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The formation of water ice clouds can significantly influence the Martian climate, although the Martian atmosphere contains low water vapor concentrations compared to terrestrial levels. The lower Martian atmosphere exhibits three global water ice cloud systems: Aphelion cloud belt (ACB), polar hoods (PHs), and orographic clouds. These clouds are associated with topography, solar heating, global atmospheric circulation, wave activity, and local convection. An appreciable amount of research has been conducted on the first two regimes (ACB and PHs) and very little attention has been given to the third regime (orographic clouds). In general, orographic clouds are observed in northern Spring and summer since they are associated with the major Martian volcanoes. Water ice optical depths provided by the Emirates Exploration Imager (EXI) of the Emirate Mars Mission (EMM) will be used to investigate seasonal and diurnal variations of such clouds in the Tharsis volcanic region: Ascraeus Mons, Pavonis Mons, Arsia Mons, and Olympus Mons. Additionally, context will be provided using the meteorological fields from the Mars PCM (Mars Planetary Climate Model led by Laboratoire de Meteorologie Dynamique Paris, France). This study provides a general picture of how Martian water ice clouds correlate with Mars PCM's meteorological variables: water ice optical depth, atmospheric temperature, meteorological winds, and water vapor mixing ratio.

We present results of diurnal temperature variations and thermal tides in the Martian atmosphere using observations obtained by the Emirates Mars InfraRed Spectrometer (EMIRS) onboard the Emirates Mars Mission (EMM) Hope probe during its primary mission. The novel orbit design of the spacecraft allows a full geography and local time to be covered every 10 Martian days, approximately ~5° of solar longitude (LS). Diurnal temperature variations are derived for the first time on a planetary scale without any significant gaps in local time or interference from seasonal changes. Contributions of thermal tides are then analyzed. The dataset of the EMM primary mission covers one Martian Year (MY) starting from MY 36 LS=49°. Seasonal changes of the diurnal temperature variations and thermal tides are investigated. The results show good agreements with predictions provided by the Mars Planetary Climate Model (PCM), but with noticeable differences in the phases and wavelengths of the thermal tides. This work provides valuable information on understanding the diurnal climate of Mars, and inspires future advances of Mars GCMs.

The physics of the Mars PCM (previously LMD Mars GCM) has been improved : cloud nucleation now has a temperature-dependent scheme, latent heat of ground ice sublimation is computed and overall physical resolution is enhanced. Under these conditions, we find that retroactions of albedo and thermal inertia allow perennial deposition of ice outside the polar regions when increasing the obliquity of Mars from its present day value of 25° toward 35°, with accumulation rates compatibles with the formation of a "Latitude-Dependent Mantle" during the last high obliquity excursion.

The heat flow and physical properties package measured soil thermal conductivity at the landing site in the 0.03 to 0.37 m depth range. Six measurements spanning solar longitudes from 8.0$^\circ$ to 210.0$^\circ$ were made and atmospheric pressure at the site was simultaneously measured using InSight’s Pressure Sensor. We find that soil thermal conductivity strongly correlates with atmospheric pressure. This trend is compatible with predictions of the pressure dependence of thermal conductivity for unconsolidated soils under martian atmospheric conditions, indicating that heat transport through the pore filling gas is a major contributor to the total heat transport. This implies that any cementation or induration of the soil sampled by the experiments must be minimal and that the soil surrounding the mole at depths below the duricrust is unconsolidated. Thermal conductivity data presented here are the first direct evidence that the atmosphere interacts with the top most meter of material on Mars.

We present CO density profiles up to about 100 km in the Martian atmosphere obtained for the first time from retrievals of solar occultation measurements by the Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). CO is an important trace gas on Mars, as it is controlled by CO2 photolysis, chemical reaction with the OH radicals, and the global dynamics. However, the measurements of CO vertical profiles have been elusive until the arrival of TGO. We show how the NOMAD CO variations describe very well the Mars general circulation. We observe a depletion of CO in the upper troposphere and mesosphere during the peak period, LS = 190°–200°, more pronounced over the northern latitudes, confirming a similar result recently reported by Atmospheric Chemistry Suite onboard TGO. However, in the lower troposphere around 20 km, and at least at high latitudes of the S. hemisphere, NOMAD CO mixing ratios increase over 1,500 ppmv during the GDS (Global Dust Storm) onset. This might be related to the downwelling branch of the Hadley circulation. A subsequent increase in tropospheric CO is observed during the decay phase of the GDS around LS = 210°–250° when the dust loading is still high. This could be associated with a reduction in the amount of OH radicals in the lower atmosphere due to lack of solar insolation. Once the GDS is over, CO steadily decreases globally during the southern summer season. A couple of distinct CO patterns associated with the Summer solstice and equinox circulation are reported and discussed. © 2023. American Geophysical Union. All Rights Reserved., 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 Astrofisica de Andalucia (SEV-2017-0709) and funding by Grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). F.G.G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00 and from Grant CEX2021-001131-S funded by MCIN/AEI/https://doi.org/10.13039/501100011033. 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). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493) as well as by UK Space Agency through Grants ST/V002295/1, ST/V005332/1 and ST/S00145X/1 and Italian Space Agency through Grant 2018-2-HH.0. US investigators were supported by the National Aeronautics and Space Administration.

