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International audience; In this paper, we explore the advances made in France in astronomical optics. They were quite important in the seventeenth century thanks to Mersenne, Auzout and Picard. Progress in the eighteenth century was less remarkable and many instruments had to be imported from England, but in the following century the developments were again significant thanks in particular to Arago, Foucault, Fizeau, Loewy and the Henry brothers, working with very competent instrument builders. The French school of optics flourished at the end of the nineteenth century and during the twentieth century, thanks to Fabry, his collaborators and successors, as illustrated by Perot, Chrétien, Lyot, Danjon, Paul, Couder, Courtès, Connes, Labeyrie, Baranne and Lemaitre, among others. However, from time to time there was a trend to build instruments that were too original and with little or no future, at the expense of more conventional but better-adapted instruments.

International audience; The French Central Seismological Bureau (BCSF) is celebrating its centenary this year. However, from the macroseismic studies point of view, which is the main activity of BCSF, it would be more accurate to celebrate its 92nd anniversary of activity. This is because between 1978 and 1986, macroseismic studies were assigned to the Geological and Mining Research Bureau (BRGM) owing to an obvious failure of BCSF to fulfill its mission. In this article, I aim to bring a new insight on this unfortunate, tragic episode by following two main actors of BCSF history: Edmond and Jean-Pierre Rothé, father and son. Through them I will relate the story of French macroseismic studies and, more broadly, French seismicity. In order to do so, I will focus on how they built themselves a full system of monitoring and processing earthquake data, and also on how together they owned all the macroseismic data in France for almost 60 years. I will explore how their dominance brought about the failure of BCSF after the collapse of the legitimacy of Rothé’s expertise at a time when earthquake issues were intertwined in nuclear industry stakes. This brings to light not only the history of French seismicity but also the vulnerability of seismic hazard assessment practices.

International audience; 3200 Phaethon is one of the largest potentially hazardous asteroids. It is also the first asteroid to be discovered in spacecraft images, the parent body of the Geminid meteor stream, and the target of JAXA's upcoming DESTINY+ mission. We have developed a physical model of Phaethon's shape and rotation state, using radar data from Arecibo and Goldstone in 2007 and 2017, stellar occultations from 2019 through 2021, and lightcurves from many apparitions (from 1989 through 2021). Phaethon has a volume-equivalent diameter of about 5.3 kilometers. It is approximately spheroidal with an equatorial ridge, resembling the shapes of 101955 Bennu and 162173 Ryugu. The earliest available lightcurve of Phaethon is from 1989 October 9 (published in Wisniewski et al. 1997). Hanuš et al. (2016) noticed that their shape model's rotation phase differed from that 1989 observation by about 20 minutes. They noted that this may be from Phaethon's rotation period changing due to activity, but they could not say whether this was real or just a timing error in that one lightcurve, since the next lightcurves are from 1994. A model with a constant rotation period provided a good fit to all of the data from 1994 through 2020. However, this model could not adequately fit the lightcurves that were acquired from four different observatories in 2021. There was a difference of about 15 minutes between the predicted and observed rotation phases — clearly greater than what the observations' uncertainties could permit. We initially considered that Phaethon's rotation period may have changed before the 2021 observations, perhaps due to activity when it was near perihelion in December 2020. However, we found that a constant rotational acceleration provides a good fit to all of the data from 1989 through 2021, clearly accounting for the discrepancies seen in 1989 and 2021 while also slightly improving the model's agreement with the data during other apparitions. We find that Phaethon's sidereal rotation period in December 2017 was 3.603944 hours. Its spin rate is increasing at a rate of 2.1×10-6 deg/day2, which corresponds to its rotation period decreasing by about 4 milliseconds per year.

Le projet Relev s’appuie sur une approche interdisciplinaire en intégrant des compétences en risques naturels (géographie, génie civil, géologie), aménagement du territoire (urbanisme, architecture, génie urbain) et sciences humaines (psychologie, sociologie, histoire), pour permettre d’améliorer la gestion de la reconstruction des territoires et des populations à la suite de catastrophes naturelles.Le projet se concentre sur le relèvement en cours des îles de Saint-Martin et Saint-Barthélemy, à la suite des ouragans Irma et Maria en septembre 2017. L’approche s’est articulée autour de deux temporalités d’étude pour mieux comprendre l’évolution des stratégies de développement de ces territoires exposés aux catastrophes naturelles : d’une part, une analyse historique des stratégies d’aménagement ante-Irma (de 1947 à 2017), d’autre part un retour d’expérience interdisciplinaire post-Irma (2017-2022) pour suivre la reconstruction de ces territoires. Ce retour d’expérience s’est focalisé plus particulièrement sur :• La reconstruction physique des infrastructures endommagées (bâtiments, infrastructures et réseaux techniques),• Le redémarrage des activités du tourisme et des PME en incluant les conséquences de la crise sanitaire de la Covid-19,• Le relèvement humain du point de vue individuel et collectif (état de stress, solidarité, vie sociale, autonomie économique, habitat, etc.),• La réorganisation de la gouvernance locale.L’objectif est de s’appuyer sur une approche intégrée pour contribuer à l’émergence de nouveaux savoirs sur l’efficacité des stratégies de reconstruction post-catastrophe et de renforcer de manière cohérente la résilience des territoires face aux catastrophes naturelles,et par là même, l’adaptation au changement climatique. Les enseignements du projet Relev documentent la gestion de la phase de reconstruction post-catastrophe à Saint-Martin et Saint-Barthélemy, et soulignent la pertinence de planifier cette phase selon des modalités proches de celles déjà adoptées pour anticiper et préparer la gestion de crise. L’analyse interdisciplinaire a permis de mieux comprendre les liens de causalité entre la gouvernance de ces 2 îles, le relèvement psychosociologique des sinistrés, la reconstruction des infrastructures endommagées, la reprise des activités touristiques et l’histoire de l’urbanisation d’îles exposées aux risques naturels.En amont de futures catastrophes, les enseignements du projet alimenteront également l’élaboration d’outils et de méthodes pour anticiper la gestion de la phase de reconstruction post-catastrophe. L’approche interdisciplinaire initiée dans le projet Relev nous incite à poursuivre cet effort de rapprochement et d’échange entre les disciplines à l’avenir, notamment sur des sujets mêlant enjeux environnementaux et sociétaux.

Today on a global level, there is a continuous fermentation to change the established views about human. There are strong tendencies by certain groups of people on the planet that desire a more advanced human, but unknowingly perhaps, they are sketching a human with diminished potential, a human who will essentially have lost the world. A tragic human in the immense loneliness of the absence of the neighbor and the God. A human, who by mutating his nature and desiring to succeed in being omnipresent and immortal with the help of technology, ends up building a bottomless hell for himself. This study attempts a brief discussion of who human is, in the context of Christianity, as opposed to the aggressively imposed view of human that appears in today's narcissistic technological culture.

