Viking Biology Experiments and the Martian soil

The Viking Biology Experiments (VBE) are the most informative database on the wet chemistry and reactivity of the Martian soil available today. The simulation and chemical interpretation of the results have given valuable hints towards the characterization of the soils' mineralogy, adsorption properties, pH and redox. The characterization of Mars' soil on the basis of ten years of labelled release (LR) and other VBE simulations are reviewed

N2O fluxes at the soil-atmosphere interface in various ecosystems and the global N2O budget

The overall purpose of this research task is to study the effects of soil properties and ecosystem variables on N2O exchanges at the soil-atmosphere interface, and to assess their effects on the globle N2O budget. Experimental procedures are implemented in various sites to measure the source/sink relations of N2O at the soil-atmosphere interface over prolonged periods of time as part of the research of biogeochemical cycling in terrestrial ecosystems. A data-base for establishing quantitative correlations between N2O fluxes and soil and environmental parameters that are of potential use for remote sensing, is being developed

Workshop on chemical weathering on Mars, part 2

The third Mars Surface and Atmosphere Through Time (MSATT) Workshop, which was held 10-12 Sep. 1992, at Cocoa Beach/Cape Kennedy, focused on chemical weathering of the surface of Mars. The 30 papers presented at the workshop described studies of Martian weathering processes based on results from the Viking mission experiments, remote sensing spectroscopic measurements, studies of the shergottite, nakhlite, and chassignite (SNC) meteorites, laboratory measurements of surface analog materials, and modeling of reaction pathways. A summary of the technical sessions is presented and a list of workshop participants is included

The spectroscopic, chemical, and photophysical properties of Martian soils and their analogs (MERC, phase 2)

A series of variably proportioned iron/calcium smectite clays and iron loaded smectite clays containing iron up to the level found in the Martian soil were prepared from a typical montomorillonite clay using the Banin method. Evidence was obtained which supports the premise that these materials provide a unique and appropriate model soil system for the Martian surface in that they are consistent with the constraints imposed by the Viking surface elemental analysis, the reflectance data obtained by various spacecraft instruments and ground based telescopes, and the chemical reactivity measured by one of the Viking biology experiments, the Labeled Release (LR) experiment

MSATT Workshop on Chemical Weathering on Mars

The topics covered with respect to chemical weathering on Mars include the following: Mars soil, mineralogy, spectroscopic analysis, clays, silicates, oxidation, iron oxides, water, chemical reactions, geochemistry, minerals, Mars atmosphere, atmospheric chemistry, salts, planetary evolution, volcanology, Mars volcanoes, regolith, surface reactions, Mars soil analogs, carbonates, meteorites, and reactivity

Use of near infrared correlation spectroscopy for quantitation of surface iron, absorbed water and stored electronic energy in a suite of Mars soil analog materials

A number of questions concerning the surface mineralogy and the history of water on Mars remain unresolved using the Viking analyses and Earth-based telescopic data. Identification and quantitation of iron-bearing clays on Mars would elucidate these outstanding issues. Near infrared correlation analysis, a method typically applied to qualitative and quantitative analysis of individual constituents of multicomponent mixtures, is adapted here to selection of distinctive features of a small, highly homologous series of Fe/Ca-exchanged montmorillonites and several kalinites. Independently determined measures of surface iron, relative humidity and stored electronic energy were used as constituent data for linear regression of the constituent vs. reflectance data throughout the spectral region 0.68 to 2.5 micrometers. High correlations were found in appropriate regions for all three constituents, though that with stored energy is still considered tenuous. Quantitation was improved using 1st and 2nd derivative spectra. High resolution data over a broad spectral range would be required to quantitatively identify iron-bearing clays by remotely sensed reflectance

Characteristics and mode of palagonite - A review

The characteristics on which identification of palagonite is based, are reviewed. The varying chemistry, as well as the large number of minerals identified, suggest that palagonite covers the products of a continuous, time/temperature dependent and frequently over-lapping series of interlocking processes. Micromorphological features, detailed analyses of natural products, as well as experimental studies suggest that palagonite formation entails the complete dissolution of volcanic glass along interfaces, accompanied by the precipitation of authigenic minerals principally smectite and zeolites, with hydrotalcite as a short-lived interim mineral. The rate of palagonite formation is strongly temperature related.Singer Arieh, Banin Amos. Characteristics and mode of palagonite - A review. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol IV : Clays in sediments. Diagenesis and hydrothermalism. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 173-181. (Sciences Géologiques. Mémoire, 88

