Bedform migration on Mars: Current results and future plans

With the advent of high resolution imaging, bedform motion can now be tracked on the Martian surface. HiRISE data, with a pixel scale as fine as 25 cm, shows displacements of sand patches, dunes, and ripples up to several meters per Earth year, demonstrating that significant landscape modification occurs in the current environment. This seems to consistently occur in the north polar erg, with variable activity at other latitudes. Volumetric dune and ripple changes indicate sand fluxes up to several cubic meters per meter per year, similar to that found in some dune fields on Earth. All transverse aeolian ridges are immobile. There is no relationship between bedform activity and coarse-scale global circulation models, indicating that finer scale topography and wind gusts, combined with the predicted low impact threshold on Mars, are the primary drivers. Several techniques have been developed to measure bedform changes and are largely dependent on dataset availability and the type of questions being pursued. Qualitative visual inspection can determine whether or not changes have occurred. Offsets registered to fixed tie points yield approximate migration rates of nearby crests and dune lee fronts. To compute volumetric sand flux requires precise orthorectification and registration using a digital elevation model base. Using this technique combined with sophisticated change detection software has the potential to detect changes as fine as 1/3 of a pixel (similar to 8 cm) or less. (C) 2013 Elsevier B.V. All rights reserved.