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IntroductionDuring the only flyby of Triton by Voyager 2 in 1989, a dense ionosphere was observed (Tyler et al. 1989). Results were surprising as the solar irradiation of this satellite is ten times lower than on Titan, and yet its ionosphere is denser. Thus, electronic precipitation from Neptune’s magnetosphere was hypothesized to bring the needed extra input energy (Krasnopolsky et al. 1993), as high energy electrons have been observed by the spacecraft in this area (Krimigis et al. 1989). To understand how this precipitation could impact the composition of Triton’s atmosphere, we coupled an electron transport code to a photochemical model of this atmosphere.Methodology We used the electron transport code TRANS that was utilized to compute the transport of electrons in various planetary atmospheres (see Gronoff et al. 2009 and references therein). We adapted it to Triton’s conditions and used the results from Strobel et al. (1990) and Sittler and Hartle (1996) to compute the input precipitation. This led us to calculate the mean magnetic field and the mean precipitation before adjusting it depending on energy, as detailed in Sittler and Hartle (1996). We then coupled TRANS with our most recent photochemical model of Triton’s atmosphere (Benne et al. 2022) by using TRANS outputs to compute the reaction rates of the electro-dissociation and electro-ionization reactions. Iterations were performed between the two codes until steady state was reached. After determining the nominal composition of the atmosphere, we ran a Monte Carlo simulation to characterize the effect of chemical uncertainties on the model results.ResultsWith our previous model presented in Benne et al. (2022), we found a peak electronic number density larger by a factor of 2.5 to 5 compared to the one derived from Voyager 2 observations. By coupling the photochemical model with TRANS, we find that our electronic profile is now in agreement with these measurements, resulting from a significant decrease of the electro-ionization rate. In contrast with the results of Benne et al. (2022), Krasnopolsky and Cruikshank (1995) and Strobel and Summers (1995), the main ionization source is solar EUV radiation instead of magnetospheric electrons. This work also allows us to better understand how the varying magnetic environment impacts the atmospheric chemistry.References[1] Tyler, G. L. et al. Science 246, no. 4936 (December 15, 1989): 1466–73.[2] Krasnopolsky, V. A. et al. Journal of Geophysical Research 98 (February 1, 1993): 3065–78.[3] Krimigis, S. M. et al. Science 246, no. 4936 (December 15, 1989): 1483–89.[4] Gronoff, G. et al. Astronomy & Astrophysics 506, no. 2 (November 2009): 955–64.[5] Strobel, Darrell F. et al. Geophysical Research Letters 17, no. 10 (1990): 1661–64.[6] Sittler, E. C., and R. E. Hartle. Journal of Geophysical Research: Space Physics 101, no. A5 (May 1, 1996): 10863–76.[7] Benne, B. et al. Astronomy & Astrophysics 667 (November 2022): A169.[8] Krasnopolsky, Vladimir A., and Dale P. Cruikshank. Journal of Geophysical Research 100, no. E10 (1995): 21271.[9] Strobel, D. F., and M. E. Summers. 1995, 1107–48. Cruikshank, Dale P., Mildred Shapley Matthews, et A. M. Schumann. « Neptune and Triton », 1995.

We report on a combined experimental and theoretical investigation of the N(2D) + C6H6 (benzene) reaction of relevance in the atmospheric chemistry of Titan. Experimentally, the reaction was studied (i)...

Search for organic bioindicators in the solar system is a fundamental challenge for the space research community. If tremendous improvements have been achieved in detection, little or no research has been dedicated to extraction of the targets from the studied mineral matrices. Apart from thermodesorption, no extraction step was ever performed in situ within the context of biomarker detection experiments. This work presents an extraction protocol compatible with in situ space constraints. Two extraction methods, i.e., microwave-assisted extraction (MAE) and focused ultrasonic extraction (FUSE), were optimized with the aim of extracting molecules having an astrobiological interest (amino acids, nucleobases, polyaromatic carboxylic acids) and that are included in mineral matrices representative of the Martian soil. Higher efficiency was obtained with the FUSE method (20 kHz, amplitude 80%, pulse and relaxation 1 s each, for 10 min) with yields ranging from 30 to 95%. It was then applied on an Atacama Desert soil sample and Aguas Zarcas meteorite fragment. Both water-soluble and organic-soluble compounds present at trace levels were extracted using this short extraction time, and small amounts of sample and solvent compliant with in situ requirements (50 mg, 500 μL). This unique FUSE/derivatization-GC-MS approach gave similar yields to usual 24 h hot water extraction and increased the recovery of the target molecules compared to the derivatization-GC-MS method already used for in situ space experiments by a factor from 2 to 8. The data highlighted the suitability of a focused ultrasonic method for the extraction of trace organic compounds from extraterrestrial samples.

The localized delivery of new long-lived species to Jupiter’s stratosphere by comet Shoemaker-Levy 9 in 1994 opened a window to constrain jovian chemistry and dynamics by monitoring the evolution of their vertical and horizontal distributions. ALMA observations of HCN and CO in March 2017 show that CO was meridionally uniform and restricted to pressures lower than 3±1 mbar. HCN shared a similar vertical distribution in the low-to-mid latitudes, but was surprisingly depleted at pressures higher than 0.04(-0.03; +0.07) mbar in the polar regions. We propose that heterogeneous chemistry bonds HCN on large aurora-produced aerosols at these pressures in the jovian polar regions causing the observed depletion. We also propose that a relatively small fraction of CO causes enhanced production of CO2 inside the aurora to explain the long-term decrease of the CO column density and the CO2 peak observed only at southern polar latitudes in 2000.

Jupiter's stratospheric chemistry and dynamics are poorly understood as a function of latitude. The Shoemaker-Levy 9 comet impacts in Jupiter's atmosphere in 1994 have offered us with a unique means to characterize Jupiter's stratospheric chemistry and dynamics. We can indeed use the delivery at 44°S of the long-lived species HCN, CO, H2O, and CS and the subsequent temporal evolution of their spatial distribution as constraints for vertical and meridional mixing, zonal winds and chemistry as a function of latitude. We mapped HCN and CO in Jupiter's stratosphere with ALMA in March 2017. These observations have already been used in Cavalié et al. (2021) and Benmahi et al. (2021) to derive the stratospheric zonal wind field. In this paper, we use the same observations to retrieve the vertical and meridional distributions of HCN and CO, almost 25 years after the comet impacts. We will present the spatial distributions of both species and discuss the implications on Jupiter's stratospheric chemistry, and vertical and horizontal mixing.