This study focuses on the water cycle around the seasonal polar caps during the winter/spring seasons, and more precisely on the progression and retreat of CO2 and H2O frosts derived from the Martian Planetary Climate Model (PCM) of the LMD and from the OMEGA imaging spectrometer onboard Mars Express. In a previous study, Appéré et al. (2011) used a series of OMEGA observations from the end of autumn of MY 27 (Ls ~260°) to the end of spring of MY 28 to describe the temporal evolution of H2O and CO2 ice deposits, constantly evolving northwards through sublimation and deposition of the corresponding ice/frosts. This ends just before the summer solstice (around Ls ~70°) after the complete disappearance of CO2 ice. At high latitudes, the sublimation of H2O frost then contributes to an abundant emission of water vapor. The LMD Martian PCM (Forget et al., 1999) reproduces the global and seasonal water and CO2 cycles during the winter-spring seasons. In the previous version (v. 5.3), it releases excessive humidity in the polar regions. We compare the southernmost position of frosts and their poleward progression on the old (v. 5.3) and new (v. 6.1) versions of Martian PCM data, and on data from OMEGA spectral images. In OMEGA data, water and CO2 frosts can be detected by absorption bands at 1.5 μm, respectively at 1.43 μm (Langevin et al., 2007). Similarly, when the depth of the absorption band falls below a chosen value, the frost is considered as having disappeared. On one orbit-segment image, the southernmost pixels form a more or less continuous line corresponding to the frost boundary (“crocus-line” type). We use the surface ice content (in v. 5.3) or directly the seasonal frost amount (v. 6.1) in the model simulations, in order to detect the frost dissipation. Water (resp. CO2) ice content values (in kg/m2) are calculated on a regular grid (5.625° longitude x 3.75° latitude) every 2 hours over one standard (climatological) Martian year. In most cases, all the OMEGA pixels of an image are observed at the same local time. We calculate an average GCM frost dissipation time Lsfd_GCM from the 4 closest GCM neighbor grid points, weighted by the distance between each GCM grid point and the OMEGA frost line. Then the time interval between the dissipation of frost in OMEGA water (CO2) ice absorption depth profile and in the collocated (interpolated) water ice disappearance on the GCM can be determined. When the frost time dissipation interval ΔLsfd = Lsfd_OMEGA - Lsfd_GCM is positive (respectively negative), the model is late (in advance) w.r.t. observations. Preliminary results show that CO2 frost dissipates later in the PCM v. 5.3 dataset than on OMEGA data near the North Pole. We will also present other comparisons of the evolution of the frost time dissipation.

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.

Introduction The thermal (Jeans) escape of Hydrogen accumulated during the history of Mars has been one of the major mechanisms explaining the transition of Mars from a thicker and wetter atmosphere in the past to the current thin and dry atmosphere (Brain et al., 2017). Recent observations (Heavens et al., 2018, Chaffin et al., 2021) have revealed a clear link between the water cycle in the lower atmosphere, the transport of water to the middle/upper atmosphere, and the thermal escape of Hydrogen. However, many unknowns remain, including the role of the different processes responsible of transporting water from the lower to the upper atmosphere and converting it to Hydrogen atoms, or the effects of global dust storms (GDS hereafter) compared to the regular seasonal variability. While different 1D models have been used to reproduce and understand some of the observations (e.g. Chaffin et al., 2017), until now global models have failed to reproduce the observed variability of the H escape. In particular, a recent study with the Laboratoire de Météorologie Dynamique Mars Global Climate Model (LMD-MGCM hereafter) evidences that the model significantly underestimates the H escape rate when comparing with Mars Express SPICAM observations, in particular during the perihelion season (Chaufray et al., 2021). In this work we will summarize the recent improvements that we have included in the LMD-MGCM in order to better reproduce the observed Hydrogen escape rate, and will discuss some of the results obtained with the improved model. Model description We have included three improvements with respect to the version of the LMD-MGCM used in Chaufray et al., 2021. First, we have incorporated in the simulations a sophisticated model of the microphysics of water ice clouds allowing for the formation of supersaturated water layers (Navarro et al., 2014). Second, we have extended the photochemical model in the LMD-MGCM to incorporate the chemistry of H2O+ and derived ions, as well as of deuterated (both neutral and ion) species. Third, we have also included in the calculations an improved model of deuterium fractionation (Vals et al., 2022). While this allows us to study the D escape, we will focus here only on the H escape; simulations of the deuterium escape are discussed in Chaufray et al. (this issue). Preliminary results The incorporation in the calculations of the microphysical model allowing for the formation of supersaturated water layers significantly increases the amount of water in the upper atmosphere of the planet with respect to the previous calculations, producing a strong enhancement of up to one order of magnitude in the H escape rate. The incorporation of the chemistry of water-derived ions further increases the escape rate in between ~20 and ~40%, depending on the season. This results in a better agreement with observations of H escape (figure 1). However, significant differences still remain. In particular, the decrease in the rate of H escape at the end of the year is not well captured by the model, suggesting that, in the model, water remains in the upper atmosphere longer than observed. We study also the interannual variability of the simulated escape rate. While the solar activity seems to play a secondary role, dust storms in the lower atmosphere have a clear effect over the H escape rate. Our simulations show, for example, that the global dust storm in MY34 increased the annually integrated H escape rate in about 30%. This confirms the importance of taking into account the effects of GDSs when calculating the accumulated escape rate over Martian history. This work opens the doors to studying the H escape rate at past Mars conditions characterized by different orbital parameters (e.g. obliquity, time of perihelion, etc.). See Gilli et al., this issue, for a first study in this direction. Figure 1. H escape rate simulated for MY28 (light green line) and MY33 (orange line). The black thin line shows the escape rate for MY28 simulated with the previous model version, taken from Chaufray et al. (2021). The green and red symbols represent measured values of the H escape rate during MY28 and MY33, respectively, taken from Chaffin et al. (2014) and Heavens et al. (2018) Acknowledgements F.G-G. and G.G. are funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00. AB and MALV were supported by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). The IAA team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the Center of Excellence “Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709) References Brain, D., et al., (2017), Solar Wind Interaction and Atmospheric Escape. Chapter 15 in “The Atmosphere and Climate of Mars”, Cambridge University Press, doi:10.1017/9781139060172.015 Chaffin, M., et al. (2021), Martian water loss to space enhanced by regional dust storms, Nat. Astron. doi:10.1038/s41550-021-01425-w Chaufray, J.-Y., et al. (2021), Study of the hydrogen escape rate at Mars during martian years 28 and 29 from comparisons between SPICAM/Mars express observations and GCM-LMD simulations. Icarus, doi:10.1016/j.icarus.2019.113498 Heavens, N., et al. (2018). Hydrogen escape from Mars enhanced by deep convection in dust storms. Nat. Astron., doi:10.1038/s41550-017-0353-4 Navarro, T., et al. (2014), Global climate modeling of the Martian water cycle with improved microphysics andadiatively active water ice clouds. JGR (Planets), doi.org:10.1002/2013JE004550 Vals, M., et al. (2022), Improved modeling of Mars' HDO cycle using a Mars' Global Climate Model. Paper submitted to JGR-Planets.

