TERRESTRIAL AND MARTIAN ANALOGUES TO THE SAND SEAS ON TITAN

We describe terrestrial and martian analogues for the vast sand seas of longitudinal dunes recently discovered on Titan. Features in various places on Earth (Tamlamakan Desert, China; Namib Desert, Namibia; Thar Desert, India; Sahara Desert, Mauritania and Niger; Rub al Khali, Saudi Arabia) and Mars (Chasma Boreale, Noachis Terra, Wirtz Crater) provide insights into the characteristics and origin of wind-related landforms on Titan seen by the Cassini RADAR. Longitudinal duneforms are the most common depositional features seen in the equatorial regions of Titan and indicate supplies of sand-sized particles blown generally by bidirectional winds. The terrestrial analogue sites chosen exhibit diverse wind features that are generally well understood and have morphologies comparable to those on Titan. Key features of terrestrial and martian dune morphology may that appear in the comparatively lower resolution RADAR images of Titan in the equatorial regions include extension of barchan horns (e.g. T3 swath at ~30 lat, 15 lon; T28 swath at ~0 lat, 28 lon), merging barchan convoys (T3 swath at ~30 lat, 15 lon), climbing dunes (T3 swath at ~10 lat, 120 lon), sand streaks indicating seasonal wind directions (T3 swath at ~10 lat, 115 lon; T25 swath at ~0 lat, 40 lon), and transitions of linear dunes to transverse dunes (T8 swath at ~10 lat, 230 lon). Although these features appear on Titan at resolutions that often preclude definitive characterization, their presence strengthens the case for the dune fields having familiar characteristics and behaviors and being active currently or in the past. Analysis of these features and application to Titan adds to the understanding of the evolution of the Titanian dune forms and their transition to other terrains as well as implications for global climate models and wind patterns.