R. Amils and the IPBSL team Centro de Astrobiología(CSIC-INTA) and Centro de Biología Molecular Severo Ochoa (UAM-CSIC) Although Darwin predicted life in the subsurface, the first paper describing life associted to deep basalt aquifers has les than 20 years. Terrestrial subsurface geomicrobiology is a matter of growing interest. On a fundamental level it seeks to determine whether life can be sustained in the absence of radiation, whereas it also aims to develop practical applications in environmental biotechnology. Subsurface ecosystems are also of interest in astrobiology. In spite of its interest, information concerning microbial abundance, diversity and sustainability in the subsurface is still scarce, mainly due to methodological limitations. We will report our experience on two drilling projects, MARTE and IPBSL devoted to understand the origin of Río Tinto, an extreme acidic river of 92 km in the western part of Spain.