LIBS (Laser-induced breakdown spectroscopy) pour l'exploration martienne

ChemCam est à bord de la mission Mars Science Laboratory (MSL) qui a décollé pour Mars le 26 novembre 2011. Cet instrument est très innovant car c'est la première fois que la technique du LIBS ("Laser-Induced Breakdown Spectroscopy") est utilisée pour l'exploration planétaire, afin d'étudier la géochimie des sols et roches à la surface de la planète rouge. Cette technique permet de déterminer la composition chimique de la cible analysée, en focalisant un laser à sa surface. Un plasma se créé alors par échauffement de la matière. L'analyse spectrale de la lumière émise du plasma permet d'identifier les éléments présents dans la roche, ainsi que leur concentration. Ce travail de thèse contribue à la préparation du retour scientifique de la mission MSL et de l'instrument ChemCam autour de quatre axes principaux : (i) identification et caractérisation des raies spectrales pertinentes, (ii) test des méthodes de classification des roches avec ces mesures, (iii) étude de la sensibilité aux vernis d'altération des roches ou à la couche de poussière, (iv) analyse des données pour extraire des informations sur la structure et la composition des roches. Une station sol a été développée afin de reproduire les conditions atmosphériques à la surface de Mars. Une bibliothèque de raies élémentaires a été réalisée. Cette dernière est spécifique à ChemCam et à la géochimie de Mars, et contient plus de 1300 raies. Les outils de classification des roches avec les données de ChemCam se sont montrés efficaces. ChemCam permet de réaliser des analyses quantitatives, que ce soit par des méthodes statistiques ou plus conventionnelles. Nous avons montré que cet instrument est capable d'analyser aussi-bien la couche d'altération d'un basalte que la roche saine au dessous. Il permet également d'effectuer des analyses très fines, comme la comparaison de différentes matrices de roches volcaniques, ou encore de la structure interne des argiles. Pour finir, ces études expérimentales réalisées durant la thèse ont démontré que ChemCam répondait à toutes les spécifications imposées au début de sa conception.ChemCham is onboard the Mars Science Laboratory (MSL) mission, which was launched the 26th November 2011. This instrument uses the LIBS (Laser-Induced Breakdown Spectroscopy) technique to study the geochemistry of the Martian surface. This technique is used for the first time for the Space and Planetary exploration. In LIBS technique a pulsed laser beam is focused on a target, creating a plasma. The spectral analysis of the plasma light is collected to observe the characteristic emission lines of the elements present in the sample. This work contributes to the preparation of the scientific returns of the MSL mission but also of ChemCam, with four principal axes: - identification and characterization of the significant elemental lines, - test of the method used to distinguish rocks with these measurements, study of the capacity to analyze the alteration coating on rocks, - data analysis to extract informations about the structure and/or composition of rocks A ground station was developed in order to be representative of the Martian surface conditions. An elemental lines database specific of ChemCam and Mars is performed, with up to 1300 lines. Several experimental studies let us to characterize some of the ChemCam capabilities. First, rocks classification is successful whatever the kind of the sample. Some parameters were studied to understand their influence on the classifications. Then, quantitative analysis with ChemCam are feasible, not only using statistical methods. We show that ChemCam is able to analyze the composition of the alteration coating before the one from the unaltered rock, deeper. It is also able to make some differences between several kinds of basalts with their texture and matrix, and between several kinds of clays, looking at their internal structure

Observations of Rocks in Jezero Landing Site: SuperCam/LIBS technique overview of results from the first six months of operations.

