Globorotalia bouregregensis, a new species of planktonic foraminifer from the latest Miocene–early Pliocene of the Rifian Seaway (northwest Morocco)

Abstract. Globorotalia bouregregensis, n. sp., is described and documented from the latest Miocene-early Pliocene sequence of the Rifian Seaway, northwest Morocco. By its short stratigraphic distribution, persistence and distinctive morphologic features, the new taxon is well differentiated within the scituline assemblage

<i>In Situ</i> Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions

During a field campaign in the Sahara Desert in southern Morocco, spring 2012, we sampled the vertical grain size distribution of two active dust devils that exhibited different dimensions and intensities. With these in situ samples of grains in the vortices, it was possible to derive detailed vertical grain size distributions and measurements of the lifted relative particle load. Measurements of the two dust devils show that the majority of all lifted particles were only lifted within the first meter (~46.5% and ~61% of all particles; ~76.5 wt % and ~89 wt % of the relative particle load). Furthermore, ~69% and ~82% of all lifted sand grains occurred in the first meter of the dust devils, indicating the occurrence of ‘‘sand skirts.’’ Both sampled dust devils were relatively small (~15m and ~4–5m in diameter) compared to dust devils in surrounding regions; nevertheless, measurements show that ~58.5% to 73.5% of all lifted particles were small enough to go into suspension (<31 mm, depending on the used grain size classification). This relatively high amount represents only ~0.05 to 0.15 wt % of the lifted particle load. Larger dust devils probably entrain larger amounts of fine-grained material into the atmosphere, which can have an influence on the climate. Furthermore, our results indicate that the composition of the surface, on which the dust devils evolved, also had an influence on the particle load composition of the dust devil vortices. The internal particle load structure of both sampled dust devils was comparable related to their vertical grain size distribution and relative particle load, although both dust devils differed in their dimensions and intensities. A general trend of decreasing grain sizes with height was also detected

Etude morphologique de la formation des ravines sur les dunes martiennes (approche comparative Terre/Mars.)

L histoire géologique récente de Mars reste peu étudiée, comparativement à l histoire primitive de Mars (>3,5 Ga). Cependant, l arrivée de nouvelles images haute résolution a permis d identifier la présence de ravines à la surface de terrains très récents. Dans ce travail, nous nous sommes attaché à caractériser la morphologie des ravines et les processus qui les ont générés. Ces nouvelles observations relancent la question de la présence d eau liquide actuellement à la surface de Mars que ce soit à l état pur ou sous forme de mélange (saumure, coulée de débris...). Des simulations expérimentales en chambre froide à la pression atmosphérique de Mars et de la Terre ont été menées. Elles ont notamment permis de quantifier le rôle de la teneur en eau dans la couche active du pergélisol sur le mécanisme de formation des ravines et leur mobilité. Nous avons également décrit l évolution saisonnière de petits réseaux ramifiés qui se sont développés chaque année au printemps durant la période 2007-2012.The recent geological history of Mars remains poorly studied, in comparison to theearly history of Mars (>3,5 Ga). However, the acquisition of new high-resolution imagesallowed to identified the presence of gullies on the surface of recent landforms such asdunes. In this work, we focused on characterizing the morphology of gullies and theirprocess(es) of formation. These new observations revive the issue of the presence of liquid water present on the surface of Mars than either pure or as a mixture (brine, debris flow ...). Experimental simulations in a cold room at Martian and terrestrial atmospheric pressure have been conducted. In particular, they allowed us to quantify the role of water content in the active layer of the permafrost in order to better constrain the mechanism of formation of gullies and their motion. We also described the seasonal evolution of small branched networks developed at spring during the 2007-2012 period.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Ultra-small microorganisms in the polyextreme conditions of the Dallol volcano, Northern Afar, Ethiopia

The Dallol geothermal area in the northern part of the Danakil Depression (up to 124–155 meter below sea level) is deemed one of the most extreme environments on Earth. The area is notable for being part of the Afar Depression, an incipient seafloor-spreading center located at the triple junction, between Nubian, Somali and Arabian plates, and for hosting environments at the very edge of natural physical-chemical extremities. The northern part of the Danakil Depression is dominated by the Assale salt plain (an accumulation of marine evaporite deposits) and hosts the Dallol volcano. Here, the interaction between the evaporitic deposit and the volcanisms have created the unique Dallol hot springs, which are highly acidic (pH ~ 0) and saline (saturation) with maximum temperatures ranging between 90 and 109 °C. Here we report for the first time evidence of life existing with these hot springs using a combination of morphological and molecular analyses. Ultra-small structures are shown to be entombed within mineral deposits, which are identified as members of the Order Nanohaloarchaea. The results from this study suggest the microorganisms can survive, and potential live, within this extreme environment, which has implications for understanding the limits of habitability on Earth and on (early) Mars

