Interestingly, the fans appear in many cases to follow layer boundaries of the polar layered deposits. Presumably, these boundaries represent zones of weakness, where the escaping and dust-laden CO₂ jets can break through the seasonal ice cap surface more easily. Another interesting observation is that the dark fans also appear to show higher concentrations at southern flanks of hills and troughs where they might receive more sunlight than at other locations. Some places are very dark in color caused by the dark fan concentration and could therefore even accelerate the sublimation process.