When asked for the driest place on Earth, most people immediately think of the Sahara Desert or the Atacama Desert in Chile. While the Atacama is the driest 'non-polar' place, the actual driest place on Earth is located in Antarctica. The 'McMurdo Dry Valleys' have not seen a drop of rain or snow for an estimated 2 million years. The region is free of ice and snow because the surrounding mountains are high enough to block seaward-flowing ice from the East Antarctic ice sheet, and the extremely cold air contains almost zero moisture. Gravity-driven 'katabatic winds' also blow through the valleys at speeds up to 200 mph, evaporating any moisture that might appear.