Rio Tinto, Spain

The Río Tinto is a river in southwestern Spain that originates in the Sierra Morena mountains of Andalusia.. It flows generally south-southwest, reaching the Gulf of Cádiz at Huelva. It is characterized by deep red water that is highly acidic (pH 1.7—2.5) and rich in heavy metals. Over 5000 years of mining pollution have contributed to the river becoming an extreme environment.

This river has gained recent scientific interest due to the presence of extremophile aerobic bacteria that dwell in the water. These life forms are considered the likely cause of the high acid content of the water. The subsurface rocks on the river bed contain iron and sulphide minerals on which the bacteria feed.

The extreme conditions in the river may be analogous to other locations in the solar system thought to contain liquid water, such as subterraneam Mars. NASA scientists have also directly compared the chemistry of the water in which the rocks of Meridiani Planum were deposited in the past with the Río Tinto. Likewise Jupiter’s moon Europa is theorized to contain an acidic ocean of water underneath its ice surface. Thus the river is of interest to astrobiologists.

Source: Wikipedia / Astrobiology Magazine