and inverted channels likewise give evidence for net precipitation and erosion at elevation and net deposition and water transport below the global dichotomy at 0 km and extinction at −2.78 km. VN distribution patterns also requires an intertropical convergence zone (ITCZ). I propose that my results are most consistent with emerging PMGCMs incorporating atmospheric collision-induced-absorption (CIA) of CO2 and H2, bypassing the Faint Young Sun Paradox. I propose that statistical evidence derived from geomorphological features on Mars should be used as boundary conditions for future Mars global climate models.

Morphological characteristics of impact craters with diameters of 5–20 km on the Moon

The morphology of impact craters on the Moon plays an important role in understanding impact cratering process, surface and subsurface properties, and their evolutions. In this study, we systematically analyzed the depth, rim height, slope, and rock abundance of 15,135 impact craters between 5 and 20 km in diameter on the Moon, covering the simple and simple-to-complex transitional crater regimes. We found that the decline rates of inner average slopes of mare craters are generally larger than those of non-maria craters and that the degradation rate of inner upper wall slopes around rim crest is not uniform, which decreases rapidly when the depth/diameter ratio (d/D) lies in 0.25–0.15 but slowly when d/D is in 0.15–0.05. However, we found that there is no difference in crater rim height between different terrains (e.g., maria and highlands). In addition, we also found the decrease in rock abundance is more rapid than the ejecta infilling of the crater floor, especially for large simple craters. Moreover, we investigated the diameter-dependent morphological features of fresh craters in different terrains and revised the onset of transitional crater diameters based on the 180 freshest craters. We found that crater initial depth depends on target properties (e.g., strength and porosity) whereas that the degradation rate of the crater depth is independent of terrains. Furthermore, we found that the power-law relations for depth and diameter of fresh simple craters are d = 0.293D0.865 (mare), d = 0.297D0.884 (highland), d = 0.221D0.959 (north pole) and d = 0.209D0.981 (south pole). The onsets of transitional crater diameters are ∼14.2 km (mare), ∼15.7 km (highland), ∼16.6 km (north pole), and ∼ 16.8 km (south pole). These morphological characteristics and their differences in different terrains suggest that target properties (e.g., strength, layering, and porosity) affect the formation and degradation of larger simple and transitional craters.

A new compositional, mineralogical and chronological study of the Leibnitz crater within the SPA basin

Leibnitz is an impact crater 237 ​km in diameter located on the lunar farside within the South Pole–Aitken (SPA) basin. It shares much of its southern rim with the Von Kármán crater (186 ​km in diameter), which is currently the focus of in situ exploration by the Yutu-2 rover, part of the Chang'e−4 mission. This complementary study analyzes Leibnitz's surface materials mineralogy and age using remote sensing data. We focused on the spectral information from 95 fresh craters within Leibnitz to minimize the effects of weathering on the exposed materials. Subsequently, we employed the Modified Gaussian Model to derive a distribution map for the high to low Ca pyroxene ratio values. Finally, we derived absolute model age estimations of the mare basalts using the lunar crater chronology method. A new geologic map of the Leibnitz crater summarizes the results of this study. The results show that the interiors of Von Kármán and Leibnitz share a degree of similarity in mineral composition, with strong absorption features around the 1 ​μm and 2 ​μm bandcenters, due to the spectral dominance of mafic minerals. The ejecta from the adjacent Finsen crater have higher Ca/Fe and HCP/LCP ratios than the exposed materials of the Leibnitz crater. This study also finds evidence to support an older age of formation of the crater than age estimates to date from previous studies of the Leibnitz crater.

Understanding the mineralogy of a compositional anomaly north of the Korolev basin using Moon mineralogy mapper

The work attempts to understand the mineralogy of the reported geochemical anomaly located in the north – northeast region of the Korolev basin using Moon Mineralogy Mapper (M3) onboard Chandrayaan −1 and other lunar datasets. To understand the mineralogy, colour composite images using integrated band depth parameters and mineral indices were prepared, and the M3 spectral signatures corresponding to the unique colours of these colours composites were investigated. Further, Modified Gaussian Model (MGM) deconvolution was applied to these spectra. The results of spectra studies reveal that the area is made up of heterogeneous lithologies, predominantly composed of anorthosite along with minor occurrences of pyroxene-bearing (both low-calcium and high-calcium variety) and spinel-bearing lithologies. Correlation of spectral studies with the morphology revealed that pyroxene was typically associated with fresh craters and their ejecta. Spinel was found to be ubiquitous and is well-dispersed, possibly distributed along with the ejecta blanket of large impact craters. This association hints that the pyroxene-hosted layer most likely occurs beneath the spinel-bearing layer. Such observed assemblages may have resulted from physical mixing during the impact cratering events. This mixed lithology could arise due to the mafic mineral-bearing ejecta of the South-Pole Aitken (SPA) basin and spinel-bearing Orientale ejecta. Korolev most likely impacted on a thick layer of SPA ejecta, and impact basins such as Hertzsprung and Orientale have occurred post-Korolev formation. Orientale being the youngest of the large impact basins, its ejecta carrying the light plain material would have overprinted the older SPA ejecta. Smaller impact craters would have churned the ejecta so that presently we observe a composite lithology with a variable abundance of pyroxene and spinel.