On-board the Perseverance rover, the SuperCam instrument is being used as a remote-sensing facility to analyze rocks and soils targets. SuperCam is a suite of five coaligned techniques: just like ChemCam (onboard MSL/Curiosity rover on Mars since 2012), it uses the Laser Induced Breakdown Spectroscopy (LIBS) technique to determine the elementary composition of the targets, but it also uses Raman (for the first time in planetary science) and visible-infrared (VISIR - for the first time in situ) spectroscopic methods in order to access some mineralogical and structural information. A microphone gives access to some physical parameters of the sampled rocks (such as hardness) as well as to some atmospheric parameters (wind direction). These chemical and mineralogical analyses are contextualized thanks to a color remote micro-imager (RMI). In this study, we focus mainly on the LIBS results obtained so far

SuperCam Calibration Targets: Design and Development

SuperCam is a highly integrated remote-sensing instrumental suite for NASA’s Mars 2020 mission. It consists of a co-aligned combination of Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), Visible and Infrared Spectroscopy (VISIR), together with sound recording (MIC) and high-magnification imaging techniques (RMI). They provide information on the mineralogy, geochemistry and mineral context around the Perseverance Rover. The calibration of this complex suite is a major challenge. Not only does each technique require its own standards or references, their combination also introduces new requirements to obtain optimal scientific output. Elemental composition, molecular vibrational features, fluorescence, morphology and texture provide a full picture of the sample with spectral information that needs to be co-aligned, correlated, and individually calibrated. The resulting hardware includes different kinds of targets, each one covering different needs of the instrument. Standards for imaging calibration, geological samples for mineral identification and chemometric calculations or spectral references to calibrate and evaluate the health of the instrument, are all included in the SuperCam Calibration Target (SCCT). The system also includes a specifically designed assembly in which the samples are mounted. This hardware allows the targets to survive the harsh environmental conditions of the launch, cruise, landing and operation on Mars during the whole mission. Here we summarize the design, development, integration, verification and functional testing of the SCCT. This work includes some key results obtained to verify the scientific outcome of the SuperCam system

LIBS (Laser-Induced Breakdown Spectroscopy) pour l'observation martienne

ChemCham is onboard the Mars Science Laboratory (MSL) mission, which was launched the 26$^{th}$ November 2011. This instrument uses the LIBS (Laser-Induced Breakdown Spectroscopy) technique to study the geochemistry of the Martian surface. This technique is used for the first time for the Space and Planetary exploration. In LIBS technique a pulsed laser beam is focused on a target, creating a plasma. The spectral analysis of the plasma light is collected to observe the characteristic emission lines of the elements present in the sample. This work contributes to the preparation of the scientific returns of the MSL mission but also of ChemCam, with four principal axes : - identification and characterization of the significant elemental lines, - test of the method used to distinguish rocks with these measurements, - study of the capacity to analyze the alteration coating on rocks, - data analysis to extract informations about the structure and/or composition of rocks A ground station was developed in order to be representative of the Martian surface conditions. An elemental lines database specific of ChemCam and Mars is performed, with up to 1300 lines. Several experimental studies let us to characterize some of the ChemCam capabilities. First, rocks classification is successful whatever the kind of the sample. Some parameters were studied to understand their influence on the classifications. Then, quantitative analysis with ChemCam are feasible, not only using statistical methods. We show that ChemCam is able to analyze the composition of the alteration coating before the one from the unaltered rock, deeper. It is also able to make some differences between several kinds of basalts with their texture and matrix, and between several kinds of clays, looking at their internal structure.ChemCam est à bord de la mission Mars Science Laboratory (MSL) qui a décollé pour Mars le 26 novembre 2011. Cet instrument est très innovant car c'est la première fois que la technique du LIBS ("Laser-Induced Breakdown Spectroscopy") est utilisée pour l'exploration planétaire, afin d'étudier la géochimie des sols et roches à la surface de la planète rouge. Cette technique permet de déterminer la composition chimique de la cible analysée, en focalisant un laser à sa surface. Un plasma se créé alors par échauffement de la matière. L'analyse spectrale de la lumière émise du plasma permet d'identifier les éléments présents dans la roche, ainsi que leur concentration. Ce travail de thèse contribue à la préparation du retour scientifique de la mission MSL et de l'instrument ChemCam autour de quatre axes principaux : (i) identification et caractérisation des raies spectrales pertinentes, (ii) test des méthodes de classification des roches avec ces mesures, (iii) étude de la sensibilité aux vernis d'altération des roches ou à la couche de poussière, (iv) analyse des données pour extraire des informations sur la structure et la composition des roches. Une station sol a été développée afin d'imiter les conditions atmosphériques à la surface de Mars. Une bibliothèque de raies élémentaires a été réalisée. Cette dernière est spécifique à ChemCam et à la géochimie de Mars, et contient plus de 1300 raies. La classification des roches est efficace, quelque soit le type de cible. Les différents paramètres (distance, traitement des données, ..) pouvant influencer ces classifications ont également été caractérisés. ChemCam permet de réaliser des analyses quantitatives, que ce soit par des méthodes statistiques ou plus conventionnelles. Nous avons montré que cet instrument est capable d'analyser aussi-bien la couche d'altération d'un basalte que la roche saine au dessous. Il permet également d'effectuer des analyses très fines, comme la comparaison de différentes matrices de roches volcaniques, ou encore de la structure interne des argiles. Pour finir, ces études expérimentales réalisées durant la thèse ont démontré que ChemCam répondait à toutes les spécifications imposées au début de sa conception

