Université Nantes Angers Le Mans

About: Université Nantes Angers Le Mans is a education organization based out in Nantes, France. It is known for research contribution in the topics: Geology & Population. The organization has 434 authors who have published 249 publications receiving 7208 citations. The organization is also known as: PRES Universite Nantes Angers Le Mans.

Degradation processes on ice-cored moraines on Svalbard: a terrestrial analog for Mars

Abstract: <p>The mid-latitudes of Mars host a large amount of buried ice deposits [1], which bear a record on the very Late Amazonian climate evolution (~10<sup>7</sup> to 10<sup>8</sup> yr.) [2] and are a possible resource for future exploration [3]. The reconstruction of the history of these ice reservoirs and the characterization of their current state is critical to enable putting constraints on the interplay between climate change, volatile migration and landform evolution. Examination of terrestrial analogs can help to identify similarities and – equally important – differences between the response of buried ice on Mars and Earth to changing environmental parameters. Here we report on our long-term investigations of an ice-cored moraine on Svalbard, a proxy for mid-latitude debris-covered glacier on Mars [4].</p> <p>Our study area is an ice-cored lateral moraine of Kongsvegen glacier on the southern shore of Kongsforden in NW Spitsbergen (Svalbard). This site is subject to rapid degradation by melting and redistribution of surficial sediment, e.g., by thaw slumps and debris flows [5]. We couple multi-year fieldwork with repeat remote-sensing observations. Fieldwork includes DGPS-supported monitoring of surface changes by several imaging methods comparisons to environmental data (e.g., [6]). In 2008, a flight campaign with HRSC-AX (an airborne version of DLR’s High Resolution Stereo Camera on Mars Express) provided orthoimages (20 cm/px) and a Digital Elevation Model (DEM; 50 cm ground sampling distance, GSD) [7]. In 2020 a repeat campaign with DLR’s MACS (Modular Airborne Camera System) achieved ground pixel sizes between 5 cm and 10 cm for RGB images, and 10 cm to 15 cm for NIR images. The associated DEM has the same resolution [8]. MACS also acquires TIR data,which we use to identify regions with anomalous temperatures (e.g., exposed ice). We use for detailed mapping of ice-rich viscous flow features on Mars [9]. This study focuses on the Nereidum Montes area in the northern part of the Argyre basin. Image analysis, mapping of landforms and documentation of results were carried out using the QGIS software.</p> <p>A difference DEM was generated to determine the elevation differences (i.e. volume changes) on the ice-cored moraine between 2008 and 2020. Hillshade layers were created for each dataset to facilitate quick visual identification of morphological changes. Slump scars were digitized in 2008 and 2020 on orthoimages and hillshade views, and prominent slumps of 2020 (most recent, visible and best preserved) have been geomorphologically mapped with a focus on buried dead ice, collapsed sediment, and the relative activity of mud flows. Image analysis and mapping of Martian landforms is currently ongoing.</p> <p><img src="" alt="" /></p> <p>There are 4 areas of major activity within the ice-cored moraine (Fig.1.a) highlighted by the four red boxes b, c, d and e, with more than 10m of elevation losses. There are many areas showing a neutral balance in terms of topographic evolution (white pixels). Hillshade layers from 2008 (Fig.1.f) and 2020 (Fig.1.g) correspond to the area of box d and show that significant changes have occurred in 12 years, indicating a massive degradation of ice-cored moraine in the last decade. This also demonstrates that the general trend is towards a heterogenous loss of material. The slump scars appear to be concentrated in the same areas described above. In 2008, 85 scars were counted against 157 scars in 2020, i.e. almost twice as many. It also appears that the 2020 scars are following the outlines of high activity areas while the 2008 scars are within these areas.</p> <p><img src="" alt="" /></p> <p>Regarding the detailed mapping of slumps, the area corresponding to the buried dead ice, mapped with the TIR channel, can vary in shape and size depending on the shape of headscarp and the other units, i.e. the collapsed sediments and the mudflows (Fig.2.b,d). The collapsed sediments are washed away by the mudflows. The mudflow seems more active near the previously exposed dead ice. Therefore, the degradation of ice-cored moraines takes place mainly through the melting of the ice, which leads to mass wasting and rapid degradation. As Mars does not have the same climatic conditions, it is interesting to see whether the same landforms can be found on it at a very local scale.</p> <p><img src="" alt="" /></p> <p>The Mars case study displays gullies, arcuate ridges with small gullies superposed on their slopes, flow features and also possible sublimation features such as pitted terrain, broad pits, and lineated patterned ground (Fig.3.b). The area is also filled with washboard terrain which is only found at steep slopes, above the lobate flow feature. It is marked by a close alternation of closely-spaced scarps which are parallel to the contour lines (possible evidence for paraglacial sacking [10]). Tension cracks are also found at the ridges and parallel to gully headscarps indicating recent activity. These tension cracks may be similar to headscarp retreats on backwasting processes on ice-cored moraines (Fig.3.d). The ice-cored ridge or arcuate ridge may still undergo degradation. The first results show that the degradation processes are rather related to potential ice sublimation and that signs of melting ice, if they exist on Mars, are not strongly encountered, which is consistent with the studies on very Late Amazonian climate evolution.</p> <p> </p> <p><strong>References</strong></p> <p>[1] Levy, J. S. et al. (2014), <em>J. Geophys. Res. Planets</em>, 119, 2188– 2196. [2] Bramson, A. et al. (2021), <em>Bull. Amer. Astron. Soc.</em>, 53(4), e-id. 115. [3] Putzig, N. et al. (2022) <em>LPSC 53</em>, #2443. [4] Petersen,E. et al. (2017) <em>LPSC 48</em>, #2966. [5] Bennett, M. et al. (2000) <em>Geomorphology</em>, 35, 21-40. [6] Boike, J. et al. (2018), <em>Earth Syst. Sci. Data</em>, 10, 355–390. [7] Hauber, E. et al. (2011), <em>Geological Society of America</em>, 483, 177–201. [8] DLR - Institut für Optische - Sensorsysteme, (2020). [9] Souness, C. and Hubbard, B. (2012), <em>Progress in Phys. Geog</em>. 36(2), 238-261. [10] Jawin, E. R. et al. (2018), <em>Icarus</em>, 309, 187-206.</p>

