1. Hawai’i Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822, USA.
2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
3. Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA 94720, USA.
4. Applied Physics Laboratory Johns Hopkins, Laurel, MD 20723, USA.
5. Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA.