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The atmosphere of Mars is enriched in heavy isotopes with respect to Earth as a result of the escape of the atmosphere to space over billions of years. Estimating the enrichment in heavy isotopes due to atmospheric escape requires a rigorous understanding of all atmospheric processes that contribute to the evolution of isotopic ratios between the lower and upper atmosphere, where escape processes take place. Using a combination of vertical profiles from the Atmospheric Chemistry Suite (ExoMars Trace Gas Orbiter) with the predictions of a photochemical model, we provide evidence for a new process of photochemistry-induced fractionation that depletes the heavy isotopes of C and O in CO. Accounting for this new source of fractionation, we find that only a fraction of ≈12% of the atmosphere needs to have been lost to space through CO photochemical escape to explain the enrichment of 13C/12C in CO2 measured by the Curiosity Rover.

Carbon monoxide is a non-condensable gas in the Martian atmosphere produced by the photolysis of CO2. Its abundance responds to the condensation and sublimation of CO2 from the polar caps, resulting in seasonal variations of the CO mixing ratio. ACS onboard the ExoMars Trace Gas Orbiter have measured CO in infrared bands by solar occultation. Here we provide the first long-term monitoring of the CO vertical distribution at the altitude range from 0 to 80 km for 1.5 Martian years from Ls = 163° of MY34 to the end of MY35. We obtained a mean CO mixing ratio of ∼960 ppmv at latitudes from 45°S to 45°N and altitudes below 40 km, mostly consistent with previous observations. We found a strong enrichment of CO near the surface at Ls = 100–200° in high southern latitudes with a layer of 3,000–4,000 ppmv, corresponding to local depletion of CO2. At equinoxes we found an increase of the CO mixing ratio above 50 km to 3,000–4,000 ppmv at high latitudes of both hemispheres explained by the downwelling flux of the Hadley circulation on Mars, which drags the CO enriched air. General circulation models tend to overestimate the intensity of this process, bringing too much CO. The observed minimum of CO in the high and mid-latitudes southern summer atmosphere amounts to 700–750 ppmv, agreeing with nadir measurements. During the global dust storm of MY34, when the H2O abundance peaks, we see less CO than during the calm MY35, suggesting an impact of HOx chemistry on the CO abundance.

One of the goals of the ESA and Roscosmos Exomars Trace Gas Orbiter (TGO) is the exploitation of the two solar occultation instruments NOMAD [1] and ACS [2] to characterize the thermal structure of the Martian atmosphere with unprecendented vertical resolution, and from the ground up to the thermosphere. Specifically for the upper atmosphere this is a unique opportunity [3] and we present here an on-going effort to retrieve CO2 abundance and temperature profiles simultaneously from each of these instruments and to combine them for a mutual validation and for obtaining a most complete mapping from the TGO orbit. We developed a retrieval suite common for both instruments, comprising: (a) a cleaning/pre-processing module to build vertical profiles of calibrated transmittances which computes and correct for residual calibration and instrumental effects like spectral shifts, bending of the continuum and variations in the instrument line shape; (b) a state-of-the-art retrieval scheme designed originally for Earth atmospheric remote sensing [4,5,6] and applied to Mars [7], in order to derive simultaneous density and temperature profiles allowing for hydrostatic adjustments during the internal iteration.Recently the first application of this retrieval scheme focused on measurements by the NOMAD SO channel at altitudes below 100 km, and for the first year of TGO operations, from April 2018 to March 2019 (second half or “perihelion” season of MY34), and revealed very interesting results [8]. The thermal structure is strongly affected by the MY34 global dust storm at all altitudes, a cold mesosphere (in comparison to global climate models) was found during the post-GDS period, and wavy structures at mesospheric altitudes in the morning terminator seem to reveal very strong thermal tides at low-mid latitudes.In this presentation we also focus on the Martian troposphere and mesosphere and build upon the above mentioned work during the 1st year of TGO by extending the study to a full Mars year and adding retrievals from ACS MIR channel. Both NOMAD/SO and ACS/MIR channels observe the strong CO2 ro-vibrational band at 2.7 micron in the same spectral region with some differences in spectral resolution and noise level, in addition to very differnet instrument characteristics, which are included in our retrieval approach. In obth cases we use calibrated atmospheric transmittances to tackle three targets, CO2 density, temperature, and dust loading, in a simultaneous global-fit inversion, including contaminant species like H2O. The contamination by aerosol can severely limit the ability to sound low tangent altitudes with both instruments, when the gas absorption lines become hidden within the aerosol continuum. But also these measurements permit a good characterization of aerosol properties [9]. Propagation of measurement noise, tunning of regularization, and computation of averaging kernels are performed with the same code and the comparison of the retrieval performance is a first step towards a common validation between these two instruments, considering that a complete correlation is not possible since the two instruments' individual solar occulation scans are non-coincident in time and space. Our results will be discussed and compared to paralell retrieval efforts by other teams within the NOMAD and ACS consortia using the same datasets [10, 11, 12]. We will also compare them with specific runs of the LMD-Mars GCM (see also a companion presentation in this conference on this specific topic [13]). One of the important applications of our inversion is to supply true-field and a.priori inputs for the inversion of trace species from collocated NOMAD spectra, as we are doing for water vapour [14] and carbon monoxide [15]. AcknowledgmentsThe IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and funding by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration.References[1] Vandaele et al., Space Science Reviews 214, 5, 2018[2] Korablev et al., Space. Sci. Rev. 214, 7 (2018).[3] Lopez-Valverde et al., Space Sci Rev, 214, 29 (2018)[4] Funke, B., et al. , Atmos. Chem. Phys., 9(7), 2387–2411 (2009).[5] Stiller et al., JQSRT, 72, 249–280 (2002)[6] von Clarmann et al., J. Geophys. Res. 108, 4746 (2003)[7] Jimenez-Monferrer et al., Icarus, 353, 113830 (2020), doi.org/10.1016/j.icarus.2020.113830.[8] Lopez-Valverde et al., JGR-Planets (submitted, 2022)[9] Stolzenbach et al., JGR-Planets (submitted, 2022) and Stolzenbach et al., EPSC 2022 (this conference)[10] Trompet et al., JGR-Planets (submitted, 2022)[11] Belyaev et al., GRL[12] Belyaev et al., JGR-Planets (submitted, 2022)[13] Gonzalez-Galindo et al., EPSC 2022 (this conference)[14] Brines et al., JGR-Planets (submitted, 2022) and Brines et al., EPSC 2022 (this conference)[15] Modak et al., JGR-Planets (submitted, 2022) and Modak et al., EPSC 2022 (this conference)

This article analyzes the movement of material particles in the central and peripheral parts of the working chamber of a disk mill. A diagram of a disk mill and a diagram of the movement of particles in its working chamber are presented. The cutting elements are blades in the shape of a parabola located on the disks having an inclined surface. An expression is found for determining the time when a particle is located inside the grinding chamber of a mill. It is determined that this time depends on the geometric (x1; y1; x2; y2; ) and technological (ω) parameters. The dependence of the time spent on the change in the angle of deviation of the surface of the curved blade from the radial direction is shown in figure 3. As a result of theoretical research, an analytical expression is obtained that allows to determine the particle size at the output of the grinding chamber. According to the found expression, the final particle size at the output of the grinding chamber depends on such parameters as d0, σ, ω, and . As a result, the dependence (figure 4) of the ratio of the initial particle size to the final one ( 0 ) on the time change is constructed. According to the obtained graphs, as the angle increases, the particle time in the grinding chamber decreases, in result of which the final size of the particle at the output increases.

On Mars, condensation is the major factor constraining the vertical distribution of water vapor. Recent measurements of water and temperature profiles showed that water can be strongly supersaturated at and above the level where clouds form during the aphelion and perihelion seasons. Since 2018, the near-infrared spectrometer (NIR) of the Atmospheric Chemistry Suite onboard the Trace Gas Orbiter has measured H2O and temperature profiles using solar occultation in the infrared from below 10 to 100 km of altitude. Here, we provide the first long-term monitoring of the water saturation state. The survey spans 2 Martian years from Ls = 163° of MY34 to Ls = 170° of MY36. We found that water is often supersaturated above aerosol layers. In the aphelion season, the water mixing ratio above 40 km in the mid-to-high latitudes was below 3 ppmv and yet is found to be supersaturated. Around the perihelion, water is also supersaturated above 60 km with a mixing ratio of 30–50 ppmv. Stronger saturation is observed during the dusty season in MY35 compared to what was observed in MY34 during the Global Dust Storm and around the perihelion. Saturation varied between the evening and morning terminators in response to temperature modulation imparted by thermal tides. Although water vapor is more abundant in the evening, colder morning temperatures induce a daily peak of saturation. This data set establishes a new paradigm for water vapor on Mars, revealing that supersaturation is nearly ubiquitous, particularly during the dust season, thereby promoting water escape on an annual average.

Currently, disintegrators are one of the types of equipment used for grinding and mixing various materials. The advantages of disintegrators are the ability to control the speed of rotation of the rotors and change the geometric parameters to obtain a grinding product with the desired grain composition, as well as the simplicity of the design. In this paper, as a result of theoretical research, analytical expressions and are obtained, which define the radial size between adjacent rows of impact elements of the grinding chamber with a periodically varying distance. This change in the radial size has a high-frequency character, which determines the destruction of material particles under the influence of tangential stresses arising in them. To perform the necessary transformations, the article presents a design scheme of the disintegrator grinding chamber with a changing radial distance between adjacent rows. In the inter-row space, due to the inequality of the circumferential velocities of moving particles, tangential stresses acting on these particles occur. According to the result of, the value of tangent stresses in the inter-row space depends on the circumferential velocity of the particle, the coefficient of pseudo-viscous flow grinding and the value of the inter-row distance. The value of the row spacing, due to its periodic nature, can be represented as a function of the amplitude of the change in this distance and the angle measured from the initial direction of the axis. By solving a first-order differential equation with separable variables, it is possible to determine the initial and final value of the particle velocity in the region (0 ≤φ≤ /2) of an inter-row space of variable cross-section. The destruction of a material particle in an area with a periodically changing distance will be carried out if the change in the kinetic energy of the particle exceeds the work on its destruction as a result of collision.

