[1
]M. J. S. Belton, National Optical Astronomy Observatories, 950 North Cherry Ave, Tucson,
AZ 85719, USA.
[2
]J. W. Head III, R. Pappalardo, G. Collins, Department of Geological Science, Brown
University, Providence, RI 02912, USA.
[3
]A. P. Ingersoll and A. R. Vasavada, Department of Geology and Planetary Sciences,
California Institute of Technology, Pasadena, CA 91125, USA.
[4
]R. Greeley and R. Sullivan, Department of Geology, Arizona State University, Tempe,
AZ 85287-1414, USA.
[5
]A. S. McEwen, P. Geissler, R. Greenberg, Lunar and Planetary Laboratory, University
of Arizona, Tucson, AZ 87721, USA.
[6
]K. P. Klaasen, D. Senske, T. V. Johnson, G. S. Orton, R. A. West, Jet Propulsion Laboratory,
California Institute of Technology, Pasadena, CA 91109, USA.
[7
]D. Simonelli, J. Veverka, P. J. Gierasch, D. Banfield, M. Bell, J. A. Burns, P. Thomas,
Department of Astronomy, Cornell University, Ithaca, NY 14853, USA.
[8
]M. H. Carr, U.S. Geological Survey, Menlo Park, CA 94025, USA.
[9
]M. E. Davies, RAND, Santa Monica, CA 90406, USA.
[10
]C. R. Chapman, Southwest Research Institute, Boulder, CO 80302, USA.
[11
]C. Anger, ITTRES Ltd, Calgary, Alberta TIY 5Z6, Canada.
[12
]G. Neukum, Institute for Planetary Exploration, Deutsche Forschunganstalt für Luft
und Raumfahrt, Berlin, Germany.
[13
]C. B. Pilcher, National Aeronautical and Space Administration, Washington, DC 20546,
USA.
[14
]R. F. Beebe, Department of Astronomy, New Mexico State University, Las Cruces, NM
88003, USA.
[15
]F. Fanale, Institute for Geophysics, University of Hawaii, Honolulu, HI 96822, USA.
[16
]W. Ip, Max Planck Institute für Aeronomie, Lindau, Germany. D. Morrison and J. Moore,
NASA Ames Research Center, Moffett Field, CA 94035, USA.