The work was organized in 4 Research Themes (RTs). Major scientific developments have included, in each RT:
• RT1, Geology: Publication of a new geomorphological map of the Sinus Sabaeus region of Mars, a basis for identifying the ancient presence of water in the region. First identification of rythmites on Mars, verifying that impact events were a major source for liquid water on early Mars. Documentation of the history of one specific aqueous episode on early Mars, providing first evidence for powerful storms, torrential rains, megafloods, and strong waves in a martian paleolake. Calculation of the volume of water accumulated on the Martian lowlands, using the early Noachian crater distribution.
• RT2, Geochemistry: Analysis of the reactivity of pyrite to ferric oxides and sulfate minerals under present and early Martian surface conditions, explaining the scarcity of disulfide deposits on the Martian surface. Reconstruction of the environmental conditions that facilitated iron oxidation during the anoxic and iron-rich Archean conditions, to better understand the connection between iron mineralogy and the formation of carbonate minerals on Mars. Quantification of how past fluids on Mars interacted with and altered the surface, depending on fluid pH, and how this alteration modified the preservation potential of organic matter embedded in clay minerals.
• RT3, Mineralogy: First identification of glauconite minerals on Mars using in situ data from the Curiosity rover, contributing to clarify the formation of clays on early Mars. First identification of a subsoil wet clay layer in the hyperarid core of the Atacama Desert, harvesting new data to help determine the preferred mineral sequences where to look for biosignatures in the Martian subsurface. Development of a statistical mass-balance calculation procedure to narrow the range of chemical composition of the clay minerals and amorphous phases observed in Mars, providing the basis for their identification and subsequent interpretation of their formation environment.
• RT4, Geomicrobiology and Astrobiology: Using a novel methodology, µ-DSC, identification of the ability of microorganisms to change the freezing/melting curve of cold salty solutions, expressing proteins that can affect the liquid-to-ice transition. Contribution of a new instrument concept to search for evidences of an ancient biosphere on Mars. Investigations in 4 Mars bioanalogs. (1) The Atacama Desert, deciphering the dispersion of microbial life using dust transported by wind, proposing the term “dark biosphere” referred to microorganisms with a high rate of phylogenetic indeterminacy, and deciphering the metabolic strategies available to potential martian microorganisms during their adaptation to water stress. (2) Antarctica, describing the geomicrobiology of the permanently exposed lithic substrates of nunataks. (3) Rio Tinto, characterizing the microbial diversity existing in the deep subsurface of the Iberian Pyrite Belt. And (4) Tirez Lake, describing the evolution of the microbial communities during desiccation of the endorheic hypersaline lagoon, and proposing the concept of “astrobiological time-analogs”, referred to terrestrial analogs that can help understand environmental transitions and the related possible ecological successions on early Mars.
Our work has generated 49 peer-reviewed scientific papers, 69 meeting communications, a dozen of press releases, another dozen of press inquiries, and 3 tailored dissemination pieces.
