As dust settles through the atmosphere, it traps volatile material, forming a mantle of icy dust.Later on, the volatile ices turn to gas, leaving pits.

• 沙尘自大气沉降时会捕捉挥发物质，形成一层覆盖冰尘，一段时间后，挥发性的冰转为气体，留下孔隙。