International audience; Since its landing in Jezero crater in February 2021, the western delta of Jezero has been one of the main targets for the Perseverance rover to explore and sample sedimentary rocks that lead us to better understand the environmental evolution of the region, and could host traces of past biosignatures.During the first year, the rover explored the floor of Jezero crater, focusing on aqueously altered igneous rocks. It also provided the opportunity to remotely observe the main delta front and its remnants (e.g., the Kodiak butte). This allowed us to distinguish several beds of sandstones (with local occurrences of boulders up to 30 cm) arranged into bottomsets, foresets and topsets morphologies. This tripartite geometry and steep slopes of foresets are characteristic of a Gilbert-type delta, formed by the deposition of fluvial sediments prograding into a standing body of water, here a paleolake whose level can be constrained by the transition from the foresets to topsets. Massive beds of boulder conglomerates (with boulders up to 1.5 m) have also been observed at or close to the top of many locations along the delta’s front, hinting at a transition to higher energy flows. Collectively, these elements argue for a polyphase complex depositional history of the delta through time.The toe of the current delta front was reached by the rover on Sol 422 (April 2022) when Perseverance arrived at the Enchanted Lake outcrop, at the base of the southeastern end of the promontory informally named Cape Nukshak on the distal end of the delta. The first in-place sedimentary rocks that were observed were a succession of thinly-laminated medium/coarse sandstones and mudstones. Then, Perseverance pursued its route towards the delta and started its ascension at Hawksbill Gap to assess the first half of the lower delta succession. Strata at the base of Hawksbill Gap are mostly composed of fine to coarse-grained rocks ranging from mudstones to granule conglomerates, displaying planar to low-angle cross-stratifications.These fine-grained detrital rocks are likely to have been deposited by fluvial to deltaic processes. There, the rover collected the first sets of paired sedimentary rock samples (coarse sandstone to micro-conglomerate) that will represent the fine- and coarse-grained lower delta succession once returned to Earth.

In this work, we address the difficulty of reliably identifying traces of life on Mars. Several independent lines of evidence are required to build a compelling body of proof. In particular, we underline the importance of correctly interpreting the geological and mineralogical context of the sites to be explored for the presence of biosignatures. We use as examples to illustrate this, ALH84001 (where knowledge of the geological context was very limited) and other terrestrial deposits, for which this could be properly established. We also discuss promising locations and formations to be explored by ongoing and future rover missions, including Oxia Planum, which, dated at 4.0 Ga, is the most ancient Mars location targeted for investigation yet.

International audience; Since 2015, in addition to the traditional green (532nm), infrared (1064nm) has been the preferred wavelength for lunar laser ranging at the Calern lunar laser ranging (LLR) site in France. Due to the better atmospheric transmission of IR with respect to Green, nearly 3 times the number of normal points have been obtained in IR than in Green [ C.Courde et al 2016 ]. In our study, in addition to the historical data obtained from various other LLR sites, we include the recent IR normal points obtained from Calern over the 1 year time span (2015-2016), constituting about 4.2% of data spread over 46 years of LLR. Near even distribution of data provided by IR on both the spatial and temporal domain, helps us to improve constraints on the internal structure of the Moon modeled within the planetary ephemeris : INPOP [ Fienga et al 2015 ]. IERS recommended models have been used in the data reduction software GINS (GRGS,CNES) [ V.Viswanathan et al 2015 ]. Constraints provided by GRAIL, on the Lunar gravitational potential and Love numbers have been taken into account in the least-square fit procedure. New estimates on the dynamical parameters of the lunar core will be presented.

International audience; Seismic Full Waveform Inversion has clearly demonstrated its efficiency in providing accurate quantitative information about the subsurface. Its implementation strongly depends on the resolution of the forward problem which is performed repeatedly in an iterative inversion process. In this work, we perform seismic FWI when the forward problem is solved with a face-based discontinuous finite element method. Discontinuous finite elements are particularly efficient for solving wave equations in heterogeneous media since with the hp-adaptivity feature, they not only can handle the topography of the propagation domain but also resist numerical pollution, which can be important in large-scale computations. Herein, we consider a Hybridizable Discontinuous Galerkin method based upon a mixed formulation of the problem coupled with static condensation. The computational burden mostly comes from the resolution of the global discrete problem whose size is proportional to only the degrees of freedom of the mesh skeleton. We work with the elastic wave equation in the frequency domain. We consider two different mixed formulations, the so-called strain-stress, and stress-strain formulations. This first one is widely used while the second one allows us to easily consider varying parameters inside the cells of the mesh. The HDG approximation of the elastic wave is the first step in the design of the FWI process. The second and critical step consists in deriving the adjoint state in the same approximation framework. This turns out not to be an obvious task and thus deserves some attention. We illustrate the numerical performances of the HDG-based FWI with time-harmonic elastic wave equations on two and three-dimensional test cases.

Introduction: The Rosetta mission is one of the latest great scientific and technological European successes. The probe and its lander Philae, transported some very audacious and inventive instruments that for some worked beyond expectations, and gave the scientists and engineers involved an expertise and experience that we should try to build on. The COmetary Secondary Ion Mass Analyser (COSIMA) onboard Rosetta, was the first instrument applying in situ analyses of cometary grains [1]. This instrument already combined two techniques: visible microscopy that was crucial to detect routinely the collected dust and characterize its structure [2], and Time-Of-Flight Secondary Ion Mass Spectrometry that mainly allowed us to determine the elemental composition of the dust [3-4]. COSIMA covered a mass range 1–1200 u but was limited to a mass resolution m/Δm of 1400 at mass 100 u at Full Width Half Maximum (FWHM), which made the assignment of molecular signals difficult. For the next generation of extraterrestrial (especially, primitive) dust analyzers, we are proposing an instrument that combines near infrared (NIR) and visible microscopy with laser ionization mass spectrometry (LIMS). This multi-analysis instrument (named dPCA for dust Particle Composition Analyzer) was part of the Castalia+ mission proposition to the ESA M7 call, but it is potentially suited for any space mission aiming to characterize dusty materials, especially complex ones containing organic and mineral phases. In the prospect to build a new generation of mass spectrometer offering High Resolution Mass Spectrometry (HRMS) collaborative effort between consortium of French and Czech laboratories (LPC2E, LATMOS, LISA, IPAG, IJCLab, J. Heyrovsky Institute of Physical Chemistry) and University of Maryland and NASA GSFC, are on-going to settle a pulsed UV laser source with an Orbitrap™ [5] mass analyzer for planetary applications. The spaceflight and ruggedized version of the Orbitrap cell and its electronics (preamplifier, ultra-stable High Voltage), the CosmOrbitrap mass analyzer/detector, is capable of discriminating isobaric interferences with ultrahigh mass resolution m/Δm > 100,000 (FWHM), high mass accuracies and dual polarity measurements [6-10]. The NIR channel of the microscope will be based on the MicrOmega hyperspectral instrument developed at IAS (Orsay, France). Several replicas of this instrument have already flown or are currently working aboard MASCOT/Hayabusa2, on the ExoMars rover [11] and currently in the JAXA curation facility for Ryugu dust analysis [12]). In this study, we investigated the analytical value of combining these two techniques. We will show through laboratory measurements how combining infrared and mass data could be extremely useful to unambiguously characterize the targeted dust. Experimental Procedure: The main well known inputs given by the NIR spectra are: the detection and characterization of hydration signatures, especially on silicates, the detection and partial characterization of carbonates and sulfates, the detection of ammoniated compounds, the detection of the presence of organic compounds and the detection and identification of ices (H2O, CO2, etc.). In the context of main belt comets, asteroids and even the Martian moons and surface, the full characterization of hydration signatures is one of the most important information needed to complete the mass spectra characterization. For this reason, we started our set of experiments and measurements on both instruments, a laboratory MicrOmega replica at IAS, and a laboratory instrument prototype of a laser ablation / ionization Orbitrap™ mass spectrometer, the LAb-CosmOrbitrap, developed at LPC2E (Orléans, France), by focusing on hydrated and anhydrous silicates. The LAb-CosmOrbitrap integrates i) a commercial pulsed Nd-YAG laser used at 266 nm UV wavelength, ii) a set of ion focusing lenses without C-trap, and iii) a spaceflight CosmOrbitrap mass analyzer/detector. Variable output energy of laser beam can be operated thanks to a polarizing prism. Samples: To explore the capabilities of the LAb-CosmOrbitrap instrument to characterize silicate in both positive and negative ion mode, we started with analyses of a San Carlos olivine, and a natural Mg-rich serpentine dominated by antigorite and chrysotile. Both samples are obviously silicates, but the former is an anhydrous ionic solid (no covalent bond between O and Mg) and the latter is a phyllosilicate (= a hydrated silicate) where Mg is covalently bonded to O and OH. Same samples have been analyzed with MicrOmega replica instrument. Results: LAb-CosmOrbitrap measurements in positive ion modes of the serpentine sample enables detection of various oxide and hydroxide magnesium peaks at high mass accuracy (< 2.5 ppm) during a single laser shot experiment, with high mass resolution (for examples m/∆m ~ 160,000 (FWHM) for 24MgOH+ and m/∆m > 130,000 (FWHM) for 24Mg2O+). In this study, we explored the best suitable laser energy and consecutive shot sequences to find reproducible and robust measurements of oxide and hydroxide ions. These results will be presented among those on olivine and the spectra obtained with NIR microscopy. Conclusions: This study demonstrates the capabilities of a UV Laser-CosmOrbitrap instrument combined with a NIR spectrometer to detect and characterize hydrated signatures of a serpentine with an optimized protocol. Next steps that will be pursued are among others the analyses of other types of silicates and minerals, of silicate doped with organic compounds. In the prospect of a future space instrument, it is obvious that IR microscopy would be of great benefit for a fast screening of the area of the targeted dust in order to further perform LIMS analyses and increase the confidence in the identification of molecular and structural indices. Acknowledgement: We thank the Centre National des Etudes Spatiales (CNES) for their financial support. References: [1] Hilchenbach et al. (2016) ApJL 816, L32. [2] Langevin et al. (2016) Icarus 271, 76–97. [3] Fray et al. (2016) Nature 538, 72–74. [4] Bardyn, Baklouti et al. (2017) MNRAS 469, S712–S722. [5] Makarov (1999) US Patent 5, 886, 346. [6] Briois et al. (2016) PSS 131, 33–45. [7] Arevalo Jr. et al. (2018) Rapid Comm 32, 1875–1886. [8] Selliez et al. (2019) PSS 170, 42–51. [9] Selliez et al. (2020) Rapid Comm 34, e8645. [10] Cherville et al. (2021) COSPAR2021, Abstract B0.4-0018-21. [11] Pilorget and Bibring (2014) PSS 99, 7–18. [12] Pilorget et al. (2021) Nature Astronomy 6, 221–225.

