David se présente lui même ci-dessous (anglais)

Biosketch

I am planetary scientist and geobiologist researching the Mars past environmental conditions and the preservation of biomolecules under extreme environments to use them as valid and robust biosignatures for searching life on other planetary bodies. For a long time, I have conducted research on the geobiology and biogeochemistry of different Mars analogs. One of them is the acidic environment of Rio Tinto that is being used as a universal reference for ancient conditions that are believed to have existed on early Mars. My research at Rio Tinto went against the paradigm that extreme and acidic environments are harmful to preserve biological information. In this regard, the preservation of body fossils and biosignatures is showing that such environment has a high preservation potential that includes peptide sequences and other large biomolecules. I have also explored some other Mars analogs and very ancient terrestrial environments (including the Pilbara and Barberton Archean Cratons) to monitor the preservation of traces of life over large temporal scales, as well as by comparing modern environments and their ancient counterparts. During my research, I have also focused on the study of the physical, chemical and climatic evolution of the Mars surface/subsurface paleoenvironments through the study of different regions in the red planet as Aram Chaos, and Terra Sirenum. I have performed a multidisciplinary approach that involves a geological/geomorphological, mineral/geochemical, and paleohydrological study to understand the paleoenvironmental changes and the potential occurrence of habitable areas in Mars. In this context, and by integrating the information from terrestrial analogs and the environmental conditions of Mars, the evaluation of the potential preservation of traces of life in the red planet can be proceeded.

Scientific interests and projects

In Grenoble we will going to evaluate the preservation potential of biomolecules in ancient salts along a deep temporal scale that can be comparable to the formation ages of chlorides and other evaporites on Mars. It is based on the working hypothesis asserting that chlorides and other salts formed in a temporal scale of billions of years can potentially preserve traces of biomolecules. However, the preservation potential also depends on different (paleo)environmental conditions (e.g., temperature, UV radiation, water activity, mineralization rate, pH, Eh), which can also act as limiting conditions for preserving the biomolecules in the salty matrix. In addition, the preservation degree is also the result of the process in the maturation of the mineral matrix containing the biomolecules. The integrity of biomolecules will also be by far different if the evaporitic deposits have been exposed to a complex diagenesis and maturation processes affecting the composition of the primary mineral matrix. Therefore, we will infer the preservation potential for nucleic acids, proteins and other biomolecules (e.g. phospholipids and polysaccharides) in the Mars salt deposits by using information collected in ancient and modern terrestrial hypersaline deposits. This will be also complemented by the study of the preservation over an extended range of time comparable to the geological record preserved on Mars. It will include the study of the fossilization process at a spatial scale below the nanometer in different materials of the Archean and Proterozoic (> 1000 Ma).