The Earth as an extrasolar transiting planet - II: HARPS and UVES detection of water vapor, biogenic O2_2, and O3_3

The atmospheric composition of transiting exoplanets can be characterized during transit by spectroscopy. For the transit of an Earth twin, models predict that biogenic $O_2$ and $O_3$ should be detectable, as well as water vapour, a molecule linked to habitability as we know it on Earth. The aim is to measure the Earth radius versus wavelength $\lambda$ - or the atmosphere thickness $h(\lambda)$ - at the highest spectral resolution available to fully characterize the signature of Earth seen as a transiting exoplanet. We present observations of the Moon eclipse of 21-12-2010. Seen from the Moon, the Earth eclipses the Sun and opens access to the Earth atmosphere transmission spectrum. We used HARPS and UVES spectrographs to take penumbra and umbra high-resolution spectra from 3100 to 10400 Ang. A change of the quantity of water vapour above the telescope compromised the quality of the UVES data. We corrected for this effect in the data processing. We analyzed the data by 3 different methods. The 1st method is based on the analysis of pairs of penumbra spectra. The 2nd makes use of a single penumbra spectrum, and the 3rd of all penumbra and umbra spectra. Profiles $h(\lambda)$ are obtained with the three methods for both instruments. The 1st method gives the best result, in agreement with a model. The second method seems to be more sensitive to the Doppler shift of solar spectral lines with respect to the telluric lines. The 3rd method makes use of umbra spectra which bias the result, but it can be corrected for this a posteriori from results with the first method. The 3 methods clearly show the spectral signature of the Rayleigh scattering in the Earth atmosphere and the bands of H$_2$O, O$_2$, and O$_3$. Sodium is detected. Assuming no atmospheric perturbations, we show that the E-ELT is theoretically able to detect the $O_2$ A-band in 8~h of integration for an Earth twin at 10pc.Comment: Final version accepted for publication in A&A - 21 pages, 27 figures. Abstract above slightly shortened wrt the original. The ArXiv version has low resolution figures, but a version with full resolution figures is available here: http://www.obs-hp.fr/~larnold/publi_to_download/eclipse2010_AA_v5_final.pd

The Earth as an extrasolar transiting planet: Earth's atmospheric composition and thickness revealed by Lunar eclipse observations

An important goal within the quest for detecting an Earth-like extrasolar planet, will be to identify atmospheric gaseous bio-signatures. Observations of the light transmitted through the Earth's atmosphere, as for an extrasolar planet, will be the first step for future comparisons. We have completed observations of the Earth during a Lunar eclipse, a unique situation similar to that of a transiting planet. We aim at showing what species could be detected in its atmosphere at optical wavelengths, where a lot of photons are available in the masked stellar light. We present observations of the 2008 August 16 Moon eclipse performed with the SOPHIE spectrograph at the Observatoire de Haute-Provence. Locating the spectrograph fibers in the penumbra of the eclipse, the Moon irradiance is then a mix of direct, unabsorbed Sun light and solar light that has passed through the Earth's limb. This mixture essentially reproduces what is recorded during the transit of an extrasolar planet. We report here the clear detection of several Earth atmospheric compounds in the transmission spectra, such as ozone, molecular oxygen, and neutral sodium as well as molecular nitrogen and oxygen through the Rayleigh signature. Moreover, we present a method that allows us to derive the thickness of the atmosphere versus the wavelength for penumbra eclipse observations. We quantitatively evaluate the altitude at which the atmosphere becomes transparent for important species like molecular oxygen and ozone, two species thought to be tightly linked to the presence of life. The molecular detections presented here are an encouraging first attempt, necessary to better prepare for the future of extremely-large telescopes and transiting Earth-like planets. Instruments like SOPHIE will be mandatory when characterizing the atmospheres of transiting Earth-like planets from the ground and searching for bio-marker signatures.Comment: 15 pages, 14 figures, 2 tables. Accepted for publication in Astronomy and Astrophysic

Gas–Solid Chromatography on Organic Crystals

THE full potential of gas–solid chromatography has not yet been revealed. Theoretically it could be used to obtain much greater selectivity and higher efficiency than gas–liquid chromatography1–4. So far the characteristics required of an adsorbent have limited the use of gas–solid chromatography

MEASUREMENT OF THERMODYNAMIC EQUILIBRIA BY CHROMATOGRAPHY

International audienceAfter a brief recall of the chromatographic principles, the different applications of gas chromatographic measurements of thermodynamic equilibria were reviewed. Gas and liquid chromatographies are now well known and elegant methods for measuring the physicochemical properties and phase equilibrium thermodynamic constants. Although fundamentally a dynamical method and mostly known as a powerful separation technique, chromatography can be schematized by a succession of equilibria of a chemical species partitioning between a mobile phase and a fixed liquid or solid stationary phase. It can be operated in either infinite dilution or finite concentration conditions and permits to collect a large number of data for calculating molecular interactions for solutes which are either rare or available at the trace level. Gas chromatography permits the measurement of gas adsorption isotherms, gas-liquid equilibria, molecular diffusion and interaction virials. The modelization of successive partition equilibria occuring in the chromatographic column leads to rather simple expressio is of differential enthalpy, entropy, free energy of adsorption or solution, variation of heat capacity, complexation constant, second virial coefficients, gas-solid and gas-liquid isotherms and also binary or ternary equilibria. The possibilities of High Performance-Liquid Chromatography to investigate adsorption from solutions and chemical equilibria are also discussed

