Valleys, Paleolakes and Possible Shorelines at the Libya Montes/Isidis Boundary: Implications for the Hydrologic Evolution of Mars

Abstract

We describe the results of our morphologic, stratigraphic and mineralogic investigations of fluvial landforms, paleolakes and possible shoreline morphologies at the Libya Montes / Isidis Planitia boundary between 85°/86.5°E and 1.8°/5°N [1]. The landforms are indicative of aqueous activity and standing bodies of water, that are attributed to a complex hydrologic cycle that may have once existed on Mars in the Noachian (>3.7 Ga) and perhaps also in the Hesperian (>3.1 Ga). At the Libya Montes / Isidis Planitia boundary, we identified series of morphologic landforms at three different elevation levels (Fig. 1). The morphologies have been associated with intense fluvial activity, standing bodies of water, hydrous alteration, wave-cut action, distinct still stands as well as freezing and sublimation of a cold ocean [e.g., 1-10]. We can distinguish between (1) local occurences of fluvial and lacustrine landforms of the Libya / Isidis contact between -2500 and -2800 m, (2) a series of cliffs of the Arabia shoreline at -3600 and -3700 m, and (3) the Deuteronilus contact that occurs as an onlap morphology at the boundary between the Isidis interior plains and the Isidis exterior plains.