Antarctica is a land of extremes: it is the coldest and driest continent on Earth and has the highest average elevation. Antarctica is technically a dessert. It receives less than two inches of precipitation a year, about the same amount of precipitation as the Sahara Desert. One interior region of the Antarctic is known as The Dry Valleys. These valleys have not seen rainfall in over two million years. With the exception of one valley, whose lakes are briefly filled with water by inland flowing rivers during the summer, the Dry Valleys contain no moisture (water, ice, or snow). The reasons why the Dry Valleys exist are the 200 mph Katabatic down winds which evaporate all moisture. The dry valleys are strange: except for a few steep rocks they are the only continental part of Antarctica devoid of ice. Located in the Trans-Antarctic Range, they correspond to a mountain area where evaporation (or rather, sublimation) is more important than snowfall, thus all the ice disappears, leaving dry barren land. The freezing temperatures and the absence of water, plant life, and animal life simulate, to a degree, conditions on the Planet Mars. Consequently, the Dry Valleys are used as training grounds for astronauts who may one day make a voyage to our neighboring planet.