The Martian mesosphere, and in particular the upper mesosphere, above about 80 km from the surface, remains poorly explored in comparison with the troposphere and the thermosphere/ionosphere. Observations by the NOMAD and ACS instruments on board the ExoMars Trace Gas Orbiter mission (TGO in what follows) are starting to fill this gap by providing measurements such as the abundance of mesospheric water and the effects of global dust storms (Vandaele et al., 2019; Belyaev et al., 2021; Brines et al., 2022), the CO variability (Modak et al., 2022) or the temperature and density structure (López-Valverde et al., 2022). For the first time we have a set of diverse atmospheric parameters derived simultaneously with good vertical resolution and from a single instrument, which is ideal for model validation purposes.In this work, we will compare the predictions of the LMD-Mars GCM (LMD-MGCM) in the mesosphere with the NOMAD results (abundances of CO2, CO, and H2O, as well as temperature) obtained by the retrieval scheme developed at the Instituto de Astrofisica de Andalucia-CSIC (IAA), in order to validate the model and to gain insight into the physical processes at the origin of the observed structures. In particular, we will focus on the comparison of the CO2 density and temperature structure observed below ~120 km (López-Valverde et al., 2022) during the second half of Mars Year 34, a period including the MY34 global dust storm. We will show that the model reproduces well the strong seasonal variations of the CO2 density observed by NOMAD. However, the model tends to overestimate the temperatures above ~50 km.AcknowledgmentsF.G-G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00. MALV, AB, AM, and AS were supported by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). The IAA team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709)

Previous CO2 ice cloud modeling studies [Colaprete et al., 2003, Tobie et al., 2003, Forget et al., 1998, Kuroda et al., 2013, Colaprete et al., 2008] allowed to develop and test ideas on CO2 ice cloud formation; however, the studies were often made in idealized settings and included simplified physics and/or limited model boundaries such as a low model top. Listowski et al. [2014] developed refined CO2 cloud microphysics adapted for the Martian conditions of a near-pure vapor condensing in highly supersaturated conditions [Listowski et al., 2013]. They showed with a one-dimensional model and a temperature structure including tidal and gravity wave effects that an additional source of condensation nuclei (CN) was required in the mesosphere for the formation of observed-like clouds. The model of Listowski et al. [2014] has now been coupled with the LMD Mars GCM (MGCM), jointly developed by several laboratories, including LATMOS, LMD, and IAA. The MGCM is now able to simulate the formation of CO2 ice clouds in the Martian atmosphere taking into account mineral dust particles and water ice crystals as potential condensation nuclei (CN). The first simulations are used for testing the new microphysics and comparing its results to the previous simplified CO2 condensation parameterization. The simulations are compared to the published CO2 ice cloud observations. We are using the most recent version of the MGCM and most of the included processes have been described in Navarro et al. [2014], including water ice cloud microphysics and their radiative effect. The new CO2 ice cloud microphysics follow closely the implementation of water ice cloud microphysics in the MGCM, performed via the so-called modal approach, frequently used in GCMs. This means that the particle size distribution is described assuming a lognormal form for the distribution and its evolution is described through the integral properties (moments) of the distribution. We have performed three simulations, one with the previous, simple parametrization of CO2 condensation, one with the new CO2 cloud microphysics but only including dust particles as CN, and one using both dust and water ice as CN, respectively called PARAM, MPCO2, and MPCO2+H2OCN. The simulations have been run for three Martian years and we take the results from the last simulation year to insure convergence. We use the climatological dust scenario that describes well an average Martian Year without a global dust storm. We use a spatial resolution of 5.6258° longitude x 3.758° latitude, corresponding to a 64 longitude x 48 latitude horizontal grid, and 32 vertical levels. The model top is defined at the pressure level 3x10-3 Pa that corresponds approximately to an altitude of 120 km. The model produces CO2 ice clouds in the polar regions in the troposphere during the winter and in the mesosphere at equatorial altitudes. Figure 1 shows the CO2 ice column density as a function of latitude and solar longitude for the two simulations: MPCO2 and MPCO2+H2OCN with observations from several instruments [Clancy et al., 2007, Montmessin et al., 2006, Määttänen et al., 2010,McConnochie et al., 2010, Scholten et al., 2010, Vincendon et al., 2011, Aoki et al., 2018, Clancy et al., 2019, Jiang et al., 2019, Liuzzi et al., 2021]. The polar clouds are formed in a larger altitude range than in the observations, reaching from the surface up to 40 km altitude. The polar atmosphere is cold and supersaturated in a deeper layer than in the observations, causing the thicker cloud formation that forms earlier and lasts longer. The cause of the colder polar winter troposphere may be the prescribed dust column depth coming from observations: as there are very few observations in the polar night, the column depth has been given a minimum value that might still be too high compared to reality. This larger dust content in the polar night causing a too large radiative cooling may be the reason for the cold temperatures. The snowfall from polar clouds contributes about 10% to the formation of the polar ice caps. Substantial mesospheric clouds only form when the model takes into account CO2 ice nucleation on both water ice crystals and dust grains. The seasonal distribution of the clouds agrees well with observations during most of the mesospheric cloud season, but the pause in cloud formation around the aphelion is more clear-cut than in the observations where cloud formation seems to continue during the whole cloud season, although at a lower frequency during a certain period around the aphelion. The clear pause in cloud formation in the model is due to the rise in mesospheric temperatures that seems to be related to a change in the circulation regime and winds in the mesosphere. The optical thickness of the clouds remains two orders of magnitude below observed values, pointing to a need for an exogenous CN source (meteoritic dust: [Listowski et al., 2014, Plane et al., 2018]). Such a source is being added to the model. Acknowledgements We thank the Agence National de la Recherche for funding (projet MECCOM, ANR18CE310013), the LabEx ESEP, CNES, PNP, and the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00, and the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This work was performed using HPC computing resources from GENCI/CINES (Grant 2021A0100110391), and resources at the ESPRI mesocentre of the IPSL institute.

