1. M. C. Malin, M. A Caplinger, M. A. Ravine, J. L. Warren, Malin Space Science Systems, Post Office Box 910148, San Diego, CA 92191–0148, USA.
2. M. H. Carr, U.S. Geological Survey, Menlo Park, CA 94025, USA.
3. G. E. Danielson and A. P. Ingersoll, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
4. M. E. Davies, The Rand Corporation, Santa Monica, CA 90406–2138, USA.
5. W. K. Hartmann, Planetary Science Institute, Tucson, AZ 85719, USA.