In recent decades, disintegrator type mills have become widely used for grinding, activating and mixing construction materials. The efficiency of these mills is largely influenced by the design parameters of the working chamber, loading and unloading units, as well as some technological parameters, such as the speed of rotation of the rotors. In this article, an attempt is made to determine the conditions for the departure of material particles from the disintegrator grinding chamber into the tangential discharge pipe and the geometric parameters of this pipe, based on the conditions for the flow of a two-phase medium from the external row of shock elements to the discharge zone. Figure 1 shows the flow diagram of the two-phase medium from the disintegrator grinding chamber to the tangential discharge pipe. It is assumed that the speed of movement of the two-phase medium in this section does not change modulo and the length of the tangential branch pipe is significantly greater than its width. The formula (26) shows the density of the unit volume of kinetic energy of a two-phase medium along the "oy" axis, as well as the change in the density of the unit volume of energy spent on the rotation of the velocity vector relative to the "oy"axis. As a result of theoretical calculations, the obtained formula (15) allows to determine the diameter of particles entering the tangential discharge pipe from a circular trajectory (11), and formulas (36) and (37) describe the process of rotation of the velocity vector of a two-phase medium when the disintegrator flows into the tangential discharge pipe. Figure 2 shows a graph based on the intersection of expression (15), which allows to determine the range of diameters of particles entering the tangential branch pipe, depending on the specified conditions, design and technological parameters. Figures 3 and 4 show graphs in accordance with the analytical expression (35) describing the change in the rotation angle of the velocity vector of a two-phase medium. The results of this article can be used to design the discharge unit of the disintegrator with a tangentially located discharge pipe.

Currently, disintegrators are equipment used for grinding and mixing various materials. The ad-vantages of disintegrators are the ability to control the rotation frequency of the rotors and change the geometric parameters to obtain a grinding product with the required grain composition, as well as the simplicity of the design. This article describes the flow of a two-phase medium from the grinding chamber to the outlet pipe, whose axis is shifted relative to the plane passing through the center of rotation of the rotors. A design scheme for the two-phase flow into the outlet pipe in a plane perpen-dicular to the axis of the cylindrical body is presented. It is assumed that the movement of the two-phase medium from the grinding chamber to the outlet pipe occurs at a constant modulus speed. The diagram of the two-phase flow is considered taking into account that the length of the outlet pipe sig-nificantly exceeds its width. The relations determining the change of the velocity vector components near the two-phase flow outlet to the outlet pipe are obtained. Based on the obtained expressions, the trajectory of the two-phase flow from the grinding chamber to the outlet pipe is determined. Thus, us-ing the results of this theoretical study, it is possible to provide a rational ratio of the main design pa-rameters of the disintegrator unloading unit.

Introduction Infrared O2 (α1Δg) airglow at 1.27 μm on the night side of Venus was for the first time identified during ground-based observations in 1975 (Connes et al., 1979). The airglow reaches its maximal intensity at ~96 km. These altitudes correspond to the transitional region between two regimes of global atmospheric circulation on Venus. Below 70 km, the cloud layer is involved in the zonal super-rotation. At altitudes higher than 110 km, the subsolar to anti-solar (SSAS) circulation transfers atoms and ions produced by photolysis in the sunlit hemisphere to the night side. Here, dowelling oxygen atoms recombine to the exited O2 (α1Δg) molecules which radiative relaxation to the ground state results in the IR emission formation. Thus, the O2 (α1Δg) airglow is a tracer of the dynamical processes occurring in the 90-100 km range on the night side. The maximal emission brightness was observed around the anti-solar point by ground-based and orbital measurements; this result demonstrated a domination of the SSAS circulation in the 90-100 km range. The VIRTIS-M infrared spectrometer on board the Venus Express spacecraft studied in detail the morphological features of the emission in 2006-2009 (Gérard et al., 2008; Piccioni et al., 2009; Shakun et al., 2010; Soret et al., 2012). Gérard et al. (2008) and Piccioni et al. (2009) concluded that intensity of the anti-solar emission maximum is ​​equal to 3 МR and 1.2 МR respectively. The work of Shakun et al. (2010) revealed a slight shift of the nightglow's statistical maximum towards the evening terminator and a latitude of ~10° N. However, a simultaneous independent analysis of VIRTIS-M limb and nadir observations (Soret et al., 2012) confirmed the previous conclusions. Analysis of the SPICAV IR observations contributes to the O2 (α1Δg) airglow study. The instrument dataset extends the long-term and latitudinal coverage of the VIRTIS-M experiment, which poorly observed the Northern Hemisphere of Venus at night. Data analysis The SPICAV IR instrument (0.65-1.7 µm) accumulated a dataset encompassing almost the entire Venus globe by nadir night observations in 2006-2014. The spatial resolution changes in range of 50-1000 km depending on the spacecraft distance to the planet due to the orbit elongation (Korablev et al., 2012). The SPICAV IR spectral range also covers several transparency windows where the thermal emission originating from the Venus deep atmosphere and surface escapes to space. The transparency window at 1.28 μm overlaps the O2 (α1Δg) emission band at 1.27 μm. However, the high resolving power of the spectrometer (~1400) allows a robust algorithm to extract the oxygen emission spectrum. For each measurement Venus thermal emission is optimized by a 1-D radiative transfer model with multiple scattering. The direct model is computed by the SHDOMPP program solving the radiative transfer equation by the method of discrete ordinates and spherical harmonics in a plane-parallel atmosphere. This routine developed by Bézard et al. (2011) and Fedorova et al. (2015) is used in this study with a cloud layer model of Haus et al. (2016). The thermal emission model is computed for three atmospheric windows at 1.1, 1.18 and 1.28 μm to increase the accuracy, and it is set by 3 free parameters: a scaling factor applied to mode 2 and 3 particle distributions of the cloud layer model, the H2O mixing ratio in the lower atmosphere of Venus and the surface emissivity. Result In total, 605 sessions of nadir observations (~6000 spectra) with chosen emission angle ≤2° were analysed. Based on these observations, the local time and latitude distribution of the O2 (α1Δg) airglow in the night hemisphere was obtained. It has the maximum at the anti-solar point with the intensity value of ~2 MR. An emission tendency to be slightly shifted towards the morning terminator can be suggested. In general, the pattern is fairly symmetrical about the equator. The result is in correspondence with the analysis of VIRTIS data (Shakun et al., 2010; Soret et al., 2012). References Bézard, B., et al., 2011. The 1.10-and 1.18-μm nightside windows of Venus observed by SPICAV-IR aboard Venus Express. Icarus, 216(1), 173- 183. Connes, P. et al., 1979. O2(1Δ) emission in the day and night airglow of Venus. The Astrophysical Journal, 233, L29-L32. Fedorova, A., et al., 2015. The CO2 continuum absorption in the 1.10-and 1.18-μm windows on Venus from Maxwell Montes transits by SPICAV IR onboard Venus express. Planetary and Space Science, 113, 66-77. Gérard, J. C., et al., 2008. Distribution of the O2 infrared nightglow observed with VIRTIS on board Venus Express. Geophysical research letters, 35(2). Haus, R., et al., 2016. Radiative energy balance of Venus based on improved models of the middle and lower atmosphere. Icarus, 272, 178-205. Piccioni, G., et al., 2009. Near-IR oxygen nightglow observed by VIRTIS in the Venus upper atmosphere. J. Geophys. Res. – Planets, 114. Shakun, A. V., et al., 2010. Investigation of oxygen O2 (a1Δg) emission on the nightside of Venus: Nadir data of the VIRTIS-M experiment of the Venus Express mission. Cosmic Research, 48(3), 232-239. Soret, L., et al., 2012. Atomic oxygen on the Venus nightside: Global distribution deduced from airglow mapping. Icarus, 217(2), 849-855.

