Planet-wide sand motion on Mars

Bedform migration on Mars: Current results and future plans

“…Global studies show that bright TARs are generally older than dark dunes and lack any clear evidence of recent activity (Balme et al, 2008;Bridges et al, 2012a). This seems confirmed by evidence of cratered and eroded TARs reported from several areas of Mars (Reiss et al, 2004;Golombek et al, 2010;Kerber and Head, 2011).…”

“…For example, local landslides on lee slopes can bias inferences on overall dune motion to high values unless other boundary areas are accounted for. A robust technique to compute net displacement is to measure the lee or stoss boundary in two images, compute the area subtended by the dune advance, and divide this area by the boundary length (Hansen et al, 2011;Bridges et al, 2012a). Isolated dune motion can also be computed by determining the offset in the centroid position, as with sand patches.…”

“…However, geometric distortions that arise from the difference in viewing geometry cannot be corrected for ripples by orthorectification because the resolution of the HiRISE DEMs cannot resolve their height. Therefore, in areas for which fixed benchmarks are lacking, such as in the interior of dunes, displacements are most accurately measured using change detection pairs with minimal parallax angles between them, as has been done in the Nili Patera studies (Silvestro et al, 2010b;Bridges et al, 2012a).…”

“…Mapped ripple crests on the coregistered images can be used to measure displacement with manual (Silvestro et al, 2010b;Bridges et al, 2012a;Geissler et al, 2012a) or automatic (Silvestro et al, 2011;Bridges et al, 2012b) techniques (Figs. 5 and 6).…”

Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux

“…Aeolian processes are known to dominate the current Martian climate through the modulation of atmospheric thermal forcing by suspended dust [3][4][5][6] . However, the intensity of wind activity has been judged as significantly lower than on Earth, such that recent evidence for currently active dune migration [7][8][9] and measurements of Martian sand fluxes comparable to terrestrial values 10 came as a surprise. Prevailing expectations based on wind tunnel experiments, theory for initiation of saltation, atmospheric modelling and limited in situ wind measurements suggested that sand-moving winds should be very rare [11][12][13][14][15][16] .…”