Rio Tinto field site

Scientific Contact:

Local administrative contact (once a TNA visit is awarded):

Phone 00 34 91 520 1690 Fax 00 34 91 520 1612

Provided by: Astrobiology Center (CAB); INTA

The Tinto River (Iberian Pyritic Belt) is an unusual acidic ecosystem (100 km long, mean pH 2.3) containing a high concentration of heavy metals (Fe, Cu, Zn, As and Cr) and an unexpected level of microbial diversity (Bacteria, Archaea and Eukaryotes). In the past, the extreme conditions of the river were considered the result of intense mining activity. Geomicrobiological analysis of the Tinto ecosystem strongly suggests that these conditions are the result of the metabolic activity of chemolithotrophic prokaryotes, mainly iron- and sulfur- oxidizers. The system seems to be controlled by iron, which is not only used as an electron donor, but also as an electron acceptor, allowing a full iron cycle to operate. Furthermore, ferric ion is responsible for the maintenance of the constant pH of the ecosystem and can protect the different organisms thriving in its waters from radiation. Laminar, iron-rich stromatolitic formations are generated by the precipitation of different iron minerals on the surface of the biofilms that cover most of the rocks in the river. These structures are similar to ancient massive bioinduced laminated iron formations formed long before the first mining activities started in the area 5000 years ago. Given these characteristics, we postulate that the Tinto River operates as a Gaian system in which the (extreme) environmental conditions are generated and regulated by the biological components of the ecosystem. This place has been used for space missions instrument testing in several projects.