Xiaojian Xu

Recently, possible exceptionally young mare volcanic glass beads were discovered in Chang'e‐5 (CE‐5) samples. Isotopic dating suggests an age of approximately 120 Ma, presenting new challenges to existing lunar thermal evolution models. Thus, our research focuses on the source region of Rima Mairan, a branch of Rima Sharp, and its surrounding area, located southeast of the CE‐5 landing site. In this area, numerous small irregular mare patches (IMPs) were identified and analyzed to explore their formation timing and possible origins. To investigate the debated formation ages of IMPs (3.5 Ga), we carried out statistical, classification, morphological, and chronological analyses and find: (a) Approximately 75% of small IMPs are located within or along crater rims (50–500 m in diameter). (b) Morphological measurements and diffusion modeling estimate the ages of these craters from 2 Ga to the present, indicating a gradual, time‐variable formation process rather than a single event. (c) Surface features such as lobate contacts, limited thickness (∼6 m), and compositional similarities to CE‐5 basalts imply that they were likely influenced by late‐stage localized magmatic or thermal processes after 2 Ga. However, their final morphology may also record modification using non‐volcanic processes such as collapse, regolith redistribution, or seismic activity. These findings reveal complex resurfacing processes possibly sustained by localized thermal anomalies, suggesting that geological activity persisted longer than previously thought. Further high‐resolution imaging and in situ analyses are needed to clarify IMP origins, evaluate their relationship to CE‐5 materials, and refine models of late‐stage lunar thermal evolution.

Evidence from instruments in Mars orbit and from the Zhurong rover suggests that oceans may have existed in the northern plains of Mars. Sedimentary stratification is a key indicator for verifying the historical presence of oceans on the Martian surface. However, there is still disagreement about the formation mechanism of sedimentary stratification at the Zhurong rover landing site. In this study, three-dimensional point clouds are generated from images taken by the Zhurong rover's navigation stereo camera. These point clouds are used to perform quantitative measurements and statistical analyses of the cross-bedding angles in sediments in rocks, and these angles are then compared with sedimentary bedding angles from various terrestrial environments to infer the dynamic sedimentary processes in the Zhurong landing area. The dip angles of the rocks at the Zhurong landing site on Mars range from 18.5° to 51.5°, with a median of 33.4°. The dip angles of the rocks in Gale Crater range from 14.7° to 41.7°, with a median of 31.5°. On Earth, the dip angles of strata in humid regions range from 7.4° to 38.4°, with a median of 27°, whereas in arid regions, the dip angles of strata range from 7.6° to 38°, with a median of 22.6°. These dip ranges indicate that the cross-bedding angles of sedimentary rocks on the Martian surface are similar to those of coastal aeolian cross-bedding on Earth, which indicate that their formation mechanism was comparable to the formation mechanism of coastal dunes. The sedimentary rocks at the Zhurong landing site were concluded to have formed in a nearshore marine depositional environment. This study represents the first statistical analysis of critical information on cross-bedding in Martian surface rocks compared with that in similar terrestrial environments, providing evidence from a sedimentary dynamics perspective for the depositional evolution of the Martian Utopia Planitia and indicating the historical presence of an ancient ocean in this region.

As the closest celestial body to Earth, the Moon has become a major focus of scientific research due to its unique position and environment. Although the Moon is often thought of as a 'dead' planet, in fact there is still some faint but continuous activity in its interior and on its surface. One particularly interesting phenomenon is lunar degassing, which reveals dynamic changes in its current environment. Interestingly, these degassing regions are often associated with distinctive lunar topography. Early lunar radon measurements, although made from orbits with considerable noise, showed that there were regions with enhanced radon exhalation, particularly in the Aristarchus crater region, which has been highlighted by the Apollo 15, Lunar Prospector and Kaguya-Selene missions. The recent Chang'e 6 mission successfully deployed the DORN instrument, which resulted from a collaboration between France and China, to perform both orbital and in-situ lunar surface measurement of radon and polonium. Although the Rn-222 was not detected in situ, the likely presence of faint polonium isotope peaks indicates that there was only a weak release of radon gas in the landing site region. Therefore, the primary objective of this study is to investigate the relationship between lunar degassing phenomena and topography by comparing the geomorphological features of the Aristarchus region with those of the Chang'e 6 landing site. The purpose of this study is to explore the relationship between lunar degassing phenomena and topography by comparing the morphological differences between the Aristarchus crater and the Chang'e-6 landing site. LRO WAC images are used to compare the topographic differences between the two regions, and SLDEM2015 data are used to calculate the elevation and slope differences within the regions to hypothesise the potential impact of these topographic features on radon gas release. In addition, data from the Chang'e-2 microwave radiometer are used to calculate the diurnal temperature variation at the Chang'e-6 landing site, with a detailed investigation of how temperature anomalies reflect the subsurface stratigraphy of the lunar surface. Based on the results of the data processing, We will analyse the geological environmental differences between the two regions and investigate the possible effects of these differences on the release of radon gas and the possible sources of the weak radon gas in the landing area.

