1. Istituto Nazionale di Astrofisica; Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS); Via del Fosso del Cavaliere 100 I-00133 Rome Italy
2. Max Planck Institute for Solar System Research; Justus-von-Liebig-Weg 3 D-37077 Göttingen Germany
3. Italian Space Agency (ASI); Via del Politecnico snc I-00133 Rome Italy
4. Institute of Planetary Research; German Aerospace Center (DLR); Rutherfordstrasse 2 D-12489 Berlin Germany
5. Department of Earth, Environmental and Planetary Sciences; Brown University; 324 Brook Street Providence Rhode Island 02912 USA
6. NASA/Jet Propulsion Laboratory and California Institute of Technology; 4800 Oak Grove Drive Pasadena California 91109 USA
7. Institute of Geophysics and Planetary Physics; University of California at Los Angeles; 3845 Slichter Hall, 603 Charles E. Young Drive, East Los Angeles California 90095-1567 USA