1. D. J. Lindstrom, Planetary Science Branch, SN4, NASA Johnson Space Center, Houston, TX 77058, USA.
2. B. C. Schuraytz and V. L. Sharpton, Lunar and Planetary Institute, Houston, TX 77058, USA.
3. R. R. Martinez, D. W. Mittlefehldt, S. J. Wentworth, Lockheed Martin, Engineering and Sciences, Houston, TX 77058, USA.