1. Hawaii Institute of Geophysics and Planetology, SOEST, University of Hawaii, 1680 East-West Road, POST 602, Honolulu, Hawaii 96822 (S.K.S., A.K.M., P.G.L.); Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208 (S.M.A.); and NASA Ames Research Center, Space Science Division, Moffett Field, California 94035 (C.P.M.)