Imaginaires de guerre. Claude Simon et Pascal Quignard

Simon/Quignard : two life periods during wars (for one, his father’s death in 1914 on the battlefield and his own experience in 1939-40; for the other, the ruins and destructions seen from his window and the family stories) call two very differing fiction worlds. Nevertheless both, when deconstructing the war engines, are producing an analysis in similar terms: war’s cruelty, far from the hero building story tale is the mark of humanity. Its images, in their power of destruction, are one of the springs of their writing practice, although so different when writing the fragmentation. Their imaginary of war suggests the power of literature

« Lire. Aimer. Le corps-à-corps. »

Si dans l’amour la présence du corps va de soi, il n’en va pas de même dans la lecture. Or, Pascal Quignard le met au jour au fil de ses livres, quand la lecture est une expérience qui revivifie l’attache primitive à la mère, elle est un toucher, une présence quasi corporelle qui n’exclut pas un risque d’effondrement, de vide, prix à payer pour découvrir en soi du nouveau, pour que la lecture soit, à l’égal de l’amour, la « vraie vie »

Mise au point de techniques d'évaluation de la sudation

POITIERS-BU Médecine pharmacie (861942103) / SudocSudocFranceF

WP2 – Emissions de gaz à effet de serre en milieu agricole

National audienc

An approach to provide maps of the N2O emission risks by soils at the regional scale: A case-study at the Haut-Loir watershed, France

International audienceNitrous oxide (N2O) is often emitted by soils after nitrogen fertilization when the reduction of nitrate into N2 is incomplete and the soil is in hydromorphic condition. To take action to reduce N2O emissions, it is necessary to identify and locate areas that present a risk of N2O emissions. In this study, an approach to map N2O emission risk by soils was therefore developed based on soil properties. The risk of N2O emission was assessed through two components linked to static properties, independent on climate and agricultural practices; the Vulnerability: the ability of the soil to reduce N2O and the Hazard: the probability of soil water-logging. This approach was tested in the Haut-Loir watershed (3600 km2), a highly cropped area in the French Center Region. Vulnerability and hazard were estimated using French soil databases. The databases contain the drainage class information which allowed inferring the hazard. They also have measurements of pH, CEC and clay content which allowed estimating vulnerability through a pedotransfer function. In this watershed, contrasting risks were highlighted between different soil types and agricultural regions. High risk soils (∼2% of the studied area) were generally found in valleys and were not under crop because of their hydromorphy and acidity. However, attention should be given to medium risk soils (∼32% of the area) which were mainly found in the western region. Oppositely, soils of the eastern region present generally no risk of N2O emissions. Some former field studies have been reported in the studied watershed: they generally supported this soil risk classification. For medium-risk soils, different actions of mitigation depending on the degree of risk were suggested: liming or adjusting nitrogen input periods. This risk mapping approach could be applied in other cropland regions to help mitigation strategy

An approach to map nitrous oxide emission risk by soils at regional scale based on soil properties

International audienc