It is evident that a variety of metals are deposited in the Earth’s mesosphere and lower thermosphere (MLT, ~70-120 km) through meteoric ablation when the cosmic dust particles enter the atmosphere at high entry velocity (11-72 km/s). However, it is still unclear how much and accuarate cosmic dust enters the atmosphere of Mars (though the estimation of global dust input would be a few tons per sol) and what is the difference comparing to Earth’s atmosphere (which has a 1-2 order global input range from different estimations). We have developed global atmospheric meteoric models of Na, Fe, K, Mg, Ni, Ca, Al, Si, P, S etc) into the Whole Atmosphere Community Climate Model (WACCM) and its vertical extensions to 600 km (WACCM-X) from US National Center for Atmospheric Research (NCAR, termed WACCM-metals), which simulate well the metal layers compared with the available lidar/rocket/satellite measurements. New observations of some metals for the Martian atmosphere (i.e., Mg+ observations from IUVS (Imaging UV Spectrometer) and Mg+, Na+ and Fe+ from NGIMS (Neutral Gas Ion Mass Spectrometer)) instruments on NASA’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft are available from 2014. Therefore, we have incorporated the chemistry of three metals (Mg, Na and Fe) in the Laboratoire de Météorologie Dynamique (LMD) Mars global circulation model (termed as LMD-Mars-Metals), following similar work we have done for the Earth’s atmosphere. The model has been developed by combining three components: the state-of-the-art LMD-Mars model covering the whole atmosphere from the surface to the upper thermosphere (up to ~ 2 x10-8 Pa or 240 km), a description of the neutral and ion-molecule chemistry of Mg, Fe and Na in the Martian atmosphere (where the high CO2 abundance produces a rather different chemistry from the terrestrial atmosphere), and a treatment of injection of the metals into the atmosphere from the ablation of cosmic dust particles. The LMD-Mars model contains a detailed treatment of atmospheric physics, dynamics and chemistry from the lower atmosphere to the ionosphere. The model also includes molecular diffusion and considers the chemistry of the C, O, H and N families and major photochemical ion species in the upper atmosphere, as well as improved treatments of the day-to-day variability of the UV solar flux and 15 mm CO2 cooling under non-local thermodynamic equilibrium conditions. We have incorporated the chemistries of Mg, Fe and Na into LMD-Mars because these metals have different chemistries which control the characteristic features of their ionized and neutral layers in the Martian atmosphere. The Mg chemistry adds 7 neutral and 8 ionized Mg-containing species, connected by 42 neutral and ion-molecule reactions. The corresponding Fe chemistry has 39 reactions with 14 Fe-containing species. Na chemistry adds 7 neutral and only 2 ionized Na-containing species, with 32 reactions. The injection rate of these metals as a function of latitude, solar longitude at different pressure levels is pre-calculated from the Leeds Chemical Ablation Model (CABMOD) combined with an astronomical model which predicts the dust from Jupiter Family and Long Period comets, as well as the asteroid belt, in the inner solar system. The model has been evaluated against by Mg+, Na+ and Fe+ observations from IUVS and NGIMS measurements. The comparison of these metal layers between Earth’s and Mar’s atmospheres will be discussed, which allows us to understand the meteor astronomy, chemistry and transport processes that control the different metal layers in the upper atmosphere on different planets.

Poster for the SEA 2022 meeting describing the comparison between ExoMars NOMAD solar occultation observations retrieved at the Instituto de Astrofísica de Andalucía and the predictions of a ground-to-exobase Global Climate Model. The temperature structure and the abundances of CO2, CO, and H2O in the mesosphere (up to ~100 km) are compared., This work was supported by the Spanish Ministry of Science and Innovation, the Agencia Estatal de Investigación, and by the UE FEDER funds under grants RTI2018-100920-J-I00 and PGC2018-101836-BI00. 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)

After 18 years in orbit Mars Express remains one of ESA’s most scientifically productive Solar System missions, with a publication record now exceeding 1450 papers. Characterization of the surface geology on a local-to-regional scale by HRSC, OMEGA and partner experiments on NASA spacecraft has allowed constraining land-forming processes in space and time. Recent studies characterized the geology of Jezero crater in great detail and provided Digital Elevation Model (DEM) of several equatorial regions at 50 m/px resolution. New maps and catalogues of surface minerals with 200 m/px resolution were released. MARSIS radar published new observations and analysis of the multiple subglacial water bodies underneath the Southern polar cap. Modelling suggested that the “ponds” can be composed of hypersaline perchlorate brines.Spectrometers and imagers SPICAM, PFS, OMEGA, HRSC and VMC continue adding to the longest record of atmospheric parameters such as temperature, dust loading, water vapor and ozone abundance, water ice and CO2 clouds distribution and observing transient phenomena. More than 27,000 ozone profiles derived from SPICAM UV spectra obtained in MY#26 through MY#28 were assimilated in the OpenMARS database. A new PFS “scan” mode of the spacecraft was designed and implemented to investigate diurnal variations of the atmospheric parameters. Observations of Tharsis region and Hellas basin contribute to mesoscale meteorology.ASPERA measurements together with MAVEN “deep dip” data enabled assessment of the conditions that lead to the formation of the dayside ionopause in the regions with and without strong crustal magnetic fields suggesting that the ionopause occurs where the total ionospheric pressure (magnetic + thermal) equals the upstream solar wind dynamic pressure.In 2021 Mars Express successfully performed two types of novel observations. In egress-only radio-occultations a two-way radio link was locked at a tangent altitude of about 50 km. This is well below the ionospheric peak and would allow perfect sounding of the entire ionosphere thus doubling the number of ionospheric soundings. MEX and TGO performed several test UHF occultations. The dual-spacecraft radio-occultation technique would allow much broader spatial distribution of the missions’ radio occultation profiles. Mars Express is extended till the end of 2022. A science case for the mission extension till the end of 2025 will be developed and submitted in March 2022. The talk will give the Mars Express status, review the recent science highlights, and outline future plans including synergistic science with TGO and other missions.

