McMurdo Dry Valleys

The McMurdo Dry Valleys are a series of largely snow free desert valleys on the coast of Victoria Land in Antarctica, lying between the East Antarctic Ice Sheet and McMurdo Sound, and together form the largest ice free area on the Antarctic continent at roughly 4,500 square kilometers. Katabatic winds evaporate what little snow falls and a snow shadow cast by the Transantarctic Mountains limits average annual precipitation to about 100 millimeters, making the valleys the coldest and driest desert environment on Earth. The bare landscape of granite and gneiss, glacial deposits and loose gravel nonetheless supports a distinct ecosystem built around extremophiles rather than visible plant or animal life: photosynthetic bacteria live inside translucent rocks, and anaerobic microbial communities persist beneath the valleys' glaciers. The valleys hold more than 6,000 lakes and ponds, including the saline Lake Vida, and the Onyx River, Antarctica's longest waterway, which flows for a few weeks each summer. Because their extreme aridity and cold closely resemble conditions on Mars, the McMurdo Dry Valleys are used as a terrestrial research analog for Mars, and the area is protected as an Antarctic Specially Managed Area.