How Life has emerged on Earth? Can we find signs of Life on other celestial bodies in the Solar System? Are they harboring liquid water and complex-enough organic matter to initiate Life? What actually complex-enough organic matter means? Among other scientific questions, those related to astrobiology drive the future space missions for decades to come. The search for organic compounds in the Solar System, such as bio- and prebiotic molecules, has been defined as one of the highest priority by the Space Agencies [1, 2]. Significant improvements of the analytical performances of the future instruments will increase our knowledge of targets of interest for the search of Life, present or past, such as comets, asteroids, icy moons or ocean worlds. New generation of High Resolution Mass Spectrometers (HRMS) is currently being developed in order to provide univocal identifications, study of isotopic abundances and determination of mixing ratios with high analytical performances [3-6], including very HRMS-CosmOrbitrap based under collaborative development with University of Maryland/NASA Goddard Space Flight Center. The CosmOrbitrap mass analyzer is mainly funded by CNES, the French space agency, and developed by a consortium of 6 laboratories (LPC2E, LATMOS, LISA, IPAG, IJC lab, J. Heyrovsky Institute of Physical Chemistry) [7]. Here we address the results of a repeatability study based on three organic compounds and obtained with the LAb-CosmOrbitrap (Laser Ablation CosmOrbitrap) equipped with a commercial laser ionization system at 266 nm and no C-trap system. Organics studied are nitrogenous and sulfurous compounds, HOBt (C6H5N3O+H) at m/z 136 and BBOT (C26H26N2O2S+H) at m/z 431; and a prebiotic compound, the well-known adenine (C5H5N5+H) at m/z 136. Hundreds of mass spectra have been recorded to demonstrate the reproducible analytical performances of the laser-CosmOrbitrap set-up. Mass resolving power has been studied as a function of the acquisition time and the FFT length. Different kind of mass calibrations have been tried to show the effect on the mass accuracy (internal mass calibration on the species of interest and external mass calibration on the metallic sample-holder). Finally, preliminary results on isotopic abundances (13C/12C, 15N/14N and 34S/32S replacements) have been obtained. This work provides key information for specifying the required performances of future HRMS space instruments. Acknowledgement: We thank the Centre National des Etudes Spatiales (CNES), the French space agency, for their financial support. References: [1] National Academies (2022) Origins, Worlds and Life. [2] ESA (2021) Voyage 2050 [3] Waite et al. (2019) Abstract Vol.13, EPSC-DPS2019-559-1 [4] Shimma et al. (2010) Anal. Chem. 82, 20, 8456-8463 [5] Willhite et al. (2021) IEEE Aerospace, 1 – 13 [6] Willhite et al. (2021) Annual Meeting of the Lunar Exploration Analysis Group, LPI Contribution No. 2635, id.5034 [7] Briois et al. (2016) PSS 131, 33 – 45

