South Pole Residual Cap - Swiss-Cheese Terrain Monitoring (Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)

Like Earth, Mars has concentrations of water ice at both Poles. Because Mars is so much colder however, CO2 ice is deposited at high latitudes in the Winter and is removed in the Spring, analogous to winter-time water ice/snow on Earth.
Around the South Pole there are areas of this CO2 ice that do not disappear every Spring, but rather survive Winter after Winter; this persistent CO2 ice is called the "South Pole Residual Cap". The retention of CO2 ice throughout the year by the Southern Polar Cap is one characteristic that distinguishes it significantly from Mars' North Polar Cap.
As can be seen in this HiRISE image of the South Pole Residual Cap, relatively high-standing smooth material is broken up by circular, oval, and blob-shaped depressions. This patterned terrain is called "Swiss Cheese" terrain.