Crater Size-frequency Distribution Research Articles

Crater Detection and Population Statistics in Tianwen-1 Landing Area Based on Segment Anything Model (SAM)

Crater detection is useful for research into dating a planetary surface’s age and geological mapping. The high-resolution imaging camera (HiRIC) carried by the Tianwen-1 rover provides digital image model (DIM) datasets with a resolution of 0.7 m/pixel, which are suitable for detecting meter-scale craters. The existing deep-learning-based automatic crater detection algorithms require a large number of crater annotation datasets for training. However, there is currently a lack of datasets of optical images of small-sized craters. In this study, we propose a model based on the Segment Anything Model (SAM) to detect craters in Tianwen-1’s landing area and perform statistical analysis. The SAM network was used to obtain a segmentation mask of the craters from the DIM images. Then non-circular filtering was used to filter out irregular craters. Finally, deduplication and removal of false positives were performed to obtain accurate circular craters, and their center’s position and diameter were obtained through circular fitting analysis. We extracted 841,727 craters in total, with diameters ranging from 1.57 m to 7910.47 m. These data are useful for further Martian crater catalogs and crater datasets. Additionally, the crater size–frequency distribution (CSFD) was also analyzed, indicating that the surface ages of the Tianwen-1 landing area are ~3.25 billion years, with subsequent surface resurfacing events occurring ~1.67 billion years ago.

Interpretation of Geological Features and Volcanic Activity in the Tsiolkovsky Region of the Moon

The Tsiolkovsky crater is located on the farside of the Moon. It formed in the late Imbrian epoch and was filled with a large area of mare basalts. Multisource remote sensing data are used to interpret the geological features of the Tsiolkovsky area. Compared with previous studies, new remote sensing data and a chronological model based on crater size–frequency distribution are used to further refine the stratigraphic units and determine the absolute ages of the mare basalt units. The evolution of volcanic activity in this crater is discussed. The results are as follows: Abundances of major elements, Th, and silicate minerals suggest that the mare basalt in the crater floor is not a uniform unit but rather nine units with different compositions. The nine basalt units are divided into two episodes of volcanic activity: The first occurred at 3.5–3.7 Ga, when highly evolved lava erupted at the crater floor at a large scale; the second occurred at ~3.4 Ga, when a small area of more primitive lava extended to the northern portion of the crater floor.

Geomorphology, Mineralogy, and Chronology of Mare Basalts in the Oceanus Procellarum Region

Mare basalts on the lunar surface are tangible expressions of the complex thermal evolution and geological processes that have occurred within the lunar interior. These basaltic manifestations are highly important because they provide invaluable insights into lunar geological evolution. Notably, the Oceanus Procellarum region, which is renowned for its extensive and long-lasting basaltic volcanism, is a premier location to investigate late-stage lunar thermal evolution. The primary aim of this research is to elucidate the geomorphological, compositional, and temporal attributes that define the mare basalts within the Oceanus Procellarum region. To achieve this aim, we comprehensively analyzed the geomorphological features present within the region, leveraging Kaguya/SELENE TC images and digital elevation models. Specifically, these geomorphological features encompass impact craters, wrinkle ridges, sinuous rilles, and volcanic domes. Subsequently, we thoroughly examined the mineralogical attributes of basalts in the Oceanus Procellarum region, leveraging Kaguya/SELENE MI data and compositional map products. To more accurately reflect the actual ages of the mare basalts in the Oceanus Procellarum region, we carefully delineated the geological units within the area and employed the latest crater size-frequency distribution (CSFD) technique to precisely determine their ages. This refined approach allowed for a more comprehensive and accurate understanding of the basaltic rocks in the study area. Overall, our comprehensive study included an in-depth analysis of the volcanic activity and evolution of the Oceanus Procellarum region, along with an examination of the correlation between the mineralogical composition and ages of mare basalts. The findings from this exhaustive investigation reveal a definitive age range for basalt units within the Oceanus Procellarum region from approximately 3.69 Ga to 1.17 Ga. Moreover, the latest mare basalts that formed were pinpointed north of the Aristarchus crater. Significantly, the region has experienced at least five distinct volcanic events, occurring approximately 3.40 Ga, 2.92 Ga, 2.39 Ga, 2.07 Ga, and 1.43 Ga, leading to the formation of multiple basalt units characterized by their unique mineral compositions and elemental abundances. Through the application of remote sensing mineralogical analysis, three primary basalt types were identified: low-titanium, very-low-titanium, and intermediate-titanium basalt. Notably, the younger basalt units exhibit an elevated titanium proportion, indicative of progressive olivine enrichment. Consequently, these younger basalt units exhibit more intricate and complex mineral compositions, offering valuable insights into the dynamic geological processes shaping the lunar surface.

