Extraterrestrial dunes: An introduction to the special issue on planetary dune systems

Aeolian dune fields have been described on Earth, Mars, Venus and Titan. The plethora of data returned from recent planetary missions has enabled a new era in planetary geomorphic studies. Much of our understanding of planetary dune systems comes from the application of Earth analogs, wind tunnel experiments and modeling studies. Despite the range of atmospheric pressures, composition and gravity, many of the dune forms on extraterrestrial surfaces are similar to those on Earth, although some have notable differences in bedform scale and composition. As an introduction to the special issue on planetary dune systems this paper summarizes the current state of knowledge of planetary dune studies and highlights outstanding questions that require further investigation.