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Cooperative robotic exploration of a planetary skylight surface and lava cave
No full textInternational audienceExploration of lava caves on the surface of planetary bodies near Earth is of high importance for scientific research and space exploration. The natural shielding that these caves offer against radiation and small meteorites makes them well suited for preserving exobiological signatures and protecting human-made facilities. The use of a robot team arises as the safest and most cost-efficient way to explore extraterrestrial lava caves because they are difficult to access. Although the approach has been demonstrated in similar scenarios on Earth, its adaptation to space conditions needs further research. Here, we define a lava cave exploration mission concept, including four mission phases that are performed by a heterogeneous team of three robots equipped with the required hardware and software. This mission concept was validated in a relevant scenario, a lava cave on Lanzarote island (Spain), where the team of robots was able to build a three-dimensional model of the surrounding area and skylight, introducing a scout rover through rappelling and exploring the inner part of the cave. The results obtained demonstrate the proposed mission concept's feasibility, including three next-generation planetary exploration rovers that were coordinated to obtain meaningful information about the lava cave's external and internal morphology
Substantial increase in wildfire danger conditions under anthropogenic climate change in Southwest France
No full textInternational audienceWildfires are an increasing concern under climate change, which may raise the frequency and intensity of fire-prone conditions. Here we assess summer wildfire danger evolution in Southwestern France under three climate scenarios (Representative Concentration Pathways RCP2.6, RCP4.5 and RCP8.5), using six climate models. Alongside the Fire Weather Index (FWI), widely used by operational services to assess daily fire danger, a complementary index, SM6-T3-VPD3 (soil moisture integrated backward to 6 months, surface air temperature and vapour pressure deficit backward to 3 months), is also used to assess prolonged hot and dry conditions. Results indicate that under the highest emission scenario, the probability of extreme compound hot and dry events increases from 0.04 to 0.49 in August during the twenty-first century. Even under the lowest emission scenario, their likelihood increases from 0.03 to 0.15. Therefore, this study underscores the importance and complementarity of mitigation and adaptation strategies in addressing wildfire dange
Record-breaking 2023 marine heatwaves
No full textInternational audienceThe year 2023 witnessed an extraordinary surge in marine heatwaves (MHWs) across Earth’s oceans, setting new records in duration, extent, and intensity, with MHW activity totaling 53.6 billion °C days square kilometer—more than three standard deviations above the historical norm since 1982. Notable events include the North Atlantic MHW (276-year return period) and the Southwest Pacific (141 years). Using ECCO2 (Estimating the Circulation and Climate of the Ocean-Phase II) high-resolution daily data, we conducted a mixed-layer heat budget analysis and identified region-specific drivers: enhanced shortwave flux and a shallower mixed layer in the North Atlantic and North Pacific, reduced cloud cover and increased advection in the Southwest Pacific, and oceanic advections in the Tropical Eastern Pacific. The 2023 MHWs highlight the intensifying impacts of a warm climate and the challenges in understanding extreme events
Soulèvement quaternaire et sismicité en contexte continental stable : mêmes causes, mêmes effets ?