Paleoenvironment implications of layered ejecta craters in the Chryse Planitia, Mars

The formation of martian layered ejecta craters (LECs), which have one or multiple distinctive fluidized layered ejecta deposits, is generally hypothesized to be directly related to subsurface volatiles. Using a high-resolution (5 m/pixel) context camera (CTX) mosaic as a base map, 525 LECs (including 157 newly identified) were catalogued in the Chryse Planitia and divided into three types according to the number of layered ejecta, i.e., single layer ejecta (SLE), double layer ejecta (DLE), and multiple layer ejecta (MLE). It is found that the minimum crater diameter (here called the onset diameter) decreases with increasing latitude, and could be as small as 1 km. The average ejecta mobility (EM) values usually increase from the low to the high latitude interval for each LEC type and gradually increase with the number of layered ejecta within each latitude interval. The lobateness values of the SLE craters have a decreasing trend with increasing latitude, however, such a trend is not obvious for the DLE and MLE craters. The absolute model ages (AMAs) of 135 LECs were determined from the crater size-frequency distribution (CSFD) method to constrain the timing of the fluvial activities of the circum-Chryse outflow channels and to investigate the local temporal-spatial evolution of the subsurface volatile-rich layer. The superposition relationship between the LECs and circum-Chryse channels suggests fluvial activity might have extended into the early Amazonian. Floods that carved the Ares, Tiu, and Simud Valles likely ended before ∼μ2.7 Ga, while those relating to theVedra, Manmee, and Maja Valles ceased between ∼μ2.2 Ga and ∼ μ1.9 Ga. The fluvial resurfacing activities in the Kasei Valles likely did not last past ∼μ2.8 Ga. The dating results and excavation depths of LECs (diam. < 6 km) suggest that the minimal roof depth of the volatile-rich layer has remained relatively stable at least around 560– 590 m since the early Amazonian, and regional differences indicate that it could be as shallow as ∼440 m at high latitudes and ∼540 m at low latitudes.

Slopes of Lunar Crater Size‐Frequency Distributions at Copernican‐Aged Craters

AbstractCraters on the lunar surface can provide valuable information about the timing and sequence of surface‐forming processes on the Moon. A commonly used method for age determination is the analysis of the crater size‐frequency distribution (CSFD) to which a production function (PF) is fitted that represents the size‐frequency distribution of the impactors. However, the commonly used PF of Neukum (1983) is valid for crater diameters between 10 m and 300 km. Neukum et al. (2001, https://doi.org/10.1007/978-94-017-1035-0_3) revised the PF for crater diameters of 100 m–200 km. However, it is suggested to also be valid for the diameter range of 10 m–300 km as well. To assess whether we can extend a PF to craters ≤10 m in diameter, we investigated the slopes of the CSFDs of small craters formed on ejecta of young Copernican‐aged craters Giordano Bruno, Moore F, North Ray, and South Ray. A PF for smaller diameters would allow dating of young geological units, which are typically small, and would reduce the statistical error in age determinations, since smaller craters are more abundant. However, small craters are strongly influenced by geological factors, such as target properties, crater degradation, and secondary craters. For craters between 10 and 20 m we obtain a steeper CSFD slope than Neukum's proposed −3 slope (cumulative), whereas for craters ≤10 m the slope is about −3. We conclude that the PF of Neukum (1983) provides a reasonable CSFD slope for smaller craters, although it was not developed for this crater diameter range.

Stratigraphy, Crater Size–Frequency Distribution, and Chronology of Selected Areas of Ganymede’s Light and Dark Terrains

The stratigraphy of the largest natural satellite of our solar system, Ganymede, is investigated using available global mosaic (basemap) and high-resolution images. We are focusing on the reconstruction of the formation and tectonic evolution of selected areas of dark and light terrain units and investigate their morphological characteristics and relative ages at a local scale using high-resolution images from the sub-Jovian and anti-Jovian hemispheres. For this, geological maps and crater size–frequency distributions for each of the terrain units were prepared, and relative as well as absolute ages were derived by applying the currently available lunar-derived impact chronology model and the Jupiter-family comet chronology model. The relative ages obtained from the cross-cutting relationships of terrain units are not always consistent with the ages derived from the crater size–frequency distributions. Some regions are influenced by secondary and sesquinary craters and tectonic resurfacing activities. Independent of the applied model, the derived crater size–frequency distribution showed that the light terrain started to form soon after the completion of dark terrain formation.

