seafloor, which was essential for later diversification of metazoans in the Ediacaran. Such sub-ice Cryogenian biochemical systems may provide Earth-based analogs for life on ice-covered worlds, such as Europa and Enceladus.

Hickman-Lewis, K., Foucher, F., Pelletier, S., Messori, F., Westall, F., 2020. Geological appraisals of core samples using the ExoMars 2020 rover instrumentation. Planetary and Space Science 180, 104743.

http://www.sciencedirect.com/science/article/pii/S0032063319301321 The ExoMars 2020 mission will characterise a Martian locality with potential former habitability - Oxia Planum - and attempt to identify preserved morphological and chemical biosignatures. The payload will include a drill retrieving cores from the subsurfa ce (up to 2 mdepth), which will be imaged at high resolution by two instruments: the Panoramic Camera High Resolution Camera (PanCam HRC) and CLose UP Imager (CLUPI). These instruments will provide guiding interpretation and govern the approach used by the analytical instruments, which will conduct their analyses after crushing of the core sample. Blind tests using Mars- analogue lithological samples provide valuable mission training in terms of maximising scientific return. Previous blind tests evaluating the abilities of the ExoMars 2020 payload to conduct geological approaches used solid rock hand samples as test specimens. Here, we prepared test samples of ExoMars mission-equivalent shapes and dimensions (3 × 1 cm cores) to evaluate the extent of geologi cal interpretation possible using only the images of the core that will obtained during the mission. In the worst-case scenario, core samples will be different from outcrop rock and these images and associated organogeochemical analyses on crushed powders by the other rover instruments will be the sole basis for their interpretation. Imaging these samples using mission-equivalent original resolutions to avoid image processing artefacts, we found that the difficulty inherent in making definitive geological c onclusions using traditional 'field petrography' approaches is increased when only limited amounts of core sample are available for observation. Challenges involved in the interpretation of core samples include representativeness problems inherent to small samples, distinction between layer-specific characteristics at the sub-centimetre to centimetre scale, and mechanical effects, such as drill marks and dust covering. These issues vary depending upon the rock type and change as a function of the mechanical properties (and thus composition) of the sample. Despite these challenges, we find that CLUPI and PanCam HRC images alone allow many accurate and detailed geological observations; however, confidence and detail of interpretation are notably increased when additional geochemical data are provided, in this case, Raman spectra reflecting the contribution of the Raman Laser Spectrometer (RLS) instrument. Our results argue for the importance of detailed core imaging during the experimental phase of the rover mission despite the challenges involved in interpretation, since HRC and CLUPI images offer a degree of synergy. Inter-instrumental collaboration will be essential during the ExoMars 2020 rover mission (and indeed in any rover mission), since no single payload instrument is able to perform a comprehensive assessment of a putative biosignature within its geological context, and since the instrument suite provides highly complementary data at multiple scales that are key to maximising scientific return.

Hidalgo, K.J., Teramoto, E.H., Soriano, A.U., Valoni, E., Baessa, M.P., Richnow, H.H., Vogt, C., Chang, H.K., Valéria, M.O., 2020. Taxonomic and functional diversity of the microbiome in a jet fuel contaminated site as revealed by combined application of in situ microcosms with metagenomic analysis. Science of The Total Environment 708, 135152.

http://www.sciencedirect.com/science/article/pii/S0048969719351447 Natural attenuation represents all processes that govern contaminant mass removal, which mainly occurs via microbial degradation in the environment. Although this process is intrinsic its rate and efficiency depend on multiple factors. This study aimed to characterize the microbial taxonomic and functional diversity in different in situ aquifer sediments collected in the saturated zone and microcosms (BACTRAP®s) amended with 13 hydrocarbons ( C-labeled and non-labeled benzene, toluene and naphthalene) using 16S rRNA gene and shotgun ' ' Illumina high throughput sequencing at a jet -fuel contaminated site. The BACTRAP®s were installed to assess hydrocarbon metabolism by native bacteria. Results indicated that Proteobacteria, Actinobacteria and Firmicutes were the most dominant phyla (~98%) in the aquifer sediment samples. Meanwhile, in the benzene- and toluene-amended BACTRAP®s the phyla Firmicutes and Proteobacteria