Efficient waterlines cleaning protocols in post-weaning rooms: a new way to reduce antibiotic consumption?

Abstract: In this study, we have chosen a sensitive period, the weaning period, to evaluate in pig farms the effects of different mechanical and chemical waterlines cleaning protocols similar to those used in poultry farms. The experiment has been set up during the down period in two post-weaning rooms with two different protocols. They combined the mechanical action of draining, one detergent (either alkaline or enzymatic), another draining state, and finally one acid used at an antibacterial concentration. To follow the bacteriological quality of water during protocols, we have counted the total flora at 22°C and 37°C in water. Before and after the experiment, cotton swabs were applied into the pipes to evaluate the biofilm. Bacterial concentration in water increased along the pipelines: total flora was higher at watering place than at the entry of the building. Both protocols combining mechanical and chemical procedures reduced total flora, improved water quality and cleanliness of pipes. Our results show that waterlines cleaning protocols used in poultry farms can be transferred in post-weaning rooms. By reducing water’s total flora and the formation of biofilms, they could be part of the health prevention measures for troubles which are linked to a poor water quality.

The morphology of glacier-associated layered deposits on Mars

Abstract: <p>Mars is thought to have been a hyperarid desert for at least the last one billion years of its history and so water is locked up in the two polar ice caps, ground ice and an extensive band of debris covered glaciers found in the mid-latitudes. Layers expressed by the polar caps are thought to record the most recent climate cycles of Mars – up to a few tens of Ma. The debris covered glaciers are thought to date to hundreds of millions of years in age and potentially record a deeper climate record. Here, we report on the widespread occurrence of layered outcrops intimately associated with glaciated terrains in Deuteronilus Mensae and the Eastern Hellas region – two areas renowned for their extremely extensive and well-preserved debris covered glaciers. We explore the relationship between these layered outcrops and the debris covered glaciers by exploiting images and elevation data from the High Resolution Science Imaging Experiment (HiRISE) at 25 cm/pixel, Context camera (CTX) at 6 m/pixel and Colour and Stereo Imaging System (CaSSIS) at 4.5 m/pixel. Because these outcrops have similar morphology in both the northern and the southern hemisphere they point to a globally relevant process. Our aim is to test the hypothesis that these deposits represent remnant glacial deposits, which could give information of Mars climate beyond that obtainable by studying the polar caps.</p>

Mean-Field Backward-Forward SDE with Jumps and Storage problem in Smart Grids

Abstract: In this paper, we prove the existence and uniqueness of the solution of a coupled Mean-Field Forward-Backward SDE system with Jumps. Then, we give an application in the field of storage problem in smart grids, studied in [4] in the case where the production of electricity is not predictable due, for example, to the changes in meteorological forecasts.

Experimental CO2-driven granular flows under Martian atmospheric conditions 

Abstract: <p>Martian gullies are alcove-channel-fan systems that have been hypothesized to be formed by the action of liquid water and brines, the effects of sublimating CO<sub>2</sub> ice, or a combination of these processes. Recent activity and new flow deposits in these systems have shifted the leading hypothesis from water-based flows to CO<sub>2</sub>-driven flows, as it is hard to reconcile present activity with the low availability of atmospheric water under present Martian conditions. Direct observations of flows driven by metastable CO<sub>2</sub> on the surface of Mars are however nonexistent, and our knowledge of CO<sub>2</sub>-driven flows under Martian conditions remains limited. For the first time, we produced CO<sub>2</sub>-driven granular flows in a small-scale flume under Martian atmospheric conditions in the Mars Chamber at the Open University (UK). The experiments were used to quantify the slope threshold and CO<sub>2 </sub>fraction limits for fluidization. With these experiments, we show that the sublimation of CO<sub>2</sub> can fluidize sediment and sustain granular flows under Martian atmospheric conditions, and even transport sediment with grain sizes equal to half the flow depth. The morphology of the deposits is lobate and depends highly on the CO<sub>2</sub>-sediment ratio, sediment grain size, and flume angle. The gas-driven granular flows are sustained under low (<20º) flume angles and small volumes of CO<sub>2</sub> (around 5% of the entire flow). Pilot experiments with sediment flowing over a layer of CO2 suggest that even smaller percentages of CO<sub>2</sub> ice are needed for fluidization. The data further shows that the flow dynamics are complex with surging behavior and complex pressure distribution in the flow, through time and space.</p>