Gas Solid Chromatography Measurements of the Change in the Heat Capacity during Adsorption on Graphitized Thermal Carbon Black

Gas chromatography is widely used to measure the thermodynamic functions of adsorption on the homogeneous surface of graphitized thermal carbon black in the region where Henry\u27s adsorption law is valid. A high-precision instrument with computer data acquisition measures the isosteric heat of adsorption and the change of the heat capacity during adsorption. The method is used to study the adsorption of benzene and n-pentane on different graphitized thermal carbon black samples. The data are directly comparable with the values calculated from statistical thermodynamics on graphite since it is shown that adsorbateadsorbate interactions are negligible and that the behavior of the bulk gas phase is nearly ideal. The results obtained for benzene could be compared with the molar heat capacity of adsorbed benzene measured by calorimetric methods and extrapolated at zero surface coverage. With n-pentane, however, the gas solid chromatographic method is unique, as extrapolation of calorimetric measurements is impossible because of strong adsorbate-adsorbate interactions at relatively low surface coverage

Gas-solid and gas-liquid chromatography using porous layer open tube columns made with graphitized thermal carbon black

International audienceThe preparation of porous-layer open-tubular columns for gas—liquid chromatography with graphitized thermal carbon black as a solid support and a polar stationary phase is described. The application of these columns is demonstrated by an example.The reaction products from two oxidation reactions for the production of synthetic citral have been analysed by combined gas chromatography—mass spectrometry. About 30 trace substances rsulting from redox reaction and cyclization of the starting materials were found

Analyse par chromatographie des constituants minoritaires de l'atmosphere

Action concertee: Variations climatiques naturelles ou provoqueesSIGLEAvailable from Centre de Documentation Scientifique et Technique, CNRS, 26 rue Boyer, 75971 Paris Cedex 20 (France) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Adsorption kinetics of β-lactoglobulin on a polyclonal immunochromatographic support

β-Lactoglobulin is one of the main components of whey proteins. Among other reasons, its allergenicity makes its determination in hypoallergenic foods and bio-pharmaceutical products necessary. Immunoaffinity chromatography is a widely accepted technique for purification and analysis of proteins. Knowledge of the apparent kinetics of the adsorption of b-lactoglobulin onto the anti-b-lactoglobulin immunochromatographic column is important to optimize the analytical process. High-performance frontal affinity chromatography was used to study the apparent kinetics of the adsorption process. Langmuir and bi-Langmuir kinetic models, assuming one and two kinds of binding sites, respectively, were used to characterize the adsorption kinetics of b-lactoglobulin B on a polyclonal immunoadsorbent. Very good fits were obtained with the bi-Langmuir model for two different concentrations of b-lactoglobulin and this allowed us to calculate the apparent adsorption rate constants and the column capacities for both kinds of sites. Experimental results indicate the possibility that the adsorption process is not irreversible. The values of the apparent dissociation rate constants leading to the best fit were estimated and the affinity constants were calculated. Ó 2002 Elsevier Science B.V. All rights reserved.A.P. acknowledges the Spanish Ministry of Sci-ence and Technology for a predoctoral grant. This work has been supported by CICYT (project AGL2000-1480). Collaboration between our labora-tories has been possible thanks to French–Spanish Cooperation between CNRS and CSIC (project 7954, 2000).Peer reviewe

Frontal analysis for characterizing the adsorption-desorption behavior of beta-lactoglobulin on immunoadsorbents

High-performance frontal affinity chromatography was employed to study the adsorption–desorption kinetics characterizing the retention of Beta-lactoglobulin (Beta-LG) onto polyclonal anti-Beta-lactoglobulin (anti-Beta-LG) chromatographic supports. The adsorption and desorption processes were studied by analyzing two different elution fronts separated by a relatively long rinsing step. The method consists in performing two successive frontal injections of the protein. In between, the column was rinsed with a given volume of mobile phase (buffer alone). During this rinsing stage, a partial desorption may occur and a novel amount of protein could be adsorbed in the second frontal injection step. The whole process (first adsorption, possible desorption, and second adsorption) was simulated by a numerical procedure, in which the column was divided into a large number of slices. A model based on bi-Langmuir type kinetics was used to describe the adsorption of the protein on the support. The model assumes a non-uniform adsorbent with two types of binding sites. At equilibrium the adsorption isotherm is of the bi-Langmuir type. A global adsorption effect was considered which includes the effective binding process and the mass transfer resistances due to the transport to the binding site. Therefore, the column capacity and the kinetic parameters of the model (apparent adsorption and desorption rate constants) were determined from the best fit of the first and second adsorption fronts to the experimental ones. The other parameters of the model are the saturation capacities for the adsorption on each type of sites. The equilibrium affinity constants were estimated in a single experiment from the ratio of the apparent adsorption and desorption rate constants. The high values found (around 108 M−1) reveal a strong interaction of -LG with the immunoadsorbent. Kinetic measurements were carried out at different flow rates. Both the apparent adsorption and desorption kinetics were faster at larger flow rates, indicating an important contribution of the mass transfer resistance in the stagnant fluid at the particle boundary. However, as expected, close values were found for the resulting equilibrium constants calculated from the ratio of the apparent adsorption and desorption rate constant determined at various flow rates.A.P. acknowledges Spanish Ministry of Science and Tech- nology for a predoctoral grant. This work has been supported by Spanish CICYT (Project TIC2003-01906) and Foundation Ramon Areces. Collaboration between laboratories has been possible thanks to French-Spanish Cooperation between CNRS and CSIC.Peer reviewe