Introduction Vertical profiles of CO2 and temperature with good vertical resolution are key measurements to characterize the Martian atmosphere, although difficult to obtain from remote observations [1]. For the first time these vertical profiles can be routinely obtained with a solar occultation technique by the instruments NOMAD and ACS on board the Exomars Trace Gas Orbiter [2,3]. A state-of-the-art retrieval scheme designed to derive atmospheric profiles of CO2 and temperature from the bottom to the top of the Martian atmosphere [4] is adapted to solar occulation and applied to exploit the operational sounding of these two instruments. The final goal of this on-going work is to characterize the Martian thermal structure from the troposphere up to the thermosphere with unprecedented vertical resolution and also to cross-validate both TGO instruments as best as possible, with a single retrieval code and entirely consistent data analysis approaches. Retrieval approach This work is focussed on the solar occultation channels NOMAD-SO and ACS-MIR, in routine operations since April 2018. To exploit these unique datasets, it is of paramount importance to examine the performance of the two instruments and to cross-validate their retrieval results as accurately as possible. For this purpose we apply a flexible and well tested Earth atmosphere retrieval scheme [5,6,7], to both of them, after adaptation to Mars atmospheric conditions [4] and the necessary accomodation of these channels characteristics [8]. The retrievals use calibrated transmittance spectra to tackle three targets, CO2 density, temperature, and dust loading, in a simultaneous global-fit inversion, with updated hydrostatic equilibrium in every iteration, including contaminant species like H2O, and after a pre-processing/data cleaning analysis which is also similar in both instruments. A first error analysis is performed for both instruments with the help of synthetic retrievals and a series of sensitivity tests performed with the same inversion scheme and similar treatment of the key error terms (measurement noise and systematics). Comparison of results We will present data obtained in the 2.7 µm region, dominated by a well known ro-vibrational band of CO2, and sampled by NOMAD-SO in a mixture of diffraction orders that are used routinely in the operational sounding in the vertical. Similarly, we used 3 consecutive orders in one of the ACS-MIR difraction positions, which contain a sufficient number of CO2 lines in the same 2.7 µm band with the capability to sample the whole atmosphere, up to about 180 km, in a single vertical scan. For both instruments the sounding of the lowest troposphere is limited by the amount of atmospheric dust, which is also retrieved simultaneously with CO2 and temperature. We will compare the vertical profiles obtained in a small sample of profiles from each instrument which span different seasons, latitudes and atmopheric dust loadings, during the first year of TGO operations. The comparisons take into account that the two instruments' individual solar occulation scans are non-coincident in time and space. Comparions are also peformed with results from similar efforts by other groups in the NOMAD and ACS teams [9]. Two important applications of the obtained retrievals are : (i) to supply the most appropriate inputs to the retrieval of other atmospheric species from the same instruments and the same scans, without the need to assume a prior or first guesses from global circulation models (GCM), see companion contributions to this conference [10,11], and (ii) to validate predictions from these GCMs, and therefore, to help to improve them, particularly at high altitudes and at the terminator, where these datasets are particularly valuable [1]. Acknowledgements The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and funding by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. Thanks are extensive to all members of the NOMAD Science Team and the ACS Science Team. References [1] Lopez-Valverde et al., Space Sci Rev, 214, 29 (2018) [2] Vandaele et al., Space Science Reviews 214, 5, 2018 [3] Korablev et al., Space. Sci. Rev. 214, 7 (2018). [5] Funke, B., et al. , Atmos. Chem. Phys., 9(7), 2387–2411 (2009). [4] Jimenez-Monferrer et al., Icarus, 353, 113830 (2020), doi.org/10.1016/j.icarus.2020.113830. [6] Stiller et al., JQSRT, 72, 249–280 (2002) [7] von Clarmann et al., J. Geophys. Res. 108, 4746 (2003) [8] Lopez-Valverde et al., EPSC Abstracts, Vol. 14, EPSC2020-924 (2020), doi.org/10.5194/epsc2020-924 [9] Trompet et al., "Update on CO2 and temperature profiles retrievals from NOMAD-SO on board ExoMars TGO", contribution to this conference, EPSC 2021. [10] Brines et al., "Martian water vapor vertical profiles with data from solar occultation measurements by NOMAD onboard TGO/ExoMars", contribution to this conference, EPSC 2021. [11] Modak et al., "Retrieval of Martian CO vertical profiles from NOMAD solar occultation measurements", contribution to this conference, EPSC 2021.

Disintegrators are one of the types of equipment that has the ability to combine grinding, mixing and activation of materials of medium strength and hardness. The advantages of disintegrators are the ability to integrate into existing technological schemes and obtain a grinding product with a given particle size distribution, as well as the simplicity of the design. This article analyzes the kinetics of particle destruction in the inter-row spaces of the disintegrator grinding chamber. A diagram of the disintegrator grinding chamber is presented. The mathematical description of impact destruction of particles in the grinding chamber is considered in the framework of the inhomogeneous Markov process. An equation is presented that describes the change in the statistical quantity m (t) - the mathematical expectation. It has been suggested that the intensity of the Markov process ( ) is proportional to the frequency (ω) of rotor rotation multiplied by the time function f (t). This functional dependence is determined from the condition of the same interaction time 0 of the material particle in the inter-row spaces of the grinding chamber. If we assume that the probability of destruction of the particles of the material in the interaction with each shock element is constant, then the mathematical expectation value m (t) will be proportional to the number of particles n (t). The resulting relation (11) determines the law of change in the number of particles during the passage of each row of shock elements. The article derived formulas for determining the change in the number of particles in each inter-row space of the grinding chamber. The obtained relations (24) and (25) describe the kinetics of grinding material particles in the grinding chamber of the disintegrator in the framework of the statistical approach and make it possible to determine the relationship between the size of the initial particles and the size of the grinding product.

This article analyzes the movement of particles of different components in the inter-row space and in the peripheral part of the disintegrator's working chamber. The diagram of the disintegrator with the component loading unit and the diagram of the disintegrator's working chamber are presented. The loading unit consists of two screw feeders, which supply various components to the conical loading hopper. The capacity of the screw feeders is matched with the capacity of the hopper and the vertical cylindrical branch pipe. The mass capacity of the mixing chamber and the grinding of the disintegrator is determined. Mass throughput is determined using the functional dependence of the change in the bulk density of the material during its passage in the radial direction from the radius of scattering disk Rд to the radial size of the disintegrator body. It is determined that the mass throughput depends on the geometric (Rk, Rg, H) and technological (ϑ_r ) parameters of the disintegrator. The movement of the material in the working chamber of the disintegrator and the change in the concentration of the selected components of the mixture are presented on the basis of the cell mixing model. It allows to determine the concentration of the selected component of the mixture at the outlet of the body of the disintegrator in the tangential discharge pipe. According to expression, the concentration of the selected components of the mixture when passing through the disintegrator body of the presented construction is about half (0.57) of the initial value.

In this paper, we consider the implementation of the “cloud” computing strategy to study data sets associated to the atmospheric exploration of the planet Venus. More concretely, the Venus Monitoring Camera (VMC) onboard Venus Express orbiter provided the largest and the longest so far set of ultraviolet (UV), visible and near-IR images for investigation of the atmospheric circulation. To our best knowledge, this is the first time where the analysis of data from missions to Venus is integrated in the context of the “cloud” computing. The followed path and protocols can be extended to more general cases of space data analysis, and to the general framework of the big data analysis.

International audience; Carbon monoxide (CO) is the main product of CO2 photolysis in the Martian atmosphere. Production of CO is balanced by its loss reaction with OH, which recycles CO into CO2. CO is therefore a sensitive tracer of the OH-catalysed chemistry that contributes to the stability of CO2 in the atmosphere of Mars. To date, CO has been measured only in terms of vertically integrated column abundances, and the upper atmosphere, where CO is produced, is largely unconstrained by observations. Here we report verti- cal profiles of CO from 10 to 120 km, and from a broad range of latitudes, inferred from the Atmospheric Chemistry Suite on board the ExoMars Trace Gas Orbiter. At solar longitudes 164–190°, we observe an equatorial CO mixing ratio of ~1,000 ppmv (10–80 km), increasing towards the polar regions to more than 3,000 ppmv under the influence of downward transport of CO from the upper atmosphere, providing a view of the Hadley cell circulation at Mars’s equinox. Observations also cover the 2018 global dust storm, during which we observe a prominent depletion in the CO mixing ratio up to 100 km. This is indicative of increased CO oxidation in a context of unusually large high-altitude water vapour, boosting OH abundance.

International audience; We present the first water vapor profiles encompassing the upper mesosphere of Mars, 100–120 km, far exceeding the maximum altitudes where remote sensing has been able to observe water to date. Our results are based on solar occultation measurements by Atmospheric Chemistry Suite (ACS) onboard the ExoMars Trace Gas Orbiter (TGO). The observed wavelength range around 2.7 μm possesses strong CO2 and H2O absorption lines allowing sensitive temperature and density retrievals. We report a maximum H2O mixing ratio varying from 10 to 50 ppmv at 100–120 km during the global dust storm (GDS) of Martian Year (MY) 34 and around southern summer solstice of MY 34 and 35. During other seasons water remains persistently below ∼2 ppmv. We claim that contributions of the MY34 GDS and perihelion periods into the projected hydrogen escape from Mars are nearly equivalent.

The molecular oxygen (O2) and carbon oxide (CO) are minor constituents of the Martian atmosphere with the annual mean mixing ratio of (1560 ± 60 ppm) and (673 ± 2.6 ppm), respectively (Krasnopolsky, 2017). Both are non-condensable species and their latitudinal variations are induced by condensation and sublimation of CO2 from the polar caps that result in enrichment and depletion and seasonal variations are following the total CO2 amount in the atmosphere.The Atmospheric Chemistry Suite (ACS) is a set of three spectrometers (-NIR, -MIR, and -TIRVIM) intended to observe Mars atmosphere onboard the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission (Korablev et al., 2018). The near infrared channel (NIR) is a compact spectrometer operating in the range of 0.7–1.7 µm with a resolving power of λ/Δλ ~ 25,000. It is designed to operate in nadir and in solar occultation modes. The simultaneous vertical profiling of the O2 and CO density at altitudes of 10-60 km based on 0.76 µm and 1.57 µm bands, respectively, is a unique feature of the ACS NIR science in occultation. In this work we present the seasonal and latitudional distribution of the O2 and CO mixing ratios obtained for period of 2018-2020 (MY34 and35) and the comparison with the LMD General Circulation model. We report the averaged mixing ratio for CO of ~950 ppm and for O2 of~1800 ppm at low altitudes (~20 km). Also, we detected extremely enriched CO layer at 10-15 km in the southern polar region at Ls=100-200° both for MY34 and MY35.