Introduction: Determining the age of a planet's surface can not only help distinguish the sequence of geological events and reveal clues of the planet's evolution, but can also support the selection of lunar exploration sites. Therefore, the determination of the lunar surface ages is very important for characterizing different geological units and investigating the geological history of the landing sites. At present, the widely used method for lunar surface dating is the measurement and fitting of crater size-frequency distributions (CSFD) [1]. One major challenge for this method is to avoid and/or remove of secondary craters that would yield incorrect ages if included in the CSFD. Secondary craters are typically identified based on their irregular morphology and shape compared to primary craters. However, there are some limitations in this method, because remote field secondary craters may have morphologies very similar to primary craters. Therefore, we developed a method to identify secondary craters on mare surfaces based on a contrast between the iron content of the surface inside and outside the crater.Approach: The lunar regolith has unique mineralogical compositions and contains large quantities of nanoscale elemental iron due to space weathering [2]. In the study of data from Clementine and Apollo lunar highlands and mare, Ye et al. [3] found that the concentration of FeO inside craters was much lower than in their surroundings.Figure 1. Distribution of iron in and around craters and identification of secondary craters. (a) Effect picture of error elimination (N39°-40° E323°-324°, the lower iron regions are shown in yellow, whereas higher iron areas are shown in gray). (b) Test Results and details for the Sinus Iridum area (yellow: primary craters; red: secondary craters; green: isolated secondary craters; purple: secondary craters with diameters larger than 400 m).Because the depth/diameter ratio for primary craters is 0.12 and 0.06 for secondary craters [4], we infer that the iron content for secondary craters is more similar to that in the lunar surface soil than for primary craters. Hence, we first determine the mean FeO abundance within a given crater and then the mean FeO abunddance of the lunar soil outside the crater. The difference between these two abundances is calculated and a threshold value is obtained through comparative analysis to identify secondary craters. After the secondary craters are eliminated, the remaining craters are used to date lunar surface unit. We then compare our new results with known ages [5] to iteratively adjust the threshold and improve the method. However, possible sources of uncertainty in our method include potential compositional layering in the regolith. Ongoing work will examine this and other potential effects on our approach.Figure 2. Flowchart for the determination of the recognition threshold for secondary craters.Results: We selected areas in Tsiolkovsky crater and Sinus Iridum to develop our method. We used the multispectral data obtained by the multi‑band imager of the Japanese Selene Mission to determine the iron abundance. The result for the Sinus Iridum area is shown in Figure 1b. Most craters are primary craters (yellow). The identified secondary craters (red) are either chain-like or isolated (green), rather than clustered. Some of the secondary craters have diameters larger than 400 m (purple).Discussion: To improve the reliability of secondary crater identification, the results were verified by CSFD. Our dating results were compared with existing ages. The similar age indicates that the method can identify secondary craters (Table 1). Besides morphological considerations and spatial patterns of secondary craters, our secondary crater identification method might provide an additional possibility to detect secondary craters and to eliminate them from CSFD measurements. Secondary Craters Not ExcludedTable 1. Dating Results (Ga) Area Pasckert, 2015 Hiesinger, 2011 Secondary Craters Not Excluded Excluded Secondary Craters Tsiolkovsky Crater Area 3.2 3.37 3.22 Sinus Iridum Area 1 3.0 3.47 3.02 Sinus Iridum Area 2 3.0 3.43 3.04 References: [1] Hiesinger, H., van der Bogert, C. H., Michael, G., Schmedemann, N., Iqbal, W., Robbins, S. J., Ivanov, B., Williams, J. P., Zanetti, M., Plescia, J., Ostrach, L. R., & Head, J. W., III. (2023). The Lunar Cratering Chronology. Reviews in Mineralogy and Geochemistry, 89(1), 401-451. [2] Taylor, L. A., & Meek, T. T. (2005). Microwave sintering of lunar soil: properties, theory, and practice. Journal of Aerospace Engineering, 18(3), 188-196. [3] Ye, L., Xu, X., Luan, D., Jiang, W., & Kang, Z. (2017). Automatic Detection and Recognition Of Craters Based on The Spectral Features Of Lunar Rocks and Minerals. Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-3/W1, 199-204. [4] Plescia, J. B. (2015, March). Lunar crater forms on melt sheets—Origins and implications for self-secondary cratering and chronology. In 46th Annual Lunar and Planetary Science Conference (No. 1832, p. 2054). [5] Hiesinger, H., Head, J. W., III, Wolf, U., Jaumann, R., Neukum, G., Ambrose, W. A., & Williams, D. A. (2011). Ages and stratigraphy of lunar mare basalts: A synthesis. In Recent Advances and Current Research Issues in Lunar Stratigraphy (Vol. 477, pp. 0). Geological Society of America.