We report on a combined experimental and theoretical investigation of the N(

Triton is the largest satellite of Neptune and probably a Kuiper Belt Object that was captured by the planet. It has a tenuous nitrogen atmosphere similar to the one of Pluto and may be an ocean world. The Neptunian system has only been visited by Voyager 2 in 1989. Over the last few years, the demand for a new mission to the Ice Giants and their systems has increased so that a theoretical basis to prepare for such a mission is important. We aim to develop a photochemical model of Triton's atmosphere with an up-to-date chemical scheme, as previous photochemical models date back to the post-flyby years. This is done to better understand the mechanisms governing Triton's atmospheric chemistry and highlight the critical parameters having a significant impact on the atmospheric composition. We also study model uncertainties to find what chemical studies are necessary to improve the modeling of Triton's atmosphere. We adapted a model of Titan's atmosphere to Triton's conditions. We first used Titan's chemical scheme before updating it to better model Triton's atmosphere. Once the nominal results were obtained, we studied model uncertainties with a Monte-Carlo procedure. Then, we performed global sensitivity analyzes to identify the reactions responsible for model uncertainties. With the nominal results, we determined the composition of Triton's atmosphere and studied the main chemical processes. We highlighted key chemical reactions that are the most important for the overall chemistry. We also identified some key parameters having a significant impact on the results. Uncertainties are large for most of the main atmospheric species as the atmospheric temperature is very low. We identified key uncertainty reactions that have the largest impact on the results uncertainties. These reactions must be studied in priority in order to improve the significance of our results., Comment: 35 pages, 11 Figures, 7 Tables, 1 Appendix

Observational data of Titan's atmosphere composition, gathered in particular by the Cassini mission, allow accessing latitudinal, longitudinal and temporal variations of the altitudinal profiles of several species. While 1D models are a powerful tool to gain insight into the chemistry occurring in Titan's atmosphere, they cannot capture the four-dimensional nature of these processes at the same time. However, due to the large extent of the atmosphere and the complexity of chemistry, global 2D and 3D models with the chemical complexity of 1D models do not exist yet. On the way of developing a 2D photochemical model of Titan, including the very complex chemical schemes used in 1D models and also taking latitudinal variations into account, we developed an ultraviolet radiative transfer model to compute the actinic flux in a 2D geometry. We found that photolysis rates calculated in classical plane-parallel models to derive the rates in mean conditions give results notably different from a model that calculates the mean rates with a 2D geometry. We demonstrate that the introduction of the 2D geometry affects significantly the density profiles on both neutrals and ions, especially on nitriles. As a consequence, we advocate using radiative transfer model in 2D geometry from now on to interpret the wide diversity of observational data about Titan's atmosphere (pending the emergence of 2D models with complex chemical schemes).

Introduction Triton is the biggest satellite of Neptune. Discovered in 1846 by W. Lassell, it was visited by Voyager 2 in 1989. It was the only spacecraft to study the neptunian system. Very little was known about Triton at the time of the flyby, except its highly inclined retrograde orbit suggesting that it is a Kuiper Belt object captured by Neptune. This idea was also comforted by the similarities between Triton and Pluto. The flyby allowed to take high resolution pictures of the surface, to determine its temperature, pressure and the composition of the surface ices (N2, CH4, CO, CO2 and water ice). Clouds and haze were also observed respectively under 10 and 30km of altitude as well as plumes of organic material propagating up to 8km, pointing out the existence of a troposphere. It appeared that the low atmosphere was at vapor pressure equilibrium with the surface’s ices (Yelle et al. 1995). The atmosphere was also studied by measuring its airglow and by performing stellar occultations (Broadfoot et al. 1989). It revealed that it is mainly composed of N2, and N with traces of CH4 near the surface. CO was not detected and so only an upper limit on its abundance had been set. An important ionosphere was also observed with an important peak at 340km (Tyler and al. 1989). As Triton is far from the Sun, this important ionosphere cannot be explained by solar ionization only. So, it was hypothesized that energy was brought by precipitating electrons from the magnetosphere of Neptune (Strobel et al. 1990b). Another source of power is the interplanetary Lyman-Alpha flux that is not negligible at Triton’s distance from the Sun (Strobel et al. 1990a). However, since the Voyager 2 mission and its only flyby, Triton remains poorly understood in comparison to Titan which was intensely studied during the Cassini-Huygens mission (despite some observations with ALMA and the VLT, see Lellouch et al. 2010 and Merlin et al. 2018). And as for Titan, it is now supposed that Triton is an ocean world (Fletcher et al. 2020). Sending a new mission to the neptunian system appears as a necessity to increase our knowledge about ice giants and their systems. In order to prepare such a mission, having a theoretical photochemical model for Triton can be useful to have a reference against which we would compare data collected during such a mission. The photochemical model As a starting point, we used the photochemical model of Titan (see Dobrijevic et al. 2016) and adapted it to Triton. In particular, we used the chemical scheme developed for Titan (with recent updates presented in Hickson et al. 2020), as the two atmospheres are mainly composed of N2, with presence of CH4. Our methodology is presented on Figure 1. On Titan, CH4 is the second most abundant species but only traces were observed on Triton. Strobel et al. (1990a) suggested that this species was destructed by solar and interplanetary Lyman-Alpha radiation (as Triton is at 30 UA from the Sun, the interplanetary Ly-Alpha flux is comparable to the solar one). The atmosphere of Triton is also much less dense as the surface pressure is 14 bar against 1.5 bar on Titan. We use data from Strobel and Zhu (2017) for the initial temperature, pressure, density and eddy coefficient profiles. To obtain a first validation of our model, we compare our results with the Voyager 2 data and with the results presented in the principal articles about the photochemistry of Triton published after the Voyager 2 flyby: Strobel and Summers (1995), Krasnopolsky and Cruikshank (1995). Our model takes the interplanetary Ly-Alpha flux into account as well as the energy input of precipitating electrons from the neptunian magnetosphere by adding reactions of electron impact ionization and dissociation for N2. The ionization profile was taken from Strobel et al. (1990b). We modified the chemical network to adapt it to Triton’s atmospheric composition in order to get a nominal chemical scheme. The eddy coefficient profile is constrained to match our CH4 profile to the one measured by Voyager near the surface, as it was done in Strobel et al. (1990a) and Krasnopolsky and Cruikshank (1995). Our model takes actually into account 204 species (117 neutrals and 87 ions). Our chemical scheme is composed of 1570 reactions (154 photodissociations, 597 neutral reactions, 31 photoionizations and 788 ionic reactions). We use an altitudinal grid varying in H/5, H being the height scale of the atmosphere, giving 96 levels from 0 to 1026km. First results Our first results confirm that precipitation of magnetospheric electrons is very important to explain the composition of the ionosphere. The solar flux is also a critical parameter of the model since the CH4 abundance profile near the surface depends on the solar activity (the Voyager 2 flyby occurred near a solar maximum). This abundance profile also depends on the eddy diffusion coefficient. We also observed that the results depend strongly on some reactions. A study of the model’s uncertainties seems mandatory and will allow us to identify these key reactions. Uncertainties may indeed be large due to the low temperature of Triton’s atmosphere.