Introduction With 13 years of observations, the Visual And Infrared Mapping Spectrometer (VIMS) onboard the \textit{Cassini} spacecraft has observed the surface and atmosphere of Titan through two seasons: winter and spring. In VIMS-IR spectra the surface is only seen in seven atmospheric windows due to the strong methane absorption. To retrieve the surface albedo we use radiative transfer (RT) models to compensate for the signal due to the atmosphere. Thanks to the lander Huygens, we have information about the optical properties of the aerosols above the equator that can be used in RT models. However, using the same aerosols vertical profile at high latitude doesn't work. With the help of the results of and Global Circulation Models and the Composite InfraRed Spectrometer onboard Cassini, we changed the aerosol vertical profile and optical properties in our RT model to better fit VIMS data at high latitude. While this model is not well constrained due to a lack of data, we manage to adjust the optical properties so our RT model based on Coutelier et al., (2021) retrieve surface albedo mostly between 0 and 1 instead of values crossing these boundaries like we had previously. It allow us to study with a RT model the shores and polar seas of Titan. We applied this new model on the same area of Kraken Mare in three consecutive VIMS cubes of the same flyby (subsequently named C1, C2 and C3). It allow us to validate our model on terrains with different albedo, and to notice an interesting feature in Kraken Mare that could be interpreted as sediment transport into the sea. Adaptation of the aerosols optical properties and vertical profile We decided to keep a 2 layers-based aerosol model, separated into haze and mist. We first changed the haze opacity vertical profile, using an exponential law : with the altitude of transition between mist and haze Ztr=70 km, and the scale height Hh=40 km. τh1µm is the opacity calculated by Doose et al., 2016 at 1 µm. We then changed the spectral slope of the optical depth of the mist with a simple power law as a first approximation : with Δτmnorm the normalized optical depth of the atmospheric layer of mean altitude z, τhλ0 the total optical depth at λ0 = 1 µm calculated by Doose et al 2016., λ the wavelength, and the parameter b = 2.2 +/- 0.2 The most influent parameter is the mist single scattering albedo ωm. we decided to change it depending on that of the haze ωh and a factor α = 0.4 +/- 0.1. Application and results on Kraken Mare We tuned and applyed this model on three successive VIMS cubes (full names in Fig. 1) subsequently called C1, C2 and C3. We retrieved the albedo on a zone crossing Kraken Mare, containing pixels from land, shore and methane sea. They are circled in red in Fig.1. The top part shows the VIMS cubes, and the bottom part their footprint on the geomorphologic map of Titan. That way we can have an expectation on the retrieved albedo: dark in the sea, and bright on land. Figure 1 : (top) Successive VIMS cubes from flyby 292TI (colors : R : 5.01, V : 1.28, B : 2.79 μm).(bottom) : Footprint of the VIMS pixels on the geomorphologic map from Lopez et al., 2020. The pixels in our study are circled in red. The pixels circled in blue have mixed signatures. The retrieved albedo are on Fig. 2. We still have remaining problems with negative albedo on dark pixels, mostly in the first atmospheric window. We can still differentiate very well the signatures from different terrains. Those coming from Kraken Mare are in blue, and those coming from the land are in green in Fig. 2. In C2, we have a pixel localized on the shore containing part of land and sea, circled in pink. Its signature is mixed, as we expected. However, we notice that on C1 and C3, two pixels localized in Kraken Mare (also circled in pink) also have a mixed signature. We did check that it was not a mistake in the cube geolocalization, or a difference due to a cloud. Figure 2 : Retrieved albedo of the selected pixels in Fig. 1. from the cubes C1, C2 and C3. The errors bar are calculated from the error on VIMS, and not from the error on the model. They are underestimated as a consequence. Discussion Infrared can penetrate deeply into liquid methane and ethane. The mixed signature we noticed can come from sediment transport carried by rivers flowing into Kraken Mare, issued from the erosion of the bedrock. While this aerosol model for the poles is not exact, nor well constrained, the RT model is working and gives reasonable results on different cubes from the same flyby. We can compare the different surface albedos instead of the absolute values, because the atmospheric model is the same for all of the studied pixels. The combination of the RT analysis with the geomorphologic map is a powerful tool that leads to notice unexpected signatures. With the seasons changes, we can expect that the improved polar aerosol model is not constant, so further studies should be made on other cubes through different seasons. We could that way follow through an other method the seasonal variation of the polar haze and mist layers. References Doose et al. (2016) Vertical structure and optical properties of Titan’s aerosols from radiance measurements made inside and outside the atmosphere. Icarus 270 : 355-375. Coutelier et al. (2021) Distribution and intensity of water ice signature in South Xanadu and Tui Regio. Icarus 364 : 114464. Lopes et al. (2020) A global geomorphologic map of Saturn’s moon Titan." Nature astronomy 4.3 : 228-233.

The D/H ratio is a key parameter to understand the atmospheric evolution of a planet. On Mars a D/H ~ 5 times larger than the ratio on Earth is measured. This large ratio can be explained by a preferential escape of the hydrogen compared to the deuterium due to its lower mass. However, while the thermal escape (Jeans escape) is strongly mass dependent other non-thermal processes are less mass dependent and would impact the time needed to fractionate the water from the terrestrial value to the current value. After the first detections of the deuterium Lyman-α emission from Earth (Bertaux et al. 1992, Krasnopolsky et al. 1998), the mission MAVEN performed the first systematic observations of the atomic deuterium Lyman-α emission around Mars showing a brightness of several hundreds of Rayleigh near Mars winter solstice (Clarke et al. 2017, Mayyasi et al. 2017), much larger than the Earth detections done near aphelion (~ 20 – 50 Rayleighs). This seasonal variation of the deuterium Lyman-α brightness is consistent with the variations of the hydrogen Lyman-α brightness observed from Mars Express (Chaffin et al. 2014, Chaufray et al. 2021), HST (Clarke et al. 2014), and MAVEN/IUVS (Clarke et al. 2017, Chaffin et al. 2018) and should result from the processes transporting the water vapor from the lower atmosphere to the upper atmosphere (Vals et al. 2022). In this work we will present preliminary simulations of the 3D deuterium abundance in the Martian upper atmosphere (Fig. 1) using a 3D time dependent global circulation model, including the chemical reactions between HD and HDO with the ions in the upper atmosphere, its extension in the exosphere, and a comparison of the simulated D Lyman-α brightness with the brightness measured by MAVEN/IUVS (Mayyasi et al. 2017) for the Martian year 33. Fig. 1 Simulated average dayside and nightside D density at different altitudes in the thermosphere and exosphere along one Martian year. We will also present first results of the simulated non-thermal escape of H and D produced by collisions between hot oxygen with H, D, H2 and HD as well as the escape of planetary H+ and D+ driven by the solar wind interaction. We will compare the D and H thermal escape rate with the non-thermal escape rates. References: Bertaux et al. (1992), in ESOC conference and workshop proceedings, 44, 459. Chaffin, M. et al. (2014), Geophys. Res. Lett., 41, 314-320 Chaffin, M. et al. (2018), J. Geophys. Res., 123, 2192-2210 Chaufray et al., (2021), Icarus, 353,113498 Clarke et al. (2014), Geophys. Res. Lett., 41, 8013-8020 Clarke et al. (2017), J. Geophys. Res., 122, 2336-2344 Krasnopolsky et al., (1998), Science, 280, 1576 Mayyasi et al., (2017), J. Geophys. Res., 122, 10811-10823 Vals et al. (2022), J. Geophys. Res., under revisions

Vine introduction in Burgundy (east central France) two millennia ago is responsible for land use changes and increased soil erosion to which societies have tried to adapt. In this paper we seek to figure out the relationship between land uses, agricultural practices and geomorphic dynamics in the Mercurey terroir during the Late Holocene. The method employed is based on the analysis of sedimentary deposits observed in the valley bottom and along hillslopes. It is complemented by a pedoanthracological study derived from a trench excavated into a riverbank, in order to interpret the variability of the reconstituted sedimentary signal. Our results highlight two major stages of detritism over the last 2,800 years. At least from 800 cal. BC, frost heave screes (stored since the Late Pleistocene) are transported from the upper part of hillslopes to the valley bottom by high-energy geomorphic processes (e.g., solifluction flows). This sequence of coarse colluviums is associated with the development of an agro-pastoral landscape marked by an opening forest cover. A second phase begins after 1400 cal. AD. It is characterized by a fine sedimentation and a high concentration of vine charcoal. Indeed, wine-growing spread in the medieval landscape comes with the building of agricultural infrastructures. It leads to a decrease of sediment connections from the source areas to valley bottom. The coarser sediments are retained on the hillslopes, thus bringing out soil maintenance strategy.

International audience; Cave levels at high elevations (2250-2370 m), hosting allochthonous sediments with clear provenance from the Pelvoux External Crystalline Massif were identified in the Obiou mountain, Dévoluy Massif (French Western Alps). These deposits result from burial of alluvial sediments of the paleo-Drac River in Miocene times (burial ages of ca. 10-15 Ma). The Drac River is currently situated 1600 m below the caves, indicating significant post-middle Miocene fluvial incision. The pollen analysis on clay cave infill indicates a humid and warm climate, typical for Western Europe in the mid-late Miocene. It also reveals the presence of dinoflagellate cysts from coastal and lagoon environments suggesting deposition of the clays in the caves when they were close to sea level. These findings indicate uplift of the caves of at least 2000 m since the mid-late Miocene. Furthermore, the pollen assemblage originated from different vegetation belts, in agreement with existing data for mid-late Miocene deposits in the western Alps. The pollen flora includes cool-temperate and boreal trees, suggesting high-elevated source areas for the deposits within the Pelvoux catchment. These data confirm the exceptional character of the Obiou cave deposits that provide new geomorphologic constraints for the evolution of the French Western Alps.

