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While the planet Mars is today a dry and cold wasteland dominated by aeolian processes, a large diversity of geomorphologies observed from orbit suggests that aqueous processes took place there. Most of these morphologies implies the presence of developed fluvial networks at the surface of the planet about 3.5 Ga ago. However, the precise conditions behind the formation of these valleys and the climate they evolved in are still being debated, as some of them could be linked to episodic events set in a cold climate. For more than a decade now, the rovers Curiosity and Perseverance helped to shed light on these questions thanks to a detailed in situ analysis of fluvial and lacustrine deposits.The Curiosity rover landed in August 2012 in Gale crater, and since then observed more than 500 meters of a sedimentary succession including lacustrine mudstones and fluvial sandstones and conglomerates. Locally, clay minerals have been observed to make as much as 30 % of the bulk composition, with a substantial degree of chemical alteration, highlighting the role of water in the rock formation processes. The succession, and locally alternation and interfingering of fluvial and lacustrine facies suggest rapid and marked evolutions of the depositional setting, in relation with changing environmental and climatic parameters. However, no (peri-)glacial facies has been found to date, even if glacial processes could have affected those terrains later in their history.In February 2021, the Perseverance rover landed in Jezero crater, which was chosen after the observation from orbit of both a large-scale fan-shaped edifice and the presence of clay and carbonate minerals. Remote observations of the fan and its remnants allowed to identify characteristic sigmoid structures of a deltaic architecture (bottomsets-foresets-topsets), confirming the presence of a perennial lake at the time of the deposition. Observations from both rovers illustrate that liquid water was not ephemeral at the surface of Mars. Nevertheless, the duration and extent of these processes are still yet to be exactly constrained. The detailed analysis of the delta by Perseverance and the returned samples on Earth (by a future mission early in the 2030’s) would hopefully allow to constrain these chronological questions, as well as to allow to look for potential biosignatures. International audience

Une importante occupation du secteur au cours des VIe-IVe siècles avant J.-C. a été mise en évidence au sein d’un diagnostic archéologique au lieu-dit La Novialle, au pied de Gergovie, sur la rive sud de Bassin de Sarliève. Ceux-ci sont tout à fait remarquables de par leur nature, la qualité de conservation ainsi que par le mobilier récolté (nouvelle forme céramique, indices anciens de métallurgie du fer, possible proto urbanisation…). Ils s’insèrent dans une séquence sédimentaire hydromorphe complexe, typique de la plaine de Limagne. Le potentiel d’étude paléoenvironnementale de ce site est très important. En effet, l’emprise s’implante sur les paléo-berges du Lac de Sarliève. Cette zone lacustre a subi des variations importantes avec une alternance entre des périodes de basses eaux (palustre) et des périodes de hautes eaux (lacustre) répondant à des commandes climatiques mais aussi anthropiques. La séquence caractéristique de ces milieux semi-humides dans lesquels se sont installés les Hommes, de la Protohistoire jusqu’à la fin de l’Antiquité, est conservée sous un important recouvrement sédimentaire allant jusqu’à plus de 3,50 m d’épaisseur. Cette puissance stratigraphique est issue de la monté de niveau du lac avant son assèchement au cours des périodes moderne et contemporaine. Pour cette opération, des carottages jusqu’à 8 m de profondeur ont été réalisés avec pour but premier, d’aider à la compréhension de l’étendue spatiale du site rattaché à l’occupation protohistorique. En effet, la nappe phréatique est de nos jours plus haute qu’au cours de VIe-IVe siècles, et l’ennoiement des tranchées a limité les observations. Cependant, les niveaux dans lesquels s’insèrent les vestiges ont été parfaitement identifiés et leur présence dans les carottes (dans lesquelles se trouvait du mobilier) a permis d’estimer la surface d’occupation à minimum 7 ha au sein de l’emprise prescrite. Ces carottes vont également nous permettre d’étudier la totalité de la séquence sédimentaire et ainsi de restituer l’évolution de la rive méridionale du paléolac de Sarliève en particulier durant la Protohistoire et d’appréhender comment s’insèrent les niveaux d’occupation par rapport aux phases de hautes et basses eaux du lac mais aussi pour la période médiévale où le lac de Sarliève a connu sa période de transgression maximale. Cette opération constitue une fenêtre unique d’observation pour la micromorphologie mais également pour la carpologie, la palynologie et l’anthracologie. En effet, les prélèvements réalisés ont livré des milliers de carporestes dont l’étude à venir participera à la reconstitution des paléoenvironnements. A major occupation of the area during the 6th-4th centuries BC was revealed during an archaeological survey at La Novialle, at the foot of Gergovie, on the south bank of the Sarliève Basin.The finds are quite remarkable in terms of their nature, the quality of their conservation and the material collected (new ceramic forms, ancient evidence of iron metallurgy, possible proto-urbanisation, etc.). They are part of a complex hydromorphic sedimentary sequence typical of the Limagne plain. This site offers considerable potential for palaeoenvironmental studies. In fact, the site is located on the paleoberges of Lac de Sarliève. This lacustrine area has undergone major variations, with periods of low water (palustrine) alternating with periods of high water (lacustrine) in response to both climatic and anthropogenic controls. The sequence characteristic of these semi-humid environments in which humans settled, from Protohistory to the end of Antiquity, is preserved under a significant sedimentary cover, up to more than 3.50 m thick. This stratigraphic power is the result of the lake’s rising level before it dried up during the modern and contemporary periods. For this operation, core samples were taken to a depth of 8 m, with the primary aim of helping to understand the spatial extent of the site associated with protohistoric occupation. The water table is higher today than it was in the 6th-4th centuries, and the flooding of the trenches has limited observations. However, the levels into which the remains are inserted have been perfectly identified, and their presence in the cores (in which furniture was found) has enabled us to estimate the surface area of occupation at a minimum of 7 ha within the prescribed area. These cores will also allow us to study the entire sedimentary sequence, enabling us to reconstruct the evolution of the southern shore of the Sarliève palaeolake, particularly during Protohistory, and to understand how the levels of occupation relate to the phases of high and low water in the lake, as well as to the medieval period when the Sarliève lake experienced its maximum transgression. This operation provides a unique window of opportunity to observe not only micromorphology, but also carpology, palynology and anthracology. The samples taken yielded thousands of carporestes, the future study of which will contribute to the reconstruction of paleoenvironments. International audience