International audience; The paper presents observations of gravity wave-induced temperature disturbances in the Martian atmosphere obtained with the mid-infrared (MIR) spectrometer, a channel of the Atmospheric Chemistry Suite instrument on board the Trace Gas Orbiter (ACS/TGO). Solar occultation measurements of a CO2absorption band at 2.7 µm were used for retrieving density and temperature profiles between heights of 20 and 160 km with vertical resolution sufficient for deriving small-scale structures associated with gravity waves. Several techniques for distinguishing disturbances from the background temperature have been explored and compared. Instantaneous temperature profiles, amplitudes of wave packets and potential energy have been determined. Horizontal momentum fluxes and associated wave drag have been estimated. The analyzed data set of 144 profiles encompasses the measurements made over the second half of Martian Year 34, from the Solar longitude 165° through 355°. We observe enhanced gravity wave dissipation/breaking in the mesopause region of 100-130 km. Our analysis shows no direct correlation between the wave amplitude and Brunt-Väisälä frequency. It may indicate that convective instability may not be the main mechanism limiting gravity wave growth in the middle atmosphere of Mars.

Phosphine (PH3) is proposed to be a possible biomarker in planetary atmospheres and has been claimed to have been observed in the atmosphere of Venus, sparking interest in the habitability of Venus’s atmosphere. Observations of another biomarker, methane (CH4), have been reported several times in the atmosphere of Mars, hinting at the possibility of a past or present biosphere. The Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter has a spectral range that includes several absorption lines of PH3 with line strengths comparable to previously observed CH4 lines. The signature of PH3 was not observed in the 192 observations made over a full Martian year of observations, and here we report upper limits of 0.1–0.6 ppbv.

Context. Reports on the detection of methane in the Martian atmosphere have motivated numerous studies aiming to confirm or explain its presence on a planet where it might imply a biogenic or more likely a geophysical origin. Aims. Our intent is to complement and improve on the previously reported detection attempts by the Atmospheric Chemistry Suite (ACS) on board the ExoMars Trace Gas Orbiter (TGO). This latter study reported the results of a campaign that was a few months in length, and was significantly hindered by a dusty period that impaired detection performances. Methods. We unveil 640 solar occultation measurements gathering 1.44 Martian years worth of data produced by the ACS. Results. No methane was detected. Probing the clear northern summer season allowed us to reach 1σ upper limits of around 10 pptv (20 pptv at 2σ), with an annual mean of the smallest upper limits of 20 pptv. Upper limits are controlled by the amount of dust in the atmosphere, which impairs detection performance around the equator and during the southern spring and summer seasons. Observations performed near Gale crater yielded 1σ upper limits of up to four times less than the background values measured by the Curiosity rover during the corresponding seasons. Conclusions. Reconciliation of the absence of methane in the TGO spectra with the positive detections by Curiosity is even more difficult in light of this annual survey performed by ACS. Stronger constraints are placed on the physical and chemical mechanism capable of explaining why the mean of the best overall upper limits of ACS is ten times below the smallest methane abundances measured by Curiosity. The ACS investigation was developed by the Space Research Institute (IKI) in Moscow, and the Laboratoire Atmospheres, Milieux, Observations Spatiales (LATMOS) in Guyancourt. The investigation was funded by Roscosmos, the National Centre for Space Studies of France (CNES) and RSF (Russian Science Foundation 20-42-0903). This work was funded by CNES, the Agence Nationale de la Recherche (ANR, PRCI, CE31 AAPG2019, MCUBE project), the Natural Sciences and Engineering Research Council of Canada (NSERC) (PDF–516895–2018), the UK Space Agency (ST/T002069/1), the UK Science and Technology Facilities Council (ST/R001502/1, ST/P001572/1). All spectral fitting was performed by F.M. The interpretation of the results was done by F.M. and O.K. The preparation of ACS spectra is done at LATMOS by L.B. and at IKI by A.T. Ancillary data are produced in LATMOS by G.L. and in IKI by A.P. Input and aid on spectral fitting were given by K.O. and A.T. The ACS instrument was designed, developed, and operated by A.P., A.S., A.T., F.M., and O.K. Peerreview

The dual spacecraft mission BepiColombo is the first joint mission between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) to explore the planet Mercury. BepiColombo was launched from Kourou (French Guiana) on October 20th, 2018, in its packed configuration including two spacecraft, a transfer module, and a sunshield. BepiColombo cruise trajectory is a long journey into the inner heliosphere, and it includes one flyby of the Earth (in April 2020), two of Venus (in October 2020 and August 2021), and six of Mercury (starting from 2021), before orbit insertion in December 2025. A big part of the mission instruments will be fully operational during the mission cruise phase, allowing unprecedented investigation of the different environments that will encounter during the 7-years long cruise. The present paper reviews all the planetary flybys and some interesting cruise configurations. Additional scientific research that will emerge in the coming years is also discussed, including the instruments that can contribute. Open Access funding provided by Istituto Nazionale di Astrofisica within the CRUI-CARE Agreement. Peerreview

International audience; The current Martian atmosphere is about five times more enriched in deuterium than Earth’s, providing direct testimony that Mars hosted vastly more water in its early youth than nowadays. Estimates of the total amount of water lost to space from the current mean D/H value depend on a rigorous appraisal of the relative escape between deuterated and non-deuterated water. Isotopic fractionation of D/H between the lower and the upper atmospheres of Mars has been assumed to be controlled by water condensation and photolysis, although their respective roles in influencing the proportions of atomic D and H populations have remained speculative. Here we report HDO and H2O profiles observed by the Atmospheric Chemistry Suite (ExoMars Trace Gas Orbiter) in orbit around Mars that, once combined with expected photolysis rates, reveal the prevalence of the perihelion season for the formation of atomic H and D at altitudes relevant for escape. In addition, while condensation-induced fractionation is the main driver of variations of D/H in water vapour, the differential photolysis of HDO and H2O is a more important factor in determining the isotopic composition of the dissociation products.

International audience; The nighttime ozone and sulfur dioxide distributions were analyzed using the entire SPICAV‐UV/Venus Express stellar occultation dataset. After the discovery of an ozone layer at 100 km in the mesosphere reported by Montmessin et al. (2011), 132 other detections were made during the entire 8 years long observing period of the SPICAV UV instrument. In the rare detections the peak abundances of O3 accumulating in the mesosphere are observed with densities from 107 to 108 molecules⋅cm‐3 at 85‐110 km. The ozone layer is estimated to vary from 1 ppbv to 30 ppbv at 85‐95 km while at 95‐105 km the VMR is expected within an interval from 6 ppbv to 120 ppbv. Below 93 km, a puzzling decrease of mixing ratio is observed toward midnight at 30°N. Our work also provides an improved sequel to the analysis of the sulfur dioxide survey previously made in the upper mesosphere by Belyaev et al. (2017). On average, the SO2 content is found to remain constant throughout the vertical profile at a value of around 135±21 ppbv between 85 and 100 km. Rapid and large variations prevent to conclude firmly on any time or space pattern of SO2.

Introduction The southern spring and summer on Mars in the 34th Martian Year (MY34, Ls 180o-360o) was decorated by two dust storms: the global one (GDS) at Ls 190o-240o, and the regional one at Ls 320o-330o. Just before the onset of the GDS, the nominal ExoMars Trace Gas Orbiter mission began (April 2018) with an onboard solar occultation experiment by the spectrometric Atmospheric Chemistry Suite (ACS) [1]. The first ACS-NIR retrievals of the temperature and water mixing ratio revealed an increase the H2O abundance up to altitudes of 80-100 km not only in the stormy events but also at the perihelion in the southern hemisphere (around Ls~270o) [2]. Moreover, as it was shown, the water supersaturation occurs even in presence of the ice clouds, while the stormy warm atmosphere rises the hygropause level [2, 3]. This phenomenon increases a capability of water escape from Mars. Simultaneous investigation from the NOMAD/TGO solar occultations demonstrated analogue results for the H2O enhancement up to 80 km in the stormy seasons, but without the saturation estimations [4]. In this paper, we present results from more sensitive solar occultation measurements in the 2.65-2.7 μm spectral range by the middle infrared channel of ACS (ACS-MIR). The channel allows mesospheric and thermospheric retrievals of temperature and CO2 density in parallel with the mesospheric water abundance. Our results confirm the ACS-NIR and NOMAD conclusions concerning the H2O vapour behaviour in the second half of the MY34. We report the most humid mesosphere occurred in the perihelion season where the water enrichment was established about 5-10 ppbv at altitudes of 110-120 km. We also present the temperature and CO2 density seasonal distribution covering the troposphere, the mesosphere and the thermosphere of Mars. Measurements The ACS-MIR channel is a cross-dispersion echelle spectrometer dedicated to solar occultation measurements in the 2.3–4.3 μm wavelength range [1]. The instrumental resolving power λ/Δλ reaches ~30 000, while the altitude resolution is 1-2 km and the signal/noise ratio is about ~1000. Each occultation session covers a spectral interval with one or a few CO2 absorption bands appropriate for the atmospheric density and temperature retrievals. In this work, we perform data analysis in the 2.65-2.7 μm spectral range, which occupies echelle diffraction orders from 221 to 224, observed simultaneously. This spectral region hosts strong CO2 and H2O absorption bands that are sensitive to detections of CO2 density up to 180-190 km and H2O density up to 120-130 km. For the MY34 the MIR dataset in the considered spectral range is made of ~100 occultation profiles in the Northern hemisphere and of ~90 in the Southern one encompassing seasonal period from Ls 165o to 355o. Retrieval concept The temperature and densities retrieval scheme consists of several iterations with a fitting of a forwardly modelled transmission spectrum to a measured one at each observed altitude. The model includes line-by-line calculations CO2 and H2O absorption cross sections depending on specified temperature and pressure. The fitting procedure is based on Jacobian matrix containing transmission derivatives on free parameters: temperature, CO2 density and H2O density. The clue contribution to an optimal estimation comes from the molecular cross sections derivatives on temperature; they differ significantly from line to line in the considered spectral range. Thanks to that, an independent and simultaneous retrieval of temperature and density is possible. Once the altitude profiles of these parameters are estimated at the first iteration, we calculate the atmospheric pressure profile assuming the hydrostatic equilibrium. This assumption was successfully tested by other vertical profile retrievals from the ACS data [1, 5]. The uncertainty of the retrievals is determined by the transmission errors and the Jacobian matrix for each of free parameters. This estimation allows establishing maximal altitudes with a positive detection of CO2 and H2O densities. Results ACS-MIR solar occultations in the 2.65-2.7 μm spectral range provide us with unprecedented capability to profile CO2 density and temperature from 20 to 180 km, covering the troposphere, the mesosphere and the thermosphere of Mars. The homopause varies around ~130 km and CO2 mixing ratio decreases from 96% to 20-40% at 180 km due to photolysis and molecular diffusion. In parallel with the same dataset, we report very high altitude water abundance, at 110-120 km, that occurred in the southern spring and summer including the GDS and the perihelion in the 34th Martian Year. However, our measurements in the northern hemisphere revealed such a high H2O enrichment only at the stormy events. Comparison of our climatology with some improvements in the Global Circulation Model for the MY34 is in progress. Acknowledgements The retrievals of density/temperature profiles in IKI are funded by the RSF grant #20-42-09035. References [1] Korablev O. et al., 2018. The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter. Space Sci. Rev., 214:7. DOI 10.1007/s11214-017-0437-6. [2] Fedorova A. et al., 2020. Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season. Science, eaay9522. DOI: 10.1126/science.aay9522. [3] Fedorova A. et al., 2018. Water vapor in the middle atmosphere of Mars during the 2007 global dust storm. Icarus 300: 440-457. [4] Aoki S. et al., 2019. Water vapor vertical profiles on Mars in dust storms observed by TGO/NOMAD. JGR Planets, 124, 3482-3497. https://doi.org/10.1029/2019JE006109. [5] Alday J. et al., 2019. Oxygen isotopic ratios in Martian water vapour observed by ACS MIR on board the ExoMars Trace Gas Orbiter. A&A, 630, A91. DOI: 10.1051/0004-6361/201936234.

