1. Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA.
2. Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
3. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
4. Department of Physics, University of Idaho, Moscow, ID 83844, USA.
5. Jet Propulsion Laboratory, Pasadena, CA 91109, USA.
6. NASA Goddard Institute for Space Studies, New York, NY 10025, USA.
7. Dipartimento di Fisica, Università degli Studi di Roma “Tor Vergata,” 00133 Rome, Italy.
8. Proxemy Research, Rectortown, VA 20140, USA.