The Collisional Evolution of the Primordial Kuiper Belt, Its Destabilized Population, and the Trojan Asteroids

The tumultuous early era of outer solar system evolution culminated when Neptune migrated across the primordial Kuiper Belt (PKB) and triggered a dynamical instability among the giant planets. This event led to the ejection of ∼99.9% of the PKB (here called the destabilized population), heavy bombardment of the giant planet satellites, and the capture of Jupiter’s Trojans. While this scenario has been widely tested using dynamical models, there have been fewer investigations into how the PKB, its destabilized population, and the Trojans experienced collisional evolution. Here we examined this issue for all three populations with the code Boulder. Our constraints included the size–frequency distributions (SFDs) of the Trojan asteroids and craters on the giant planet satellites. Using this combination, we solved for the unknown disruption law affecting bodies in these populations. The weakest ones, from an impact energy per mass perspective, were diameter D ∼ 20 m. Overall, collisional evolution produces a power-law-like shape for multikilometer Trojans and a wavy-shaped SFD in the PKB and destabilized populations. The latter can explain (i) the shapes of the ancient and younger crater SFDs observed on the giant planet satellites, (ii) the shapes of the Jupiter family and long-period comet SFDs, which experienced different degrees of collision evolution, and (iii) the present-day impact frequency of superbolides on Jupiter and smaller projectiles on Saturn’s rings. Our model results also indicate that many observed comets, the majority which are D < 10 km, are likely to be gravitational aggregates formed by large-scale collision events.

Dendritic ridges in Antoniadi basin, Mars: Fluvial or volcanic landforms?

Antoniadi basin displays dark-toned dendritic ridges previously interpreted as inverted fluvial channels. Detailed observations of these dark-toned ridges as well as the geological units in the central region of Antoniadi basin are provided emphasizing images from the Colour and Stereo Surface Imaging System (CaSSIS), the High Resolution Stereo Camera (HRSC) and the High Resolution Imaging Science Experiment (HiRISE) instruments. Results show that the dark-toned ridges are part of the most recent geological unit as they overlie, and thus postdate all plains of the central Antoniadi basin, which is Early Amazonian based on its crater size-frequency distribution. Our observations of the dark-toned ridges are not consistent with inverted fluvial channels: they do not widen in the expected downstream direction, they display a rubbly texture and lack layering at high resolution, and have lobes with local levees in place of channel heads. In addition, the branched ridges are more mafic in composition and display a relatively higher thermal inertia than their surroundings. This suite of characteristics is better explained by volcanic flows developed as distributary channels rather than fluvial tributary channels. The occurrence of dikes in the east and west of the studied region supports that these flows were formed by lava, perhaps a'a like flows as suggested by the rubbly texture, but with an unusually high degree of digitation. Alternatively, such a geometry could be explained by the emplacement of the lava along pre-existing fluvial valleys, but neither the underlying topography, nor two nearby older craters, exhibit signs of fluvial erosion.

A subsurface layer on asteroid (101955) Bennu and implications for rubble pile asteroid evolution

We use observations of Bennu's impact craters, and measurements of particle sizes seen in images from the OSIRIS-REx (the Origins, Spectral Interpretation, Resource Identification Regolith Explorer sample-return mission) sampling event, to conclude there is a ∼ global sub-surface layer of finer-grained material on Bennu. The layer is evident in particle measurements from areas inside and around craters, roughness assessments of crater interiors vs. surrounding terrain, crater colors, crater depth-to-diameter (d/D) ratios, and the global crater size-frequency distribution. All data sets show a transition in behavior at crater diameters between 20 m and 40 m, with the most abrupt changes at ∼25 m diameter. Based on the depth of ∼25 m diameter craters, we infer that the layer is 1–4 m thick. The reddest craters are the youngest craters, and there is a trend to older ages as redness decreases. The decrease in redness is characterized by an initial, rapid fade, followed by a slower fade. The reduction in expected crater abundance with diameters ∼40–80 m, when extrapolating from larger sizes, is consistent with impact armoring caused by deeper, large sub-surface boulders depressing crater diameter. The existence of the layer appears to be a natural byproduct of impacts across a wide energy range and can be described as a “punctuated equilibrium”: small, frequent impacts contribute to the local production of finer-grained particles and locally mix smaller particles into the subsurface; larger, less-frequent large impacts eject the fine-grained material, exposing interior boulders, and resetting the finer-grained particle population in that area. Other processes, e.g. thermal fracturing, could also contribute to the production of fine-grained material on rapid timescales. Extrapolating to the broader asteroid population and considering the production and preservation of small particles is related to target strength, surface acceleration, and impact speeds, we expect to find such layers on other asteroids, and that the layer thickness and depth will vary with composition, size, and orbital parameters.