Newly formed craters on Mars located using seismic and acoustic wave data from InSight

Meteoroid impacts shape planetary surfaces by forming new craters and alter atmospheric composition. During atmospheric entry and impact on the ground, meteoroids excite transient acoustic and seismic waves. However, new crater formation and the associated impact-induced mechanical waves have yet to be observed jointly beyond Earth. Here we report observations of seismic and acoustic waves from the NASA InSight lander’s seismometer that we link to four meteoroid impact events on Mars observed in spacecraft imagery. We analysed arrival times and polarization of seismic and acoustic waves to estimate impact locations, which were subsequently confirmed by orbital imaging of the associated craters. Crater dimensions and estimates of meteoroid trajectories are consistent with waveform modelling of the recorded seismograms. With identified seismic sources, the seismic waves can be used to constrain the structure of the Martian interior, corroborating previous crustal structure models, and constrain scaling relationships between the distance and amplitude of impact-generated seismic waves on Mars, supporting a link between the seismic moment of impacts and the vertical impactor momentum. Our findings demonstrate the capability of planetary seismology to identify impact-generated seismic sources and constrain both impact processes and planetary interiors. Impact-induced acoustic and seismic wave events on Mars recorded by the InSight lander’s seismometer have been traced to fresh craters observed in spacecraft imagery.

Clay sediments derived from fluvial activity in and around Ladon basin, Mars

The morphology and mineralogy of light-toned layered sedimentary deposits were investigated using multiple orbital datasets across the Ladon basin region, including within northern Ladon Valles, southern Ladon basin, and the southwestern highlands of Ladon basin. Light-toned layered deposits are particularly widespread in Ladon Valles and Ladon basin, ranging laterally for distances over 200 km, with the thickest exposure (54 m) located at the mouth of Ladon Valles. The restriction of layered sediments below a common elevation (−1850 m) in Ladon Valles and Ladon basin and their broad conformable distribution with bedding dips between 1 and 4° favor a lacustrine environment within this region during the Late Noachian to Early Hesperian. The Ladon layered deposits have spectral signatures consistent with Mg-smectites, even when the morphology of the layering varies considerably in color and brightness. These phyllosilicates were most likely eroded from the highlands upstream to the south, but the lacustrine environment may have also been favorable for in situ alteration and formation of clays. The southwestern highlands also display light-toned layered deposits within valleys and small basins. These sediments predominantly have signatures of Mg-smectites, although we also identified Fe/Mg-smectites and additional hydrated phases in some deposits. One of these altered deposits was found within a younger Holden crater secondary chain, possessing a Late Hesperian to Early Amazonian age for valleys and sediments that postdate the deposits within Ladon Valles and Ladon basin. Phyllosilicate signatures were also detected in the ejecta from two fresh craters that exposed highland materials upstream of Arda Valles, revealing that the highlands are clay-bearing and may be the most plausible source of the clay-bearing fluvial-derived sediments found within the valleys and basins downstream. Some of the highland deposits are likely coeval to similar clay-bearing sediments found to the south within Holden and Eberswalde craters, indicating late, widespread fluvial activity and deposition of allochthonous clays within the broader Margaritifer Terra region when Mars was thought to be colder and drier.

Global geologic map of asteroid (101955) Bennu indicates heterogeneous resurfacing in the past 500,000 years

Global geologic maps are useful tools for efficient interpretation of a planetary body, and they provide global context for the diversity and evolution of the surface. We used data acquired by the OSIRIS-REx spacecraft to create the first global geologic map of the near-Earth asteroid (101955) Bennu. As this is the first geologic map of a small, non-spherical, rubble-pile asteroid, we discuss the distinctive mapping challenges and best practices that may be useful for future exploration of similar asteroids, such as those to be visited with the Hera and Janus missions. By mapping on two centimeter-scale global image mosaics (2D projected space) and a centimeter-scale global shape model (3D space), we generated three input maps respectively describing Bennu's shape features, geologic features, and surface texture. Based on these input maps, we defined two geologic units: the Smooth Unit and the Rugged Unit. The units are differentiated primarily on the basis of surface texture, concentrations of boulders, and the distributions of lineaments, mass movement features, and craters. They are bounded by several scarps. The Rugged Unit contains abundant boulders and signs of recent mass movement. It also has fewer small (<20 m), putatively fresh craters than the Smooth Unit, suggesting that such craters have been erased in the former. Based on these geologic indicators, we infer that the Rugged Unit has the younger surface of the two. Differential crater size-frequency distributions and the distribution of the freshest craters suggest that both unit surfaces formed ~10–65 million years ago, when Bennu was located in the Main Asteroid Belt, and the Smooth Unit has not been significantly resurfaced in the past 2 million years. Meanwhile, the Rugged Unit has experienced resurfacing within the past ~500,000 years during Bennu's lifetime as a near-Earth asteroid. The geologic units are consistent with global diversity in slope, surface roughness, normal albedo, and thermal emission spectral characteristics. The site on Bennu where the OSIRIS-REx mission collected a regolith sample is located in the Smooth Unit, in a small crater nested within a larger one. So although the Smooth Unit is an older surface than the Rugged Unit, the impact-crater setting indicates that the material sampled was recently exposed. Several similarities are apparent between Bennu and asteroid (162173) Ryugu from a global geologic perspective, including two geologic units distinguishable by variations in the number density of boulders, as well as in other datasets such as brightness.