The stratigraphy preserved within Aeolis Mons in Gale crater (Mars) shows a major transition from a 100s m thick package of phyllosilicate-bearing stratigraphic units, which are composed of mudstone (with subordinate sandstones) that record deposition in lacustrine, fluvial, and aeolian settings into a sulphate-bearing unit that is hundreds of meters thick (LSu). This transition from clay minerals to sulphates is proposed to record a planet-wide change in climate from warm and wet to cold and arid. The lower stratigraphic units of the LSu contains cross-bedded then planar stratified facies that are interpreted to record a purely dry aeolian dune and sand sheets environments. However, we observe metre-scale-thick interstratified lenses within these aeolian strata that record interactions of fluvial and/or lacustrine systems in a dominantly aeolian setting. One of such lenses - the Prow - structure comprises a lower section of cross-bedding likely formed by fluvial currents, overlain by a section dominated by cm-scale ripples with convex upper surfaces, suggestive of a formation under oscillatory wind-generated waves in ponds or small ponds within an interdune setting. Higher in the succession, Curiosity investigated a metre-thick dark-toned, resistant unit set within aeolian strata - the “Marker Band” – which can be traced for tens of kilometers around Aeolis Mons. Here we observe the presence of well-defined, fully preserved symmetrical ripples. Our observations imply that arid desert conditions were episodically interrupted by establishment of lake systems either by rising groundwater or collecting upon mineralized surfaces of variable spatial extent that co-existed within the aeolian landscape. International audience

The Perseverance rover is exploring a sedimentary deposit within the Late Noachian-aged (4.0-4.8 Ga) Jezero Crater interpreted to be the remnants of a delta. From April 2022 through February 2023, Perseverance investigated the basal 25 m of sediments exposed in the fan’s eastern scarp. Rover instruments collected a suite of imaging, geochemical, mineralogical, and ground-penetrating radar data.Perseverance made detailed observations through two sections of the lower fan ~600 m apart. Similar facies and stratigraphic trends are present in both sections. Each section contains two coarsening-up successions. While some finer-grained units are laterally continuous between the two sections, the coarser-grained bodies that cap each section are laterally discontinuous and do not extend between sections.Both sequences are 10 - 15 m thick. Their lower strata are dominated by sulfate-cemented, planar laminated, very fine- to medium-grained sandstone and siltstone with rare low-angle truncations. Soft-sediment deformation occurs in the form of decimeter-scale lateral folds. Laminae are normally graded. These sequences are capped by meter-scale thick sheets of coarse-grained sandstone, pebbly sandstones, and conglomerates that are variably low-angle cross-bedded, trough cross-bedded, and planar-stratified. Plane beds are massive or normally graded.Two hypotheses for the depositional environment have emerged for this succession: a sub-aerial setting with extensive “overbank” facies and shallow braided channels and a proximal pro-deltaic setting with deposition driven by hyperpycnal flows. These hypotheses will be tested against observations made by Perseverance as it traverses the “Fan Top” and by more comprehensive studies of the “Delta Front” data. International audience

The ERC-funded ModERN project is investigating 18th-century authorship practices using data-rich computational techniques to examine the digital archive of the Enlightenment period. This paper explores the use of new large-scale text reuse detection and network analysis to identify intertextual 'influencers' in a large heterogeneous collection of 18th-century French texts.

