The Río Tinto (red river) 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.
This unearthly, reddish river in southwestern Spain is unlike any you've ever seen before. The water gets its coloration from iron dissolved in the water, and is notable for being extremely acidic. This may not sound like a suitable place to find life, but living in the bizarre waters of Rio Tinto are extremophile aerobic microorganisms that feed on the iron and sulphide minerals plentiful in the river.
Since ancient times, a site along the river has been mined for copper, silver, gold, and other minerals. In approximately 3,000 BC, Iberians and Tartessians began mining the site, followed by the Phoenicians, Greeks, Romans, Visigoths, and Moors. After a period of abandonment, the mines were rediscovered in 1556 and the Spanish government began operating them once again in 1724. As a possible result of the mining, Río Tinto is notable for being very acidic (pH 2) and its deep reddish hue is due to iron dissolved in the water. Acid mine drainage from the mines leads to severe environmental problems due to the heavy metal concentrations in the river. In 1873, Rio Tinto Company was formed to operate the mines; by the end of the 20th century it had become one of the world's largest multinational mining companies, although it no longer controls the Rio Tinto mines; these are now owned by EMED Mining plc.
Scientists now believe that these conditions could be the perfect analogue to what happens when liquid water flows on other planets or moons, such as on Mars or perhaps on Jupiter's moon, Europa. If life can survive under these conditions here on Earth, then it's possible that it also has survived elsewhere, making Rio Tinto an important case study into astrobiology.
In fact, data retrieved from NASA's Opportunity rover has shown that similar conditions to those at Rio Tinto have existed on Mars in the past.
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