Saltation, the motion of sand grains in a sequence of ballistic trajectories close to the ground, is a major factor for surface erosion, dune formation, and triggering of dust storms on Mars. Although this mode of sand transport has been matter of research for decades through both simulations and wind tunnel experiments under Earth and Mars conditions, it has not been possible to provide accura...

The transport of sand in saltation is driven by the persistently unsteady stresses exerted by turbulent winds. Based on coupled high-frequency observations of wind velocity and sand flux on a desert dune during intermittent saltation, we show here how observations of saltation by natural winds depend significantly on the timescale and method used for determining shear stress and sand flux. The ...

Wind erosion of soil is an appreciable but unstudied event following fires in cold desert. We examined aeolian transport of sediment for one year following fire in semiarid shrub steppe of southern Idaho. Sediment collectors were used to determine horizontal mass transport of soil ( ) and saltation sensors and anemometers were used to determine saltation activity (# seconds saltation is detecte...

I will deiscuss the drag of particles on granular surfaces by a fluid. I will present simulations using FLUENT of Aeolian saltation under Earth and Mars conditions obtaining among others the static and dynamic threshold shear and the height of the saltation layer as function of the wind strength. A universal quadratic increase of the saturated flux as function of the difference from the thresho...

We present an analytical model of aeolian sand transport. The model quantifies the momentum transfer from the wind to the transported sand by providing expressions for the thickness of the saltation layer and the apparent surface roughness. These expressions are derived from basic physical principles and a small number of assumptions. The model further predicts the sand transport rate (mass flu...

In this study, we extend the mechanistic equilibrium saltation model of Ashida and Michiue (1972) for nearly horizontal sand beds to the case of spatial nonequilibrium sand transport, which allows us to calculate sand transport rates over varying mildly-sloped topographies. Our model incorporates a generalized description of the reduction of the Shields stress within the saltation layer due to ...

In aeolian transport saltation is an important link by which momentum is transmitted from the air to the bed through grain impact, but momentum transfer, impact and subsequent entrainment take place in a very shallow layer at the air-bed interface with large velocity gradients. Consequently, experimental evidence on the impact-entrainment processes has been obtained from few and simplified stud...

We present the first calculation of saltation transport and dune formation on Mars and compare it to real dunes. We find that the rate at which grains are entrained into saltation on Mars is 1 order of magnitude higher than on Earth. With this fundamental novel ingredient, we reproduce the size and different shapes of Mars dunes, and give an estimate for the wind velocity on Mars.