UNDERSTANDING PLANETARY EOLIAN PROCESSES AND LANDFORMS: THE ROLE OF TERRESTRIAL ANALOG STUDIES

Understanding of the nature and dynamics of planetary surfaces must begin with Earth as a reference. Reasoning by analogy has a long and distinguished history in the earth sciences. Its main strength is the suggestion of multiple working hypotheses, but this approach cannot determine which of them is correct. For this reason, studies of terrestrial analogs of planetary surface processes, landforms, and their remote sensing signatures are needed to develop robust models of planetary evolution and to understand current environments. Because planetary atmospheres differ in composition and density, fundamental understanding of the physical processes of sediment transport by wind on Earth and the resulting landforms is necessary for appropriate interpretations of processes on other planets.

The use of planetary analog sites has proved to be a productive approach to the understanding of eolian processes and landforms on Mars. Such sites possess landforms and surface characteristics similar to those indicated by orbital and lander data (e.g. variable rock cover, low soil moisture, absence of vegetation), conditions that are found in many terrestrial hot and cold desert areas. Process studies at such sites aim to understand the relations among boundary-layer winds, surface conditions, and eolian processes, with the goal of extrapolating to martian conditions, scaled to equivalent flow and particle Froude and Reynolds numbers. An important aspect of recent terrestrial analog studies is the development of indices of surface conditions (e.g. roughness) that affect eolian processes and can also be assessed via remote sensing. In addition to assisting in the interpretation of spacecraft data, terrestrial analog studies can also guide selection of instrumentation and experiments deployed at landing sites and indicate potential hazards to spacecraft.