Morphometrics on Mars and Earth – comparative geomorphology

Over the last 15 years, various orbiting spacecraft have returned a variety of image and topographic data of the Martian surface that globally cover the planet. Image resolution varies depending on the camera, but a large part of the surface is now available at a resolution of ~5-6 m per pixel. Global topography from laser altimetry has a vertical accuracy of ~1 m and a lateral resolution of ~500 m, increasing towards the poles. Stereo images provide higher-resolution topography, e.g., the High Resolution Stereo Camera (HRSC) enables deriving gridded Digital Elevation Models (DEM) with cell sizes of 50 to 100 m. The combination of imaging and topographic information at local to regional scales has led to a multitude of geomorphological and geological investigations that analyse the surface in three dimensions. Such quantitative studies have increased our knowledge of the planet’s physiographic characteristics, and allowed to place constraints on the rates of surface processes. Examples of scientific applications of morphometrics include endogenic processes (rheology of lava flows, crustal deformation by tectonic processes) and exogenic processes (fluvial and lacustrine processes, ice rheology). We present an overview of available data and demonstrate their use in established geoscientific methods. We also compare the landforms on Mars with well-known terrestrial counterparts (terrestrial analogues), which serve to create working hypotheses for Martian surface processes. As a case study, we present remote-sensing data from Svalbard (acquired by an airborne version of the HRSC camera and accompanied by field work) that show periglacial and glacial landforms that are analogous to mid-latitude landforms on Mars, hypothesised to be signals of recent ice ages. Our results suggest that these landforms are indeed related to ice, but that – other than on Svalbard – thaw is only of minor importance on recent Mars, and that sublimation dominates over melting