We present simultaneous retrievals of vertical profiles of CO2 and temperature obtained from a small sample of solar occultation scans by the NOMAD-SO [1] and ACS-MIR [2] instruments on board the ExoMars Trace Gas Orbiter (TGO). The orbits or scans selected from each instrument's observations are sufficiently close in time and space so that the atmospheric variability plays a minor role and a meaningful comparison of the performance of both instrument channels is possible. This is an on-going work devoted to a proper validation of both instruments. We will present a small selection of retrievals than can be used for a critical analysis of the results obtained and as a first step into the mutual validation of NOMAD-SO and ACS-MIR.1. Instruments and observationsOur work is focussed in the NOMAD-SO and the ACS-MIR channels, those specifically devoted to operational observations in solar occultation. Several groups in the NOMAD and ACS teams are performing retrievals of species abundances from these signals and some are reported in this conference [3,4]. We focus on the retrieval of CO2 and temperature in the 2.7 µm range, the strongest IR bands by this gas in the spectra region coverd by SO and ACS [5]. The spectra correspond to calibrated transmittances derived from SO difraction orders 164 and 165 and from MIR position 4 spectra. About a dozen strong CO2 lines are observed in these spectra up to very high tangent altitudes, around 170-180 km. The present study targets at both solar occultation signals, NOMAD-SO and ACS-MIR, but unfortunately, due to some unexpected miss-alignments among the different channels in each instrument and between NOMAD and ACS, an entirely simultaneous observation of the solar disc as it emerges or hides behind the atmosphere is not possible with both SO and MIR channels. Instead this work study the inversions from the two channels in nearly coincident solar occultations, with small changes in latitude, longitude, solar longitude and time.2. Retrieval Scheme We have performed the present retrievals using an inversion code previously used in the Earth upper atmosphere for routine operations of the MIPAS instrument on board the Envisat mission [6]. The inversion scheme, which has been recently adapted to Mars for limb sounding in emission from the OMEGA spectrometer on board the Mars Express spacecraft [7], is adapted here for occultation observations. At the core of the inversion scheme is the forward model KOPRA (Karlsruhe Optimized and Precise Radiative transfer Algorithm [8] ) and the inversion processor (RCP), jointly developed by the Institute for Meteorology and Climate Research (IMK) and the IAA [9].As mentioned above we used here CO2 calibrated transmittances obtained from routine processing by the PI teams. But before injection into the inversion algorithm, a pre-processing of every orbit or scan is performed in order to correct every spectrum of spurious effects. These are essentially two: residual spectral shifts and artificial bending in single spectra. The magnitude of these two effects changes from order to order and between SO and ACS. In spite of these differences, the pre-processing is conceptually similar to both signals, and is actually performed with the same Python code. Further, the ILS associated to each of the signals is best reproduced by a double gaussian, whose detailed description (parameters describing their FWHM and peak ratios, for example) requires also a precise determination by the user, as apparently it slightly varies with time and observing conditions.It is specially useful to obtain both density and temperature information from a single scan, and this is the purpose of the present study. The simultaneous retrieval from a given scan actually derives a CO2 density profile, and after an iterative process, a temperature profile assuming hydrostatic equilibrium. An adjustment for the pointing is also intruduced, and the aerosol extinction and possible interference from species like H2O are also considered during the inversion to obtain the best fits.3. Results We will discuss the fist comparisons of CO2 and temperatures from NOMAD-SO and ACS-MIR, using a common pre-processing and inversion code. The retrievals perform in a similar manner, as in both cases the number of lines, the ro-vibrational bands and the spectral region are similar. Small differences in noise and spectral resolution have some impact but overall both channels permit sounding the Mars atmosphere up to the upper thermosphere with just one single scan. Averaging kernels indicate effective vertical resolutions around 4-6 km in the middle atmosphere (50-100 km), both in CO2 and temperature. The inversion is affected by heavy dust loading and in general degrades below about 30 km and above 150 km due to saturation and noise, respectively. AcknowledgementsThe IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). MALV was funded by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. References[1] Vandaele et al., Space Science Reviews 214 (5), 2018 [2] Korablev et al., Space. Sci. Rev. 214, 7 (2018). [3] Loic et al., Update on CO2 and temperature profiles retrievals from NOMAD-SO on board ExoMars TGO, contribution to this conference, 2020. [4] Shohei et al., Water vapor vertical profiles on Mars: Results from the first full Mars Year of TGO/NOMAD science operations, contribution to this conference, 2020. [5] Lopez-Valverde et al., Space Sci Rev (2018) 214:29 [6] Funke, B., et al. , Atmos. Chem. Phys., 9(7), 2387–2411, 2009.Funke et al., ACP, 9, 2387–2411, 2009. [7] Jimenez-Monferrer, Icarus in press, 2020 [8] Stiller et al., JQSRT, 72, 249–280, 2002 [9] von Clarmann et al., J. Geophys. Res. 108, 4746, 2003 How to cite: Lopez-Valverde, M. A., Funke, B., Hill, B., Gonzalez-Galindo, F., Aoki, S., Trompet, L., Thomas, I., Villanueva, G., Erwin, J., Olsen, K., Belyaev, D., Trokhimovskiy, A., Alday Parejo, J., Lopez-Puertas, M., Lopez-Moreno, J. J., Montmessin, F., Patel, M., Bellucci, G., Vandele, A. C., and Korablev, O.: CO2 and temperature retrievals in the Mars atmosphere from solar occultation by NOMAD-SO and ACS-MIR: performance and cross validation., Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-924, 2020

