Winds of some 150 kph are estimated as minimum for initiation of particle movement. Streaks appear to be zones in which fine grained particles are redistributed in response to wind patterns generated around craters and other landforms. Some areas on Mars appear to be zones of deposition for windblown particles, as evidenced by enormous dune fields. These areas include the north polar region, the floor of the large impact basin, Hellas, and the floors of other smaller impact craters. The most spectacular of the dune fields, those at the north pole, are discussed in the section Polar Regions.
Wind eroded features include yardangs and grooves etched in some plains.
Because the atmosphere is very thin the wind speeds needed to move particles are much higher on Mars than on Earth, so that the grains travel much faster once set into motion. Consequently, when they strike other particles and bedrock surfaces, they have a greater erosion capability than they would have on Earth. Mass wasting is the downslope movement of materials, primarily caused by gravity, and is seen as landslides, avalanches, and soil creep. Its effectiveness is controlled by factors like cohesion of the material, steepness of slope, gravity, and the presence of lubricants such as liquids and volatiles. Mariner 9 and Viking pictures show many features that can be attributed to mass wasting.