Characteristics and mode of palagonite - A review

The characteristics on which identification of palagonite is based, are reviewed. The varying chemistry, as well as the large number of minerals identified, suggest that palagonite covers the products of a continuous, time/temperature dependent and frequently over-lapping series of interlocking processes. Micromorphological features, detailed analyses of natural products, as well as experimental studies suggest that palagonite formation entails the complete dissolution of volcanic glass along interfaces, accompanied by the precipitation of authigenic minerals principally smectite and zeolites, with hydrotalcite as a short-lived interim mineral. The rate of palagonite formation is strongly temperature related.Singer Arieh, Banin Amos. Characteristics and mode of palagonite - A review. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol IV : Clays in sediments. Diagenesis and hydrothermalism. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 173-181. (Sciences Géologiques. Mémoire, 88

Diffuse reflectance spectra of smectite minerals in the near infrared and their relationship to chemical composition / Spectres de réflectance diffuse de smectites dans le proche infrarouge, en relation avec la composition chimique

High resolution reflectance spectra of 12 selected smectite minerals were determined in the near infrared (NIR) region (1.0-2.5 μm). The total concentration of four constituents (AI, Mg, Fe and Si) in the minerals was determined by XRF. Two approaches were studied in order to get the best correlation between chemical and spectroscopical data : (I) Selection of bands according to known OH-cation absorption features and calculation of the correlation between corrected absorption values and the constituent concentration. Some trends, but generally poor correlations (r2= 0.36-0.85) were obtained between chemical and spectroscopic data. (II) Selection of wavelengths from all the spectral regions in which high linear correlation exists between a given constituent concentration and the absorption intensity. Using the wavelengths for which the highest correlation coefficient exists, calibration equations were then fitted for each element by a forward multivariate linear regression procedure. Most wavelengths selected by approach II were spectroscopically explained as overtones and combinations of various OH-cation fundamental modes. High R2values were obtained (0.97-0.99) and correspondingly low standard error of calibration. Validation was done using a procedure adapted for the relatively small suite of samples under study. Reasonable precision was obtained with coefficient of variation for the studied suite of smectites in the range of 5-29% for the four elemental constituents, provided one outlier was omitted from each set. Near infrared analysis (NIRA) based upon approach II may have promising applications as a non-destructive and rapid method for analysis of constituent concentration in clays.Spectres de reflectance diffuse de smectites dans le proche infrarouge en relation avec la composition chimique. — Les spectres-de réflectance haute résolution de 12 smectites sélectionnées ont été réalisés dans le domaine du proche infrarouge (1,0 à 2,5 μm). Les teneurs en Al, Mg, Fe et Si de ces minéraux ont été déterminées par fluorescence X. Deux méthodes ont été étudiées pour trouver la meilleure corrélation entre les données chimiques et spectroscopiques : (I) sélection des bandes en fonction de structures d'adsorption cation-OH connues, et calcul de la corrélation entre les valeurs d'absorption corrigées et la concentration du constituant. Quelques tendances ont été décelées mais les corrélations étaient généralement faibles (r2= 0,36-0,85) entre données chimiques et données spectroscopiques ; (II) sélection de longueur d'onde dans toutes les régions du spectre où existe une forte corrélation linéaire entre une concentration d'un élément donné et l'intensité d'absorption. En utilisant les longueurs d'onde pour lesquelles on détecte le plus fort coefficient de corrélation, les équations de calibration étaient ajustées pour chaque élément par une méthode de régression linéaire multivariable. La plupart des longueurs d'onde sélectionnées par l'approche II ont été expliquées spectroscopiquement comme étant des harmoniques et des combinaisons de modes fondamentaux de diverses liaisons OH-cation. Des valeurs élevées du coefficient R2 (0.97-0.99) ont été obtenues et correspondaient à de faibles erreurs standard de calibration. La validation a été faite en utilisant une procédure adaptée aux séries relativement petites d'échantillons étudiés. Une précision acceptable a été obtenue pour les quatre éléments constituants à condition qu'un point aberrant soit exclu dans chaque lot. L'analyse dans le proche infrarouge fondée sur l'approche II pourrait avoir des applications prometteuses comme méthode rapide et non destructive d'analyse des concentrations des constituants des argiles.Ben-Dor Eyal, Banin Amos. Diffuse reflectance spectra of smectite minerals in the near infrared and their relationship to chemical composition / Spectres de réflectance diffuse de smectites dans le proche infrarouge, en relation avec la composition chimique. In: Sciences Géologiques. Bulletin, tome 43, n°2-4, 1990. Minéraux argileux dans les sols et les sédiments. pp. 117-128