International audience; The photochemical processes at work in the atmosphere of Titan are very complex and lead to a great variety of compounds with aerosols as an end-product. One of the most complex molecules detected so far is benzene (C6H6). In the present work, we have updated and improved the chemistry of aromatics in order to better understand the main chemical pathways leading to the production of benzene and determine what other aromatics could be produced efficiently in the atmosphere. This new chemical scheme has been incorporated in our 1D photochemical model corresponding to mean conditions. We confirm the importance of ionic chemistry for benzene production in the upper atmosphere and we have found that excited benzene is an important intermediate in benzene production due to the exothermicity of many production reactions. Among the 24 aromatics included in the model, neutral aromatics like toluene (C6H5CH3) and ethylbenzene (C6H5C2H5) are relatively abundant, suggesting in particular that toluene could be detectable in the infrared, and eventually microwave wavelength ranges. However, we obtained large uncertainties on model results highlighting the need for more experiments and theoretical studies to improve the chemistry of aromatics.List of reactions (with rate constants) and references used in the present model.List of photodissociations and references used in the present model.For each reaction included in the model, the integrated column rate scaled to the surface (in cm-2 s-1) and the mean altitude (in km) of the production are given.In the three following files, we list the key reactions at 300 km, 500 km and 1000 km of altitude for all species in the present model.

Context. The tropospheric wind pattern in Jupiter consists of alternating prograde and retrograde zonal jets with typical velocities of up to 100 m/s around the equator. At much higher altitudes, in the ionosphere, strong auroral jets have been discovered with velocities of 1-2 km/s. There is no such direct measurement in the stratosphere of the planet. Aims. In this paper, we bridge the altitude gap between these measurements by directly measuring the wind speeds in Jupiter's stratosphere. Methods. We use the Atacama Large Millimeter/submillimeter Array's very high spectral and angular resolution imaging of the stratosphere of Jupiter to retrieve the wind speeds as a function of latitude by fitting the Doppler shifts induced by the winds on the spectral lines. Results. We detect for the first time equatorial zonal jets that reside at 1 mbar, i.e. above the altitudes where Jupiter's Quasi-Quadrennial Oscillation occurs. Most noticeably, we find 300-400 m/s non-zonal winds at 0.1 mbar over the polar regions underneath the main auroral ovals. They are in counter-rotation and lie several hundreds of kilometers below the ionospheric auroral winds. We suspect them to be the lower tail of the ionospheric auroral winds. Conclusions. We detect directly and for the first time strong winds in Jupiter's stratosphere. They are zonal at low-to-mid latitudes and non-zonal at polar latitudes. The wind system found at polar latitudes may help increase the effciency of chemical complexification by confining the photochemical products in a region of large energetic electron precipitation., 7 pages and 3 figures (+ 5 pages and 5 figures for the appendix). Published in A&A 647, L8

The upper tropospheric zonal winds have been measured since decades using cloud tracking with maximum winds speeds of ∼ 100 m/s in the tropical region (Ingersoll et al. 1979). Juno measurements have shown that these winds extend in the deep layers of the planet (Kaspi et al. 2018). In the ionosphere, jets have been detected in the auroral zone with velocities of 1-2 km/s (Rego et al. 1999). In-between these atmospheric regions, in the stratosphere, there are no such tracers as clouds. Even if zonal winds can in principle be indirectly derived from temperature field by assuming the thermal wind balance (e.g. Flasar et al. 2004), this technique relies on a boundary condition often taken as the cloud-top structure which is located at levels that are separated from where the stratospheric temperature field is constrained. Also, this technique breaks down at equatorial latitudes.Using the Atacama Large Millimeter/submillimeter Array, we mapped Jupiter’s stratospheric HCN emission in March 2017 to directly measure wind-induced Doppler shifts on the spectral lines. We imaged the HCN limb emission with an angular resolution of 1” and a very high spectral resolution. After subtracting the rapid rotation of the planet from the Doppler shifts measured on the spectral lines, we derived the wind speeds as a function of latitude on both limbs.We find strong tropical jets at 1 mbar with velocities of 100-200 m/s lying atop the layers where the Quasi-Quadrennial Oscillation occurs. Most surprisingly, we find strong non-zonal winds in Jupiter’s polar regions at 0.1 mbar with counter-rotation velocities of 300-400 m/s. Their position coincides with the location of the main auroral oval.In this paper, we will present our observations and results. We will also discuss their implications on the dynamics and chemistry of Jupiter’s stratosphere.

In response to ESA Voyage 2050 announcement of opportunity, we propose an ambitious L-class mission to explore one of the most exciting bodies in the Solar System, Saturn largest moon Titan. Titan, a "world with two oceans", is an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. Titan is also one of the few places in the Solar System with habitability potential. Titan remarkable nature was only partly revealed by the Cassini-Huygens mission and still holds mysteries requiring a complete exploration using a variety of vehicles and instruments. The proposed mission concept POSEIDON (Titan POlar Scout/orbitEr and In situ lake lander DrONe explorer) would perform joint orbital and in situ investigations of Titan. It is designed to build on and exceed the scope and scientific/technological accomplishments of Cassini-Huygens, exploring Titan in ways that were not previously possible, in particular through full close-up and in situ coverage over long periods of time. In the proposed mission architecture, POSEIDON consists of two major elements: a spacecraft with a large set of instruments that would orbit Titan, preferably in a low-eccentricity polar orbit, and a suite of in situ investigation components, i.e. a lake lander, a "heavy" drone (possibly amphibious) and/or a fleet of mini-drones, dedicated to the exploration of the polar regions. The ideal arrival time at Titan would be slightly before the next northern Spring equinox (2039), as equinoxes are the most active periods to monitor still largely unknown atmospheric and surface seasonal changes. The exploration of Titan northern latitudes with an orbiter and in situ element(s) would be highly complementary with the upcoming NASA New Frontiers Dragonfly mission that will provide in situ exploration of Titan equatorial regions in the mid-2030s., Comment: arXiv admin note: substantial text overlap with arXiv:1908.01374

Uranus and Neptune have only been visited by one spacecraft, Voyager 2. Their atmospheres thus remain mysterious in terms of composition and dynamics, despite repeated efforts to observe them from the ground and earth-orbiting telescopes. Deep composition is key to constrain internal and formation processes but is difficult to measure with remote sensing techniques because of the condensation into various cloud layers of several key volatiles. Chemical complexification initiated by solar UV and magnetospheric electrons, as well as contamination by external sources (dust, comets, ring and satellite material), all occurring in the upper atmosphere but diffusing downward, can further complicate the situation because of the mixing of these various components caused by dynamics. In this context, an atmospheric entry probe to measure key volatiles (e.g. noble gases, C, N, S, P) in the upper troposphere is highly desirable (Mousis et al. 2018, Cavalié et al. 2020) and would benefit from direct observational support from an orbiting spacecraft (Fletcher et al. 2020), as well as contextual ground-based supporting observations. All these measurements are essential to constrain the chemistry models we develop to better understand the composition and dynamics in the Ice Giant atmospheres. With a coherent set of models, ranging from 1D thermochemical and diffusion models for the tropospheres (Cavalié et al. 2017, Leconte et al. 2017, Venot et al. 2019, 2020) to 2D time-dependent photochemical models for the stratospheres and ionospheres (Hue et al. 2018, Dobrijevic et al. 2020), we aim at contributing to a better understanding of the Ice Giant composition and dynamics.

