The Rio Parana in Argentina (running north-south through image center) appears brown from its sediment; it eventually drains into the Delta del Parana and the Rio de la Plata estuary. Where the Rio de la Plata empties into the Atlantic, the brown, sediment-filled river water mixes with clearer ocean water and creates swirls and cloudy formations. Visible in this image (in gray) is Buenos Aires, the capital city of Argentina, located where the Rio Parana meets the Rio de la Plata. Montevideo, Uruguay's capital, is located on the opposite side of the Rio de la Plata. Photo courtesy of NASA.