Sand dunes are an essential component of coastal landscapes. The understanding of their long-term mobility is crucial to design appropriate management methods, especially in a context of global sea level rise and associated coastal erosion. Along the coasts of Western Europe, the mor-phological evolution of coastal dunes has been characterized by several periods of stability and remobilization of aeolian sands during the last millennia of the Holocene. Well-constrained chro-nologies of dune mobility periods have been reconstructed in Ireland, UK, Portugal based on radi-ocarbon dating of palaeosols interbedded in aeolian sand deposits. In western France, the absence of palaeosols has limited such approaches. Recently, archaeological and historical remains have been used but such an approach has many methodological limitations.The objective of this study is to provide robust chronological evidence for the Holocene mo-bility of coastal dunes in western France. It focuses on the chrono-stratigraphic analysis of the sandy cover of Béniguet Island, located at the western tip of the Brittany peninsula (W France). The geometry of the coastal sedimentary deposits was reconstructed about 40 vibro-cores taken from aeolian sands covering the central part of Béniguet Island over a thickness between 2 and 4 m, near an archaeological site currently being excavated. Four archaeological levels were identified and dated to the Bell Beaker, Early Bronze Age, High Middle Ages and Late Middle Ages periods.The chronology of the Holocene deposits is based on a dozen radiocarbon dates obtained on the anthropogenic levels and on 8 Optically Stimulated Luminescence (OSL3) ages obtained on the aeolian sand layers. Equivalent doses were mesured from multi-grain aliquots and the dose rate was obtained from high resolution gamma spectrometry. The chronology of the sequence was modeled by combining OSL ages and radiocarbon dates in a Bayesian framework using the R package BayLum4. The anthropogenic levels are overlain by a series of aeolian sand layers dated by OSL to ca. 4000 BP, 2700 BP, 1000 BP. These results are consistent with the regional chronology established for western France and clarify the timing of coastal sand-drift events. International audience

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The Perseverance rover landed on the floor of Jezero crater on 18 February 2021. The landing site is located ~2.2 km from the SE-facing erosional scarp of the western fan deposits. Images obtained using the Mastcam-Z camera and the Remote Micro-Imager (RMI) of the SuperCam instrument provided the first Mars ground-based observations of this western fan. These images show a deltaic architecture consistent with a paleolake, but at a level ~100 m lower than expected, suggestive of a closed system [1]. Here we report new observations made during the “rapid traverse” in March-April 2022, a period during which the rover traveled fast along the eastern and southeastern side of Jezero fan taking only a few remote sensing observations on the way. International audience

The Perseverance rover landed in Jezero crater on February 18, 2021, with the mission goals to explore the geology, astrobiological potential, and modern environment of the crater floor and delta, and to collect and cache well-documented samples for Mars Sample Return. After completion of the “Crater Floor” science campaign [1], the rover conducted a rapid traverse (sols 379-414) to the Three Forks region of the crater floor adjacent to the delta front. From here, Perseverance’s second “Delta Front” science campaign (DFC) began on Sol 415, April 20, 2022. The DFC has explored two lobes of the delta front, the neighboring crater floor, and their contact zone, focusing on the lowest geologic exposures composing the Jezero delta (largely mapped within the delta “thin layered unit” [2]). As of January 1, 2023, Perseverance has covered 14325 km of traverse distance and collected 15 rock sample cores, 2 regolith samples, 1 atmospheric sample, and 3 witness tubes, employing a sample pair strategy where each unique sample is paired with a companion sample core from the same location, to enable the construction of two different caches [3]. After sample depot construction at Three Forks, the DFC will conclude upon re-ascent of the delta front, and the next “Delta Top” science campaign will start. International audience

The “Marker Band” (previously called the Marker Bed and Marker Horizon [1-4]) in Gale crater is a distinctive indurated and dark-toned unit observed in the strata of Mount Sharp. From orbital data, the Marker Band (MB) was mapped across much of the western and southern edges of Mount Sharp, spanning over 80 km in distance and 1.6 km in elevation [4]. CRISM spectra of the MB show no hydration signatures and broad absorptions around~1 and 2 μm interpreted to be from high-Ca pyroxene [4]. Favored origins for the MB based upon orbital observations included a more indurated sulfate, a sandstone, and a volcanic ash deposit. The Curiosity rover recently reached the MB and is now collecting critical in situ measurements to test these postulated and other origins and make new discoveries at the finer mm- to cm-scale that could not be assessed from orbital data. Here we provide a summary of several of the most crucial MB observations made by the rover thus far from sols 3640-3645 and 3668-present. International audience