Understanding the Noachian-Hesperian transition in the area of Meridiani Planum, Mars: a stratigraphic, compositional and morphological study

Numerous exploration missions over the last decades have gathered compelling evidence that early Mars experienced a warm climate with abundant liquid water at the surface. During this period, termed as Noachian, water carved out fluvial valleys, filled craters to create lakes, and transported sediments that formed deltas and alluvial fans, while the prolonged interaction of alkaline water with the Martian crust led to the formation of several types of clay minerals. This exceptional period came to an end about 3.7 billion years ago. The subsequent period, the Hesperian, saw a net decrease in fluvial erosion and the build up of sulfates in some regions of the planet, indicating enhanced water evaporation and increasingly acidic conditions. The Noachian-Hesperian climatic transition eventually led to the current cold, dry, and inhospitable surface. However, its exact characteristics remain largely unknown and subject of debate. This thesis focuses on the orbital morphological, mineralogical, and stratigraphic characterization of selected areas in Meridiani Planum, where a complex, regionally-extensive, sequence of layered sedimentary rocks rich in clays and sulfates are key evidence of the Noachian-Hesperian transition. High-resolution hyperspectral imaging data is combined with digital elevation models for a detailed characterization of the units. Spectral analysis is approached with a wide range of methods, from traditional spectral index analysis to advanced approaches based on unsupervised machine learning. Results indicate that the Noachian-Hesperian climatic transition was highly complex and dynamic, and that the shift from a warm and wet to a cold and dry environment was not linear, but likely underwent cyclical oscillations at different frequencies.