No abstract

We compiled a high‐resolution, global lunar impact crater database composed of 5,505 pristine craters ≥ ~3 km. This database contains detailed morphometric data, and their trends are examined with best‐fit power‐laws. We compared several different functions for simple, transitional, and complex craters to report one best‐fit representation. We integrated transitional craters into these fits as an independent crater class. Transitional craters are in a transitional state, between simple and complex craters. They are devoid of a central uplift and terraces but show wall slumping and a flat floor. In regard to depth‐diameter relationships, simple craters exhibit similar scaling all over the Moon, whereas larger craters are different in highland and mare regions. In the present work, we sought the best representation of the simple‐to‐complex transition diameter. The intersection of simple power‐law fits for simple and complex crater populations is shown to be a poor representation of the transition diameter. We used a misclassification method for finding transition diameters. This process reveals a transition from simple to transitional craters at diameters of ~17 km (highland) and ~14 km (mare). Transitional morphology is replaced by complex morphology at diameters of ~ 28 km (highland) and ~ 24 km (mare). The lower transition diameters of mare craters are attributed primarily to the layered mare basalts, which enables an earlier onset of crater modification. We also analyzed the relationship between aspect ratio and depth‐diameter ratio of simple craters: Simple craters with ε ≥ 1.1 are significantly shallower in depth/diameter plots than craters with ε < 1.1.

We investigate the elevated crater rims of lunar craters. The two main contributors to this elevation are a structural uplift of the preimpact bedrock and the emplacement of ejecta on top of the crater rim. Here, we focus on five lunar complex mare craters with diameters ranging between 16 and 45 km: Bessel, Euler, Kepler, Harpalus, and Bürg. We performed 5281 measurements to calculate precise values for the structural rim uplift and the ejecta thickness at the elevated crater rim. The average structural rim uplift for these five craters amounts to SRU = 70.6 ± 1.8%, whereas the ejecta thickness amounts to ET = 29.4 ± 1.8% of the total crater rim elevation. Erosion is capable of modifying the ratio of ejecta thickness to structural rim uplift. However, to minimize the impact of erosion, the five investigated craters are young, pristine craters with mostly preserved ejecta blankets. To quantify how strongly craters were enlarged by crater modification processes, we reconstructed the dimensions of the transient crater. The difference between the transient crater diameter and the final crater diameter can extend up to 11 km. We propose reverse faulting and thrusting at the final crater rim to be one of the main contributing factors of forming the elevated crater rim.

The investigation of terrestrial impact structures is crucial to gain an in‐depth understanding of impact cratering processes in the solar system. Here, we use the impact structure Jebel Waqf as Suwwan, Jordan, as a representative for crater formation into a layered sedimentary target with contrasting rheology. The complex crater is moderately eroded (300–420 m) with an apparent diameter of 6.1 km and an original rim fault diameter of 7 km. Based on extensive field work, IKONOS imagery, and geophysical surveying we present a novel geological map of the entire crater structure that provides the basis for structural analysis. Parametric scaling indicates that the structural uplift (250–350 m) and the depth of the ring syncline (<200 m) are anomalously low. The very shallow relief of the crater along with a NE vergence of the asymmetric central uplift and the enhanced deformations in the up‐range and down‐range sectors of the annular moat and crater rim suggest that the impact was most likely a very oblique one (~20°). One of the major consequences of the presence of the rheologically anisotropic target was that extensive strata buckling occurred during impact cratering both on the decameter as well as on the hundred‐meter scale. The crater rim is defined by a circumferential normal fault dipping mostly toward the crater. Footwall strata beneath the rim fault are bent‐up in the down‐range sector but appear unaffected in the up‐range sector. The hanging wall displays various synthetic and antithetic rotations in the down‐range sector but always shows antithetic block rotation in the up‐range sector. At greater depth reverse faulting or folding is indicated at the rim indicating that the rim fault was already formed during the excavation stage.