The unequal distribution of volcanic products between the Earth-facing lunar side and the farside is the result of a complex thermal history. To help unravel the dichotomy, for the first time a lunar landing mission (Chang’e-4, CE-4) has targeted the Moon’s farside landing on the floor of Von Kármán crater (VK) inside the South Pole-Aitken (SPA). We present the first deep subsurface stratigraphic structure based on data collected by the ground-penetrating radar (GPR) onboard the Yutu-2 rover during the initial nine months exploration phase. The radargram reveals several strata interfaces beneath the surveying path: buried ejecta is overlaid by at least four layers of distinct lava flows that probably occurred during the Imbrium Epoch, with thicknesses ranging from 12 m up to about 100 m, providing direct evidence of multiple lava-infilling events that occurred within the VK crater. The average loss tangent of mare basalts is estimated at 0.0040-0.0061.

We report on a newly discovered morphological feature on the lunar surface, here named Ring‐Moat Dome Structure (RMDS). These low domes (a few meters to ~20 m height with slopes <5°) are typically surrounded by narrow annular depressions or moats. We mapped about 2,600 RMDSs in the lunar maria with diameters ranging from tens to hundreds of meters. Four candidate hypotheses for their origin involving volcanism are considered. We currently favor a mechanism for the formation of the RMDS related to modification of the initial lava flows through inflated flow squeeze‐ups and/or extrusion of magmatic foams below a cooling lava flow surface. These newly discovered features provide new insights into the nature of emplacement of lunar lava flows, suggesting that in the waning stages of a dike emplacement event, magmatic foams can be produced, extrude to the surface as the dike closes, and break through the upper lava flow thermal boundary layer (crust) to form foam mounds and surrounding moats.

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Ring‐moat dome structures (RMDSs) are positive morphologic features found clustered across many mare regions on the Moon, of which only a few isolated examples have been previously reported. Our continuing survey has expanded the known locations of the RMDSs from ~2,600 to over 8,000, indicating that RMDSs are more common geological features than previously thought. This work presents a detailed geomorphological analysis of 532 RMDSs identified in several mare basins. The combination of detailed elemental mapping, morphological and morphometric analyses, spatial distribution relationships with other geologic structures, and comparison with terrestrial analogs lead us to conclude that (1) RMDSs represent low circular mounds with diameters of a few hundred meters (average about 200 m) and a mean height of 3.5 m. The mounds are surrounded by moats ranging from tens to over 100 m in width and up to several meters in depth; (2) there is a wide variation of titanium abundances, although RMDSs are more commonly found in mare regions of moderate‐to‐high titanium content (>3 wt% TiO2); (3) RMDSs are found to occur on or around fractures, graben, and volcanic edifices (small shields and cones); (4) a spatial association between RMDSs and Irregular Mare Patches (see Braden et al., 2014, https://doi.org/10.1038/ngeo2252) is observed, suggesting that both may form from related lava flows; (5) comparisons between RMDSs and lava inflationary structures on Earth support an inflation‐related extrusive nature and a genetic relationship with host lava flow processes; and (6) RMDS embayment relationships with craters of different degradation ages superposed on the host mare, and regolith development models, produces conflicting age relationships and divide theories of RMDS origin into two categories, (1) synchronous with the emplacement and cooling of the host lava flows ~3–4 Ga and (2) emplaced substantially after the host mare lava unit, in the period ~0–3 Ga. We outline the evidence supporting this age conundrum and implications for the different theories of origin and describe future research avenues to help resolve these outstanding questions.