The southern part of the smooth plain of Chryse Planitia on Mars hosts a large population of kilometer‐sized (from ~0.2 to ~20 km) landforms spread over a wide area. Based on the investigation of a small part of this area, Komatsu et al. (2016, https://doi.org/10.1016/j.icarus.2015.12.032) proposed that the edifices may be the result of the subsurface sediment mobilization. We mapped the full extent of these landforms within Chryse Planitia and performed a morphological and spatial analysis in an attempt to further test this hypothesis. We identified a total number of 1,318 of these objects, which we grouped into five different morphological classes. The edifices can be observed over an area of 700,000 km² near the termini of the large outflow channels, Ares, Simud, and Tiu Valles, with a nonrandom spatial distribution. The features are clustered and anticorrelated to the ancient highlands, which form erosional remnants shaped by the outflow events. This suggests a genetic link between the distribution of the edifices and the presence of the sedimentary deposits on which they are superposed. Such distribution is consistent with the previous notion that subsurface sediment mobilization may be the mechanism for their formation and is less consistent with the alternative igneous volcanic hypothesis. We also propose a scenario in which the large morphologic variability can be explained by variations of the water content within the ascending mud and by variations in the effusion rates. The edifices may represent one of the most prominent fields of sedimentary volcanism detected on Mars.

The crater record of a planetary surface unit is often analyzed by its cumulative size‐frequency distribution (CSFD). Measuring CSFDs involves traditional approaches, such as traditional crater counting (TCC) and buffered crater counting (BCC), as well as geometric corrections, such as nonsparseness correction (NSC) and buffered nonsparseness correction (BNSC). NSC and BNSC consider the effects of geometric crater obliteration on the CSFD. On the Moon, crater obliteration leads to two distinct states in which obtained CSFDs do not match the production CSFD—crater equilibrium and nonsparseness. Crater equilibrium occurs when each new impact erases a preexisting crater of the same size. It is clearly observed on lunar terrains dominated by small simple craters with steep‐sloped production CSFDs, such as Imbrian to Eratosthenian‐era mare units. Nonsparseness, on the other hand, is caused by the geometric overlap of preexisting craters by a new impact, which is also known as “cookie cutting.” Cookie cutting is most clearly observed on lunar terrains dominated by large craters with shallow‐sloped production CSFDs, such as the pre‐Nectarian lunar highlands. We use the Cratered Terrain Evolution Model (CTEM) to simulate the evolution of a pre‐Nectarian surface unit. The model was previously used to simulate the diffusion‐induced equilibrium for small craters of the lunar maria. We find that relative to their size, large craters contribute less to the diffusion of the surrounding landscape than small craters. Thus, a simple scale dependence cannot account for the per‐crater contribution to degradation by small simple and large complex craters.

Mercury has one of the best‐preserved impact records in the inner solar system due to the absence of an atmosphere and relatively unmodified ancient surface. However, our knowledge of the early impact record and the nature of the impacting projectiles are far from complete. To get a better understanding of the early impact history, we examined large impact basins (D ≥ 300 km) on Mercury. Here we cataloged 94 basins, 80 of which we classify as certain or probable, 1.7 times more than previously recognized. We re‐evaluate the crater densities of basins using the buffered nonsparseness correction technique, which we successfully applied for the Moon. In contrast with a previous study, we find that basins have a slightly higher N(300) crater density on Mercury than on the Moon, but similar N(500) basin densities. Based on these results and comparison with the Moon, we infer that no more than half of the basin record remains observable and basins older than Borealis have generally been erased from the basin record. Furthermore, we establish the stratigraphic relationships of basins based on N(25) crater frequencies, absolute model ages, and observations of crosscutting relationships. Similarly to our previous study on the Moon, we found no evidence for a change in the size‐frequency distribution of the impacting population; thus, our results are consistent with a single impactor population that bombarded Mercury's surface.

China's Chang’e‐5 (CE‐5) has returned 1.731 kg lunar samples from a young mare unit on December 2020. Here, the authors used a spatially resolved numerical model, which considers both impact mixing and volcanic effusion, to estimate the evolving distribution of components over the landing region. Using this model, the age composition of surface scooped and sub‐surface drilled CE‐5 samples and their sources were traced back. The proposed model predicts that local mare material predominates in both surface and sub‐surface samples and the nonlocal mare component is ∼1%. There is ∼40% of nonmare component. The composition of both nonmare components in the surface and sub‐surface samples are similar: Abundant components are basin‐sourced melts, where the Imbrium melt are ∼ 25% among all the melt. The ejecta of Sharp B, Harding, Copernicus, and Aristarchus crater that possess different compositions of basin‐sourced melt may have significantly altered the material composition of the landing surface.

The analysis of crater size‐frequency distributions (CSFDs) is a widely used technique to date and investigate planetary surface processes. There are two well‐established crater measurement techniques, traditional crater counting and buffered crater counting, and two new geometric corrections, nonsparseness correction and buffered nonsparseness correction. The new techniques consider the effects of crater obliteration and subsequent recratering while measuring CSFDs in areas of high crater density. Currently, the ArcGIS add‐in CraterTools can be used to apply the well‐established techniques. The tool relies on Esri's ArcGIS environment and is restricted to 32 bit and single‐core computing. These limitations make the implementation of the new geometric corrections in CraterTools inefficient, as the new techniques are computationally more intensive than the well‐established ones. To this end, we developed CSFD Tools, an application to conduct CSFD measurements from shapefiles. It supports 64 bit and multicore data processing and uses existing open geospatial libraries. Open libraries, however, conduct spatial measurements on a Cartesian plane and do not take a curved planetary surface into account. Therefore, we implemented methods for geodesic measurements and workarounds for the geodesic modification of polygon data to minimize map distortion effects during CSFD measurements. As a result, the new nonsparseness correction and buffered nonsparseness correction techniques can be applied through a software tool.