Liquid water and ice are nonexistent on Venus, and thus the only agent of physical erosion to be found (apart from thermal erosion by lava flows) is wind. Wind tunnel experiments have shown that the density of the atmosphere allows the transport of sediments with even a small breeze. Therefore, the seeming rarity of eolian land forms must have some other cause. This implies that transportable sand-size particles are relatively scarce on the planet; which would be a result of very slow rates of mechanical erosion. The process that is most important for the production of sediment on Venus may be crater-forming impact events, which is bolstered by the seeming association between impact craters and downwind eolian land forms.