The ExoMars Trace Gas Orbiter (TGO) mission was sent to Mars in 2016 to make the most sensitive measurements of the atmosphere to date and to hunt for any trace gases diagnostic of active geologic or biogenic processes (Vago et al., 2015). After the first full Mars year of observations, we are able to report the first such discovery: gaseous hydrogen chloride (HCl) has been detected by the Atmospheric Chemistry Suite mid-infrared channel (ACS MIR). ACS science operations commenced at a crucial time for Mars observations. The first solar occultation spectra were recorded on solar longitude (Ls) 163 (late April 2018) at a time of changing seasons on Mars. The northern hemisphere was entering winter, while the southern hemisphere was beginning to warm towards summer season. Around Ls 190, we witnessed a global dust storm of unprecedented severity, with dust remaining in the atmosphere through Ls 250 (Montabone et al., 2020). HCl was observed by ACS simultaneously in both hemispheres after the main phase of the global dust storm. It remained detectable to ACS MIR for several months, while the impact of the dust was still being felt in the atmosphere, before vanishing. The dust lofted and mixed into the atmosphere caused the atmosphere to warm resulting in an expansion of the lowest layers, increasing the water vapour content, elevating the hygropause to 50-60 km, and enhancing meridional Hadley cell circulation (Fedorova et al., 2020). Fig. 1 shows a model of the absorption spectrum contributions of the Martian atmosphere as seen by ACS MIR. The HCl branches, shown in the lower panel, partially overlap with the region of interest used to investigate methane (CH4). So far, TGO instruments have found no evidence of the absorption signature of methane, but in its place ACS MIR has made two surprising discoveries: we have identified a previously unknown CO2 absorption-rotation band (Trokhimovskiy et al., 2020); and we were able to resolve the spectral signature of ozone at low altitudes in the north polar region at the start of norther winter (Olsen et al., 2020a). Methods ACS MIR is a cross-dispersion spectrometer operating in solar occultation mode (Korablev et al., 2018). This geometry provides high signal-to-noise ratios, excellent sensitivity to the vertical structure of the atmosphere, and a very long optical path, amplifying trace gas absorption. The instrument consists of a primary echelle diffraction grating to disperse infrared radiation, followed by a secondary, steerable diffraction grating to separate diffraction orders. The secondary grating position changes the instantaneous spectral range. The full coverage is 2300-4500 cm-1, and the spectral resolution achieved is 0.040-0.045 cm-1 in the region of interest for HCl. The spectral range shown in Fig. 1 covers two secondary grating positions, labelled 11 and 12. Fig. 1. Modelled gas absorption contributions as seen in the lower atmsophere by ACS MIR during solar occultation. The top panel shows contributions from major species: CO2, H2O, and HDO. The bottom panel shows contributions from HCl at 1.5 ppbv, ozone at 140 ppbv, and methane at 1 ppbv. HCl and O3 signatures at these mixing ratios have been observed, while CH4 has not. Spectral fitting was done using the JPL Gas Fitting Software Suite (GFIT) (Irion et al., 2002; e.g., Sen et al., 1996). GFIT computes volume mixing ratio scaling factors for each spectral window and at each altitude. A retrieved profile of gas abundance is derived by inverting the matrices of optical paths and the estimated column abundances. Temperature and pressure profiles are retrieved from coincident observations made with the ACS near infrared channel (ACS NIR) (Fedorova et al., 2020; Vandaele et al., 2019). A full description of the retrieval method can be found in (Olsen et al., 2020b). References Fedorova, A. A., et al.: Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season, Science, 367(6475), 297–300, doi:10.1126/science.aay9522, 2020. Irion, F. W., et al.: Atmospheric Trace Molecule Spectroscopy (ATMOS) Experiment Version 3 data retrievals, Appl. Opt., 41, 6968–6979, doi:10.1364/AO.41.006968, 2002. Korablev, O., et al.: The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter, Space. Sci. Rev., 214(1), 7, doi:10.1007/s11214-017-0437-6, 2018. Montabone, L., Spiga, A., Kass, D. M., Kleinböhl, A., Forget, F. and Millour, E.: Martian Year 34 Column Dust Climatology from Mars Climate Sounder Observations: Reconstructed Maps and Model Simulations, J. Geophys. Res., 2020. Olsen, K. S., et al.: First detection of ozone in the mid-infrared at Mars: implications for methane detection, Astron. Astrophys. in press, doi:10.1051/0004-6361/202038125, 2020a. Olsen, K. S., et al.: The vertical structure of CO in the Martian atmosphere as observed by ACS on ExoMars TGO, Nat. Geosci. submitted, 2020b. Sen, B., Toon, G. C., Blavier, J.-F., Fleming, E. L. and Jackman, C. H.: Balloon-borne observations of midlatitude fluorine abundance, J. Geophys. Res., 101, 9045–9054, doi:10.1029/96JD00227, 1996. Trokhimovskiy, A., Perevalov, V., Korablev, O., Fedorova, A. F., Olsen, K. . S., Bertaux, J.-L., Patrakeev, A., Shakun, A. and Montmessin, F.: First observation of the magnetic dipole CO₂ main isotopologue absorption band at 3.3 μm in the atmosphere of Mars by ACS, Astron. Astrophys. in press, doi:10.1051/0004-6361/202038134, 2020. Vago, J., Witasse, O., Svedhem, H., Baglioni, P., Haldemann, A., Gianfiglio, G., Blancquaert, T., McCoy, D. and de Groot, R.: ESA ExoMars program: The next step in exploring Mars, Sol. Syst. Res., 49(7), 518–528, doi:10.1134/S0038094615070199, 2015. Vandaele, A. C., et al., the NOMAD Science Team and ACS Science Team: Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter, Nature, 568, 521–525, doi:10.1038/s41586-019-1097-3, 2019.

We report retrievals in the 2.53 – 2.79 μm spectral range using the Atmopheric Chemistry Suite onboard of ExoMars Trace Gas Orbiter, which allow the simultaneous measurement of vertical profiles of H and O isotope ratios in water vapour in the Martian atmosphere. The large coverage of ACS MIR solar occultations provides the possibility to analyse the spatial, seasonal and diurnal variations of these ratios. 1. Introduction Isotopic ratios in C, O and H provide important clues to understand the history and evolution of volatiles on Mars. Enrichment of the D/H ratio by a factor of approximately 5.5 in atmospheric water vapour with respect to the Vienna Standard Mean Ocean Water [1] has often been understood as evidence of the substantial atmospheric escape into space. On the other hand, oxygen isotope ratios in both water vapour and carbon dioxide do not show substantial enrichment of the heavier isotopes (e.g. [2],[3]). The lack of substantial fractionation therefore indicates the presence of a large reservoir of oxygen to exchange with the atmosphere [4]. In this work, we use solar occultation measurements made with the mid-infrared (MIR) channel of the Atmospheric Chemistry Suite (ACS), onboard ExoMars Trace Gas Orbiter (TGO) to measure the evolution of the vertical structure of the isotopic composition of water vapour (D/H, 18O/16O and 17O/16O) at the terminator for a full Martian year. 2. Measurements ACS consists of a set of three infrared spectrometers covering a total wavelength range from 0.7 to 17 μm. The MIR channel, used in this study, is a cross-dispersion echelle spectrometer dedicated to solar occultation measurements in the 2.3-4.2 μm (2300-4400 cm-1) range, with the main objective of measuring high resolution spectra (λ/Δλ∼30000-50000) in a wide instantaneous spectral range (width 0.15-0.3 μm). In order to cover the full spectral range, MIR is equipped with a steerable secondary grating that allows the selection of different diffraction orders [5]. In this work, we analyse MIR spectra in secondary grating positions 4 and 5, which allow the simultaneous measurement of several diffraction orders covering a spectral range from 2.67 to 2.79 μm (3584-3745 cm-1) and 2.53 to 2.67 μm (3745-3952 cm-1), respectively. We select spectral windows in several diffraction orders, which show absorption lines of the four main oxygen isotopologues of water vapour (H216O, H218O, H217O, HD16O) and CO2 (see Figure 1). Figure 1: Example of one ACS MIR spectral window in diffraction order 224, measured at tangent heights of 19, 35 and 50 km. The black dots represent the measured spectra, and the green line shows the best fit to the data. The contribution from each species to the spectra is also shown, following the colours in the legend. 3. Radiative Transfer Analysis The analysis of the spectra is performed using the NEMESIS code [6], which works under the optimal estimation framework. In particular, for each solar occultation, we retrieve simultaneous vertical profiles of pressure, temperature and volume mixing ratio of the four main water isotopologues. The pressure and temperature profiles can be constrained from the CO2 absorption lines under the assumption of hydrostatic equilibrium and a given CO2 volume mixing ratio profile, which we obtain from the Mars Climate Database [7]. In the case of the water vapour isotopologues, the volume mixing ratios can be constrained from the depth of the corresponding absorption lines, which are observed up to 60 km approximately. The retrieval scheme is applied to all ACS MIR observations made with secondary grating positions 4 and 5 for a full Martian year, covering a wide range of latitudes, seasons, and local time, and enabling, for the first time, the study of the climatology of both the O and H isotopic ratios in Martian water vapour. 4. Summary and Conclusions Vertical profiles of the isotope ratios in the four main water vapour isotopologues (D/H, 18O/16O and 17O/16O) at the terminator are obtained using solar occultation measurements by the Atmospheric Chemistry Suite onboard ExoMars Trace Gas Orbiter. The large coverage of ACS solar occultation measurements allows, for the first time, the analysis of the variations of the O and H isotopic composition of water vapour for a full Martian year. References [1] Owen, T., Maillard, J. P., de Bergh, C., and Lutz, B. L..: Deuterium on Mars: The abundance of HDO and the values of D/H, Science, 240, 1767 LP - 1767, 1988. [2] Webster, C. R., Mahaffy, P. R., Flesch, G. J., Niles, P. B., Jones, J. H., Leshin, L. A., Atreya, S. K., Stern, J. C., Chrsitensen, L. E., Owen, T., Franz, H., Pepin, R. O., and Steele, A.: Isotope Ratios of H, C and O in CO2 and H2O of the Martian Atmosphere, Science, 341, 260 LP – 263, 2013. [3] Krasnopolsky, V.A., Maillard, J. P., Owen, T., Toth, R. A., Smith, M. D.: Oxygen and carbon isotope ratios in the martian atmosphere, Icarus, Vol. 192, Issue 2, 2007. [4] Jakosky, B. M.: Mars Volatile Evolution: Evidence from Stable Isotopes, Icarus, 94, 14-31, 1991. [5] Korablev et al.: The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter, Space Science Reviews, vol. 214, pag. 7, 2017. [6] Irwin, P., Teanby, N., de Kok, R., Fletcher, L., Howett, C., Tsang, C., Wilson, C., Calcutt, S., Nixon, C., Parrish, P.: The NEMESIS planetary atmosphere radiative transfer and retrieval tool, Journal of Quantitative Spectroscopy and Radiative Transfer,109, 1136-1150. [7] Forget, F., Hourdin, F., Fournier, R., Hourdin, C., Talagrand, O., Collins, M., Lewis, S. R., Read, P. L., and Huot, J-P: Improved general circulation models of the Martian atmosphere from the surface to above 80 km, Journal of Geophysical Research: Planets, 104, 24155-24175, 1999.