Geological mapping and chronology of lunar landing sites: Apollo 14

The lunar cratering chronology function is based on the careful and systematic correlation of crater size-frequency distributions (CSFDs) with radioisotopic ages of samples from the Apollo, Luna, and Chang'e landing sites. The link between the samples and the CSFDs requires a detailed understanding of the landing site geology. Therefore, in this study, we have created a new detailed regional geological map of the Apollo 14 landing site using LRO, M3, and SELENE/Kaguya data. The geologic map allows us to define homogeneous areas for new CSFD measurements, from which updated N(1) values (i.e., cumulative number of craters with diameter ≥ 1 km) can be determined for the sampled geologic units. In particular, at the Apollo 14 landing site we measured the N(1) of the Imbrian Fra Mauro Formation (Ifm), which is interpreted to be ejecta from the Imbrium basin, and can be correlated with the Apollo 14 Imbrium ejecta samples. This new calibration point can be compared with the lunar chronology of Neukum (1983). We find that the new calibration point is consistent with the lunar cratering chronology of Neukum (1983). Together with our previous studies, this result supports the validity of this chronology.

Geologic investigation of lobate scarps in the vicinity of Chandrayaan-3 landing site in the southern high latitudes of the moon

The Chandrayaan-3 primary landing site (PLS) is located in the southern high latitude region between 68–70° S and 31–33° E of the Moon. We have found two scarps (scarp #1 and #2) in the surrounding area of PLS. Since lobate scarps are one of the youngest tectonic structures on the Moon and they are seismically active recently, we have conducted a detailed morphological and topographic investigation of the scarps to examine their origin. Subsequently, chronological and seismic investigation of the inferred lobate thrust fault scarps in the PLS region was carried out to assess the safety and the possible hazards to the lander/rover of the Chandrayaan-3 mission. Our analysis reveals that out of the two scarps located in the PLS region, scarp #2 is a typical lobate thrust fault scarp, which is generally comparable in vergence direction, maximum relief, and maximum slope on the scarp face to the scarps found elsewhere on the Moon. Scarp #1 could be potentially a non-fault related scarp. The crater size-frequency distribution (CSFD) based best-fit ages derived for the scarp face, and hanging and footwalls of the scarp reveal that the scarp is a younger generation scarp (∼20–30 Ma). We have found evidence of fresh and faded boulder-fall trails on the rims and walls of multiple craters located around the scarp #2. The seismic measurements reveal potential shallow moonquakes induced by the lobate scarp #2 could have generated a moonquake of a cumulative or maximum possible moment magnitude of Mw 6.3. Based on our analysis of the potential ground shaking caused by the shallow moonquake, it appears that the landing site is safe from seismic hazards. Nevertheless, we propose that the Instrument for Lunar Seismic Activity (ILSA) onboard the Chandrayaan-3 lander could possibly detect recent Mw 4 shallow moonquakes, provided that they occur currently at a focal depth of <1 km.