In July 1994, comet Shoemaker-Levy 9 collided with Jupiter. This has introduced new chemical species into Jupiter’s atmosphere, notably H2O. We observed the disk-averaged emission H2O in Jupiter’s stratosphere at 556.936 GHz between 2002 and 2019 with the Odin space telescope with the initial goal of better constraining vertical eddy mixing (Kzz) in the layers probed by our observations (0.2-5 mbar). The Odin observations show a decrease of about 40% of the line emission from 2002 to 2019. We analyzed these observations by combining a 1D photochemical model with a radiative transfer model to constrain the vertical eddy diffusion Kzz in the stratosphere of Jupiter. We were able to reproduce this decrease by modifying a well-established Kzz profile, in the 0.2 mbar to 5 mbar pressure range. However, the Kzz obtained is incompatible with observations of the main hydrocarbons. We found that even if we increase locally the initial abundances of H2O and CO at impact, the photochemical conversion of H2O and CO to CO2 does not allow us to find the observed decrease of the H2O emission line over time, suggesting that there is another loss mechanism. We propose that auroral chemistry, not accounted for in our model, as a promising candidate to explain the loss of H2O seen by Odin. Modeling the temporal evolution of the chemical species deposited by comet SL9 in the atmosphere of Jupiter with a 2D photochemical model would be the next step in this study.

In this paper, we present the first measurements of the vertical distribution of cyanogen (${{\rm{C}}}_{2}{{\rm{N}}}_{2}$) in Titan's lower atmosphere at different latitudes and seasons, using Cassini's Composite Infrared Spectrometer far-infrared data. We also study the vertical distribution of three other minor species detected in our data: methylacetylene (${{\rm{C}}}_{3}{{\rm{H}}}_{4}$), diacetylene (${{\rm{C}}}_{4}{{\rm{H}}}_{2}$), and ${{\rm{H}}}_{2}{\rm{O}}$, in order to compare them to ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$, but also to get an overview of their seasonal and meridional variations in Titan's lower stratosphere from 85 km to 225 km. We measured an average volume mixing ratio of ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ of $6.2\pm 0.8\times {10}^{-11}$ at 125 km at the equator, but poles exhibit a strong enrichment in ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ (up to a factor 100 compared to the equator), greater than what was measured for ${{\rm{C}}}_{3}{{\rm{H}}}_{4}$ or ${{\rm{C}}}_{4}{{\rm{H}}}_{2}$. Measuring ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ profiles provides constraints on the processes controlling its distribution, such as bombardment by Galactic Cosmic Rays which seem to have a smaller influence on ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ than predicted by photochemical models.

Electronically excited nitrogen atoms N(

The distant ice giants of the Solar System, Uranus and Neptune, have only been visited by one space mission, Voyager 2. The current knowledge on their composition remains very limited despite some recent advances. A better characterization of their composition is however essential to constrain their formation and evolution, as a significant fraction of their mass is made of heavy elements, contrary to the gas giants Jupiter and Saturn. An in situ probe like Galileo would provide us with invaluable direct ground-truth composition measurements. However, some of the condensibles will remain out of the grasp of a shallow probe. While additional constraints could be obtained from a complementary orbiter, thermochemistry and diffusion modeling can further help us to increase the science return of an in situ probe., Comment: Accepted for publication in Space Science Reviews

Electronically excited nitrogen atoms N(2D) are important species in the photochemistry of N2 based planetary atmospheres such as Titan. Despite this, few N(2D) reactions have been studied over the appropriate low temperature range. During the present work, rate constants were measured for the N(2D) + ethene (C2H4) reaction using a supersonic flow reactor at temperatures between 50 K and 296 K. Here, a chemical reaction was used to generate N(2D) atoms, which were detected directly by laser induced fluorescence in the vacuum ultraviolet wavelength region. The measured rate constants displayed very little variation as a function of temperature, with substantially larger values than those obtained in previous work. Indeed, considering an average temperature of 170 K for the atmosphere of Titan leads to a rate constant that is almost seven times larger than the currently recommended value. In parallel, electronic structure calculations were performed to provide insight into the reactive process. While earlier theoretical work at a lower level predicted the presence of a barrier for the N(2D) + C2H4 reaction, the present calculations demonstrate that two of the five doublet potential energy surfaces correlating with reagents are likely to be attractive, presenting no barriers for the perpendicular approach of the N atom to the carbon double bond of ethene. The measured rate constants and new product channels taken from recent dynamical investigations of this process are included in a 1D coupled ion-neutral model of Titans atmosphere. These simulations indicate that the modeled abundances of numerous nitrogen bearing compounds are noticeably affected by these changes., Comment: 21 pages, 5 figures, 2 tables

Neptune remains a mysterious world that deserves further exploration and is a high-priority objective for a future planetary mission in order to better understand the formation and evolution of ice giant planets. We have developed a coupled ion-neutral 1D photochemical model of Neptune's atmosphere to study the origin and evolution of the hydrocarbons and the oxygen species. The up-to-date chemical scheme is derived from one used for Titan's atmosphere, which led to good agreements with the Cassini-CIRS observations for oxygen species and the main hydrocarbons. The main results we obtain are the following: The ion-neutral chemistry coupling produces aromatics (and benzene in particular) in the atmosphere of Neptune with relatively high abundances. Our model results are in good agreement with observations (taking model uncertainties into account). Two ionospheric peaks are present in the atmosphere located above the pressure level of 10$^{-5}$ mbar and around 10$^{-3}$ mbar. The influx of oxygen species in the upper atmosphere of Neptune has an effect on the concentration of many ions. We show that in situ exploration of Neptune's atmosphere would provide very interesting constraints for photochemical models concerning in particular the origin of oxygen species and the contribution of ion chemistry. A precise description of upper atmospheric chemistry is crucial for a better understanding of the internal composition and the formation processes of this planet., Comment: 40 pages, 1 table, 20 figures. Published in Icarus

