1. SETI Institute, Mountain View, California, USA.
2. Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, California, USA.
3. Instituto de Recursos Naturales, CSIC, Madrid, Spain.
4. Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA.
5. Centro de Astrobiología (INTA-CSIC), Madrid, Spain.