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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 antecedent craters, but it is unknown how the presence of antecedent 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. The rim morphology of the new crater depends on the depth of the antecedent crater and the degree of overlap between the craters. Our observations suggest that new craters do not always obliterate underlying topography and that transient rim collapse is altered by antecedent topography. 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. Plain Language Summary: Craters form on the surface of many planetary bodies and help us to understand many qualities of the surface including, critically, the age of the surface. On older surfaces with many craters, new craters that form often overlap and partially destroy older craters, though we don't know if or how the presence of the older crater changes the processes that create the new crater. Looking at large Lunar craters, we can determine that the presence of an older crater causes the rim of the new crater to be asymmetric: lower where it forms within the older crater basin. The difference in height between the new crater rim inside and outside the old crater depends on both the depth of the older crater, and where the new crater forms relative to the older crater. From this we can interpret that the presence of the older crater alters the way the new crater forms, leading to an uneven collapse of early rim materials. Key Points: Overlapping complex crater rims are lower inside the antecedent basins compared to outsideDeeper antecedent basins and more significant crater overlap tend to create larger differences in rim heightChanges in the impact crater formation process, mainly during transient rim collapse, influence the shape of overlapping crater rims [ABSTRACT FROM AUTHOR]

The Eridania Basin system, located in the martian southern highlands, may have hosted long‐lived lacustrine hydrothermalism. Despite its multi‐basin scale and suggested longevity that should pervasively alter the landscape, evidence for consistent compositional signatures of lacustrine hydrothermalism across varying spatial scales is poorly known. Here we synthesize orbital data sets (derived from the Gamma Ray Spectrometer, GRS; Thermal Emission Spectrometer, TES; and Compact Reconnaissance Imaging Spectrometer for Mars, CRISM) to characterize the composition of Eridania's landscape from regional to outcrop scales. The bulk geochemistry representing decimeter depths is broadly on par with mafic igneous compositions seen elsewhere on Mars. The landscape‐scale mineralogy of Eridania suggests a compositional distinction between Eridania's northernmost basin and the remaining basins. Meanwhile, chloride mapping and analyses of amorphous silica and acid‐altered clay phases at the outcrop scale both show that mineralogical evidence for hydrothermal alteration and putative lacustrine activity is broadly limited to the northernmost basin, and that most other amorphous silica in Eridania is consistent with low‐to‐minimal water/rock weathering. This suggests either limited regional hydrothermalism or extensive mafic resurfacing occurred in Eridania, the latter of which is consistent with previous studies. Our findings collectively suggest that Eridania underwent local crystal hydrothermal alteration, perhaps confined to the northernmost basin, while much of the remainder of the Eridania's basins either experienced low‐temperature weathering or extensive resurfacing to at least meter scale depths by later volcanism. This supports prior inferences of spatially and temporally limited surface hydrology on Mars and extensive volcanic resurfacing of basins, as in the Gusev Crater. Plain Language Summary: Eridania Basin is a system of semi‐circular depressions in the Southern Highlands of Mars that is suggested to have once held a vast lake. This lake is inferred to have hosted hydrothermal activity for hundreds of millions of years. Such a long‐lived system should have led to mineralogical and geochemical signatures on large regional scales. Analysis of regional, local, and outcrop‐scale data—using orbital gamma ray, thermal, and near infrared spectra, respectively—indicates that the geochemistry of Eridania is consistent with relatively unaltered volcanic material, while mineralogical data suggest that aqueous activity and weathering may have been confined to a smaller region than previously thought. Materials indicating hydrothermal activities, such as chlorides and altered clays, are confined to the northernmost part of the basin system, while silica formed under low temperatures is found in the southern regions of Eridania. We propose that any hydrothermal activity in a lake setting was limited to the northernmost basin of Eridania, and that it may have been less long‐lived than previously anticipated. Evidence for ancient lakes may have also been obscured by volcanism. Key Points: Across regional to outcrop scales, Eridania Basin landscapes present compositions consistent with mafic resurfacingEridania's northern basin experienced a distinct, possibly longer‐lived aqueous alteration than the southern basinsA smaller watershed for Eridania, or a volcaniclastic cap, may help explain the limited evidence for lacustrine alteration in the Gusev Crater [ABSTRACT FROM AUTHOR]