The Atmospheric Chemistry Suite (ACS) [1], one of the four science experiments on board ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission has started science operations in March 2018. ACS consists of 3 infrared spectrometers targeting the unambiguous detection of trace gases of potential geophysical or biological interest. The dataset reported here concerns the methane detection attempts conducted during the first complete Martian year (almost two Earth years) of observations using ultra-sensitive occultation observing mode in orbit around Mars. Observations The Trace Gas Orbiter (TGO) of the ESA-Roscosmos ExoMars mission has ended its trip to Mars, reaching the planet in October 2016. After a year-long aerobraking phase, its scientific mission has begun on April 22nd, 2018 with the execution of the first solar occultation. The primary objective of TGO is to detect, map and locate trace gas sources, possibly revealing a residual geophysical (or even biological) activity on Mars. The instrument of interest here is the infrared spectrometer Atmospheric Chemistry Suite (ACS). ACS covers a wavelength range from 0.7 to 17 μm at very high spectral resolution (λ / Δλ from 5,000 to 50,000). ACS operates in nadir and solar occultation. Its performances complete the TGO trace gas detection arsenal together with NOMAD, the other infrared sounder of TGO. Results A large part of the first months of the ACS observing mission has enabled the sensitive search of gaseous methane over a substantial fraction of the Martian globe. The results from the first occultation up until early September 2018 will be presented. This period incidentally covered the onset, the full development, and the demise of the Planetary Encircling Dust Event observed by several other instruments orbiting currently around Mars. Observing conditions proved more favourable than anticipated, and it was possible in a few cases to probe the Martian atmosphere close to the surface ( The first five months of ACS CH4 detection attempts were reported in [3], revealing the absence of methane detection over most of the Martian globe (Figure 1). Part of the attempts at that time was impaired by the presence of abundant amounts of dust particles that prevent observing the lower troposphere of Mars ( The ACS dataset analyzed here covers a period of more than 25 months, which is five times more data (Figure 2) than previously analyzed. This gives us a chance to perform a deeper exploration into the potential presence of methane and the consequences it may have for our understanding of active geophysical and physicochemical processes prevailing at Mars.

The ExoMars Trace Gas Orbiter (TGO) was sent to Mars in March 2016 to search for trace gases diagnostic of active geological or biogenic processes. We report the first observation of the spectral features of Martian ozone (O3) in the mid-infrared range using the Atmospheric Chemistry Suite (ACS) Mid-InfaRed (MIR) channel, a cross-dispersion spectrometer operating in solar occultation mode with the finest spectral resolution of any remote sensing mission to Mars. Observations of ozone were made at high northern latitudes (>65N) prior to the onset of the 2018 global dust storm (Ls = 163-193). During this fast transition phase between summer and winter ozone distribution, the O3 volume mixing ratio observed is 100-200 ppbv near 20 km. These amounts are consistent with past observations made at the edge of the southern polar vortex in the ultraviolet range. The observed spectral signature of ozone at 3000-3060 cm-1 directly overlaps with the spectral range of the methane (CH4) nu3 vibration-rotation band, and it, along with a newly discovered CO2 band in the same region, may interfere with measurements of methane abundance., 7 pages, 6 figures

International audience; The Bepi-Colombo mission was launched in October 2018, headed for Mercury. This mission is a collaboration between Europe and Japan. It is dedicated to the study of Mercury and its environment. It will be inserted into Mercury orbit in December 2025 after a 7-year long cruise. Probing of Hermean Exosphere By Ultraviolet Spectroscopy (PHEBUS) is an ultraviolet Spectrograph and is one of the 11 instruments on-board the Mercury Planetary Orbiter (MPO). It is dedicated to the study of the exosphere of Mercury, its composition, dynamics and variability and its interface with the surface of the planet and the solar wind. The PHEBUS instrument contains four distinct detectors covering the spectral range from 55 nm up to 315 nm and two additional narrow windows at 404 nm and 422 nm. It also has a one-degree of freedom mechanism that allows observations along a cone with an half angle of 80∘ 80 ∘ . This paper follows a detailed presentation of the PHEBUS instrument design that was presented by Chassefière et al. (Planet. Space Sci. 58:201–223, 2010). Here we present an update of the science objectives and measurement requirements following the results published by the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) mission. We also present results of the ground calibration campaigns of the flight unit that is currently on-board MPO. In the last part, we present some details of the observations that will be performed during the cruise to Mercury, such as stellar observation campaigns, interplanetary background observations and planetary flybys.

Atmospheric gravity waves (GW) are periodic oscillations of air masses that manifest themselves as fluctuations of density, temperature, pressure and other quantities. Studying vertical distributions of density and temperature helps to characterize vertical propagation of GWs and evaluate their influence on the coupling between atmospheric layers.We report on the first results of GWs retrievals in the Martian atmosphere from the solar occultation experiment performed by the Atmospheric Chemistry Suite (ACS) onboard the ExoMars Trace Gas Orbiter TGO [1]. This is the first time when GWs were measured simultaneously in almost the entire atmosphere. The ACS is a set of infrared spectrometers operating on the orbit of Mars since April 2018. The mid-infrared channel (ACS-MIR) is a cross-dispersion spectrometer covering the 2.3–4.2 µm spectral range with the resolving power reaching ~30 000. In the solar occultation mode the spectrometer can observe thin layers of the Martian thermosphere and lower atmosphere in strong (e.g. 2.7 and 4.3 μm) and weak (about 3 μm) CO2 absorption bands with vertical resolution ~1 km. The near-infrared channel (ACS-NIR) is another echelle spectrometer working in the 0.73–1.6 µm spectral range with the resolving power ~25000 [2]. Due to the high resolution, these instruments (operating simultaneously) allow for deriving the temperature, pressure and density fluctuations at the unprecedented altitude range from 10 to 180 km. The dataset we present consists of more than 100 vertical profiles derived at seasons from the second half of MY34 to the beginning of MY35 in the both Martian hemispheres. The data analysis in IKI is supported by the RSF grant #20-42-09035. REFERENCES[1] Korablev O. et al., 2018. The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter. Space Sci. Rev., 214:7. DOI 10.1007/s11214-017-0437-6.[2] Fedorova A. et al., 2020. Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season. Science, eaay9522. DOI: 10.1126/science.aay9522.

The mid-infrared channel of the Atmospheric Chemistry Suite (ACS-MIR) is a cross-dispersion echelle spectrometer dedicated to solar occultation measurements in the 2.3–4.3 μm wavelength range [1]. The instrumental resolving power λ/Δλ reaches ~30 000, while the altitude resolution is ~1 km. ACS-MIR began regular science operations in April 2018 on board the ExoMars Trace Gas Orbiter (TGO). Each occultation session covers a spectral interval with one or a few CO2 absorption bands appropriate for the atmospheric density and temperature retrievals.In this paper, we present results from data analysis in the 2.65-2.7 μm spectral range hosting strong CO2 absorption bands detectable up to 180 km. It provides us with unprecedented capability to profile CO2 from 20 to 180 km, covering the troposphere, the mesosphere and the thermosphere of Mars. The homopause is found around ~130 km and CO2 mixing ratio decreases from 96% to 20-40% at 180 km due to photolysis and molecular diffusion. A multiple iteration scheme was applied to retrieve CO2 density and temperature from the rotational absorption lines, while pressure was estimated assuming hydrostatic equilibrium. The vertical profiles coincide well with the simultaneous occultations performed below 100 km by the near-infrared channel ACS-NIR [2]. At the moment, our MIR channel dataset is made of >100 profiles encompassing the second half of MY34 and the beginning of MY35 in both martian hemispheres. The retrievals of density/temperature profiles in IKI are funded by the RSF grant #20-42-09035.REFERENCES[1] Korablev O. et al., 2018. The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter. Space Sci. Rev., 214:7. DOI 10.1007/s11214-017-0437-6.[2] Fedorova A. et al., 2020. Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season. Science, eaay9522. DOI: 10.1126/science.aay9522.

Water reaches Mars' upper atmosphere Mars once hosted abundant water on its surface but subsequently lost most of it to space. Small amounts of water vapor are still present in the atmosphere, which can escape if they reach sufficiently high altitudes. Fedorova et al. used data from the ExoMars Trace Gas Orbiter spacecraft to determine the distribution of water in Mars' atmosphere and investigate how it varies over seasons. Water vapor is sometimes heavily saturated, and its distribution is affected by the planet's large dust storms. Water can efficiently reach the upper atmosphere when Mars is in the warmest part of its orbit, and this behavior may have controlled the overall rate at which Mars lost its water. Science , this issue p. 297

International audience; Following our previous work (Marcq et al., 2013, Marcq et al., 2011), we have updated our forward radiative transfer code and processed the whole SPICAV-UV/Venus Express nadir dataset (2006-2014) in order to retrieve SO2 abundance at cloud top – assuming a SO2 decreasing scale height of 3 km and a ratio SO/SO2 tied to 10% – as well as the imaginary index of scattering mode 1 particles, representative of the remaining UV absorption, since the OSSO vertical profile found by Frandsen et al. (2016) cannot account for our observations. Our main results mostly confirm and extend the validity of those discussed by Marcq et al. (2013), namely: (i) long-term variations of low latitude SO2 at 70 km between ∼ 100 ppbv (2007, 2009) and less than 10 ppbv (2014); (ii) in average, decreasing SO2 with increasing latitude and depletion near the sub-solar point, consistent with a competition between advection and photo-chemical destruction; (iii) secular increase of mode 1 imaginary index at 250 nm, from 10−2 to 5 ⋅ 10−2 between 2006 and 2010; (iv) if not related instead to long-term variability, a possible localized enrichment of SO2 and UV brightness increase above the western slopes of Aphrodite Terra, consistent with Bertaux et al. (2016) supply mechanism through orographic gravity waves. This spatial and temporal variability underlines the need for a long term monitoring of Venus SO2 and cloud top from ground-based facilities until the next generation of Venusian orbiters is operational.

