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The X-ray Microscopy and Micro-analysis beamlines at ESRF operate complementary state-of-the-art instruments at ID21, ID22, ID18F and more recently ID22NI. Within a multi-modal strategy, these beamlines develop micro-imaging techniques with various contrast mechanisms (μXRF, μXANES, μXRD and phase contrast) and host experiments with scientific topics ranging from Geochemistry to Archeology, Environmental sciences, Biology and Material sciences. Future challenges include pushing spatial resolution down to the nano-scale and the development of innovative 3D micro-analysis techniques.

The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples. Key Words: Ground penetrating radar—Martian shallow subsurface—ExoMars. Astrobiology 17, 565–584. International audience

Abstract New fossil woods from the Keuper of Poland and France are assigned to Agathoxylon keuperianum (Unger) nov. comb. A complete nomenclatural treatment of this taxon is given, with up-dated nomenclatural synonymy and some taxonomical notes. It is shown that Zimmermann's choice of a lectotype (1953) for this species is superseded by material in the Unger collection at the Paris Museum National d'Histoire Naturelle (France). Taxomical reappraisal of Unger collection also evidenced that Simplioxylon hungaricum Andreanzsky correct name is Simplicioxylon wurtembergicum (Unger) nov. comb. and that Peuce brauneana Unger can be excluded from Agathoxylon keuperianum synonymy. Literature data for Agathoxylon keuperianum are reviewed and some are invalidated. Our new data are the first safe reports for this species outside from Germany. The systematic position of Agathoxylon keuperianum is discussed, as well as its stratigraphical and geographical range. In the present state of knowledge it seems to be restricted to the area where German Keuper is deposited. Anatomical features suggest that Agathoxylon keuperianum thrived under warm and wet conditions, whereas German Keuper sediments globally suggest hot and dry climate.