Improvement of Lunar Surface Dating Accuracy Utilizing Crater Degradation Model: A Case Study of the Chang’e-5 Sampling Area

Taking the Chang’e-5 (CE-5) sampling area as an example, this study carried out an investigation on improving the crater size-frequency distribution (CSFD) dating accuracy of lunar surface geologic units based on the crater degradation model. We constructed a three-parted crater degradation model, which consists of the diffusion equation describing crater degradation and equations describing the original crater profile for small craters (D &lt; 1 km) and larger craters (D ≥ 1 km). A method that can improve the accuracy of CSFD dating was also proposed in this study, which utilizes the newly constructed degradation model to simulate the degradation process of the craters to help determine the crater degradation process and screen out the craters suitable for CSFD analysis. This method shows a good performance in regional dating. The age determined for the CE-5 sampling area is 2.0 ± 0.2 Ga, very close to the 2.03 ± 0.004 Ga of isotopic dating result of the returned sample. We found that the degradation state of the craters simulated by our constructed degradation model is highly consistent with the real existing state of the craters in terms of their topographic, geomorphological, and compositional (e.g., FeO) features. It fully demonstrates that the degradation model proposed in this study is effective and reliable for describing and distinguishing the degradation state of craters over time due to the cumulative effects of small craters. The proposed method can effectively distinguish between diffusively degraded (which conform to the degradation model) and non-diffusively degraded (which do not conform to the degradation model) craters and improve the CSFD accuracy through the selection of the craters. This not only provides an effective solution to the problem of obtaining a more “exact” frequency distribution of craters, which has long plagued the practical application of the CSFD method in dating the lunar surface but also advances our understanding of the evolutionary history of the geologic units of the study area. The results of this work are important for the in-depth study of the formation and evolution of the moon, especially for lunar chronology.

Investigating the relaxation of small craters emplaced on solidified melt sheets on the Moon

Larger impact craters and basins on the Moon display a persistent discrepancy in crater size frequency distributions between their interior melt surfaces and exterior ejecta blankets. The population of smaller craters <1 km across used to date the melt and ejecta surfaces often indicate younger surface ages for the melt surface, even though the two should be the same age having formed at the same time from the initial impact. This work investigates the possibility of removal or deformation of these small craters by topographic relaxation via the solid-state creep of lunar mare and highlands materials that have formed on a warm but recently solidified melt sheet on the Moon. We first determine the thermal state of a solidified volume of melt as it cools from the surface to a melt interface at depth that is thick enough to accommodate the emplacement of craters 200 m or 500 m in diameter. We then examine the extent of topographic relaxation under a favorable steady state temperature profile using material rheologies for the applicable lunar materials under lunar gravity. Ultimately, our simulations show that despite elevated thermal conditions that are favorable to relaxation, the low stress state and stiffness of the material rheologies inhibit any significant crater deformation, with displacements <1 m over 10 kyr. This finding suggests that other mechanisms such as self-secondary cratering or target material contrasts, among others and possibly in combination, are likely responsible for the discrepancy in CSFD ages between the melt and ejecta surfaces.

Chronology, composition, and mineralogy of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum

The timeline of volcanic activity is critical for constraining the thermal evolution of the Moon. The spatial extents of mare basalts, major products of lunar volcanism, have been precisely extracted from LROC (Lunar Reconnaissance Orbiter Camera) image mosaics. With the maria extents newly extracted from LROC mosaics, we found that a large area of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum (the PIV region) has not yet been dated. This study analysed the chronology, composition, and mineralogy of the PIV region, aiming to finish the picture of basaltic volcanism in the Procellarum region, which is a key puzzle of our global geological mapping of the Moon. According to the topographical, spectral, and compositional characteristics, mare units of the PIV region are defined, and the crater size frequency distribution is measured. The primary craters with diameters >0.1 km in the PIV region are measured, and the absolute model ages of basalt units between ∼3.78 Ga and ∼1.71 Ga are derived. Most western PIV basalt units are Eratosthenian-aged, while eastern units mostly formed in the Imbrian period. The spectra of 4965 small impact craters are extracted to interpret the mineral compositions of the PIV basalt units using Chandrayaan-1 Moon Mineralogy Mapper data. Using a Modified Gaussian Model, the reflectance spectra are deconvoluted, and the obtained modal proportions of mafic minerals show low olivine and high low-Ca pyroxene abundances in the eastern PIV region, while the western region features high olivine and calcic pyroxene concentrations. Three episodes of volcanic events occurring in the PIV region are identified. The first (main) occurred at approximately 3.5 Ga (Late Imbrian), with erupted lava flows with less evolved compositions covering most of the PIV area. The peak of volcanic activity in the Eratosthenian period occurred around 2.5 Ga, where mare basalts with moderately evolved compositions and mineralogy were formed. The last major eruption occurred at approximately 1.8 Ga, forming mare basalts with highly evolved compositions.

