Earth's Martian laboratory
The Qaidam Basin is a hyperarid region covering about 120,000 square kilometers in the northern Tibetan Plateau. At an average elevation of 2,800 meters, it is one of the highest and driest deserts on Earth. Its environment—cold, arid, and subjected to high levels of ultraviolet radiation due to a thin atmosphere—is an exceptional analogue for the surface of Mars. The basin's floor is a mosaic of salt lakes, playas, and wind-eroded hills called yardangs, landforms also common on the Red Planet.
The chemistry of the saline lakes is why the area is so compelling for astrobiologists. A long history of evaporation in a closed basin has concentrated vast quantities of minerals. The lakes contain deposits of chlorides, carbonates, and various magnesium sulfate-bearing minerals like epsomite and hexahydrite. These are the same classes of aqueous minerals that Mars rovers have detected, suggesting that the Qaidam lakes chemically resemble ancient Martian water bodies. The daily and seasonal temperature swings are extreme; in the northwest of the basin, temperatures can range from -34.4°C to 34.2°C. This combination of Mars-like chemistry and environmental stress is a natural laboratory for testing instruments and theories for future Mars missions.