Dune Morphology and Atmospheric Models: Implications for Present-Day Martian Aeolian Activity
It has long been unclear whether the many sand dune fields on Mars are actively evolving in the present climatic era. Recent evidence of sand avalanching and active sustained saltation has been identified in high resolution images. In particular, we report the first clear indications of ripple migration over dark dune slopes observed from orbit. We propose a comprehensive study that will specifically address this knowledge gap, via the careful analysis of high-resolution spacecraft imagery over the majority of the planet (between 60° N and 60° S). In fact, even the preliminary investigation of a small sampling of such imagery has already yielded evidence of recent sand avalanching on dark dune slip faces and the first clear indications of ripple migration (superposed on the dark dunes) observed from orbit. Such morphological indications provide unprecedented details of sustained saltation on Mars. This newly found activity refutes the commonly held belief that dunes on Mars are inactive in the present-day wind regime. Such a provocative topic deserves immediate, detailed study to determine how current dune activity provides unique ground truth for today's weather patterns on Mars.
We propose to map the activity of sand dunes on Mars between 60° N and 60° S using geomorphological criteria such as sand avalanche scars, making use of overlapping MOC narrow angle, CTX, and HiRISE images. Once active dune fields have been identified, we will search for and map further evidence of the present-day movement of sand by measuring changes in the patterns of large ripples superposed on dark dune slopes. Finally, we will reconstruct the wind regime responsible for the activity of the dunes from the orientation of the active slip faces and determine the nature of and the diurnal and seasonal timing (where possible) of the present-day winds responsible for such activity. From this information we will elucidate the influence of both regional weather patterns and local topography on such flows by using global and regional climate models [the NASA Ames Mars General Circulation Model (GCM) and the Mars Regional Atmospheric Modeling System (MRAMS), respectively]. These methods are optimal for extracting the most useful and comprehensive short-term aeolian process information from the abundant imagery of dark dunes (outside the polar region) within currently available spacecraft datasets. The comparison of aeolian geomorphological features and changes (mapped and measured throughout the proposed work) to climate modeling output will significantly augment the scientific return of the overall proposed data analysis project.
This work will provide the best possible understanding of present-day dune activity on Mars. Such an investigation will serve as a partial proxy for a global meteorological network by determining martian erosional potential and wind circulation patterns, both of which are necessary for defining Mars¿ current climatic state. In addition, the proposed work is timely as it is essential for the mission safety of future lander missions that are required to avoid strong near-surface winds during descent. This multidisciplinary approach (geomorphologic and atmospheric) will lead to a better understanding of the present-day martian environmental conditions, a task of fundamental importance in the exploration of the red planet.