1. Department of Earth, Ocean and Atmospheric Sciences; University of British Columbia; Vancouver British Columbia Canada
2. Planetary Science Institute; Tucson Arizona USA
3. The Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
4. NASA Goddard Space Flight Center; Greenbelt Maryland USA
5. Department of Terrestrial Magnetism; Carnegie Institution of Washington; Washington District of Columbia USA
6. Lamont-Doherty Earth Observatory; Columbia University; Palisades New York USA