1. Istituto di Astrofisica e Planetologia Spaziali–Istituto Nazionale di Astrofisica, 00133 Roma, Italy.
2. Earth Planetary and Space Sciences, University of California–Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095-1567, USA.
3. Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA.
4. Southwest Research Institute, Boulder, CO 80302, USA.
5. NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
6. Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI 02912, USA.
7. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA.