MARS-PRIME

Orbital and in-situ detections of hydrous minerals on Mars, especially phyllosilicates, suggest a warmer and wetter climate existed in the past, but exact physico-chemical surface conditions (temperature, oxidation state, atmospheric composition and pressure) remain debated. In particular, the relative role of weathering versus hydrothermal alteration in forming phyllosilicates remains unclear and no definitive answer has emerged from a decade of local and global studies. The search for oxidizing or reducing environments and the state of iron is a major aspect of investigations of Early Mars surface conditions. Although oxidizing conditions have been locally identified from abundant iron oxides both from orbital data and in the new meteorite breccia, it remains unclear how such conditions were able to create the observed amount of phyllosilicates. In addition, new findings from the Curiosity rover and from meteorite analyses show that the Martian crust is more felsic and alkali-rich than previously expected. This finding is a change from the previous paradigm for the surface of Mars as a basalt-dominated world and opens new perspectives for the understanding of alteration products. Our project will aim to take a multi-disciplinary approach, connecting researchers who usually work in separated groups in planetary science in France: instrumental teams at the forefront of data analyses (both orbital and in situ), specialists of chemical and mineralogical analyses of Martian meteorite analyses and mineralogists/petrologists with terrestrial backgrounds. The development of experimental simulations of alteration with a well-defined set of environmental conditions and starting materials addressing the question of the alteration products of ancient crustal material under an anoxic CO2 atmosphere is central to the proposal. Indeed, the conditions on Mars are far from the usual conditions on Earth, and there is a lack of knowledge regarding alteration under an anoxic CO2 atmosphere, especially the role of oxidants such as H2O2 or perchlorates, and reducing gas species such as H2. Analyses of relevant martian meteorites, especially the recently found regolith breccias containing phyllosilicates and iron oxides, will provide support for interpretation of the experimental analyses and will help to improve our knowledge of Mars early environment. Further analyses of orbital and in situ data (Curiosity rover) will help to constrain the composition of early crust material, and the alteration conditions, focusing on the identification of weathering as opposed to higher-T alteration. Our project will build a consortium of well-established researchers in their respective fields of expertise.