Earth observation taken by the Expedition 35 crew

ISS035-E-025019 (20 April 2013) --- One of the Expedition 35 crew members aboard the Earth-orbiting International Space Station used a 400 millimeter lens to record this photograph highlighting water of different color within sub basins of the Laguna (lake) Verde in the high Andes of northwest Argentina. The lake floor as a local low point lies at 4095 meters (13,438 feet) above sea level, whereas the peak of the local volcano west of the lake (not shown) reaches almost 3000 meters higher (or about 6818 meters, 22,368 feet). Laguna Verde (58 kilo meters wide, 36 kilometers long) often appears green, giving rise to its formal name. The image shows the turquoise tint in the central sub basin (image center), with a yellow to black tinge to water in the southern sub basin at image left (also known locally as Laguna Negra). The northernmost basin at image right appears quite black, and the large gray zone comprising much of the rest of Laguna Verde is likely a combination of shallow water, only inches deep, and sunglint reflecting off the water surface. The reason for the color differences lays in the fact the many different families of salt-loving organisms occupy hypersaline lakes such as Laguna Verde. These appear as different colors ? often bright -- depending on the salinities and temperatures of each water body or sub basin. The rest of the lake floor is dry and appears white from the build-up of thick salt deposits. Parallel lines around the southern sub basin (Laguna Negro) indicate prior shorelines of this shrinking water body ? evaporation removes water but leaves ephemeral shorelines marked with white salt.