Thermal tides are planetary-scale harmonic responses driven by diurnal solar forcing and influenced by planetary topography. Excited by solar heating absorbed by the atmosphere and energy exchange with surface, thermal tides grow in Martian atmosphere. These tides usually have large amplitudes due to the low heat capacity of Martian atmosphere, and dominate its diurnal variations. In this talk, we present results of the analysis of thermal tides in Martian atmosphere using temperature profiles retrieved using infrared spectra obtained by the Emirates Mars InfraRed Spectrometer (EMIRS) instrument onboard the Emirates Mars Mission (EMM) Hope spacecraft. The first set of data obtained during the mission science phase is selected, covering a solar longitude (LS) range 60° - 80° of Martian Year (MY) 36, which is a clear season without large dust storms. The novel orbit design of the spacecraft allows a full local time coverage to be reached within 10 Martian days, approximately ~5° of LS. It enables the analysis of diurnal temperature variations without the interference of seasonal changes, which was shown to be significant in previous studies. Wave mode decomposition is also applied to these diurnal variations, and amplitudes of other tide modes are derived. The results show good agreements with predictions derived using the Laboratoire de Météorologie Dynamique (LMD) Mars Global Circulation Model (GCM), except for a noticeable phase difference of the dominant diurnal thermal tide. This work provides valuable information on understanding diurnal variations in Martian atmosphere and inspires future advances of Mars GCMs.

To accurately simulate the climate and the fate of volatiles for thousands to millions of years we must couple physical processes with very different timescale, ranging from clouds microphysics and atmospheric dynamics (represented in the GCM) to the evolution of lakes, glacier accumulation, and subsurface ice evolution. Given the diversity and the complexity of the Martian paleoclimates, we choose to use use an ambitious “asynchronous coupling” between the slow ice and water reservoirs models and the GCM. In practice our innovative Mars evolution model will use a horizontal grid identical to that of the GCM, and include the same representation of the micro-climate on slopes. In our case, we will run the Mars Evolution Model with a timestep of 50 to ~500 years, depending upon the dynamics of the modeled system (smaller timesteps must first be used so that the different volatile reservoirs reach a quasi-equilibrium, then the timestep will depends on the evolution of the forcing, which is slow in the case of obliquity, for instance) . At each timestep, the inputs from the atmosphere (e.g. mean precipitation, sublimation and evaporation, temperatures, dust deposition) will be obtained through a multi-annual run of the Global Climate model using the outcome of the Mars Evolution Model as initial state.First results about evolution of water ice and CO2 ice glacier will be presented.

Observations of the South Polar Residual Cap suggest a possible erosion of the cap, leading to an increase of the global mass of the atmosphere. We test this assumption by making the first comparison between Viking 1 and InSight surface pressure data, which were recorded 40 years apart. Such a comparison also allows us to determine changes in the dynamics of the seasonal ice caps between these two periods. To do so, we first had to recalibrate the InSight pressure data because of their unexpected sensitivity to the sensor temperature. Then, we had to design a procedure to compare distant pressure measurements. We propose two surface pressure interpolation methods at the local and global scale to do the comparison. The comparison of Viking and InSight seasonal surface pressure variations does not show changes larger than +-8 Pa in the CO2 cycle. Such conclusions are supported by an analysis of Mars Science Laboratory (MSL) pressure data. Further comparisons with images of the south seasonal cap taken by the Viking 2 orbiter and MARCI camera do not display significant changes in the dynamics of this cap over a 40 year period. Only a possible larger extension of the North Cap after the global storm of MY 34 is observed, but the physical mechanisms behind this anomaly are not well determined. Finally, the first comparison of MSL and InSight pressure data suggests a pressure deficit at Gale crater during southern summer, possibly resulting from a large presence of dust suspended within the crater.

The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission described herein has been selected for flight to Venus as part of the NASA Discovery Program. DAVINCI will be the first mission to Venus to incorporate science-driven flybys and an instrumented descent sphere into a unified architecture. The anticipated scientific outcome will be a new understanding of the atmosphere, surface, and evolutionary path of Venus as a possibly once-habitable planet and analog to hot terrestrial exoplanets. The primary mission design for DAVINCI as selected features a preferred launch in summer/fall 2029, two flybys in 2030, and descent sphere atmospheric entry by the end of 2031. The in situ atmospheric descent phase subsequently delivers definitive chemical and isotopic composition of the Venus atmosphere during a cloud-top to surface transect above Alpha Regio. These in situ investigations of the atmosphere and near infrared descent imaging of the surface will complement remote flyby observations of the dynamic atmosphere, cloud deck, and surface near infrared emissivity. The overall mission yield will be at least 60 Gbits (compressed) new data about the atmosphere and near surface, as well as first unique characterization of the deep atmosphere environment and chemistry, including trace gases, key stable isotopes, oxygen fugacity, constraints on local rock compositions, and topography of a tessera., Comment: 41 pages, 14 figures, accepted for publication in the Planetary Science Journal

The Emirates Mars Mission (EMM) – Hope Probe – was developed to understand Mars atmospheric circulation, dynamics, and processes through characterization of the Mars atmosphere layers and its interconnections enabled by a unique high-altitude (19,970 km periapse and 42,650 km apoapse) low inclination orbit that will offer an unprecedented local and seasonal time coverage over most of the planet. EMM has three scientific objectives to (A) characterize the state of the Martian lower atmosphere on global scales and its geographic, diurnal and seasonal variability, (B) correlate rates of thermal and photochemical atmospheric escape with conditions in the collisional Martian atmosphere, and (C) characterize the spatial structure and variability of key constituents in the Martian exosphere. The EMM data products include a variety of spectral and imaging data from three scientific instruments measuring Mars at visible, ultraviolet, and infrared wavelengths and contemporaneously and globally sampled on both diurnal and seasonal timescale. Here, we describe our strategies for addressing each objective with these data in addition to the complementary science data, tools, and physical models that will facilitate our understanding. The results will also fill a unique role by providing diagnostics of the physical processes driving atmospheric structure and dynamics, the connections between the lower and upper atmospheres, and the influences of these on atmospheric escape.

