1. School of Physics and Astronomy, Queen Mary University of London, Mile End Road, E1 4NS London, United Kingdom
2. Centro de Astrobiología (CSIC, INTA), Ctra. de Ajalvir, km. 4, Torrejón de Ardoz, E-28850 Madrid, Spain
3. INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Florence, Italy
4. Excellence Cluster ‘Universe’, Boltzmann str. 2, D-85748 Garching bei Muenchen, Germany
5. ESO/European Southern Observatory, Karl Schwarzschild str. 2, D-85748 Garching, Germany
6. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MA 02138 Cambridge, USA