Lunar shallow subsurface structure is important in revealing the formation and evolution of the Moon. Therefore, a review of key issues in the lunar shallow subsurface structure will help deepen our understanding of the Moon. From a global perspective, lunar shallow subsurface structure is formed by endogenic and exogenic geological processes such as volcanic activities, tectonic activities, meteorite impacts, and space weathering. Its morphological characteristics and stratigraphic structure record the evolution of these geological processes. Recent lunar exploration missions have returned new samples and high-resolution data that have greatly enriched our knowledge. On the basis of reviewing the research progress of radar detection, crater-based excavation analysis, material inversion, and heat flow measurement, we also discuss the processes that contribute to the formation of the lunar shallow surface structure, such as volcanoes, impacts, tectonics, and space weathering. The main hot issues were sorted out and focused on 3 areas: transformation of lunar shallow subsurface structure by geological processes, environment and material composition of the lunar shallow surface structure, and physical properties of lunar shallow surface structure. Overall, existing research on the lunar subsurface has made significant progress, but it has also brought more new unsolved mysteries. It is necessary to introduce new applied payloads such as synthetic aperture radar (SAR), orbiter subsurface investigation radar (OSIR), or time-domain electromagnetic sounding (TDEM) to provide higher-resolution subsurface data, and develop better interpretation methodologies, to further deepen the understanding of the lunar shallow subsurface structure and indeed reveal the mechanism of lunar geological evolution.

China’s first Mars Exploration Mission Tianwen-1 achieved full success. The loaded Zhurong Rover landed south of the Utopia Planita. The Tianwen-1 orbiter also sending back high-resolution images. We utilized the High-Resolution Imaging Camera (HiRIC) of Tianwen-1 and Context Camera loaded on the Mars Reconnaissance Orbiter to collect the image data and construct a 3D strata model of the Zhurong landing site. Using this model, we analyzed the material loss of ghost craters. Judging from the morphological characteristics of pitted cones at the Zhurong landing site, we confirmed their classification as mud volcanoes. We also analyzed the possible cause of formation by combining the gravity field and magnetic field data. The experimental results indicate that (1) the Zhurong landing site can be divided into the dry sedimentary, moisture sedimentary, and Vastitas boreal (VB) members as three strata and another ejecta blocks. The three strata are categorized into VB formations with an integral width of 1.2 km. (2) The cones at the Zhurong landing site are mud volcanoes formed by groundwater thermal activity, and the heat source originate from a southern underground magma chamber. The density of mud volcanoes signifies the existence of ejecta blocks. (3) Apart from volumetric compaction, some ghost craters show eruption of underground substances. Generally, after the VB unit located on the surface of the Zhurong landing site formed at 3.43 Ga, the current geomorphology of the landing site was altered due to the differentiation of water evaporation above ground and underground, underground thermal activity, and meteorite impacts.

