Wind erosion could be the driving force for the formation of the spiral troughs, as suggested by the analysis of radar data. One theory is that the spiral troughs are cyclic steps formed by katabatic winds blowing over ice. A katabatic wind denotes a downslope gravity flow of cold, dense air. It often initiates on higher-elevation areas with cold dry air, e.g. glacial or snow-covered plateaus, and flows down to lower-elevation areas such as valleys hosting warm, less dense air. In the case of the Mars polar cap, air movement is occurring radially away from the pole, and additionally controlled by Coriolis forces that lead to a spiral path of the flow.