English: Dry ice etches terrain: sunlight heats up the surface below the seasonal carbon dioxide ice caps that cover the south pole of Mars where "dry ice" is translucent and thus causes ice to sublime (transition from solid directly into gas, bypassing the liquid phase) and carve channels in the surface. Vapor carries dark sand and dust from beneath the ice onto the surface through these carved channels which can take on different forms. On relatively flat surfaces, such as on this photograph, the evaporating gas etches wide and shallow channels; in more hummocky terrain the streaks of blasted dust resemble cobwebs.