Fluvial Landforms and the Post-Noachian Environment on Mars

Several paradigm shifts have occurred over the past several decades as our understanding of the hydrologic and climatic history of Mars has evolved. It is generally accepted that the early climate on Mars was capable of sustaining an active hydrological cycle, and that (possibly episodic) precipitation and runoff formed the low-to-mid latitude belt of valley networks. Age analyses from crater counts suggests a sudden decline in fluvial activity around the Noachian-Hesperian boundary, presumably associated with the loss of the early denser atmosphere. The climate in the Hesperian and Amazonian was generally considered less favorable for precipitation (most likely snow) and runoff. This paradigm, however, is being challenged by a growing suite of post-Noachian fluvial landforms that support evidence for a late, widespread episode(s) of aqueous activity. Because modification by water and ice on a paleolandscape is one of the most unambiguous markers of past climate, this dissertation investigates fresh shallow valleys (FSVs), deltas, paleolakes, alluvial fans and aqueous-rich ejecta deposits in northern Arabia Terra and northwestern Noachis Terra that formed in the Hesperian and Amazonian. The objective of this dissertation is to provide insight into the environment and associated climate regime that permitted the formation of these post-Noachian fluvial landforms, which furthers our understanding of the potential late-stage habitability of Mars.