Western Sahara salt plains as a potential novel Mars analogue

The identification of novel terrestrial sites that are analogous for other planetary bodies is an active area of research within astrobiology, because of the logistical and financial difficulties in obtaining extraterrestrial samples for analysis. Characterisation of potential analogue sites is undertaken to assess how accurately they represent a specific extraterrestrial environment. Analysing their physicochemical conditions and microbial communities are key components of these studies to understand what metabolisms would be viable in such environments. One such novel analogue environment is the salt plains of Western Sahara. Western Sahara is one of the driest regions on Earth. It is located on the northwest coast of West Africa and is characterised by high UV exposure, low annual precipitation and water activity, subsurface water and high annual temperatures. These features make Western Sahara a potential analogue site for Mars during the Noachian-Hesperian transition period (3.5 – 3.8 Ga), when the atmosphere began to thin and surface water started evaporating (Warner et al., 2010), similar to other terrestrial deserts, such as the Atacama Desert and the McMurdo Dry Valleys. The hypersalinity, aridity and high UV radiation levels of the Western Sahara salt plains would also be appropriate to study whether dissimilatory sulfur metabolisms would be viable in a Noachian-Hesperian Mars analogue environment. Dissimilatory sulfur cycling refers to the use of inorganic sulfur compounds for energy conservation and it has been recognised as a metabolic strategy of interest for putative martian life (Macey et al., 2020). On Earth, evidence from stable sulfur isotope fractionation has suggested this metabolism emerged early in the history of life (~3.5 Ga). During this period, the conditions on Mars were predicted as being more habitable than present-day, with an active magnetic field, thicker atmosphere and liquid water on the surface. In this study, molecular and geochemical techniques were used to give first insights into the potential of the Western Sahara salt plains to serve as an analogue of Mars during the Noachian-Hesperian transition period. The microbiology was investigated through cultivation-independent and culture-dependent analyses of salt crystals, sediment and water samples obtained at three sites near Llaayoune (Fig. 1). The chemical nature of the samples was analysed through ion chromatography (IC) and inductively coupled plasma - optical emission spectrometry (ICP-OES). The geochemical characterisation confirmed the high salinity of the samples and identified that sodium, potassium, magnesium and sulfur were the most enriched elements within all samples. Cultivation-dependent work resulted in the enrichment of a wide range of metabolic strategies from the samples including aerobic heterotrophs, phototrophs and sulfate-reducers. The enrichments from the salt were dominated by strains of Bacillus, whereas sulfate-reducing strains of Clostridium were isolated from the sediment samples. Microscope analysis of phototroph-selective media also indicated that algae and Cyanobacteria were successfully enriched from the samples. 16S rRNA amplicon sequencing results will also be presented to gain further in-depth understanding of the microbial community composition. Additionally, results from quantitative polymerase chain reaction (qPCR) experiment targeting sox and dsr genes will be presented to identify the abundance of genes specific for dissimilatory sulfur metabolisms within the samples. Preliminary data shows that sulfur cycling is occurring in Western Sahara salt plains. Future characterisation of this environment will involve metagenomic analysis of the samples and genome sequencing of the isolates to identify the key metabolisms underpinning the survival and viability of the microbial community. Comparative studies with other Mars analogue environments will then be undertaken to identify metabolisms that may have been thermodynamically viable in ancient martian aqueous environments

The effect of dust lifting process on the electrical properties of the atmosphere

Airborne dust and aerosol particles affect climate by absorbing and scattering thermal and solar radiation and acting as condensation nuclei for the formation of clouds. So, they strongly influence the atmospheric thermal structure, balance and circulation. On Earth and Mars, this 'climate forcing' is one of the most uncertain processes in climate change predictions. Wind-driven blowing of sand and dust is also responsible for shaping planetary surfaces through the formation of sand dunes and ripples, the erosion of rocks, and the creation and transport of soil particles. These processes are not confined to Earth, but occur also on Mars, Venus and Titan. It is clear that the knowledge of the atmospheric dust properties and the mechanisms of dust settling and raising into the atmosphere are important to understand planetary climate and surface evolution. On Mars the physical processes responsible for dust injection into the atmosphere are still poorly understood, but they likely involve saltation as on Earth. Saltation is a process where large sand grains are forced by the wind to move in ballistic trajectories on the soil surface. During these hops they hit dust particles, that are well bound to the soil due to interparticle cohesive forces, thus transferring to them the momentum necessary to be entrained into the atmosphere. Recently, it has been shown that this process is also responsible to generate strong electric fields in the atmosphere up to 100-150 kV/m. This enhanced electric force acts as a feedback in the dust lifting process, lowering the threshold of the wind friction velocity u* necessary to initiate sand saltation. It is an important aspect of dust lifting process that need to be well characterized and modeled. Even if literature reports several measurements of E-fields in dust devils events, very few reports deal with atmospheric electric properties during dust storms or isolated gusts. We present here preliminary results of an intense field test campaign we performed in the West Sahara during the 2013 and 2014 dust storm seasons. We collected a statistical meaningful set of data characterizing relationship between dust lifting and atmospheric E-field that had never been achieved so far. <P /