International audience

The project CoRob-X develops and demonstrates enabling technologies for multi-agent robotic teams to explore planetary surfaces with a focus on hard-to-reach areas where a collaborative scheme is required to efficiently explore complex environments. Exploring lava tubes is such a challenging environment and requires a team of robots able to collaborate in an autonomous way to find their way to the subsurface tube system, descend through a natural entry hole (the so-called skylight), and explore the interior with payload instruments to provide scientific data. The developed robotic exploration system that will tackle the ambitious goal is composed of three rovers with substantially different technical characteristics. The paper presents the overall approach, i.e., the control architecture, the robotic systems, and the software to be used. It also showcases the selected mission phases that will be demonstrated in a field-test campaign. In addition, a terrestrial mining use case is presented that demonstrates how the developed autonomy-enabling software can be transferred to terrestrial applications. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Highlights • First feasibility study of respiratory viral detection in Cystic Fibrosis sputum. • High concordance between sputum and nasopharyngeal samples in viral. • Multiplex-PCR performed in 30 paired samples: 83% viral congruency. • Sputum: an optimal non-invasive sample for viral diagnosis in cystic fibrosis., Viruses are important agents in lung function deterioration in Cystic Fibrosis (CF). To date, no standard operating procedures (SOPs) have been established to determine which sampling method is the most effective for an optimal virological diagnosis of respiratory viral infections in CF. Here we investigated the performances of two sampling sites, sputum samples versus nasopharyngeal (NP) swabs, for thirty participants from three CF centres presenting an acute respiratory infection. Sputum and NP samples were simultaneously collected and multiplex PCR targeting 16 to 18 viruses were performed. Viruses were detected for 18/30 patients (60%). A high concordance between the sputum and NP samples was observed in 25 (83%) paired samples of which 13 tested positive and 12 tested negative. These results highlighted the relevance of sputum sampling for diagnostic of respiratory viruses in CF, which is less invasive and better accepted by CF patients than NP, and allows accurate bacterial detection.

Le projet HYDRODEMO a pour objectif de mieux connaître les risques liés aux crues torrentielles dans les Alpes du Nord et de pouvoir mieux s’en prémunir. Le manque d’observations hydrométéorologiques dans les Alpes du Nord, que ce soit en termes de forçages météorologiques ou hydrologiques, limite fortement nos connaissances sur ce type d'aléa. Afin de combler ce manque de connaissance, l'action 4 du projet HYDRODEMO, objet de ce présent rapport, consiste à appliquer des outils de modélisation hydrologique à des petits bassins versants torrentiels instrumentés pour, d'une part, tenter d'en caractériser et reproduire le fonctionnement, et, d'autre part, définir une méthodologie de transposition aux bassins versants non instrumentés sous la forme d'un travail de régionalisation des paramètres des modèles. L'objectif associé à cette régionalisation est d'étudier la possibilité de la mise en œuvre des modèles sur les bassins versants non instrumentés, afin d'y permettre la connaissance de valeurs statistiques de crues.Pour répondre à ces objectifs, ce rapport présente l'application de deux modèles hydrologiques, le modèle semi-distribué MORDOR-SD adapté aux zones de montagne (modules neige et glace) et le modèle distribué SMASH (Spatially-distributed Modelling and ASsimilation for Hydrology), plateforme développée par INRAE avec le soutien du Ministère de la Transition Ecologique et mise en œuvre dans le dispositif national Vigicrues Flash, dont l'adaptation aux zones de montagne a pu être réalisée dans le cadre du projet HYDRODEMO, par le biais notamment de l'introduction d'un module neige. Pour les deux modèles, le développement de la méthodologie et l'évaluation des performances sont effectués sur un ensemble de bassins versants torrentiels jaugés des Alpes du Nord. Nous montrons en particulier la sensibilité des performances aux types de forçage météorologique et à la stratégie d'estimation des paramètres (calibration à partir des mesures de débit versus méthode de régionalisation). Le travail de régionalisation mené pour les deux modèles permet d'envisager des pistes pour leur mise en œuvre sur des bassins versants non jaugés.

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International audience

International audience

Cet article présente quelques illustrations d.applications de données radar polarimétriques (complètes ou partielles) pour le suivi des surfaces terrestres. La première partie est dédiée aux données radar pleinement polarimétriques. Elle est introduite par un rappel théorique présentant leur spécificité. Puis quelques exemples sont présentés, principalement concernant la cartographie de la végétation et également les processus spatio-temporels de sédimentation dans une zone semi-aride en Tunisie. La deuxième partie est consacrée aux données partiellement polarimétriques du type de celles acquises par les capteurs Radar à Synthèse d´Ouverture (RSO) à bord des satellites Sentinel-1A/1B. Celles-ci seront largement utilisés dans les années futures en raison de leur apport significatif pour les études touchant aux observations des surfaces terrestres pour les sciences de l'environnement.

International audience; We assess how differences in the composition of exoplanet host stars might affect the availability of water in their systems, particularly the role of carbon and oxygen abundances. Water, one of the key chemical ingredients for habitability, may be in short supply in carbon-rich, oxygen-poor systems even if planets exist in the ‘habitable zone’. For the solar system, C/O = 0.55 is particularly important in determining the refractory (silicate and metal) to volatile ice ratio expected in material condensed beyond the snow line (Gaidos E. J. Icarus 145, 637, 2000; Wong M. H. et al. in Oxygen in the Solar System, G.J. MacPherson, Ed., 2008). Our analysis of published compositions for a set of exoplanet host stars (Johnson T. V. et al. ApJ. 757(2), 192, 2012) showed that the amount of condensed water ice in those systems might range from as much as 50% by mass for sub-solar C/O = 0.35 to less than a few percent for super-solar C/O = 0.7. A recent analysis using similar techniques (Pekmezci G. S., Dottorato di Ricerca in Astronomia, Università Degli Studi di Roma “Tor Vergata”, 2014) of a much larger stellar composition data set for 974 FGK stars (Petigura E. and Marcy G. Journal of Astrophysics 735, 2011), allows us to assess the possible range of water ice abundance in the circumstellar accretion disks of these ‘solar-type’ stars (of which 72 were known to have one or more planets as of 2011). Stellar C/O in a subset (457 stars) of this stellar database with reported C, O, Ni, and Fe abundances ranges from 0.3 to 1.4. The resulting computed water ice fractions and refractory (silicate + metal) fractions range from ~0 to 0.6 and 0.3 to 0.9 respectively. These results have implications for assessing the habitability of exoplanets since they constrain the amount of water available beyond the snow line for dynamical delivery to inner planets, depending on the host stars’ C/O in the circumstellar nebula. TVJ acknowledges government support at JPL/Caltech, under a contract with NASA. JIL was supported by the JWST Project through NASA. O.M. acknowledges support from CNES.

(version française d'un article publié dans Journal of Archeological Sciences : Reports en 2022)

We present observations of the He 58.4 nm emission performed with the EUV channel of the PHEBUS spectrometer on board ESA’s Mercury Planetary Orbiter during Bepi Colombo’s first Mercury Flyby in October 2021. We describe the data analysis and PHEBUS EUV calibration based on interplanetary He 58.4 nm data from observations during the cruise. We discuss the results in comparison with Mariner 10 measurements at 58.4 nm and models of Mercury’s exosphere.