Introduction The D/H ratio observed in a planetary atmosphere is a proxy for the ratio of the current water reservoir over the initial water reservoir of the planet. The current D/H ratio measured in the Martian atmosphere is at least five that of the Vienna Standard Mean Ocean Water (SMOW) (Owen et al. 1988, Encrenaz et al. 2018, Krasnopolsky 2015, Villanueva et al. 2015). This high value of the martian D/H ratio, derived from the HDO/H2O abundance ratio, is a precious indicator of the large escape of water from the martian atmosphere over time. Apart from the mass difference between both isotopes, the differential escape of H and D comes from the preferential photolysis of H2O over HDO (Cheng et al. 1999) and the Vapor Pressure Isotope Effect (VPIE) that produces an isotopic fractionation at condensation (Krasnopolsky, 2000, Bertaux et al. 2001, Fouchet et al. 2000). Modelling the HDO cycle Rossi et al. 2021 have implemented the HDO cycle, adapted from Montmessin et al. 2005, within the current version of the LMD Martian GCM (Forget et al. 1999). The fractionation effect caused by the condensation is taken into account with the calculation of a fractionation factor depending on the temperature, according to the empirical formulation of Lamb et al. 2017. In Rossi et al. (2021)’s study, clouds are produced and evolve according to simplified physics consisting in turning water vapour into ice if any supersaturation of water. In the study presented here, the HDO cycle is upgraded to the last version of the water cycle of the model, including the activation of the radiative effect of clouds and their microphysics (referring to the parametrization of the different processes of formation of the clouds, as nucleation of the ice particles on dust particles, water ice growth, dust scavenging and supersaturation), implemented in the model by Navarro et al. 2014. The calculation of the fractionation has also been improved by implementing the effect of kinetics impacting the condensation process. Indeed, the slower diffusion of the heavier HDO molecule in comparison to that of H2O reduces condensation flux, and an expression has been established by Jouzel and Merlivat 1984 to include this effect in the overall fractionation of water isotopologues during condensation into ice. Results and perspectives Our results, on the basis of these recent improvements, will be presented at the conference. Reinforcement of the Hadley circulation by the radiative effect of clouds which is now taken into account, as well as the role of nuclei played by dust in the cloud formation, do affect the transport of HDO and its vertical distribution, which directly impacts the HDO/H2O ratio in the low-to-mid atmosphere (see Figure 1). Kinetics of condensation reduces the fractionation effect whenever saturation occurs and increases with supersaturation, which means mainly at the poles (see Figure 2). Further aspects of this upgraded modelling of the HDO cycle and its sensitivity to different parameters will be explored and presented at the conference. The comparison of the model results with observations from TGO/ACS are presented by Loïc Rossi in session TP16. For now, the here-presented simulations extend to an altitude of around 120 km, and do not include the parametrizations of the thermosphere (Angelats i Coll et al. 2005, Gonzalez-Galindo et al. 2009), the photochemistry (Lefèvre et al. 2004, 2008) and the escape (Chaufray et al. 2015a), which have been recently extended to deuterated species. The ultimate goal of this work is the development of a complete representation of the deuterium cycle, from its source as HDO in the lower atmosphere, to its photodissociation and escape from the upper atmosphere. Figure 1: Meteorological variables as output of the model zonally averaged at LT=14:00 around Ls=90°. (Up) Results for the GCM simulation run with the simple physics of clouds (1). (Middle) Results for the GCM simulation run with the microphysics and the radiative effect of clouds (2). (Down) Difference between the two simulations (2) - (1). (Left) Temperature (K). (Middle) H2O ice mixing ratio (ppm). (Right) D/H ratio of the vapour phase. Figure 2: (Left) Zonal average of the integrated column of the D/H ratio of the vapour phase for a GCM simulation run with microphysics and radiative effect of clouds, and taking into account the effect of kinetics in the fractionation process. (Right) Difference between simulation with and without taking into account the effect of kinetics. Acknowledgements ExoMars is the space mission of ESA and Roscosmos. The ACS experiment is led by IKI Space Research Institute in Moscow. The project acknowledges funding by Roscosmos and CNES. Science operations of ACS are funded by Roscosmos and ESA. Science support in IKI is funded by Federal agency of science organizations (FANO). M.V. acknowledges support from the DIM ACAV labelled by the Ile-de-France region in support for the research (Domaine d’Intérêt Majeur, Astrophysique et Conditions d’Apparition de la Vie)".