No full textNational audienceSuivant la théorie de la tectonique des plaques, les régions continentales stables telles que le nord-ouest de l’Europene devraient pas se déformer. Elles sont pourtant affectées par des déformations tectoniques récentes comme le montrent la sismicité (p.ex., séisme de La Laigne, 2023, MW=4.9) ou la présence de marqueurs marins quaternaires émergés (p.ex., terrasses soulevées des côtes atlantique). Les causes proposées pour expliquer ces déformations sont nombreuses : forces tectoniques lointaines, cycles glaciaires, … Dans les années 80, le couple érosion / sédimentation a été considéré comme une cause possible de la sismicité en contexte continental stable, mais ce mécanisme a été peu étudié par la suite. Son impact sur la déformation intraplaque n’a pas non plus fait l’objet d’études détaillées, bien que le couplage érosion-déformation soit un sujet majeur dans les contextes de tectonique active.Depuis une dizaine d’années des scientifiques s’intéressent à l’effet potentiel de l’érosion sur la déformation récente et la sismicité en France
Rénag infiltre le réseau collaboratif Centipède-RTK pour augmenter la couverture GNSS du territoire
No full textNational audienceNé en 2019, le réseau Centipède-RTK est un réseau collaboratif de stations GNSS fixes, en majorité à bas coût (quelques centaines d'euros) servant de base pour du positionnement centimétrique temps réel (RTK). Il bénéficie de l'implication de ses contributeurs, mettant à disposition de tous, gratuitement et librement, les corrections générées par ces bases. Initialement limité à la France métropolitaine, le réseau s'est récemment développé en Outre-Mer et à l'étranger, avec près d'un millier de bases actives aujourd'hui. Depuis 2022, le Réseau national GNSS permanent d'Epos-France rediffuse les corrections temps-réel issues de la moitié des stations permanentes de son réseau via Centipède, ce qui a conduit à un bond d’utilisation des données issues des stations académiques. Parallèlement, le centre de données Rénag utilise le flux issu de l’ensemble des stations Centipède-RTK.Bien moins onéreux que les réseaux conventionnels en termes d’équipement et d’abonnement, le réseau Centipede-RTK permet d’envisager une nouvelle approche pour l’observation de notre environnement et de la Terre solide. Un déploiement participatif de ces bases permettrait une meilleure couverture des territoires et aiderait à la démocratisation du positionnement GNSS temps réel
Geochronology of the potential first eruptive phases of the Monte Vulture stratovolcano (Basilicata, Italy).
No full textInternational audienceThe Monte Vulture stratovolcano is located in the central part of the peninsula, 110 km east of Naples. This volcanic complex is peculiar among Italian volcanoes found at the intersection of faults, at the eastern flank of the Apennine chain, where the Apennine thrust front overlies the Apulian carbonate platform (Boenzi et al. 1987). The geodynamic as well as eruptive history and geochemistry evolution of the complex still remain poorly understood. The eruptive products are silica undersaturated including carbonatite, which is uncommon in Italy. Up to now only a handful of studies have been published on the dating of its products and many questions remain unanswered in particular concerning the early activity of the volcano during the early-middle Pleistocene. In the frame of this contribution, we will present the first results of a new 40Ar/39Ar dating effort focused on the early activity of the Monte Vulture Super-Syntem. Our new data reveal a more complex than expected chronostratigraphy of the oldest phase of activity named in literature the Foggianello units (Villa and Buettner, 2009) . Our new high precision 40Ar/39Ar on single-crystal dating demonstrate that the beginnings of the volcanic activity is marked at least by two major ignimbritic eruptions, respectively dated at 784.4±1.0 ka and 777.2±2.4 ka. After a period of about 40 ka of quiescence a new period of explosive activity occurred at around 740±2.0 ka (Fara d’Olivo sub-unit), shortly followed by an effusive phase dated at 732.0±1.0 ka- (Spinoritola sub-unit). Finally, the youngest explosive activity of the Foggianello Unit corresponds to pumice fall deposits dated between 708.9±1.8 ka and 700.2±1.3 ka (Campanile sub-unit)
First images of Antares photosphere from spectropolarimetry
No full textInternational audienceAntares is the closest red supergiant (RSG) to Earth. The discovery of linear polarization in the atomic lines of the star opens the path to produce direct images of the photosphere, hence probing the dynamics at the surface. We analyze this linear polarization signals following the same scheme as has been previously done for the RSG Betelgeuse, and find that they are comparable in all its details. This allows us to use the same models for the analysis of these polarization signals in both stars. We found that as in Betelgeuse, the linear polarization signal of Antares is due to the depolarization of the continuum combined with brightness inhomogeneities. This allows us to produce images of the photosphere of star. We show that in Antares, convective cells can last several months and occupy roughly 30% of the stellar radius for the largest ones