Context. The comet Shoemaker-Levy 9 impacted Jupiter in July 1994, leaving its stratosphere with several new species, with water vapor (H2O) among them. Aims. With the aid of a photochemical model, H2O can be used as a dynamical tracer in the Jovian stratosphere. In this paper, we aim to constrain the vertical eddy diffusion (Kzz) at levels where H2O is present. Methods. We monitored the H2O disk-averaged emission at 556.936 GHz with the space telescope between 2002 and 2019, covering nearly two decades. We analyzed the data with a combination of 1D photochemical and radiative transfer models to constrain the vertical eddy diffusion in the stratosphere of Jupiter. Results. Odin observations show us that the emission of H2O has an almost linear decrease of about 40% between 2002 and 2019. We can only reproduce our time series if we increase the magnitude of Kzz in the pressure range where H2O diffuses downward from 2002 to 2019, that is, from ~0.2 mbar to ~5 mbar. However, this modified Kzz is incompatible with hydrocarbon observations. We find that even if an allowance is made for the initially large abundances of H2O and CO at the impact latitudes, the photochemical conversion of H2O to CO2 is not sufficient to explain the progressive decline of the H2O line emission, which is suggestive of additional loss mechanisms. Conclusions. The Kzz we derived from the Odin observations of H2O can only be viewed as an upper limit in the ~0.2 mbar to ~5 mbar pressure range. The incompatibility between the interpretations made from H2O and hydrocarbon observations probably results from 1D modeling limitations. Meridional variability of H2O, most probably at auroral latitudes, would need to be assessed and compared with that of hydrocarbons to quantify the role of auroral chemistry in the temporal evolution of the H2O abundance since the SL9 impacts. Modeling the temporal evolution of SL9 species with a 2D model would naturally be the next step in this area of study.

The reactions of metastable atomic nitrogen N(

The scope of this paper is to present a gold standard method to evaluate functional activity of antibody (Ab)-based materials during the different phases of their development, after their exposure to forced degradations or even during routine quality control. Ab-based materials play a central role in the development of diagnostic devices, for example, for screening or therapeutic target characterization, in formulation development, and in novel micro(nano)technology approaches to develop immunosensors useful for the analysis of trace substances in pharmaceutical and food industries, clinical and environmental fields. A very important aspect in diagnostic device development is the construction of its biofunctional surfaces. These Ab surfaces require biocompatibility, homogeneity, stability, specificity and functionality. Thus, this work describes the validation and applications of a unique ligand binding assay to directly perform the quantitative measurement of functional Ab binding sites immobilized on the solid surfaces. The method called Antibody Anti-HorseRadish Peroxidase (A2HRP) method, uses a covalently coated anti-HRP antibody (anti-HRP Ab) and does not need for a secondary Ab during the detection step. The A2HRP method was validated and gave reliable results over a wide range of absorbance values. Analyzed validation criteria were fulfilled as requested by the food and drug administration (FDA) and European Medicines Agency (EMA) guidance for the validation of bioanalytical methods with 1) an accuracy mean value within +15% of the nominal value; 2) the within-assay precision less than 7.1%, and 3) the inter-day variability under 12.1%. With the A2HRP method, it is then possible to quantify from 0.04 × 1012 to 2.98 × 1012 functional Ab binding sites immobilized on the solid surfaces. A2HRP method was validated according to FDA and EMA guidance, allowing the creation of a gold standard method to evaluate Ab surfaces for their resistance under laboratory constraints. Stability testing was described through forced degradation studies after exposure of Ab-surfaces to storage, pH and aqueous-organic solvent mixture stresses.

Antibody-coated surfaces (Ab surfaces) play a key role in bioanalytical tools developed for biosensors and diagnostics. Therefore, a high and well-defined functional activity of the Ab surface is required. The functional activity of the Ab surface depends on its available binding sites i.e. "the active sites" that are able to capture antigen (Ag). The number of active binding sites strongly depends on the immobilization strategy used to fix the Ab on the solid surface. Determination of layer thickness or surface topology are often used to characterize the Ab surfaces but there is no gold standard method for the study of the functionality of the Ab surfaces. For that purpose, we aim at developing an assay allowing to determine the performances of Ab surfaces. In the present study, anti-horseradish peroxidase antibody (anti-HRP Ab) is used as capture Ab covalently bound to the surface and enzyme HRP as Ag. This direct assay permits, in one-step, to generate a signal utilizing the catalytic properties of HRP. The signal is directly proportional to the amount of HRP bound on the Ab surface, and therefore to the active binding sites of immobilized Ab. The HRP/anti-HRP Ab interactions may be a useful indicator to construct accurate and reproducible active Ab surfaces and also to improve their performances in term of stability and sensitivity. Optimization of the assay parameters and quality of the results are presented. A good repeatability and an acceptable inter-day precision (RSD10%) are reported.

International audience; Antibody-based analytical instruments are under development to detect signatures of life on planetary bodies.Antibodies are molecular recognition reagents able to detect their target at sub-nanomolar concentrations, withhigh affinity and specificity. Studying antibody binding performances under space conditions is mandatory toconvince space agencies of the adequacy of this promising tool for planetary exploration.To complement previous ground-based experiments on antibody resistance to simulated irradiation, weevaluate in this paper the effects of antibody exposure to real space conditions during the EXPOSE-R2 missionoutside the International Space Station. The absorbed dose of ionizing radiation recorded during the 588 days ofthis mission (220 mGy) corresponded to the absorbed dose expected during a mission to Mars. Moreover,samples faced, at the same time as irradiation, thermal cycles, launch constraints, and long-term storage. Amodel biochip was used in this study with antibodies in freeze-dried form and under two formats: free orcovalently grafted to a solid surface.We found that antibody-binding performances were not significantly affected by cosmic radiation, and morethan 40% of the exposed antibody, independent of its format, was still functional during all this experiment. Weconclude that antibody-based instruments are well suited for in situ analysis on planetary bodies. Key Words:Astrobiology—Cosmic rays—Biochip—Antibody—Planetary exploration. Astrobiology 19, 1053–1062.

The gas-phase reactions between metastable nitrogen atoms, N(

International audience; The reactions of metastable atomic nitrogen N(2 D) are important processes in the gas-phase chemistry of several planetary atmospheres. Here we present a combined experimental and theoretical investigation of the N(2 D) + acetylene reaction due to its potential significance for the photochemistry of Titan's atmosphere. Experimentally, a continuous supersonic flow reactor was used to study this reaction over the 50-296 K temperature range employing pulsed laser photolysis and vacuum ultraviolet laser induced fluorescence to produce and detect N(2 D) atoms respectively. The measured rate constants are substantially larger than those obtained in earlier work and remain constant as a function of temperature. Moreover, these results are supported by new electronic structure calculations which indicate that this process is likely to be barrierless. The impact of the new rate constants on Titan's atmospheric chemistry is tested through simulations using a 1D coupled ion-neutral photochemical model.

