a1 Centro de Astrobiologia (INTA-CSIC), Carretera de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
a2 Space Sciences Unit, European Science Foundation, B.P. 90015-1, Quai Lezay-Marnésia, F-67080 Strasbourg Cedex, France
a3 Centro de Biología Molecular ‘Severo Ochoa’, Universidad Autonoma de Madrid, Campus de Cantoblanco, Madrid 28049, Spain
a4 UVA-CSIC associated unit to Centro de Astrobiología Edificio INDITI, Parcela 203 Parque Tecnológico de Boecillo 47150, Boecillo, Valladolid, Spain
a5 Institut für Anorganische und Analytische Chemie, Johannes-Gutenberg-Universität, Staudinger Weg 9, 55128 Mainz, Germany
a6 Institute of Botany AS CR, Dukelská 135, 37982 Třeboň, Czech Republic
a7 inXitu Inc., 2551 Casey Ave Ste A, Mountain View, CA 94043, USA
a8 ILEWG c/o BH Foing, ESTECPO Box 299, 2200 AG Noordwijk, The Netherlands
a9 Jet Propulsion Laboratory, Pasadena, CA 91109, USA
a10 NASA Ames Research Center, Moffett Field, CA 94035, USA
a11 Departamento de Mineralogia y Petrologia, Universidad de Granada, Granada, Spain
a12 VU Amsterdam, Amsterdam, The Netherlands
a13 Delft University of Technology, Delft, The Netherlands
a14 Jet Propulsion Laboratory, Biotechnology and Planetary Protection Group, California Institute of Technology, M/S 89-102D 4800 Oak Grove Dr., Pasadena, CA 91109, USA
a15 NASA HQ and National Center, Pennsylvania State University, Reston, VA 20192, USA
Recently reported results from latest Mars Orbiters and Rovers missions are transforming our opinion about the red planet. That dry and inhospitable planet reported in the past is becoming a wetter planet with high probabilities of water existence in the past. Nowadays, some results seem to indicate the presence of water beneath the Mars surface. But also mineralogy studies by NASA Opportunity Rover report iron oxides and hydroxides precipitates on Endurance Crater. Sedimentary deposits have been identified at Meridiani Planum. These deposits must have generated in a dune aqueous acidic and oxidizing environment. Similarities appear when we study Rio Tinto, and acidic river under the control of iron.
The discovery of extremophiles on Earth widened the window of possibilities for life to develop in the Universe, and as a consequence on Mars and other planetary bodies with astrobiological interest. The compilation of data produced by the ongoing missions offers an interested view for life possibilities to exist: signs of an early wet Mars and rather recent volcanic activity as well as ground morphological characteristics that seem to be promoted by liquid water. The discovery of important accumulations of sulfates and the existence of iron minerals such as jarosite in rocks of sedimentary origin has allowed specific terrestrial models to come into focus. Río Tinto (Southwestern Spain, Iberian Pyritic Belt) is an extreme acidic environment, product of the chemolithotrophic activity of micro-organisms that thrive in the massive pyrite-rich deposits of the Iberian Pyritic Belt. Some particular protective environments should house the organic molecules and bacterial life forms in harsh environments such as Mars surface supporting microniches inside precipitated minerals or inside rocks. Terrestrial analogues could help us to afford the comprehension of habitability (on other planetary bodies).
We are reporting here the multidisciplinary study of some endolithic niches inside salt deposits used by phototrophs for taking advantage of sheltering particular light wavelengths. These acidic salts deposits located in Río Tinto shelter life forms that are difficult to visualize by eye. This interdisciplinary field analogue campaign was conducted in the framework of the CAREX FP7 EC programme.
(Received December 15 2010)
(Accepted January 24 2011)
(Online publication February 24 2011)