1. Department of Geological Sciences, Brown University, Providence, RI 02912, USA.
2. Southwest Research Institute, Boulder, CO 80302, USA.
3. Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
4. The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA.
5. Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC 20560, USA.
6. Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.
7. Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822, USA.
8. School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85251, USA.
9. Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, P. R. China.
10. Institute of Planetary Research, German Aerospace Center, D-12489 Berlin, Germany.