Modelling the influence of environmental factors on the acoustic presence of blue whale populations in the southern Indian Ocean
No full textInternational audienceBlue whales in the Indian Ocean have been severely depleted by previous extensive commercial whaling. A good understanding of their spatio-temporal distribution is crucial for conservation. The songs of three blue whale acoustic populations - Antarctic blue whales (Balaenoptera musculus intermedia, ANT BW) and pygmy blue whales (B. musculus brevicauda) from the Southeast (SEIO PBW) and Southwest Indian Ocean (SWIO PBW) - were analyzed using 13 years of passive acoustic recordings from 10 sites in the southwest Indian Ocean. Although blue whale vocalizations comprise both songs and non-song calls (e.g., D-calls), the present study concentrates on the examination of songs. Generalized additive models (GAMs) were used to relate acoustic presence, measured by the number of positive minutes per day (averaged weekly), to environmental drivers such as sea surface temperature (SST), chlorophyll-a concentrations, and sea ice extent. These models allowed predictions of blue whale acoustic presence across the region. Empirical orthogonal functions (EOFs) were applied for dimensionality reduction to identify key habitats, including the Kerguelen Plateau and Madagascar Basin, which may serve as important feeding and resting zones based on acoustic presence and environmental data. Antarctic blue whales were predominantly detected in austral winter and spring, associated with lower SST and higher chlorophyll-a. In contrast, SEIO and SWIO pygmy blue whales were more frequent in summer and autumn, with some overlap suggesting ecological interactions. These findings lay the groundwork for targeted conservation efforts to protect critical blue whale habitats in a rapidly changing ocean
A fast radio burst from the first 3 billion years of the Universe
No full textInternational audienceFast radio bursts (FRBs) are enigmatic millisecond-duration signals which encode otherwise unattainable information on the plasma which permeates our Universe, providing insights into magnetic fields and gas distributions. Here we report the discovery of FRB 20240304B originating at redshift 2.148 +/- 0.001 corresponding to just 3 billion years after the Big Bang. FRB 2024030 was detected with the MeerKAT radio telescope and localized to a low-mass, clumpy, star forming galaxy using the James Webb Space Telescope. This discovery doubles the redshift reach of localized FRBs and probes ionized baryons across ~80% of cosmic history. Its sightline, intersecting the Virgo Cluster and a foreground group, reveals magnetic field complexity over many gigaparsec scales. Our observations establish FRB activity during the peak of cosmic star formation and demonstrate that FRBs can probe galaxy formation during the most active era in cosmic time
Short-term durability and environmental integration of dredged sediment-based concrete in seawater
No full textInternational audienceThe increasing demand for natural sand in construction and tightening environmental regulations have prompted interest in alternative materials for concrete production. This study explores the use of untreated dredged marine sediments as a 30 % partial sand replacement in marine concrete. Two mixtures, a reference concrete (RC) and a marine sediment concrete (MSC), were evaluated before and after 70 days of seawater immersion. The experimental program evaluated compressive strength, durability (porosity, permeability, and chloride ingress), biocolonization potential, and environmental and economic viability through Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA). The results indicate that MSC achieves compressive strength comparable to RC (58.6 MPa vs. 59.7 MPa at 28 days) with lower gas permeability (64.3 × 10⁻¹⁸ m² for MSC vs. 88.9 × 10⁻¹⁸ m² for RC), suggesting a denser microstructure. Although MSC showed a higher initial chloride content (0.11 % vs. 0.05 %), this is attributed to the chloride-bearing sediment. Notably, MSC demonstrated faster biocolonization, indicating stronger ecological integration in marine environments. From a sustainability perspective, MSC reduces environmental impacts associated with sand extraction, promotes the reuse of dredged sediment, and lowers production costs. These findings suggest that MSC could be a promising material for eco-designed coastal infrastructure such as reefs, breakwaters, and offshore foundations. However, further research is needed to evaluate long-term performance, optimize mix design, and validate large-scale applications for sustainable marine constructio