1 , A. Raponi 2 , F. Tosi 2 , M.C. De Sanctis 2 , E. Ammannito 2,3 , F.G. Carrozzo 2 , M. E. Landis 4 , S. Byrne 4 , U. Carsety 5 , S. Schröder 5 , T. Platz 6 , O. Ruesch 7 , K. Hughson 3 , T. B. McCord 1 , S. Singh 1 , K. Johnson 1 , F. Zambon 2 , C.M. Pieters 8 , C.A. Raymond 9 , C.T. Russell 3 , and the Dawn/VIR Team, 1 1 Bear Fight Institute, Winthrop, WA, USA. 2 INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy. 3 University of California at Los Angeles, Los Angeles, CA, USA. 4 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA. 5 German Aerospace Center (DLR), Institute of Planetary Research, Rutherfordstrasse 2, 12489 Berlin, Germany. 6 Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany. 7 NASA/Goddard Space Flight Center, Greenbelt, MD, USA. 8 Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, USA. 9 NASA/Jet Propulsion Laboratory and California Institute of Technology, Pasadena, CA, USA.