International audience; The gas-phase reactions between metastable nitrogen atoms, N(2 D) and saturated hydrocarbons CH4, C2H6 and C3H8 have been investigated using a supersonic flow reactor over the 296-75 K temperature range. N(2 D) was generated as a product of the C(3 P) + NO ® N(2 D) + CO reaction, with C(3 P) atoms created in-situ by pulsed laser photolysis of CBr4. The kinetics of N(2 D) loss were followed by vacuum ultraviolet laser induced fluorescence. The measured rate constants for the N(2 D) + CH4 reaction are in good agreement with earlier work and extend the available kinetic data for this process down to 127 K. The measured rate constants for the N(2 D) + C2H6 and N(2 D) + C3H6 reactions are in reasonable agreement with previous work at room temperature and extend the available kinetic data for these processes down to 75 K. The rate constants for all three reactions decrease as the temperature falls, indicating the presence of activation barriers for all three processes. While the recommended values for the low temperature rate constants of the N(2 D) + CH4 reaction are close to those reported here, the previous recommendations for the other saturated hydrocarbon reactions significantly overestimate the rate constants for these processes. The effects of the new rate constants on a coupled ion-neutral photochemical model of Titan's atmosphere are discussed.

International audience; Some microarray-based instruments that use bioaffinity receptors such as antibodies or aptamers are under development to detect signatures of past or present life on planetary bodies. Studying the resistance of such instruments against space constraints and cosmic rays in particular is a prerequisite. We used several ground-based facilities to study the resistance of aptamers to various types of particles (protons, electrons, neutrons, and carbon ions) at different energies and fluences. We also tested the resistance of aptamers during the EXPOSE-R2 mission outside the International Space Station (ISS). The accumulated dose measured after the 588 days of this mission (220 mGy) corresponds to the accumulated dose that can be expected during a mission to Mars. We found that the recognition ability of fluorescently labeled aptamers was not significantly affected during short-term exposure experiments taking into account only one type of radiation at a time. However, we demonstrated that the same fluorescent dye was significantly affected by temperature variations (−21°C to +58°C) and storage throughout the entirety of the ISS experiment (60% of signal loss). This induced a large variability of aptamer signal in our analysis. However, we found that >50% of aptamers were still functional after the whole EXPOSE-R2 mission. We conclude that aptamer-based instruments are well suited for in situ analysis on planetary bodies, but the detection step requires additional investigations.

Context. The origin of water in the stratospheres of Giant Planets has been an outstanding question ever since its first detection by ISO some 20 years ago. Water can originate from interplanetary dust particles, icy rings and satellites and large comet impacts. Analysis of Herschel Space Observatory observations have proven that the bulk of Jupiter's stratospheric water was delivered by the Shoemaker-Levy 9 impacts in 1994. In 2006, the Cassini mission detected water plumes at the South Pole of Enceladus, placing the moon as a serious candidate for Saturn's stratospheric water. Further evidence was found in 2011, when Herschel demonstrated the presence of a water torus at the orbital distance of Enceladus, fed by the moon's plumes. Finally, water falling from the rings onto Saturn's uppermost atmospheric layers at low latitudes was detected during the final orbits of Cassini's end-of-mission plunge into the atmosphere. Aims. In this paper, we use Herschel mapping observations of water in Saturn's stratosphere to identify its source. Methods. Several empirical models are tested against the Herschel-HIFI and -PACS observations, which were collected on December 30, 2010, and January 2nd, 2011 (respectively). Results. We demonstrate that Saturn's stratospheric water is not uniformly mixed as a function of latitude, but peaking at the equator and decreasing poleward with a Gaussian distribution. We obtain our best fit with an equatorial mole fraction 1.1 ppb and a half-width at half-maximum of 25{\deg}, when accounting for a temperature increase in the two warm stratospheric vortices produced by Saturn's Great Storm of 2010-2011. Conclusions. This work demonstrates that Enceladus is the main source of Saturn's stratospheric water., Comment: Accepted for publication in A&A, section 10. Planets and planetary systems. 16 pages. 17 figures, 1 table

Three dimensional models that account for chemistry are useful tools to predict the chemical composition of (exo)planet and brown dwarf atmospheres and interpret observations of future telescopes. Recent Juno observations of the NH3 tropospheric distribution in Jupiter also indicate that 3D chemical modelling may be necessary to constrain the deep composition of the giant planets of the Solar System. However, due to the high computational cost of chemistry calculations, 3D chemical modelling has so far been limited. A solution to include chemical kinetics in a 3D model is to use a reduced chemical scheme. In this view, we have developed a reduced scheme containing 30 species and 181 reversible reactions, from the full chemical scheme of Venot et al. 2012. This scheme reproduces accurately the vertical profiles of the observable species (H2O, CH4, CO, CO2, NH3, and HCN) and has a large range of validity. It can be used to study all kind of warm atmospheres, except hot C-rich ones, which contains a high amount of C2H2. It can be used in 1D models, for fast computations, but also in 3D models for hot giant (exo)planet and brown dwarf atmospheres., 13 pages, 11 figures, accepted for publication in A&A

International audience

The anti-horseradish peroxidase (HRP) antibody is conventionally used in immunohistochemistry. More recently, it has been used as the key element in a gold standard method to evaluate the functionality of antibody-based materials. However, few information are available about its melting temperature and its stability after exposition to laboratory stress conditions including freeze-drying and freeze-thawing cycles. The aim of this study was to evaluate the effects of these environmental constraints on the anti-HRP antibody in order to further use it as a reference in quality control and in the development of new antibody-based materials. In the developed method, the anti-HRP antibody is covalently immobilized onto a solid surface. After the direct recognition of its antigen HRP, the signal is proportional to the number of antibody active binding sites. The method was successfully utilized to accurately evaluate the anti-HRP antibody melting temperature (Tm was 73.5 ± 0.2 °C). The method is a rapid and reliable tool with minimal cost for studying the anti-HRP antibody stability to solvent stress, freeze-thawing cycles, and freeze-drying process. The obtained information may be useful for routine analysis or in the development of antibody-based materials. This can be also proposed as an easy way to control antibody freeze-drying process.

