EARTH, MARS, AND VENUS: AEOLIAN FEATURES AND PROCESSES

Aeolian activity and features reflect the interaction of the atmosphere and the surface, requiring small particles and winds of sufficient strength to move them. Although the composition and density of the atmospheres of Earth, Mars, and Venus are different, all three planets experience aeolian activity now and in the past. Data from orbit and from landers on Mars and Venus reveal a wide variety of wind-related features, including dunes, yardangs, and ventifacts. Understanding aeolian processes and features is critical for derivation of geological histories, interpretation of remote sensing data, and for aspects of landed surface operations, such as the collection of samples for return to Earth. Analysis of the types and orientations of some aeolian features provides insight into past climates, including the directions of possible paleowinds. The approach used to derive this understanding includes physical and computer modeling under conditions appropriate for the planet under consideration, analysis of spacecraft data, and study of terrestrial analogs. This latter aspect is particularly critical because it provides the "ground truth" for understanding the fundamental physics and geology of aeolian processes.