Here we report a global model of meteoric metals including Mg, Fe and Na in the Laboratoire de Météorologie Dynamique (LMD) Mars global circulation model (termed as LMD-Mars-Metals), following on similar work as we have done for the Earth’s atmosphere. The model has been developed by combining three components: the state-of-the-art LMD-Mars model covering the whole atmosphere from the surface to the upper thermosphere (up to ~ 2 x10-8 Pa or 240 km), a description of the neutral and ion-molecule chemistry of Mg, Fe and Na in the Martian atmosphere (where the high CO2 abundance produces a rather different chemistry from the terrestrial atmosphere), and a treatment of injection of the metals into the atmosphere as a result of the ablation of cosmic dust particles. The LMD-Mars model contains a detailed treatment of atmospheric physics, dynamics and chemistry from the lower atmosphere to the ionosphere. The model also includes molecular diffusion and considers the chemistry of the C, O, H and N families and major photochemical ion species in the upper atmosphere, as well as improved treatments of the day-to-day variability of the UV solar flux and 15 mm CO2 cooling under non-local thermodynamic equilibrium conditions. So far, we have incorporated the chemistries of Mg, Fe and Na into LMD-Mars because these metals have different chemistries which control the characteristic features of their ionized and neutral layers in the Martian atmosphere. The Mg chemistry has 4 neutral and 6 ionized Mg-containing species, connected by 25 neutral and ion-molecule reactions. The corresponding Fe chemistry has 39 reactions with 14 Fe-containing species. Na chemistry has 7 neutral and only 2 ionized Na-containing species, with 32 reactions. The injection rate of these metals as a function of height is pre-calculated from the Leeds Chemical Ablation Model (CABMOD) combined with an astronomical model which predicts the dust from Jupiter Family and Long Period comets, as well as the asteroid belt, in the inner solar system. The LMD-Mars-Metals model has been run for several full Martian years under different surface dust scenarios to investigate the impact of high atmospheric dust loadings on the modelled metal layers. The model has been evaluated against Mg+ observations from IUVS (Imaging UV Spectrometer) and NGIMS (Neutral Gas Ion Mass Spectrometer) instruments on NASA’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft. We have also carried out other sensitivity experiments with different seasonality/altitude/latitudinal varying of Meteoric Input Function (MIF) of these metals in the model. These sensitivity results will be discussed.

Introduction: For many years we have been working on the modeling of the martian water cycle in the Laboratoire de Météorologie Dynamique martian Global Climate Model [1,2,3,4]. This has been challenging because of destabilizing feedbacks such as the coupling between temperatures, water vapour, clouds, and temperature changes induced by radiatively active water clouds [2]. It is interesting to accurately model Mars’s water cycle not only to understand present day Mars but also to simulate past climate changes induced by obliquity and orbital variations. This study is partly motivated by the ERC Mars Through Time project which notably aims at modeling recent ( Sensitivity to the physical timestep: The standard physical timestep used in [1] was 15 martian minutes, subsequently reduced to 7.5 minutes. The water cycle shows a significant sensitivity to the physical timestep. This is because the dust and water physics and transport are strongly coupled with boundary layer parametrization radiative transfert, and cloud microphysics. Cloud microphysics uses a dedicated subtimestep for computing efficiency, but the diversity of processes involved bind us to increase physical resolution altogether. We will discuss the influence of an even smaller physical timestep to the water cycle, and the distinct effect of the dynamical timestep. Temperature-dependant water contact parameter: The water “contact parameter” controls the effective fraction of nuclei activated for water condensation. The higher it is, the more water ice nucleation is favored and water-ice clouds form. Experimental data and literature [8] tend to show a strong dependence of the contact parameter with temperature. However, GCMs usually use constant water contact parameter. We find that using a simple linear fit from [8], albeit oversimplifying the bimodal behavior between low and high temperatures, attenuates the thickness of the northern polar hood during the second part of the year while allowing for a thick aphelion cloud belt, which was a key modeling issue in the LMD GCM (Navarro et al. 2014). Latent heat of ground ice sublimation: The latent heat of ground water ice sublimation had been neglected in our climate model, because of the low amount of water and thus energy flux involved. The sublimation of water was hitherto simply computed using surface temperature and water vapor equilibrium. Preliminary studies of martian climates at higher obliquities have shown that the energy fluxes involved may become of prime importance, as accounting for the latent heat of ground ice strongly inhibits the summer sublimation of the polar caps. Its calculation in a GCM requires an implicit numerical scheme to properly account for the coupling between temperature and sublimation during the GCM timestep. We show that the latent heat of ground ice sublimation has a minor influence on the global present-day water-cycle but may be considered for specific phenomenons such as the perenniality of crater-induced water ice ejectas [8]. Differentiation of perennial ice albedo and water frost albedo: Through sublimation, the northern polar cap around summer solstice is the dominant atmospheric source of water vapor in our GCM. It shows a strong dependence of summer surface temperature with albedo and thus sublimation [2]. While acceptable water ice albedos range from 0.3 to 0.5 on Mars [9], monitoring the northern polar cap show that the start and end of sublimation phases are correlated with albedo variations [10]. The outlier region of the polar cap is actually the main source of sublimation in the GCM, while the central cap is a cold trap where water vapor condenses into frost. The albedo of perennial water ice and frost, previously identical, are now separated in our GCM to take into account the fact that fresh frosts can exhibit higher albedos which tend to slow down their sublimation . Future enhancements may include a time-varying frost albedo, as it changes with the evolution of ice particules size (metamorphism) and dust accumulation, and thus represent more accurately the insolation on the northern polar cap during summer. These processes may play a key role in paleoclimate studies. Conclusion: Because of the intricate complexity of the feedbacks between dynamics, dust and water transport and cloud microphysics, increasing the temporal resolution in the GCM is mandatory. We have addressed the disruptions it causes to our reference water cycle simulation by taking into account previously neglected physical processes, which allow for a satisfying agreement with TES and SPICAM datasets (figure 1). Figure 1: Reference simulation (MY26) compared to TES data for water vapor column and cloud opacity at 2 PM. References: [1] Montmessin et al. (2004), Journal of Geophysical Research: Planets, 109(E10). [2] Navarro et al. (2014), Journal of Geophysical Research: Planets, 119(7), 1479-1495. [3] Pottier et al. (2017), Icarus, 291, 82-106. [4] Vals (2019), Doctoral dissertation, UPMC. [5] Smith (2004), Icarus, 167(1), 148-165. [6] Maltagliati et al. (2011), Science, 333(6051), 1868-1871. [7] Fedorova et al. (2020), Journal of Geophysical Research: Planets, e2020JE006616. [7] Määttänen et al. (2014), GeoResJ, 3, 46-55. [8] Byrne et al. (2009), Science, 325(5948), 1674-1676. [9] Wilson et al. (2007), Geophysical Research Letters, 34(2). [10] Hale, A. S. et al. (2005), Icarus, 174(2), 502-512.

