RECENT INVESTIGATIONS USING BOTH ORBITAL AND ROVER DATA HAVE RESULTED IN THE EVOLUTION OF OUR UNDERSTANDING OF THE AQUEOUS HISTORY OF MARS. AT THE GLOBAL SCALE OMEGA VISIBLE AND NEAR INFRARED SPECTRAL MAPPING REVEALED THAT PHYLLOSILICATES ARE MOST COMMONLY OBSERVED IN THE OLDEST NOACHIAN-AGED ROCKS AND THAT HYDRATED SULFATES ARE GENERALLY DETECTED IN RELATIVELY YOUNGER HESPERIAN-AGED UNITS. AS PHYLLOSILICATES TYPICALLY FORM UNDER CIRCUMNEUTRAL GEOCHEMICAL CONDITIONS AT HIGH WATER TO ROCK RATIOS THEY ARE MINERALOGIC INDICATORS FOR WETTER CONDITIONS. HYDROLOGIC MODELING SUGGESTS THAT THE MARTIAN HYDROLOGIC CYCLE WAS DOMINATED BY GROUND WATER INTERACTIONS BY THE LATE HESPERIAN WHICH RESULTED IN THE CEMENTATION OF PREDOMINATELY AEOLIAN-DERIVED EVAPORITIC DEPOSITS THAT FORMED AT LOW WATER TO ROCK RATIOS. WHILE THE GLOBAL PROSPECTIVE OF MARTIAN AQUEOUS HISTORY IS ONE OF EVOLUTION FROM RELATIVELY WETTER CONDITIONS IN THE NOACHIAN TO A HYPER ARID ENVIRONMENT BY THE END OF THE HESPERIAN THE NATURE OF THE TRANSITION BETWEEN THESE TWO REGIMES IS NOT WELL UNDERSTOOD. REGIONAL AND LOCAL STUDIES OF DEPOSITS THAT FORMED DURING THE NOACHIAN/HESPERIAN TRANSITION USING THE HIGHEST RESOLUTION DATA ARE REVEALING EVIDENCE FOR COMPLEX DEPOSITIONAL ENVIRONMENTS THAT EXHIBIT A VARIETY OF GEOMORPHIC FEATURES AND ALTERATION MINERALS INDICATIVE OF MULTIPLE GEOCHEMICAL REGIMES. THE PROPOSED WORK SEEKS TO ADVANCE OUR UNDERSTANDING OF AQUEOUS-DRIVEN SEDIMENTARY AND ALTERATION PROCESSES THAT OPERATED ON MARS AT THE REGIONAL AND LOCAL SCALES BY PERFORMING DETAILED STRATIGRAPHIC MAPPING AND MINERALOGIC ANALYSES OF WELL EXPOSED SEDIMENTARY DEPOSITS IN EASTERN SINUS MERIDIANI USING MRO HIRISE (25 CM/PIXEL) CTX (5 M/PIXEL) AND CRISM (20 M/PIXEL) DATA IN CONJUNCTION WITH OTHER ORBITAL DATASETS. THE TARGET OF THE PROPOSED INVESTIGATION ETCHED TERRAIN DEPOSITS OCCUR STRATIGRAPHICALLY ABOVE HEAVILY CRATERED NOACHIAN HIGHLANDS AND STRATIGRAPHICALLY BELOW THE LATE NOACHIAN/EARLY HESPERIAN SULFATE- AND HEMATITE- BEARING UNIT EXPLORED BY THE MER OPPORTUNITY ROVER AND ARE THEREFORE IDEALLY SUITED FOR THE STUDY OF PROCESSES THAT OPERATED DURING THE NOACHIAN/HESPERIAN TRANSITION. WE PROPOSE TO (1) DETERMINE THE REGIONAL STRATIGRAPHY IN EASTERN SINUS MERIDIANI (0E TO 8E -2N TO 4N) (2) DETERMINE THE CORRELATION BETWEEN STRATIGRAPHY AND ALTERATION MINERALOGY TO INFER REGIONAL DEPOSITIONAL AND/OR ALTERATION PROCESSES (3) PERFORM DETAILED STRATIGRAPHIC AND SPECTRAL MAPPING USING THE HIGHEST SPATIAL RESOLUTION DATA TO FURTHER CHARACTERIZE AQUEOUS PROCESSES FOR AT LEAST FOUR SUBREGIONS AND (4) INTEGRATE THE REGIONAL AND LOCAL STUDIES TO CHARACTERIZE NOACHIAN/HESPERIAN AQUEOUS-DRIVEN SEDIMENTARY AND ALTERATION PROCESSES THATOPERATED IN EASTERN SINUS MERIDIANI MARS.