DURATION OF THE MAADIM-VALLIS GUSEV CRATER HYDROGEOLOGIC SYSTEM, MARS/

Ma'adim Vallis and Gusev crater (Aeolis subquadrangle of Mars) formed a complex hydrogeologic system through time. Crater statistics over fi ve geologic units, coupled with morphologic and geologic observations, show that this system was active over a period ranging from 0.7 to ab out 2 billion years. These results make the floor of Gusev crater one of the most prominent martian depositional features. The last aqueous sedimentary deposition could have occurred during Early Amazonian. (C) 1998 Academic Press.