PhD defense of Justine Villette : ” Formation and lifespan of Martian paleolakes: a study of Jezero crater “

Abstract : On Mars, orbital and in situ observations have revealed past surface water activity, notably through the identification of lakes that are now dry. Among these lakes, Jezero crater is a prime target for study, particularly thanks to its ongoing exploration by the Perseverance rover. The aim of this thesis is to understand the evolution of Jezero and to constrain the timescale associated with is past hydrological activity. To do this, we combine morphological, stratigraphic and sedimentary observations of the lake with numerical modeling work First, the study of Pliva Vallis, the outlet of the lake, allowed us to characterize the Jezero lake as a closed system, temporarily opened during at least four overflow events, each lasting from a few days to a few weeks. Secondly, the development of a numerical model, combining climate and hydrology, enabled us to simulate the formation of the western delta of Jezero during the lake regression. This work revealed a wide range of scenarios, combining climatic conditions and the source of water feeding Neretva Vallis, able to reproduce the delta formation over timescales of 2,000 to 9,000 years. Then, this work allowed us to propose a two phase evolution scenario for the lake : (i) a quick infilling in a closed system, followed by at least four episodic events of lake overflow, which led to the formation of Pliva Vallis, (ii) the delta formation during the lake level regression over several thousand years.

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