The Rümker region (41–45°N, 49–69°W) is located in northern Oceanus Procellarum of the Moon. Mons Rümker is the most distinctive geological feature in the area. The region is characterized by prolonged lunar volcanism (Late Imbrian Period to Eratosthenian Period), forming multiple geologic units in the area, including very low‐Ti to low‐Ti mare basalts, high‐Ti mare basalts, and volcanic complexes. Each geologic unit has distinct element composition and mineral assemblages. The Rümker region, overlying the Procellarum KREEP Terrain, was selected as the landing region for China's Chang'E‐5 lunar sample return mission. Prelanding analyses of the geologic context and scientific potential are reported in this contribution. We conducted detailed geological mapping using image, spectral, and altimetry data. Fourteen geological units were defined, a geologic map was constructed, and the geologic history was outlined. The western mare units (Im1, Im2, and Im3) are Imbrian‐aged (~3.4–3.5 Ga) representing the major stage of lunar mare eruptive volcanism. The eastern young mare units (Em3 and Em4; <2 Ga) are among the youngest mare basalts on the Moon. They have never been explored in situ or studied in the laboratory. We suggest that samples returned from the eastern mare unit (Em4) could answer many fundamental questions and that this unit should be listed as the top priority landing site for Chang'E‐5 sample return mission.

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S U M M A R YModelling of deformation and stress caused by earthquake faulting (or fault motion) based on a homogeneous elastic half-space model does not include crustal rigidity layering and lateral variations. Geological data and seismic surveys indicate that the crust is elastically inhomogeneous, and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of deformation and stress. We use the finite-element method (FEM) to investigate deformation and stress generated by strike-slip, tensile and thrust faulting, considering rigidity layering in the crust. For a fault with a dimension of 25 × 10 km and a slip value of 0.5 m cutting through the top 10 km of the crust, the deformation and stress change associated with the three modes of faulting are calculated for an island arc crustal structure represented by three models of rigidity layering. The results indicate:(i) The maximum effect in horizontal displacements due to crustal layering for the investigated models is 19.7 mm and 28.8 mm for strike-slip and tensile faulting, respectively. For thrust faulting, the effect is up to 58.3 mm. This remarkable effect is due to the offset of layers by thrust faulting, which dynamically changes the crustal structure both horizontally and vertically. (ii) The maximum effect in vertical deformation due to crustal rigidity layering for strike-slip and tensile faulting is 5 mm. In contrast, the effect for thrusting is 30.3 mm. (iii)The effect in the shear stress change at a depth of 7.5 km for the different styles of faulting ranges from 0.02 MPa to 0.10 MPa.An additional modelling analysis of subduction thrusting at the Japan trench with a detailed structural model based on seismic surveys further confirms the significant distortion caused by a homogeneous model that ignores crustal structural information. Overall, the effect of crustal rigidity layering is at least 20 per cent for surface deformation and 15 per cent for stress changes at depth. In light of the present accuracy of global positioning system (GPS) observations (±2 mm) and the estimate of stress change required for earthquake hazard analysis (ca 0.01 MPa), the results from the numerical experiments indicate that crust inhomogeneity (rigidity layering and lateral variations) should be included in any quantitative models of faulting.

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Chang'e-5 (CE-5) is China's first lunar sample-return mission. It landed in northern Oceanus Procellarum on December 1, 2020, at 43. 06°N, 51.92°W (Wang et al., 2021). 1,731 g of lunar regolith was collected and are currently under laboratory investigations.The CE-5 site (Statio Tianchuan, IAU-name) is located within Eratosthenian-aged intermediate-Ti mare basalts (labeled as Em4/P58 by Qian, Xiao, Wang, et al., 2021), with an average thickness of ∼51 m, a total volume between 1,450 and 2,350 km 3 (Qian, Xiao, Head, , and a ∼7 m thick regolith superposed (Yue et al., 2019). The CE-5 sample-return strategy included a 2 m-drill (∼1 m was recovered) and a surface sampling device (Deng et al., 2021). The returned samples are thus likely to contain materials from different sources, including local basalts mixed by vertical and lateral transportation with exotic materials (Huang et al., 2017;Liu, Michael, Zuschneid, et al., 2021). The local mare materials might be erupted from Rima Sharp and will help to better understand the nature of late-stage volcanism, deep mantle properties, and lunar chronologies; the distal materials would