Depth-to-diameter (d/D) ratios of impact craters on Mars: Crater scaling as a tool to investigate mechanical properties of target rocks.

Abstract

Geometric proportions of craters, i.e., depth and diameter, are a useful tool to unveil the geologic past of planets like Mars where remote sensing is, except for rovers, still the only way to gain insights. These crater morphologies are defined by those proportions but are also probably influenced by target rock properties. Using nadir images and digital terrain models (DTMs) obtained from the High Resolution Stereo Camera (HRSC), enable the measuring of craters with diameters between 665.231 m and 50.3011 km. Conducted as a pilot project using HRSC products, this study revealed some issues regarding resolution limits of the HRSC DTMs applied to (impact) structures smaller than 3000 m. Reasons for that are manifold and need detailed future investigation. Irrespective of these issues, d/D ratios of simple impact craters show variations depending on region, latitude and geology. Chryse Planitia, Noachis Terra, the Thaumasia Plateau, i.e., mainly Solis Planum, and Utopia Planitia were investigated revealing simple crater d/D ratios of 0.18, 0.12, 0.16 and 0.11, respectively. The variances might be traced back to different lithologies and target rock properties in these areas. The general outcome of this work holds more heterogeneous, volatile-rich and less-compacted units, e.g., outflow channel deposits, the Martian regolith or volcanoclastic deposits (lahars) responsible for low d/D-ratios. Well-consolidated and homogeneous units such as lava flows on the other hand cause high d/D ratios and therefore greater crater depths. The results of this study indicate a high potential for HRSC products to be applied to crater scaling and further investigating Mars’ geology on a regional scale once the effects of resolution limits can be reliably solved.