1. Department of Molecular Evolution, Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
2. Department of Planetology and Habitability, Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
3. Department of Systems Biology, Centro Nacional de Biotecnología, CSIC, Madrid, Spain.
4. Department of Astronomy, Cornell University, Ithaca, New York, USA.