Applicant — David Horvath

Gale crater’s central sedimentary mound (Aeolis Mons or informally Mount Sharp) preserves one of the best records of the early Martian climate and hydrology. Mount Sharp’s sediment sequence is consistent with a transition from wet climatic conditions when valley networks were forming to an arid period when groundwater influenced sediment cementation was occurring to a period of primarily anhydrous sediment accumulation dominated by aeolian processes. Exhumation of the sediment under a dry climate resulted in the sediment mound observed today, which was followed by a wetter period of reactivation of valley networks and the deposition of deltas observed on Gale’s floor. However, surface conditions alone do not provide a direct constraint on this climate evolution. We use hydrological models coupled to a lake deposition model during and after the formation of Mount Sharp to infer the climate and climate evolution of Gale crater constrained by satellite and ground-based MSL observations. The sedimentary sequence within Gale crater suggests a perennial arid climate and periods of wetter climate excursions early on in Gale’s history during the late Noachian / early Hesperian. Late-stage reactivation of valley networks and deposition of deltas in Gale suggests wetter, semi-arid excursions as late as the early Hesperian. Additionally, this work shows that interpretation of the martian sedimentary record requires consideration of the full hydrological system.