Based upon data from the Mariner and Viking projects in the 1970s, the polar layered deposits have long been considered to be accumulations of dust and ice. The layering is thought to indicate changes in how ice and dust accumulate at the poles over the course of millenia. Changes in climate might affect the thickness and composition of polar layers in a way that is analogous to how years of drought and years of plentiful rain change the width of rings in a tree trunk on Earth. The pictures shown here provide new details of what the south polar layered deposits look like at extremely The thick blanket is the south polar layered deposit material. The circular features at the lower left in the context image are craters occurring outside the polar layered deposit.
More craters occur underneath the polar layered deposits.
The amount of dust versus ice in these layers is unknown.