Quantifying preferred grain orientation in Mars analogue conditions using wind tunnel experiments

The long-axis orientation of elongated sand grains in aeolian systems is dependent on saltation of grains and orientation to the dominant wind direction. This relationship can be used to understand the dynamic environment on Mars based on close-up images of the surface taken by microscope cameras. We perform(ed) experiments at the Aarhus Mars Simulation Wind Tunnel, a closed circuit, low-pressure wind tunnels that allows saltation to be studied at different pressures and friction velocities. Close-up images taken of the sandbed were used with image segmentation methods to delineate grains and determine the preferred orientation of particles. Similar methods have been used on thin sections taken from well-studied and oriented sediments on Earth. Our study aims to generate and study oriented sediments under Martian analogue conditions to investigate how grain orientation (imbrication) is modulated in low pressure environments. We will discuss the effects of different air pressures and friction velocities on the observed preferred orientation of particles in the sandbed and evaluate the implications for aeolian processes in different atmospheric conditions. While tailored to active aeolian sediments, this method could offer insights for interpreting lithified samples such as sand stone outcrops studied by Mars rover to investigate aeolian processes in the past.