The 'disparitas conjecture' states that unicellular life may be common in the galaxy, but that multicellular life might be rare in comparison. A variation of this is that unicellular life may be common in the galaxy, but that intelligent life is rare. However, microbial life can and does indeed display characteristics of intelligence. Thus, in this work it has been investigated how life potentially could have endured through the Late Heavy Bombardment (LHB) through intelligent strategies such as decision making, association and anticipation, communication and self-awareness. At the LHB there would be for microbial life an unpredictable environmental fluctuation regarding pools of amino acids, lipids and fluids available when impacts and reimpacts launched organisms into new habitats. Thus, evolutionary strategies must have been favored that could stretch the available external and internal resources as long and as efficiently as possible. Thus, inclusive fitness or kin altruism could have emerged, where organisms adapt to acquire energy and nutrients from siblings who voluntarily autolysed in order to replenish the amino acid pool for their kin. A further strategy could also evolve where members of the same species can recognize each other and actively isolate themselves from other species, which allows them to utilize the amino acid pool better. Thus, the organisms will potentially be able to survive for a long time in these ways until new impacts launch them to new spots with amino acid pools. There has thus been an alternating increase and decrease in the number of organisms during this localized planetary reseeding and life may have endured this way until the bombardments were over. Thus, if a world inhabited only by analogous of bacteria, archaea and protists is located elsewhere in the galaxy, then this does not exclude the existence of intelligent life there.

Solar flares could potentially give rise to sudden changes in the planetary ion composition in Mercury's magnetosphere. We model the time-dependent evolution of the Mg + , Na +, O + and He+ ion density distribution during the extreme X9.3-class solar flare event on 6 September 2017 with the Latmos Ionized Exosphere (LIZE) model. We find that the peak ion density in the nightside plasma sheet is delayed by ∼7−8 min compared to the dayside, and that the maximum Mg + density occurs ∼4 min before He + and O + in the whole magnetosphere. We also find that there exist two ion energy populations on the dayside which experience different dynamical evolution during the event.

La fouille archéologique préventive menée par l’Inrap durant l’été 2017 sur le site de la Grande Maison à Chamigny (Seine-et-Marne) a en outre révélé trois mégalithes distants de 60 m d’une sépulture collective utilisée de la fin du Néolithique à l’âge du Bronze ancien (ca. 3350-1800 av. n.è.) Le mégalithe le plus grand est une stèle décorée d’un format sub-rectangulaire de 2 m de haut pour 40 cm de large, 44 cm d’épaisseur et d’un poids estimé à deux tonnes. Son analyse technologique a permis d’appréhender des mises en forme successives et des degrés d’usure différentielle des arêtes vraisemblablement liés au déplacement du mégalithe. L’analyse iconographique a permis d’identifier plusieurs techniques de gravure pour la réalisation des décors. Par ailleurs, l’analyse géomorphologique de la stèle a permis de mettre en évidence des relations entre les méso-structures géomorphologiques et les modifications anthropiques et contribuent à une évocation anthropomorphe initiale soulignée par les aménagements gravés. Ce regard "géologique" a fait soupçonner que les éléments de la face avant, tout comme ceux de la face arrière, sont probablement intervenus dans la sélection de la dalle à destination anthropomorphique. Les particularités de cette stèle a permis d’envisager quelques facettes du quotidien de nos ancêtres néolithiques et de les confronter au présent pour permettre une réflexion sur le devenir de nos propres modes de vie, et ceci grâce à une valorisation muséale adaptée.

Volatile elements such as hydrogen, carbon, and nitrogen were essential for the emergence of life on Earth. However, the origin of these elements accreted by planetary bodies of the inner solar system as well as their behavior, distribution, and inventory in deep planetary reservoirs remain controversial. Recent analytical developments in noble gas mass spectrometry and secondary ion mass spectrometry have allowed me to accurately determine the abundance and isotopic composition of nitrogen trapped in terrestrial volcanic rocks, meteorites (chondrites, achondrites, iron meteorites), samples brought back to Earth by space missions as well as in synthetic samples. In parallel, based on measurements of noble gases in meteorites and lunar rocks, I was able to quantify isotopic modifications induced by the solar wind and cosmic rays. Experimental studies have provided complementary information on the effect(s) of various physico-chemical parameters on the behavior and isotopic fractionation of nitrogen during planetary differentiation. My research activity has thus mainly focused on tracing the origin and evolution of volatile elements and the chronology of their accretion by Earth, the Moon, and other planetary bodies. The results of my work demonstrate the complexity of the processes that govern the abundance and isotopic signature of volatile elements in rocks of various provenance: Earth's ocean floor, the lunar maria or the asteroid belt and beyond., Les éléments volatils comme l'hydrogène, le carbone et l'azote sont essentiels à l'émergence de la vie sur Terre. Néanmoins l'origine de ces éléments accrétés par les corps planétaires du système solaire interne ainsi que leurs comportement, distribution et inventaire dans les réservoirs profonds restent controversés. Des développements analytiques récents en spectrométrie de masse gaz rares et spectrométrie de masse à ions secondaires m'ont permis d'analyser de façon précise la teneur et la composition isotopique de l'azote piégés dans des roches volcaniques terrestres, des météorites (chondrites, achondrites, météorites de fer), des échantillons rapportés sur Terre par les missions spatiales ainsi que dans des échantillons synthétiques. En parallèle, grâce à la mesure des gaz nobles dans les météorites et roches lunaires, j'ai pu quantifier les modifications isotopiques induites par le vent solaire et les rayons cosmiques. Des études expérimentales m'ont fourni des informations complémentaires sur l'effet de divers paramètres physico-chimiques sur le comportement et le fractionnement isotopique de l'azote pendant la différenciation planétaire. Mon activité de recherche s'est ainsi principalement concentrée sur le traçage de l'origine et l'évolution des éléments volatils et la chronologie de leur accrétion par la Terre, la Lune et d'autres corps planétaires. Les résultats de mes travaux démontrent la complexité des processus qui gouvernent la teneur et la signature isotopique des éléments volatils dans les roches quelles que soient leurs provenances: les fonds des océans terrestres, les mers lunaires ou la ceinture d'astéroïdes et au-delà.

The Interstellar Probe project gives an unprecedented opportunity to study the hydrogen atom distribution from the interstellar medium to the inner heliosphere. The solar H Lyman alpha emission (121.6nm) is the brightest line in the UV range. Solar Lyman alpha photons are backscattered by hydrogen atoms in the interplanetary medium producing the interplanetary glow that extends far beyond the heliopause into the interstellar medium. A Lyman alpha spectrograph will measure the LISM H number density giving the first direct measurement of this quantity just outside of the heliospheric interface. This value is one of the critical parameters defining the size and behavior of the heliospheric interace. With a high resolution spectrograph, it will be possible to differentiate between the Lyman alpha galactic emission derived from the UVS-Voyager data and the LISM H Lyman alpha emission from the line of sight velocity of the atoms. Because of resonant charge exchange between the hydrogen atoms and the protons, the H atom distribution is strongly affected when the neutrals cross the heliospheric interface region. H atoms created after charge exchange keep the velocity distribution of the protons that they were created from. Therefore, the backscattered Lyman alpha line profile will change as the interstellar probe crosses through the inner heliosheath to the outer heliosheath and then moves into the LISM, providing a test on the proton distribution in the heliosphere regions crossed by the interstellar probe. Here, we will present an instrumental design that will allow for this study bringing new information on the heliospheric interface and the very local interstellar medium.

