[1] Univ Cologne, Bensberg Observ, Vinzenz Pallotti Str 26, D-51429 Bergisch Gladbach, Germany
[2] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
[3] Univ Paris Cite, CNRS, Inst Phys Globe Paris, F-75005 Paris, France
[4] Swiss Fed Inst Technol, Inst Geophys, Sonneggstr 5, CH-8092 Zurich, Switzerland
[5] Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, 595 Charles Young Dr East,Box 951567, Los Angeles, CA 90095 USA
[6] Univ Angers, Univ Nantes, CNRS, Lab Planetol & Geodynam,UMR6112, 2 Rue Houssiniere BP 92208, F-44322 Nantes 3, France
[7] Colorado Sch Mines, Dept Geophys, 1500 Illinois St, Golden, CO 80401 USA
[8] Inst Superieur Aeronaut & Espace SUPAERO, 10 Ave Edouard Belin, F-31400 Toulouse, France
[9] Univ Bristol, Sch Earth Sci, Wills Mem Bldg,Queens Rd, Bristol BS8 1RJ, Avon, England
[10] Univ Toulouse III Paul Sabatier, CNRS, Inst Rech Astrophys & Planetol, CNES, 14 Ave E Belin, F-31400 Toulouse, France
[11] Imperial Coll London, Dept Elect & Elect Engn, South Kensington Campus, London SW7 2AZ, England
[12] German Aerosp Ctr DLR, Inst Planetary Res, D-12489 Berlin, Germany
[13] Univ Maryland, Dept Geol, 8000 Regents Dr, College Pk, MD 20782 USA
[14] NASA MSFC, NSSTC Mail Code ST13,320 Sparkman Dr, Huntsville, AL 35805 USA
[15] Univ Cote dAzur, CNRS, Lab Lagrange, Observ Cote dAzur, Nice, France
[16] Univ Zurich, Inst Theoret Phys, Winterthurerstr 190, CH-8057 Zurich, Switzerland
[17] Geosci Barcelona CSIC, Barcelona, Spain