Orbiting spacecraft have observed many odd, and often beautiful, features and patterns on land near the poles of Mars and on the Martian polar ice caps. Seasonal freezing and sublimation of dry ice (frozen carbon dioxide) in the polar ice caps creates the weird "swiss cheese" terrain shown here. Does this image remind you of the holes in a piece of swiss cheese? Seasonal cycles also produce weird fingerprint terrain, peculiar polygon patterns, numerous pits, and strange spider web patterns. The North Pole is surrounded by a huge field of sand dunes. Dunes near both poles display odd patterns each Martian year as they lose their winter ice. Layers of ice and dust, deposited year after year, have built up extensive layered terrain near both poles.
Image courtesy of NASA/JPL/Malin Space Science Systems.