The moderately siderophile and volatile elements are strong tracers of condensation, accretion-collision and metal-silicate differentiation processes in the earliest history of the solar nebula, and of terrestrial planets, the Moon, and asteroids, respectively. Among them, germanium, with T 50% cond = 825 K and metal-silicate partition coefficient of 17 for the Earth, show significant isotopic fractionation (Δ 74 Ge metal/silicate) at two scales, namely (1) at a meteorite scale between metal and silicate phases in ordinary chondrites or pallasites, and (2) at reservoir scales, between iron meteorites taken as proxies for core and the silicate Earth. Establishing the isotopic budget of planetary mantles (e.g.Earth, Mars, Vesta) and the Moon implies to determine the isotopic composition of chondrites as proxy for undifferentiated parent bodies. Here we present new high precision germanium isotopic data obtained on (1) bulk carbonaceous (CC) and ordinary chondrites (OC), (2) Howardite-Diogenite meteorites though to originate from Vesta, (3) Martian meteorites (shergottite, nackhlites) and (4) lunar basalt meteorite, They will be compared with Ge isotopic composition of iron meteorites and Earth silicate mantle (peridotites, basalts) [3,4] to assess parent bodies composition. Samples and methods: Variable quantities of sample, from 80 mg for CC (CI, CM, CV, CO), OC (H, L, LL) and martian meteorites (shergottite, nackhlites), to up to 2 g for Ge-depleted HED (unbrecciated and brecciated eucrites, diogenite) and lunar basalt, were analyzed for Ge concentrations at the SARM (ICP-MS, CRPG-Nancy), and for bulk Ge isotopic compositions by using Ge chemistry and MC-ICPMS techniques (Hydride Generator System coupled to NeptunePlus) developed at CRPG (δ 74/70 Ge NIST3120a ≤0.1‰, 2σSD) [1,2,3]. Results and discussion: OC and CC type chondrites present fundamental Ge isotopic dichotomy that follow O and Cr isotopic anomalies [4]. Bulk ordinary chondrites values display negative values from-0.51±0.16 ‰ in H OC,-0.29±0.05‰ in L to-0.33±0.14‰ in LL, that agree within error with data on metal phase of OCs (Florin et al., 2020), then confirming that the metal phase hosts the Ge isotopic budget. By contrast, carbonaceous chondrites have positive δ 74 Ge values and show exceptional large variations of ≈1‰, from CI (Orgueil) with the heaviest composition (δ 74 Ge=0.901±0.06‰) toward lighter composition in CV (Allende) (δ 74 Ge=+0.096±0.12‰). The δ 74 Ge values and matrix fraction (%) of OCs and CCs are positively correlated and describe a mixing line between CI composition and expected chondrule composition (Fig.1). In addition large Ge isotopic composition in CC are exceptionally well correlated with Δ 17 O (Fig. 1) and ε 54 Cr, then constraining the origin and/or processes that lead to Ge isotopic signatures in the Solar System. Planetary mantles, except the Moon, have Ge isotopic compositions that are lighter than the iron meteorites, thus confirming the positive Δ 74 Ge metal/silicate during core formation [2]. In addition, distinct Ge isotopic signatures are recorded: Mars has δ 74 Ge values that overlap terrestrial mantle and crustal values, and reveals a dichotomy between shergottites with higher δ 74 Ge, lower Ge contents (+0.84‰, 0.73 ppm) than nakhlites (+0.35‰, 2.2 ppm), thus emphazing degazing processes [6]. The highly depleted HED and lunar samples (Ge =

Stray light is an issue in any optical instrumentation. It affects the accuracy and resolution of the measurements, or their dynamics, possibly the resolution of images. Methods do exist at component leval (reflectometry, scatterometry) to measure stray light. But the measurement of stray light at system level can be difficult once integration is complete: introducing a scatterometer in the instrument is likely to be impossible.We develop a general method to measure coherent stray light at system level, to determine, in the system under test (SUT) what are the different sources of stray light, and the fraction of stray light which correponds to each of them. Time-of-flight methods inject short pulses in the system, and fast signals are measured, that indicate nominal light, as well as the "echoes" corresponding to the different sources of stray light, and the corresponding delays. This implies that the photoreceivers in the SUT are fast detectors (picoseconds) and can measure small pulses: 10^-12 if fractionnal optical amplitudes of 10^-6 are to be measured, relative to the nominal amplitude.Rather than use short pulses, we use a single mode laser source with an optical frequency scanned linearly with time, and detect all output signals (optical and electrical). For each of the signals, the presence of a fringe behaviour indicates the presence of stray light, interfering with nominal light. The stray/nominal optical path length difference is obtained from the fringe frequency, similar to conventional FMCW coherent reflectometry. The measurements require no fast detection., La lumière parasite cohérente constitue naturellement, sur une instrumentation optique, un écueil à bien des égards. Elle affecte l'exactitude ou la résolution des mesures, ou leur dynamique, ou encore la résolution des images. Des méthodes existent pour la mesure de la lumière parasite au niveau composant (réflectométrie, diffusométrie). Mais la mesure de la lumière parasite au niveau système peut poser des difficultés une fois le système assemblé (impossibilité d'introduire, par exemple, une instrumentation de mesure de la lumière diffusée). Nous développons une méthode générale de mesure de la lumière parasite cohérente au niveau système, permettant de déterminer quelles sont, à l'intérieur d'un système à tester (SAT), les différentes sources de lumière parasite, et la fraction de lumière parasite qui leur correspond. Les méthodes de type "temps de vol" injectent des impulsions courtes dans le système, et on mesure des signaux rapides traduisant, outre l'impulsion de lumière nominale, les "échos" associés aux différentes sources de lumière parasite, et les retards associés. Cela implique que les détecteurs du SAT soient suffisamment rapides (picosecondes) et par ailleurs que leur dynamique permette de détecter de très petites impulsions: 10^-12 si on souhaite détecter une amplitude optique parasite de 10^-6 comparée à l'amplitude nominale. Plutôt qu'utiliser des impulsions courtes nous utilisons une source laser monomode dont la fréquence optique est balayée, et nous détectons tous les signaux sortants (optiques comme électriques). Sur chacun des signaux, l'observation d'un comportement de type frange d'interférence indique la présence de lumière parasite, interférant avec le faisceau nominal. La différence de chemin nominal/parasite est indiquée par la fréquence de ces franges d'interférence, comme en réflectométrie cohérente FMCW. Leur mesure ne requiert aucune détection rapide.