Geologic history of the south circumpolar region (SCR) of the Moon

Space exploration missions have placed renewed focus on the South Circumpolar Region (SCR) of the Moon due to its unexplored nature by landed missions, potential water resources, proximity to the ancient South Pole-Aitken (SPA) basin, and the presence of regions that provide near-permanent solar illumination. Unlike previous surface exploration sites, the SCR lacks extensive mare regions and is most similar to the Apollo 16 and Luna 20 sites, and is dominated by overlapping deposits of impact craters and basins of a wide range of sizes and ages. This renders the geologic history of individual regions difficult to determine, and the provenance of returned samples potentially enigmatic. In order to help alleviate these problems and to provide a consistent geological framework for landing site selection, mission planning and operations, and interpreting sample provenance, we have compiled a new geologic map of the SCR (1:300000 mapping scale; South pole to 70°S) using the most recently acquired orbital data (LRO LROC WAC 100 m/pix resolution image data and LOLA-based 80–20 m/pix resolution DTMs), and portraying geological units, features and structures, stratigraphic sequences, and providing a framework to address many outstanding problems in lunar science. We define and map several major types of units and structures: (1) high-standing massifs of the SPA basin, (2) crater-related units – walls, rims, and ejecta of impact craters and smaller basins, (3) plains units of both impact (impact melt and/or Cayley Formation) and volcanic origins (lava fields and pyroclastic deposits) and (4) landforms related to degradation of crater topography. Absolute Model Ages (AMAs) derived from crater size-frequency distribution (CSFD) measurements for ∼200 of these units/structures, whose relative ages were determined by superposition relations, were used to compile a correlation of map units for the SCR region.

Mapping of Compositional Diversity and Chronological Ages of Lunar Farside Multiring Mare Moscoviense Basin: Implications to the Middle Imbrian Mare Basalts

The Mare Moscoviense is an astonishing rare flatland multi-ring basin and one of the recognizable mare regions on the Moon’s farside. The mineralogical, chronological, topographical and morphological studies of the maria surface of the Moon provide a primary understanding of the origin and evolution of the mare provinces. In this study, the Chandrayaan-1 M3 data have been employed to prepare optical maturity index, FeO and TiO2 concentration, and standard band ratio map to detect the mafic indexes like olivine and pyroxene minerals. The crater size frequency distribution method has been applied to LROC WAC data to obtain the absolute model ages of the Moscoviense basin. The four geological unit ages were observed as 3.57 Ga (U-2), 3.65 Ga (U-1), 3.8 Ga (U-3) and 3.92 Ga (U-4), which could have been formed between the Imbrian and Nectarian epochs. The M3 imaging and reflectance spectral parameters were used to reveal the minerals like pyroxene, olivine, ilmenite, plagioclase, orthopyroxene-olivine-spinel lithology, and olivine-pyroxene mixtures present in the gabbroic basalt, anorthositic and massive ilmenite rocks, and validated with the existing database. The results show that the Moscoviense basin is dominated by intermediate TiO2 basalts that derived from olivine-ilmenite-pyroxene cumulate depths ranging from 200 to 500 km between 3.5 Ga and 3.6 Ga.

Shallow subsurface basalt layer along Cerberus Fossae, Mars: Insights from SHARAD, HiRISE, and CRISM analysis

We surveyed the subsurface structure along Cerberus Fossae using data from SHAllow RADar (SHARAD), High-Resolution Imaging Science Experiment (HiRISE), and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard the Mars Reconnaissance Orbiter (MRO). The subsurface structure along the Cerberus Fossae is fundamental to understanding the depositional history of the region. We identified meter-scale stratigraphy using HiRISE images and digital terrain models (DTMs) and found three distinct vertical units 1) ∼3 to 5 m thick regolith cover, 2) ∼30 m thickly layered unit, and 3) ∼260 m thick massive unit dominated by boulders. Using SHARAD radargrams, we identified a subsurface reflector at the interface between units 2 and 3, located ∼34 m deep. Our analysis suggests a real dielectric permittivity of 9.34 ± 1.01 (1σ), and a mean loss tangent of 0.027 ± 0.01 for the shallow subsurface material, thus indicating thick, dense shergottite-type basaltic material along the Cerberus Fossae. Using the dielectric permittivity mixing law, we found that the porosity of the shergottite-type basalt is ∼4%. CRISM analysis aids in further constraining the nature of the shergottite-type basalt and suggests the presence of Fe-rich olivine along the Cerberus Fossae, thus, referred as olivine-bearing shergottite-type basalt in this study. We derived the age of subsurface material using the crater size-frequency distribution and estimated the crater retention age of ∼4 Ma. Overall, this study suggests a ∼ 30 m thick dense and layered olivine-bearing shergottite-type basalt along the Cerberus Fossae, which is older than 4 Ma. The results of this study are incompatible with the hypothesis of a sea of frozen water in the shallow subsurface (up to 35 m) along the Cerberus Fossae.