China’s first Mars Exploration Mission Tianwen-1 achieved full success. The loaded Zhurong Rover landed south of the Utopia Planita. The Tianwen-1 orbiter also sending back high-resolution images. We utilized the High-Resolution Imaging Camera (HiRIC) of Tianwen-1 and Context Camera loaded on the Mars Reconnaissance Orbiter to collect the image data and construct a 3D strata model of the Zhurong landing site. Using this model, we analyzed the material loss of ghost craters. Judging from the morphological characteristics of pitted cones at the Zhurong landing site, we confirmed their classification as mud volcanoes. We also analyzed the possible cause of formation by combining the gravity field and magnetic field data. The experimental results indicate that (1) the Zhurong landing site can be divided into the dry sedimentary, moisture sedimentary, and Vastitas boreal (VB) members as three strata and another ejecta blocks. The three strata are categorized into VB formations with an integral width of 1.2 km. (2) The cones at the Zhurong landing site are mud volcanoes formed by groundwater thermal activity, and the heat source originate from a southern underground magma chamber. The density of mud volcanoes signifies the existence of ejecta blocks. (3) Apart from volumetric compaction, some ghost craters show eruption of underground substances. Generally, after the VB unit located on the surface of the Zhurong landing site formed at 3.43 Ga, the current geomorphology of the landing site was altered due to the differentiation of water evaporation above ground and underground, underground thermal activity, and meteorite impacts.

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.

Masons are often overlooked part of impact basins, but play an important role in revealing the lunar history. Previous study in masons were usually limited to gravity data. Few researches were reported on morphology features and chronology, which hampers the construction of a complete geological interpretation for the evolution of each mascons. We use multi source remote sensing data to identify the details characteristic of mascons. Result of topography, gravity and characteristic are combined to prove that a mason beside Copernicus crater is a buried peak-ring basin which is about 130km and 260km in diameter. The underground structure is of confirmed as 890m thick mare basalts by analyzing the spectral feature of the material in a geological outcrop called Copernicus H. Geology evolution analysis joint crater size-frequency distribution (CSDF) dating demonstrate that the buried basin impact event occurred in 3.6Ga. Then a hawaiian-style eruption in late Imbrian formed Sinus Aestuum Ⅰ Dark Mantling Deposit (DMD). Mare basalts filling in 3.4Ga. After that, ejecta from Copernicus impact event in about 820Ma and weathering processes cause the disappearing from lunar surface of the buried basin.

China’s first Mars Exploration Mission Tianwen-1 achieved full success. The loaded Zhurong Rover landed south of the Utopia Planita. The Tianwen-1 orbiter also sending back high-resolution images. We utilized the High-Resolution Imaging Camera (HiRIC) of Tianwen-1 and Context Camera loaded on the Mars Reconnaissance Orbiter to collect the image data and construct a 3D strata model of the Zhurong landing site. Using this model, we analyzed the material loss of ghost craters. Judging from the morphological characteristics of pitted cones at the Zhurong landing site, we confirmed their classification as mud volcanoes. We also analyzed the possible cause of formation by combining the gravity field and magnetic field data. The experimental results indicate that (1) the Zhurong landing site can be divided into the dry sedimentary, moisture sedimentary, and Vastitas boreal (VB) members as three strata and another ejecta blocks. The three strata are categorized into VB formations with an integral width of 1.2 km. (2) The cones at the Zhurong landing site are mud volcanoes formed by groundwater thermal activity, and the heat source originate from a southern underground magma chamber. The density of mud volcanoes signifies the existence of ejecta blocks. (3) Apart from volumetric compaction, some ghost craters show eruption of underground substances. Generally, after the VB unit located on the surface of the Zhurong landing site formed at 3.43 Ga, the current geomorphology of the landing site was altered due to the differentiation of water evaporation above ground and underground, underground thermal activity, and meteorite impacts.