1. Planetary Sciences Directorate, Southwest Research Institute, 1050 Walnut Street, Boulder, CO 80302, U.S.A.
2. NASA Lyndon B. Johnson Space Center Mail Code X12, 2101 NASA Parkway Houston, TX 77058, U.S.A.
3. Department of the Geophysical Sciences and Enrico Fermi Institute, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, U.S.A.
4. Carl Sagan Center for the Study of Life in the Universe, SETI Institute, 189 Bernardo Ave., Mountain View, CA 94043, U.S.A.
5. Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, U.S.A.
6. Earth and Planetary Sciences, University of California, Davis, One Shields Ave., Davis, CA 95616, U.S.A.
7. Space Studies Department, Southwest Research Institute, 1050 Walnut Street, Boulder, Colorado, 80302 U.S.A.
8. Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester, NY 14627, U.S.A.
9. Czech Geological Survey, Klárov 3 118 21 Prague 1, Czech Republic