Impact craters that form on every planetary body provide a record of planetary surface evolution. On heavily-cratered surfaces, new craters that form often overlap older craters, but it is unknown how the presence of older craters alters impact crater formation. We use overlapping complex crater pairs on the lunar surface to constrain this process and find that crater rims are systematically lower where they intersect antecedent crater basins. However, the rim morphology of the new crater depends on both the depth of the antecedent crater and the degree of overlap between the two craters. Our observations suggest that transient rim collapse is altered by antecedent topography, leading to circumferential distribution of rim materials in the younger crater. This study represents the first formalization of the influence of antecedent topography on rim morphology and provides process insight into a common impact scenario relevant to the geology of potential Artemis landing sites.

Martian meteoritic petrology and regional chemistry of Hesperian-Amazonian volcanism support secularly decreasing degrees of partial melting and thickening crust underlain by simple mantle convection. However, the applicability of this interior evolution model and resurfacing trends to the Noachian remains unknown. Using regional gamma spectroscopy and geophysical analysis, we find that supereruptions characterized Noachian volcanism in NW Arabia with co-enriched K, Th, and Si. Geophysical analysis reveals elastic thickness values below 20 km, indicating a heat flux exceeding many Hesperian volcanoes. Collectively, our results support large ion lithophile loss from low degrees of partial melting of the Noachian mantle, signifying an early stage of interior evolution that contrasts with the Hesperian-Amazonian model. Regional chemistry further suggests climate-altering supereruptive exhalations of ~109 kg S-phases.

Boulder-sized clasts are common on the surface of Mars, and many are sufficiently large to be resolved by the High Resolution Imaging Science Experiment (HiRISE) camera aboard the Mars Reconnaissance Orbiter (MRO). The size, number, and location of boulders on the surface and their spatial distribution can reveal the processes that have operated on the surface, including boulder erosion, burial, impact excavation, and other mechanisms of boulder transport and generation. However, quantitative analysis of statistically significant boulder populations which could inform these processes entails prohibitively laborious manual segmentation, granulometry and morphometry measurements over large areas. Here we develop and describe an automated tool to locate and measure boulders on the martian surface: the Martian Boulder Automatic Recognition System (MBARS). The open-source Python-based toolkit autonomously measures boulder diameter and height in HiRISE images enabling rapid and accurate assessments of boulder populations. We compare our algorithm with existing boulder-counting methodologies, manual analyses, and objects of known size to verify accuracy and precision. Additionally, we test MBARS quantitatively characterizing boulders around an impact crater in the martian northern lowlands. We compare this to previous work on rock excavation during impact cratering using manually counted boulders around lunar craters.