On the other hand, it is known that toxic water emanates from these vast underground and open pit mines and chemical ore refinement that had been active off and on for thousands of years. While it is still undetermined if the unique water chemistry of the Rio Tinto developed as a result of thousands of years of mining or by natural causes, it is possible that the river's chemical makeup is due to the combination of both natural causes and acid mine drainage. The river drains an area with huge deposits of sulfides which was formed more than 350 million years ago. When sulfides are exposed to air, water, and microorganisms, drainage from acidic rocks flows into surface and ground water. Mining, however, greatly increases exposed areas. Astrobiology This river has gained recent scientific interest due to the presence of extremophile anaerobic bacteria that dwell in the acidic water. The subsurface rocks on the river bed contain iron and sulfide 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 groundwater on Mars. Scientists have also directly compared the chemistry of the water in which the Mars rocks of Meridiani Planum were deposited in the past with the Río Tinto. Likewise, the moon Europa contains an acidic ocean of water underneath its ice surface, thus the Rio Tinto river is of interest to astrobiologists studying the environmental limits of life and planetary habitability. See also Acid mine drainage Environmental impact of mining List of rivers of Spain Tourist Mining Train References External links Mars Analog Research and Technology Experiment FAQ Protected Landscape Río Tinto Mining Park of Rio Tinto With link to The Ernest Lluch mining Museum, RioTinto, the fairly new mining museum of the area, containing a permanent exhibition on the history of mining, and geological information. Rivers of Spain Rivers of Andalusia Environmental impact of mining Environmental issues in Spain Mining in Spain