We aim at constraining the diffusive and advective transport processes in Jupiter's stratosphere. The IR spectrum recorded by Cassini/CIRS during the Jupiter flyby contains the fingerprints of several atmospheric compounds and allows probing its atmospheric composition. C2H2 and C2H6, the main compounds produced by methane photochemistry, were retrieved as a function of latitude at certain pressure levels. CIRS observations suggest a different meridional distribution for these two species, difficult to reconcile with their photochemical histories, which are thought to be coupled to the methane photolysis. While the C2H2 abundance decreases with latitude, C2H6 becomes more abundant at high latitudes. A new 2D (latitude-altitude) seasonal photochemical model is developed to study whether the addition of stratospheric transport processes, such as meridional diffusion and advection, can explain the latitudinal behavior of C2H2 and C2H6. C2H2 observations are fairly well reproduced without meridional diffusion. Adding meridional diffusion to the model provides an improved agreement with the C2H6 observations by flattening its meridional distribution, but degrades the fit to the C2H2 distribution. Meridional diffusion alone cannot produce the observed increase with latitude of C2H6. When adding advective transport between 30 mbar and 0.01 mbar, with upwelling winds at the equator and downwelling winds at high latitudes, we can reproduce the C2H6 abundance increase with latitude. However, the fit to the C2H2 distribution is degraded. The strength of the advective winds needed to reproduce the C2H6 abundances is very sensitive to the value of the meridional eddy diffusion coefficient. The coupled fate of C2H2 and C2H6 suggests that an additional process is missing in the model. Ion-neutral chemistry was not accounted for in this work and might be a good candidate to solve this issue., Comment: Received 13 October 2017 Revised 12 January 2018 Accepted 13 February 2018

Saturn's axial tilt of 26.7{\deg} produces seasons in a similar way as on Earth. Both the stratospheric temperature and composition are affected by this latitudinally varying insolation along Saturn's orbital path. A new time dependent 2D photochemical model is presented to study the seasonal evolution of Saturn's stratospheric composition. This study focuses on the impact of the seasonally variable thermal field on the main stratospheric C2 hydrocarbon chemistry (C2H2 and C2H6) using a realistic radiative climate model. Meridional mixing and advective processes are implemented in the model but turned off in the present study for the sake of simplicity. The results are compared to a simple study case where a latitudinally and temporally steady thermal field is assumed. Our simulations suggest that, when the seasonally variable thermal field is accounted for, the downward diffusion of the seasonally produced hydrocarbons is faster due to the seasonal compression of the atmospheric column during winter. This effect increases with increasing latitudes which experience the most important thermal changes in the course of the seasons. The seasonal variability of C2H2 and C2H6 therefore persists at higher-pressure levels with a seasonally-variable thermal field. Cassini limb-observations of C2H2 and C2H6 (Guerlet et al., 2009) are reasonably well-reproduced from the equator to 40{\deg} in both hemispheres, Comment: 63 pages, 26 figures, manuscript accepted for publication in Icarus

International audience; The origin of CO and the external source of H2O in the atmosphere of Titan is still a matter of debate. We investigated the chemical fractionation of oxygen isotopologues in order to give new constraints on the origin of oxygen species. We created a new chemical scheme and we developed a 1-D time-dependent photochemical model to compute the mole fraction profiles of various oxygen isotopologues. We show that the photochemical fractionation of oxygen isotopologues is quite low. Observations of C18O and CO18O are compatible with both an external origin or an internal origin of CO considering that the various sources of oxygen have a cometary 16O/18O ratio (16O/18O ≈ 500). Improvement of the measurements of the 16O/18O ratio in both Enceladus' plumes and atmospheric CO2 could give a valuable constraint on the origin of oxygen in Titan's atmosphere.

Due to the diversity of antibody (Ab)-based biochips chemistries available and the little knowledge about biochips resistance to space constraints, immobilization of Abs on the surface of the biochips dedicated to Solar System exploration is challenging. In the present paper, we have developed ten different biochip models including covalent or affinity immobilization with full-length Abs or Ab fragments. Ab immobilizations were carried out in oriented/non-oriented manner using commercial activated surfaces withN-hydroxysuccinic ester (NHS-surfaces) or homemade surfaces using three generations of dendrimers (dendrigraft of poly L-lysine (DGL) surfaces). The performances of the Ab -based surfaces were cross-compared on the following criteria: (i) analytical performances (expressed by both the surface density of immobilized Abs and the amount of antigens initially captured by the surface) and (ii) resistance of surfaces to preparation procedure (freeze-drying, storage) or spatial constraints (irradiation and temperature shifts) encountered during a space mission. The latter results have been expressed as percentage of surface binding capacity losses (or percentage of remaining active Abs). The highest amount of captured antigen was achieved with Ab surfaces having full-length Abs and DGL-surfaces that have much higher surface densities than commercial NHS-surface. After freeze-drying process, thermal shift and storage sample exposition, we found that more than 80% of surface binding sites remained active in this case. In addition, the resistance of Ab surfaces to irradiation with particles such as electron, carbon ions or protons depends not only on the chemistries (covalent/affinity linkages) and strategies (oriented/non-oriented) used to construct the biochip, but also on the type, energy and fluence of incident particles. Our results clearly indicate that full-length Ab immobilization on NHS-surfaces and DGL-surfaces should be preferred for potential use in instruments for planetary exploration.

Several instruments based on immunoassay techniques have been proposed for life-detection experiments in the framework of planetary exploration but few experiments have been conducted so far to test the resistance of antibodies against cosmic ray particles. We present several irradiation experiments carried out on both grafted and free antibodies for different types of incident particles (protons, neutrons, electrons and 12C) at different energies (between 9 MeV and 50 MeV) and different fluences. No loss of antibodies activity was detected for the whole set of experiments except when considering protons with energy between 20 and 30 MeV (on free and grafted antibodies) and fluences much greater than expected for a typical planetary mission to Mars for instance. Our results on grafted antibodies suggest that biochip-based instruments must be carefully designed according to the expected radiation environment for a given mission. In particular, a surface density of antibodies much larger than the expected proton fluence would prevent significant loss of antibodies activity and thus assuring a successful detection.

Many models with different characteristics have been published so far to study the chemical processes at work in Titan’s atmosphere. Some models focus on neutral species in the stratosphere or ionic species in the ionosphere, but few of them couple all the species throughout the whole atmosphere. Very few of these emphasize the importance of uncertainties in the chemical scheme and study their propagation in the model. We have developed a new 1D-photochemical model of Titan’s atmosphere coupling neutral species with positive and negative ions from the lower atmosphere up to the ionosphere and have compared our results with observations to have a comprehensive view of the chemical processes driving the composition of the stratosphere and ionosphere of Titan. We have updated the neutral, positive ion and negative ion chemistry and have improved the description of N 2 photodissociation by introducing high resolution N 2 absorption cross sections. We performed for the first time an uncertainty propagation study in a fully coupled ion-neutral model. We determine how uncertainties on rate constants on both neutral and ionic reactions influence the model results and pinpoint the key reactions responsible for this behavior. We find very good agreement between our model results and observations in both the stratosphere and in the ionosphere for most neutral compounds. Our results are also in good agreement with an average INMS mass spectrum and specific flybys in the dayside suggesting that our chemical model (for both neutral and ions) provides a good approximation of Titan’s atmospheric chemistry as a whole. Our uncertainty propagation study highlights the difficulty to interpret the INMS mass spectra for masses 14, 31, 41 and we identified the key reactions responsible for these ambiguities. Despite an overall improvement in the chemical model, disagreement for some specific compounds (HC 3 N, C 2 H 5 CN, C 2 H 4 ) highlights the role that certain physical processes could play (meridional dynamics or sticking on aerosols). We find that some critical key reactions are important for many compounds including both neutrals and ions and should be studied in priority to lower the remaining model uncertainties. Extensive studies for some specific processes (including photolyses) are required.

