what is life the emergence of life in a mineral world

The premise of this talk is that, apart from liquid water and carbon molecules, specific environmental components and conditions were essential for the origin of life, i.e. phosphate, reactive rock..

The CaliPhoto Method

International audienceWe propose an innovative method based on photography and image processing of interdisciplinary relevance, permitting the uncomplicated and inexpensive evaluation of material properties. This method-CaliPhoto-consists of using a dedicated colour plate with a specific design, placed in the field of view of a photograph of the material to be characterized. A specific image processing workflow is then applied to obtain colour vectors independent of illumination conditions. The method works using commercial colour cameras (e.g., smartphone cameras), and the colour plate can be printed on any colour printer. Herein, we describe the principle of the method and demonstrate that it can be used to describe and compare samples, identify materials or make relatively precise concentration measurements. The CaliPhoto method is highly complementary to any scientific research and may find applications across a range of domains, from planetary science to oceanography. The method may also be widely used in industry

Nanoscale 3D quantitative imaging of 1.88 Ga Gunflint microfossils reveals novel insights into taphonomic and biogenic characters

International audiencePrecambrian cellular remains frequently have simple morphologies, micrometric dimensions and are poorly preserved, imposing severe analytical and interpretational challenges, especially for irrefutable attestations of biogenicity. The 1.88 Ga Gunflint biota is a Precambrian microfossil assemblage with different types and qualities of preservation across its numerous geological localities and provides important insights into the Proterozoic biosphere and taphonomic processes. Here we use synchrotron-based ptychographic X-ray computed tomography to investigate well-preserved carbonaceous microfossils from the Schreiber Beach locality as well as poorly-preserved, iron-replaced fossil filaments from the Mink Mountain locality, Gunflint Formation. 3D nanoscale imaging with contrast based on electron density allowed us to assess the morphology and carbonaceous composition of different specimens and identify the minerals associated with their preservation based on retrieved mass densities. In the Mink Mountain filaments, the identification of mature kerogen and maghemite rather than the ubiquitously described hematite indicates an influence from biogenic organics on the local maturation of iron oxides through diagenesis. This non-destructive 3D approach to microfossil composition at the nanoscale within their geological context represents a powerful approach to assess the taphonomy and biogenicity of challenging or poorly preserved traces of early microbial life, and may be applied effectively to extraterrestrial samples returned from upcoming space missions

Aqueous alteration processes in Jezero crater, Mars—implications for organic geochemistry

The Perseverance rover landed in Jezero crater, Mars, in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep-ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, which probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks and are preserved in minerals related to both aqueous environments

Fossilization of Bacteria and The Implications for The Search for Early Life Forms. Biosignatures In Astrobiology Missions to Mars

International audienceThroughout the first few billion years of its history, microbial cells were the only life-forms on Earth and present the only life-forms that could have once existed or still exist on Mars. Our understanding of the formation of the signatures of microbial life-forms (biosignatures) comes from experimental fossilization studies, together with the detailed investigation of their remains throughout the preserved geological history of the Earth. We here resume mechanisms for the preservation of microbial biosignatures and review a selection of the highly diverse and well-preserved biota from the early history of the Earth. Our understanding of early life is informative for the search for life on Mars, presenting a paleontological and philosophical analogue against which putative signs of Martian life will need to be tested. Significant differences in the conditions of habitability between Mars and the Earth indicate that only primitive chemotrophic life-forms could have inhabited, or still inhabit, the Red Planet, and this may set a unique set of challenges for the proof of Martian biosignatures. We conclude by briefly outlining the findings of several decades of past and present missions of astrobiological interest to Mars and consider what additional information future missions could bring

Supplemental Material: Advanced two- and three-dimensional insights into Earth’s oldest stromatolites (ca. 3.5 Ga): Prospects for the search for life on Mars

Methods, Figures S1–S16, and Table S1.  </p