Sand Transport on Mars: Preliminary Results from Models;

Most studies of active aeolian processes on Mars have focused on dust [1], i.e., particles -1 [tm in diameter that are transported in suspension by wind. The presence of sand dunes on Mars [2-8] indicates that larger grains ( >60 _tm, transported primarily in saltation) are also present. Although indirect evidence suggests that some dunes may be active [9], definitive evidence is lacking. Nonetheless, numerous studies [10-11] demonstrate that sand is substantially easier to transport by wind than dust, and it is reasonable to infer that sand transportation in saltation occurs under present martian conditions. In order to assess potential source regions, transportation pathways, and sites of deposition for sand on Mars, an iterative sand transport algorithm was developed that is based on the Mars General Circulation Model of Pollack et al. [12]. The results of the dust transport model are then compared with observed surface features, such as dune field locations observed on images, and surficial deposits as inferred from Viking IRTM observations. Preliminary results suggest that the north polar dune fields in the vicinity of 270°W, 70°N originated from weathered polar layered plains centered at 280°W, 85°N, and that Thaumasia Fossae, southern Hellas Planitia, and the area west of Hellespontus Montes are sand depositional sites. Examples of transportation "corridors" include a westward pathway in the latitudinal band 35°N to 45°N, and a pathway southward from Solis Planum to Thaumasia Fossae, among others.