The production rates of neutral species by dissociative recombination (DR) of molecular ions with electrons in the ionosphere of Titan are quantified by a new model, including, for the first time, all the available kinetic data on this process. The calculation is based on the ion densities measured by the INMS instrument on Cassini orbiter during flyby T19 at 1100 km altitude. These production rates are compared with those predicted by photochemical models: we calculate that for many neutral species, DR has larger production rates than neutral chemistry. Concerning molecular growth in Titan’s ionosphere, DR is shown to have two antagonistic effects: (1) a global chemical lysis of ions through C–C and C–N bond breaking (missed by the “H-loss” DR paradigm); and (2) an enhancement of the neutral chemistry by production of reactive radicals, such as C 2 H or NH 2 . Further exploration of this chemistry requires the development of ionospheric coupled models taking explicitly into account the richness of the DR process and the strong impact of ions on the budget of neutral species. This study emphasizes also the urgent need of additional experimental studies about DR of molecular ions, with two priorities: evaluation of the impact of the temperature of ions on the rates and fragmentation patterns, and the systematic study of the fragmentation patterns of C x H y N z + ions with more than four heavy atoms ( m / z > 60 u).

Saturn's axial tilt produces seasons in a similar way as on Earth. Both the stratospheric temperature and composition are affected by this latitudinally varying insolation along the seasons. The thermal structure is controlled and regulated by the amount of hydrocarbons in the stratosphere, which act as absorbers and coolants from the UV to the far-IR spectral range, and this structure influences the amount of hydrocarbons. We study here the feedback between the chemical composition and the thermal structure by coupling a latitudinal and seasonal photochemical model with a radiative seasonal model. Our results show that the seasonal temperature peak in the higher stratosphere, associated with the seasonal increase of insolation, is shifted earlier than the maximum insolation peak. This shift is increased with increasing latitudes and is caused by the low amount of stratospheric coolants in the spring season. At 80$^{\circ}$ in both hemispheres, the temperature peak at 1d-2mbar is seen to occur half a season earlier than was previously predicted by radiative seasonal models that assumed spatially and temporally uniform distribution of coolants. This shift progressively decreases with increasing pressure, up to around the 0.5mbar pressure level where it vanishes. However, the thermal field has a small feedback on the abundance distributions. This feedback modifies the predicted equator-to-pole temperature gradient. The meridional gradients of temperature at the mbar pressure levels are better reproduced when this feedback is accounted for. At lower pressure levels, the thermal structure seems to depart from pure radiative seasonal equilibrium as previously suggested by Guerlet et al. (2014). Although the agreement with the absolute value of the stratospheric temperature observed by Cassini is moderate, it is a mandatory step toward a fully coupled GCM-photochemical model., 23 pages, 8 figures, accepted for publication in Icarus

International audience; n this article, we apply supersaturated strategies to identify active factors in the field of numerical simulation. As the number of simulations is inferior to the number of studied factors, new resolution techniques are proposed and provide excellent results. Indeed, classical supersaturated treatments could not be applied to the high dimensional problem. We show that these designs are well adapted to the high dimensional problem while maintaining the number of simulations at reasonable levels. Very small-sized supersaturated designs show low reliability. Keywords: Hadamard matrix; Supersaturated designs; Screening; Computer experiments; Genetic algorithm; Sensitivity analysis

International audience; The covalent immobilization of synthetic or natural macromolecular compounds containing amino groups onto polystyrene (PS) solid surfaces is of great interest in diagnostic applications. A sensitive assay allowing the determination of reactive end groups is therefore a powerful tool for predicting the performance of the active surface. Recently, we reported the use of the Coomassie brilliant blue (CBB) colorimetric reagent to quantify protonated groups (N +) in linear and dendritic structures in solution (Coussot et al., Polym Int 58(5):511- 518, 2009). In this work, a simple method using CBB dye for the characterization of PS aminated solid surfaces is developed. The proposed amino density estimation by colorimetric assay (ADECA) method is based on the reversible complexation of the dye with the N + groups on solid surfaces. The assay measures the released dye thanks to the use of a unique sodium carbonate-methanol buffer. Thereby, for the first time, the same surface can be used for characterization and for further coupling applications. A surface density of four N + groups per square nanometer can be measured in PS microwell format, the whole characterization being done within 30 min. Performances of this new colorimetric-based method are detailed. The ADECA method is further demonstrated to be useful for the characterization of aminated polypropylene and glass materials with various sizes and shapes.

International audience; Simulations with a Monte Carlo tool kit have been performed to determine the radiation environment a specific device, called a biochip, would face if it were placed into a rover bound to explore Mars' surface. A biochip is a miniaturized device that can be used to detect organic molecules in situ. Its specific detection part is constituted of proteins whose behavior under cosmic radiation is completely unknown and must be investigated to ensure a good functioning of the device under space conditions. The aim of this study is to define particle species and energy ranges that could be relevant to investigate during experiments on irradiation beam facilities. Several primary particles have been considered for galactic cosmic ray (GCR) and solar energetic particle (SEP) contributions. Ionizing doses accumulated in the biochip and differential fluxes of protons, alphas, neutrons, gammas, and electrons have been established for both the Earth-Mars transit and the journey at Mars' surface. Neutrons and gammas appear as dominant species on martian soil, whereas protons dominate during the interplanetary travel. Depending on solar event occurrence during the mission, an ionizing dose of around a few Grays (1Gy=100rad) is expected.

The use of experimental designs in the field of numerical simulation improves global sensitivity analysis compared to Monte Carlo based method by decreasing the number of simulations. More particularly, supersaturated designs can be applied to decrease the number of calculations, because the number of simulations is inferior to the number of studied factors but its use is risky and depends on “parsimony principle”. This paper shows new supersaturated designs that use the a priori knowledge and thus overcome this difficulty.

The aim of this paper is to highlight the skeletal chemistry responsible for the rich ionospheric chemistry observed in Titan's atmosphere. The present database is represented by about 700 ion–molecule reactions, which are not all important to describe the system. Our criterion to reduce the list of reactions is to reproduce a reference mass spectrum within its uncertainties. This reference mass spectrum is obtained with the complete reaction database and with neutral densities optimized for the INMS mass spectrum measured at 1200 km during the T5 flyby. We compared two mechanism reduction methods, brute force screening and global sensitivity analysis. The analysis of the residual scheme with only 35 bimolecular reactions highlights several patterns, concerning in particular ionic growth processes and introduction of nitrogen to the ionic species. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 699–709, 2008