Miranda's Thick Regolith Indicates a Major Mantling Event from an Unknown Source

We investigated “muted” craters and scarps across Miranda’s cratered terrain. The morphologies of the muted craters are most consistent with modification by regolith deposition instead of erosion or viscous relaxation. We used three techniques to estimate regolith thickness. (1) Analysis of muted crater depth–Diameter (d-D) ratios near the South Polar Terrain Chasma indicates that regolith mantling their floors ranges from 0.3 to 1.2 km thick. Because older craters may have collected more regolith than younger craters, the true thickness may be similar to the highest estimate. (2) Analysis of crater size–frequency distributions across the cratered terrain indicates a thickness of 1.0 ± 0.2 km. (3) Analysis of a central mound within Alonso Crater indicates a thickness of km near Verona Rupes and may represent an upper limit. These results indicate that Miranda has one of the thickest regoliths in the solar system, which has important implications for Miranda’s interior thermal properties. Regolith appears to mantle some scarps within Arden but not Elsinore or Inverness, indicating that Arden may be the oldest corona, contrary to previous relative age estimates. In this scenario, the mantling event was ongoing during Arden’s formation but before Elsinore or Inverness formed. We propose three possible sources for Miranda’s thick regolith: (1) giant impact ejecta, (2) plume deposits, and (3) Uranian ring deposits. We favor the ring deposit hypothesis, which is consistent with the regolith’s large spatial extent, substantial thickness, and Miranda’s slightly spectrally blue color. Follow-up studies that rigorously investigate these scenarios are required.

Study of the Buried Basin C-H, Based on the Multi-Source Remote Sensing Data

We use multi-source remote sensing data to identify the details of a mascon south-east of the lunar Copernicus crater. Studies of the topography, gravity, geochronology and mineral are combined to prove that the mascon is a buried peak-ring basin with diameters of about 130 km and 260 km. The underground structure is covered by 890 m thick mare basalts, as determined by analyzing the spectral features of the impact crater, Copernicus H. The determination of the crater size–frequency distribution (CSFD) suggests that the impact that created the C-H basin occurred earlier than 3.9 Ga. Then, a Hawaiian-style eruption in the late Imbrian period formed the Sinus Aestuum-I dark mantling deposit (DMD). Soon, mare basalts covered the basin several times from 3.8 Ga. Finally, the ejecta from the Copernicus impact event at about 800 Ma, and the weathering processes caused the disappearance of the C-H basin rim from the lunar surface.

The Age and Erosion Rate of Young Sedimentary Rock on Mars

The Medusae Fossae Formation (MFF) is an enigmatic sedimentary unit near the equator of Mars, with an uncertain formation process and absolute age. Due to the heavily wind-eroded surface, it is difficult to determine the absolute model age of the MFF using a one-parameter model based on the crater size–frequency distribution function with existing crater count data. We create a new two-parameter model that estimates both age and a constant erosion rate (β) by treating cratering as a random Poisson process. Our study uses new crater count data collected from Context Camera imagery for both the MFF and other young equatorial sedimentary rock. Based on our new model, the Central MFF formed >1.5 Gyr ago and had low erosion rates (<650 nm yr−1), whereas the East MFF, Far East MFF, and Zephyria Planum most likely formed <1.5 Gyr ago and had higher erosion rates (>740 nm yr−1). The top of Aeolis Mons (informally known as Mount Sharp) in Gale Crater and Eastern Candor have relatively young ages and low erosion rates. Based on the estimated erosion rates (since fast erosion permits metastable shallow ice), we also identify several sites, including Zephyria Planum, as plausible locations for shallow subsurface equatorial water ice that is detectable by gamma-ray spectroscopy or neutron spectroscopy. In addition to confirming <1.5 Gyr sedimentary rock formations on Mars, and distinguishing older and younger MFF sites, we find that fast-eroding locations have younger ages and MFF locations with slower erosion have older best-fit ages.