High-Resolution Geological Mapping of the Mojave Crater: A Window into Martian Impact and post-impact Processes.

Superficial processes on Mars are responsible for the erosion and degradation of impact craters Primary crater morphologies are generally not preserved and affected by a complex and multi-stage degradation history. Under present cold and dry climate, Moste cent Martian impact craters offer valuable insights into impact processes and emplacement of various impact-related units. 19 recent craters younger than ~10 Ma old were identified by Lagain et al. (2021) and are considered as potential sources of Martian meteorites recovered on Earth. Among this particular set, the Mojave crater stands out due to its complex morphology and large diameter (D~58 km). Mojave is located in Xanthe Terra (7°N, 33°W), a Noachian-aged region, between Simud Vallis and Tiu Vallis (Williams & Malin, 2008). It lies within highly dissected plateaus shaped by catastrophic flood events associated with outflow channels mainly sourced from Valles Marineris and draining toward Chryse Planitia during the early Hesperian (Nelson & Greeley, 1999).

This study has combined very high-resolution imagery data (e.g., HiRISE images (≈ 0.25–0.5 m/pixel) and CTX images (≈ 6 m/pixel) to analyze fine morphological details. In addition, digital elevation models derived from MOLA (≈ 463 m/pixel) and CTX data were used to establish a detailed geological map of Mojave crater. Our preliminary map reveals several original features, that open new perspectives for understanding impact-related processes. These include the spatial distribution of secondary craters associated with Mojave, a discontinuous and asymmetric rim, and the presence of two superposed lobate ejecta layers (Williams & Malin, 2008) terminating in distal ramparts. The ejecta blanket displays a significant asymmetry, showing a typical long run-out in the northern and northeastern sectors, but appearing more chaotic in the southern region. One proposed explanation for this asymmetry is the presence of topographic obstacles in the southern part of the crater, modifying ground-hugging ejecta trajectories leading to localized accumulation of ejected material and therefore higher ejecta thicknesses. Our mapping also revealed a significant offset in the northwest direction of the central peak with respect to the center of the crater. Such an offset may result from an oblique impact and/or pre-existing structures and may be also enhanced by post-impact erosion (Wulf et al., 2011). To elucidate the cause of this offset, we plan to achieve a new survey of central peak offsets in recent impact craters

These observations highlight the complexity of the formation a complex crater in a target with pre-existing structural heterogeneities, with consequences on both the crater morphology and structure and on the ejecta deposits