Lors d’une exposition récente sur l’Antarctique, notre attention a été attirée par des structures spectaculaires, visibles dans certains icebergs (on trouve sur le réseau Internet des vues de telles structures dans des icebergs d’origines diverses). Celles-ci sont constituées d’ensembles de prismes verticaux de glace, ou de plans parallèles (eux aussi verticaux), formant des colonnades. Ces dernières sont séparées par des surfaces horizontales du reste de l’iceberg au-dessus (les basculements de ceux-ci modifient ces directions) ; les diamètres des prismes et les épaisseurs des plans apparaissent décimétriques à pluri-décimétriques. Les structures sont inscrites dans la masse de la glace, l’érosion marine et la fonte les soulignant et les mettant en valeur (sous des surplombs de l’iceberg massif). A notre connaissance, il ne semble pas y avoir de description raisonnée, ni de proposition d’explication. Nous nous contentons ici de brosser un cadre interprétatif potentiel. Nous ne donnons pas en détail les raisons qui nous guident ; elles sont inspirées par notre connaissance de la solidification des magmas géologiques donnant des structures comparables : orgues et plans (voir les références ci-dessous). Nous imaginons ainsi que lors de son entrée dans la mer, un morceau de glacier, qui constitue une « réserve de froid » importante, peut, dans certaines conditions, faire geler la mer à son contact dans ses parties immergées (il y a donc formation de glace nouvelle). La mer étant riche en NaCl, le point de solidification de l’eau est fonction de la teneur en sel au voisinage du contact glace / mer. Suivant les gradients de température en jeu, le phénomène de surfusion de constitution peut jouer, et l’interface glace / eau montrer une instabilité ; celle-ci est responsable de la formation de digitations, c’est-à-dire que des doigts, ou des plans parallèles de glace, s’avancent dans l’eau lors de la congélation. Les spécialistes de sciences des matériaux discutent les gradients de température en trois dimensions permettant une bifurcation entre le régime colonnaire et le régime planaire. Du fait de leur croissance, les doigts / plans vont se souder ; ils vont laisser entre eux des joints correspondant à des zones plus fragiles, mises en relief par les processus d’érosion / fonte postérieurs, lors du soulèvement de l’iceberg. Si la glace d’eau ne peut contenir de sel, elle ne peut non plus contenir toute une série d’éléments chimiques, y compris des gaz, qui vont se trouver « expulsés » à l’extérieur. Est-ce là une explication des dégagements gazeux observés le long des joints par les plongeurs (Raphaël Sané, com. pers., 2022) et parfois envisagés comme responsables des structures (alors qu’ils en seraient une conséquence) ? Nous verrons dans l’avenir si ce cadre est à garder tel quel, à amender, ou à abandonner. Il nous invite à faire des observations nouvelles, des mesures de types variés (chimiques, de pétrofabrique), à lire sur des sujets connexes, à débattre avec les personnes compétentes. Des estimations préliminaires faisant intervenir les paramètres principaux du problème (températures, enthalpie de fusion, capacités calorifiques, diffusivités thermiques et moléculaires, gradients thermiques, pente du liquidus dans le diagramme de phase, intervention de la convection solutale) sont encourageantes. Nous remercions nos collègues glaciologues de Toulouse et de Grenoble pour de premiers échanges (parmi eux Frédérique Rémy, Christian Vincent), ainsi que, de façon spéciale, Raphaël Sané (guide naturaliste) pour ses photographies et ses remarques utiles (sans vouloir compromettre aucun dans les hypothèses présentées). Nous saluons les médiateurs de la Rotonde (CCSTI de la Loire et Ecole des Mines) pour l’exposition (automne 2021) à l’origine de cette réflexion.Guy B. & Lecoze J., C.R. Acad. Sc. Paris, 1990; Guy B., J. Volc. Geoth. Res., 2010; Guy B., Thiéry V., Garcia D., Bascou J. & Broekmans M., Miner. Petrol., 2020.

International audience

The ACS instrument onboard the ExoMars TGO dedicated atmospheric spacecraft has been successfully operating since March 2018, delivering unique new data. The processes of water dissipation and the boundary where the lower atmosphere interacts with the exosphere were explored. We will report a selection of results obtained from ACS solar occultations, emphasising the upper part of profiles probing the limits of the neutral atmosphere. The atmospheric profiles were obtained from the strongest CO2 bands up to 200 km altitude. The homopause altitude variation with season was studied. Gravity waves were detected and quantified. Also, the vertical distribution of atmospheric water vapour was measured up to 120 km, resulting in, combined with the altitude profiles of hydrogen and oxygen isotope ratios in CO2 and H2O, implications on the escape of hydrogen from Mars.

It is a basic requirement of special relativity theory (SRT) that all relatively moving inertial observers agree on an observable (interference fringe shift, for example). It is shown that SRT leads to a disagreement on the observables (interference fringe shift) in two relatively moving inertial reference frames.

Solar wind charge exchange (SWCX) emission contaminates all astrophysical observations in X-rays regardless of the direction. This contamination is particularly problematic when measuring astrophysical plasma temperatures due to the similar spectral distribution of the two phenomena. Since its discovery, literature has distinguished between SWCX emission resulting from solar wind-neutral interactions within the Earth's magnetosphere, called magnetospheric SWCX, and similar interactions occurring more generally throughout the heliosphere, called heliospheric SWCX. Previous work demonstrated accurate modeling of the heliospheric SWCX contribution for astrophysical observations performed at low ecliptic latitude with HaloSat, a CubeSat X-ray mission of medium spectral resolution. Here, we apply this model to similarly orchestrated observations to measure the magnetospheric SWCX contribution separately from the heliospheric SWCX and the astrophysical background contributions. We describe our observational strategy, the heliospheric SWCX model used, and our spectral fitting methods. In particular, we report on four observations with lines of sight through the Earth's magnetospheric flank with total O VII line fluxes at least 3σ above that predicted by the heliospheric SWCX model and the astrophysical background, possibly indicative of magnetospheric SWCX. We then discuss the excess emission in comparison with available magnetospheric SWCX simulations requested through the Community Coordinated Modeling Center.

Recent Mars missions have provided a wealth of observations to study the red planet and its relationship to Earth. However, only few observations of Martian upper mesosphere/lower thermosphere (~80 – 160 km) are available, a region that includes the mesopause and homopause, and is closely coupled to the atmospheric layers above and below. The existing datasets in this altitude range provide only limited temporal and spatial coverage. Stellar occultations by the Imaging Ultraviolet Spectrograph (IUVS) aboard the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission are being designed and executed in dedicated bimonthly campaigns for the last seven years to fill this observation gap. However, only the nightside observations are useable as the current data-reduction pipeline rejects any dayside occultation with stray light contamination.We have devised an improved stray light removal algorithm to process the daytime observations as well. Of the 3003 observations from March 2015 to January 2022, the reprocessed data includes 1145 dayside and 1259 nightside events, thereby resulting in the first Martian dataset that consistently measures both the dayside and the nightside mesosphere. We present the results of the study of diurnal thermal structure in ~80 – 160 km altitude range (10-6 to 10-2 Pa).The dayside is observed to be warmer than the nightside at all pressure levels, with the diurnal variations of ~30 K in the lower thermosphere, ~20 K near the mesopause, and little day/night differences at low altitudes. This is found to be consistent with short radiative time constant of the order of 1 sol, suggesting strong tidal damping. The data also shows that the regions at pressures less than 2x10-3 Pa are under strong solar control with no prominent migrating tidal signatures. Whereas, on Earth, the temperature variations due to tides are quite large near the mesopause, with radiative time constant of ~10 Earth days. The Mars Climate Database shows an opposite diurnal trend in the mesosphere, with the dayside mesopause cooler than the nightside, along with signatures of a vertically propagating tide. The IUVS dataset provides an unprecedented constraint on the structure of the Martian mesosphere. The inconsistencies with the data imply that we do not really understand the dynamics and structure of this important region.

The main objective of this research project is to develop super-resolution mapping methods to increase the spatial resolution of surface maps of icy moons of the Solar System by combining all the overlapping observations acquired during a given planetary mission. Cassini-Huygens was the first dedicated mission to Saturn, where it spent 13 years studying the gas giant and its system of moons and rings creating a treasure-trove of data. The focus of this study is to create global surface cartographic products in the infrared by evaluating the Cassini's Visual and Infrared Mapping Spectrometer (VIMS) hyperspectral dataset in its entirety. We will first focus our efforts on developing, testing and validating the methods on Enceladus, a prime astrobiological candidate, which, in contrast to Titan, does not require any atmospheric corrections. We offer a new module in Python for creating the navigation cubes necessary in merging individual cubes into global mosaics, increasing the accuracy of the covered area and maximising the number of pixels used (e.g. limb-crossing pixels). We then determine a surface photometric function which mitigates variations in the brightness due to the changing geometric conditions of the flybys. With a precise and comprehensive navigation and an accurate surface photometric correction, we will be ready for the application of the super-resolution method to enhance both the spatial resolution and the signal-to-noise ratio of our maps.