Hydrogen chloride gas was recently discovered in the atmosphere of Mars during southern summer seasons. Its connection with potential chlorine reservoirs and the related atmospheric chemistry is now of particular interest and actively studied. Measurements by the Atmospheric Chemistry Suite mid-infrared channel (ACS MIR) on the ExoMars Trace Gas Orbiter allow us to measure the ratio of hydrogen chloride two stable isotopologues, H35Cl and H37Cl. This work describes the observation, processing technique, and derived values for the chloride isotope ratio. Unlike other volatiles in the Martian atmosphere, because it is enriched with heavier isotopes, the δ37Cl is measured to be − 7 ± 20°, which is almost indistinguishable from the terrestrial ratio for chlorine. This value agrees with available measurements of the surface materials on Mars. We conclude that chlorine in observed HCl likely originates from dust and is not involved in any long-term, surface-atmosphere cycle.

HBr (1–0) R2 2605.8/6.2 cm −1 , the strongest line of the strongest band of HBr, was observed when searching for this species on Venus. The observation was conducted using the NASA IRTF and a high-resolution long-slit spectrograph CSHELL with resolving power of 4 × 10 4 . 101 spectra of Venus were analyzed, and the retrieved HBr abundances varied from -8 to + 5 ppb. Their mean value is -1.2 ppb, standard deviation is 2.5 ppb, and uncertainty of the mean is 0.25 ppb. The negative value presumes a systematic error, and the estimated upper limit of the HBr mixing ratio at the cloud tops of Venus is ∼1 ppb. From the simultaneously retrieved CO 2 abundances, this corresponds to an altitude of 78 km for the uniform distribution of HBr. A simplified version of the bromine photochemistry is included into the photochemical model (Krasnopolsky 2012, Icarus 218, 230–246). Photolysis of HBr and its reactions with O and H deplete the HBr mixing ratio at 70–80 km relative to that below 60 km by a factor of ≈300. Reanalysis of the observational data with the calculated profile of HBr gives an upper limit of 20–70 ppb for HBr below 60 km and the aerosol optical depth of 0.7 at 70 km and 3.84 µm. The bromine chemistry may be effective on Venus even under the observed upper limit. However, if a Cl/Br ratio in the Venus atmosphere is similar to that in the Solar System, then HBr is ≈1 ppb in the lower atmosphere and the bromine chemistry is insignificant. Thermodynamic calculations based on the chemical kinetic model (Krasnopolsky 2013, Icarus 225, 570–580) predict HBr as a major bromine species in the lower atmosphere.

Oxygen isotope ratios provide important constraints on the history of the Martian volatile system, revealing the impact of several processes that might fractionate them, such as atmospheric loss into space or interaction with the surface. We report infrared measurements of the Martian atmosphere obtained with the mid-infrared channel (MIR) of the Atmospheric Chemistry Suite (ACS), onboard the ExoMars Trace Gas Orbiter. Absorption lines of the three main oxygen isotopologues of water vapour (H216O, H218O, and H217O) observed in the transmission spectra allow, for the first time, the measurement of vertical profiles of the 18O/16O and 17O/16O ratios in atmospheric water vapour. The observed ratios are enriched with respect to Earth-like values (δ18O = 200 ± 80‰ and δ17O = 230 ± 110‰ corresponding to the Vienna Standard Mean Ocean Water). The vertical structure of these ratios does not appear to show significant evidence of altitudinal variations.

International audience; After the first sporadic detections of an ozone (O33 volume mixing ratio peaks in the 10 to 20 ppbv range, yielding observable column densities in the 0.1 to 0.5 Dobson units (DU), comparable to nominal values on Mars but much smaller than for Earth ( ∼ 300 DU). These measurements are supported by our 3D-photochemical model coupled with the LMD-IPSL GCM (Lebonnois et al., 2010), which indicates that the ozone layer identified by SPICAV results from downward transport of O2 ( ∼ 50 ppmv) molecules over the poles by the mean meridional circulation. Our findings do not contradict previous upper limits (

International audience; Stellar occultation is a powerful method to study vertical structure of the Venus night mesosphere. The UV channel of SPICAV spectrometer, operated in 2006–2014 on board ESA's Venus Express orbiter, allowed retrieval profiles of atmospheric gases (CO2, SO2, and O3) and aerosols. It was also able to register different UV emissions around Venus (nitric oxide airglow, Lyman-α) overlapping the absorption features at 120–300 nm. Several calibration steps convert the raw data to atmospheric transmission spectra used for the retrievals. The systematic errors of resulted gaseous concentrations mainly relate to: (i) an uncertainty of the wavelength to pixel assignment; (ii) a portion of emitting light contaminating the analyzed transmission spectra. In the present paper, we have tested a new method of the wavelength-to-pixel assignment based on the spectral features of measured stars. Secondly, using imaging capabilities of the instrument, we have demonstrated an accurate separation between different kinds of registered signal: extended UV nightglow, light from a point star, transmitted through the atmosphere, and, sometimes, solar light, scattered by Venus dusk. The efficiency of two approaches performing the separation was studied. As a result, corrected transmission spectra provided retrievals of gaseous concentrations with 20–40% higher precision respectively to those processed in previous SPICAV stellar occultation studies (Montmessin et al., 2011, Icarus 216, 82; Piccialli et al., 2015, Planet. Space Sci. 113–114, 321; Belyaev et al., 2017, Icarus 294, 58).

We report design of laboratory prototype for a compact infrared acousto-optic imaging spectro-polarimeter, which may be implemented for remote or close-up analysis of planetary surfaces. The prototype concept contains a telecentric optics, apochromatic design over the bandwidth of 0.9–3.4 μm, and simultaneous imaging of two orthogonal linear polarizations of the same scene at a focal plane array (FPA). Two acousto-optic channels, the near-IR (0.9-1.7 μm) the mid-IR (1.5–3.4 μm), were developed with spectral resolution of 100 cm-1 (10 nm at 1 μm) and 25 cm-1 (20 nm at 3 μm) respectively. When imaging samples, the spatial resolution of 0.2 mm at the target distance of one meter was reached. It corresponds to 100 by 100 elements resolved at the FPA for each of the two light polarizations. This type of instruments may be considered as a potential reconnaissance and analysis tool for future planetary or moon landers and rovers to study spectral and polarization properties of the regolith.

International audience; Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus’ mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Sulfur oxide chemistry on Venus is closely linked to the global-scale cloud and haze layers, which are composed primarily of concentrated sulfuric acid. Sulfur oxide observations provide therefore important insight into the on-going chemical evolution of Venus’ atmosphere, atmospheric dynamics, and possible volcanism.This paper is the first of a series of two investigating the SO2 and SO variability in the Venus atmosphere. This first part of the study will focus on the vertical distribution of SO2, considering mostly observations performed by instruments and techniques providing accurate vertical information. This comprises instruments in space (SPICAV/SOIR suite on board Venus Express) and Earth-based instruments (JCMT). The most noticeable feature of the vertical profile of the SO2 abundance in the Venus atmosphere is the presence of an inversion layer located at about 70–75 km, with VMRs increasing above. The observations presented in this compilation indicate that at least one other significant sulfur reservoir (in addition to SO2 and SO) must be present throughout the 70–100 km altitude region to explain the inversion in the SO2 vertical profile. No photochemical model has an explanation for this behaviour. GCM modelling indicates that dynamics may play an important role in generating an inflection point at 75 km altitude but does not provide a definitive explanation of the source of the inflection at all local times or latitudesThe current study has been carried out within the frame of the International Space Science Institute (ISSI) International Team entitled ‘SO2 variability in the Venus atmosphere’.

International audience; SPICAV IR, one channel of SPICAV/SOIR instrument suite onboard Venus Express, performed solar occultation measurements of the atmosphere at terminators in 0.65–1.7 μm spectral range. We analyze the properties of the upper part of the Venus aerosol layer (upper haze, 70−95 km altitude) from 798 observations performed from May 2006 through November 2014. Vertical profiles of slant optical depth, extinction coefficient, effective radius, and number density of haze particles from 222 orbits were analyzed in a previous publication (Luginin et al., 2016. Icarus. 277. doi: 10.1016/j.icarus.2016.05.008); their diurnal, latitudinal, and interannual variabilities were investigated. The present paper is devoted to analysis of scale heights and properties of detached haze layers from 147 orbits at mid-to-high northern latitudes, where the best spatial resolution was obtained. Scale heights retrieved from 43 orbits were equal to 4−5.5 km at the North Pole (82°N-90°N) decreasing to 2−4 km at 60°N−80°N latitudes. As an explanation of such latitudinal variations, we propose a mechanism based on vertical transport driven by winds that are directed upwards at the North Pole and downwards at 60°N−80°N latitudes. Detached layers were detected in 93 occultations at 58°N−90°N. The detached layers are presumably formed through condensation of water vapor on droplets of sulfuric acid water solution; they were mostly seen at 80−88 km at the morning terminator, and at 84−90 km at the evening one. This difference in altitude of the detached layers can be explained by diurnal variations in thermal structure of Venusian mesosphere. The vertical optical depth of detached layers varies broadly around the mean τDL ∼ 0.8−3•10−3; no difference between the morning and the evening terminators was observed. The effective radius and number density of aerosol particles in the detached layers group around a very wide maximum at the morning terminator (0.65±0.25 μm and 0.6±0.4 cm−3) and two maxima at the evening terminator (0.4±0.1 μm and 0.85±0.15 μm; 0.3±0.2 cm−3 and 4.5±2.5 cm−3). This could be explained by differences in initial altitudes at which condensation of particles occurs.