Compositional Maps of the Lunar Polar Regions Derived from the Kaguya Spectral Profiler and the Lunar Orbiter Laser Altimeter Data

Abstract Due to the challenging illumination conditions of the lunar polar regions, mineralogic maps have generally been constrained to within 0°–70°N/S. Here we generate a gridded reflectance data cube from the Kaguya Spectral Profiler measurements for each polar region and calibrate it to absolute reflectance using data from the Lunar Orbiter Laser Altimeter. We use this data set to derive the first quantitative mineral maps of iron oxide (FeO), the optical maturity parameter (OMAT), and nanophase iron poleward of 50°N/S at a spatial resolution of 1 km pixel–1. We evaluate potential latitudinal trends in space weathering and optical maturity and characterize the polar geology, with an emphasis on the Artemis region (84°–90°S). The maps of FeO are in excellent agreement with the abundances measured by the Lunar Prospector and provide an increased level of detail, such as the excavation of high- and low-FeO material by De Forest crater. The OMAT maps offer a fantastic view of both polar regions. They highlight small fresh craters, walls, and central peaks, as well as rays extending through multiple degrees of latitude, such as those from Tycho and De Forest, which extend into the Artemis region. Both polar regions are characterized by the ubiquitous presence of noritic anorthosites and anorthositic norite. Low-calcium pyroxene is largely the dominant mafic mineral present. The Artemis region has relatively homogeneous FeO and plagioclase content at the observed spatial resolution. The lowest FeO values are found near Shackleton, between Shoemaker and Faustini, and on the central peak of Amundsen crater.

Lunar Mare Fecunditatis: A Science-Rich Region and a Concept Mission for Long-Distance Exploration

Mare Fecunditatis is a ~310,000 km2 flat basalt plain located in the low-latitude area of the Moon. Plenty of volcanic features (multiple episodes of mare basalts, sinuous rilles, lava tubes, pyroclastic deposits, domes, irregular mare patches (IMP), ring-moat dome structures (RMDS), floor-fractured craters), tectonic features (grabens and wrinkle ridges), impact-related features, and other features (swirls, pit craters) are identified in Mare Fecunditatis. An in-situ mission to Mare Fecunditatis is scientifically significant to better understand the lunar thermal histories and other questions. All previous in-situ and human missions (Apollo, Luna, Chang’E) were limited to small areas, and no traverse longer than 40 km has been made yet. With the development of technology, long-distance movement will be possible in the future on the lunar surface, providing opportunities to explore multiple sites at one mission with complete documentation of the regional geology. Eight high-value targets (pit crater, IMPs, RMDSs, young basalts, high-Al basalts, pyroclastic deposits, swirls, and fresh craters) were found in Mare Fecunditatis, and a ~1400 km-traverse in 5 years is proposed to explore them to solve the most fundamental lunar questions.

Geology, in-situ resource-identification and engineering analysis of the Vernal crater area (Arabia Terra): A suitable Mars human landing site candidate

A multidisciplinary study of an ancient area of Mars (Early to Late Noachian) located in Arabia Terra is presented, centred at 6°1′N, 354°54′ E and including the 55 ​km size Vernal crater. By means of different spatial scale imagery datasets and digital terrain models (MOLA, THEMIS, HRSC, CTX, CaSSIS and HiRISE), we prepare a high-resolution geological map of the study site. We highlight the different bedrock stratigraphy inside the Vernal crater which is of particular exobiological interest given the presence of putative ancient hot springs, as well as identifying multiple transverse aeolian ridges, inverted fracture networks and paleochannels, mounds, and a 58 ​m fresh crater located just outside Vernal crater rim. Within all low-latitude regions of Mars, the studied site presents the highest values (up to 16.0 ​wt%) of water equivalent hydrogen, hence suggesting that there is a widespread presence of in situ subsurface (at maximum depths of 1–2 ​m) natural resources, such as water ice and/or hydrated minerals. The equatorial location of the area results in the maximum surface temperature and the highest mean solar flux gatherable on the surface of the planet throughout the year. The interesting scientific case, coupled with the presence of in situ exploitable resources and the thorough accomplishment of all landing/roving engineering safety requirements, make the Vernal crater area a strong landing site candidate for future human exploration of Mars.