Thermal tides in Martian atmosphere from ACS/TIRVIM Siteng Fan1 (sfan@lmd.ipsl.fr), Sandrine Guerlet1, Francois Forget1, Antoine Bierjon1, Ehouarn Millour1, Nikolay Ignatiev2, Alexey Shakun2, Alexey Grigoriev2, Alexander Trokhimovskiy2, Franck Montmessin3, Oleg Korablev2 1: LMD/IPSL, Sorbonne Université, PSL Research University, École Normale Supérieure, École Polytechnique, CNRS, Paris, France 2: Space Research Institute (IKI), Moscow, Russia 3: LATMOS/IPSL, Guyancourt, France Abstract Atmospheric thermal tides are planetary-scale temperature oscillations driven by diurnal solar forcing. On Mars, they dominate the temperature variations and winds throughout the thin atmosphere due to its low heat capacity. Given the short timescales of tide modes, which are typically equal or shorter than a Martian day, analyses of these tides require observations with large spatial coverage and high local time resolution. Observations from the TIRVIM Fourier-spectrometer, part of the Atmospheric Chemistry Suite (ACS) onboard ExoMars Trace Gas Orbiter (TGO), provide data meeting such requirement. Here we report the spatial- and temporal-dependent temperature profiles of Martian atmosphere retrieved from TIRVIM nadir data. Amplitudes and phases of thermal tide modes are obtained, and their influence on the thermal structure of Martian atmosphere is estimated using numerical simulations, The LMD Mars Global Circulation Model (GCM). Introduction Diurnal thermal forcing by solar radiation excites temperature oscillations in Martian atmosphere through direct sunlight absorption and heat exchange with Mars surface (Gierasch & Goody 1968). Influenced by surface topography, the varying solar forcing produces harmonic responses in the Martian atmosphere, thermal tides (Zurek 1976). Some modes of the tides can vertically propagate to upper altitudes with amplitudes growing exponentially with decreasing air density, which therefore influences the atmospheric circulation. The existence of such temperature and the related pressure variations has been observed by many Mars landers and orbiters (e.g., Hess et al., 1977, Banfield et al. 2000, Lee et al. 2009, Kleinböhl et al. 2013, Forbes et al. 2020), but observations are still lacking for comprehensive studies as large spatial coverage and high temporal resolution are required to study such planetary-scale diurnal/sub-diurnal variations. Methodology and Results We analyze the thermal tides using temperature structures retrieved from TIRVIM nadir data. TIRVIM is a thermal infrared Fourier-spectrometer, as part of the ACS instrument onboard the ESA-Roscosmos mission ExoMars TGO (Korablev et al., 2018, Svedhem et al. 2020). TGO is on a non-solar-synchronous orbit with a period of 2 hours, so observations obtained at nadir viewing geometry could cover a wide range of local time due to the short orbital period and orbit drifting (Capderou & Forget, 2004, Figure 1). A full diurnal cycle can be sampled between 74°N and 74°S within ~55 solar days (sols), which is equivalent to ~30° in solar longitude (Ls). Binning data within this range results in data covering most local time in a specific Martian month with little seasonal variations. TIRVIM operated from April 2018 to December 2019, nearly one Martian year (MY) from MY34 Ls134° to MY35 Ls 115°, and provides ~1.5 million thermal infrared nadir-viewing spectra with decent data quality. Despite some degeneracy, we retrieved temperature profiles together with dust and water ice from these spectra (Guerlet et al. 2018). Each profile covers a vertical range from ~2-3km above Mars surface to ~50-55km (~1-2Pa) with a vertical resolution of ~1 scale height (10km). Full coverage of local time is obtained for the first time on sub-seasonal scales (Figure 1), which makes it possible to evaluate thermal tides in Martian atmosphere with details and resolve the harmonic aliasing introduced by solar-synchronous observations, e.g., observations at 3am and 3pm local time by the Mars Climate Sounder (MCS, Lee et al. 2009). A preliminary result of the thermal structure on the Martian southern hemisphere near MY35 spring equinox (Ls=90°) is shown in Figure 2a. We binned the data between Ls 75° to 105° so that most of the local time is covered. No dust storms are identified during this period. The selected bin size of latitude is 3° and that of the local time is 1 hour. Temperature profiles are also zonal averages, so only migrating tides are shown. The diurnal temperature difference structure shows diurnal and semi-diurnal cycles at lower and middle atmosphere, respectively, with “apparent” amplitudes of ~7K. Due to the degeneracy introduced by vertically distributed sensitivity response functions of TIRVIM thermal infrared spectra, the retrieved temperature profiles are vertically smoothed (Guerlet et al. 2018). Suggested by the LMD Mars GCM (Forget et al. 1999), amplitudes of these tides are 2-3 times larger (Figure 2b), as smoothing them with the same response functions gives similar diurnal temperature difference structure (Figure 2c). A priori in the temperature profile retrieval makes a difference in extracting the diurnal temperature anomaly at low pressure level due to small weights in the convolution kernels (Figure 2b and 2c), which requires further investigation with GCMs. Figure 1. Spatial-temporal coverage of ACS/TIRVIM observations. Data from 20 orbits are shown for the purpose of illustration, with colors denoting the local time. Figure 2. (a) Diurnal temperature anomaly derived using ACS/TIRVIM observations. The data is binned between MY35 Ls 75° and 105°, and between 10.5°S and 13.5°S in latitude. (b) Result of the LMD Mars GCM. The model result has the same spatial-temporal sampling weight as observations. (c) Same as (b), but vertically convolved with the averaging kernels of TIRVIM. References Banfield, D., Conrath, B., Pearl, J. C., et al. (2000). JGR, 105, 9521. Capderou, M., & Forget, F. (2004). P&SS, 52, 789. Forbes, J. M., Zhang, X., Forget, F., et al. (2020). JGR: Space Physics, 125, e28140. Forget, F., Hourdin, F., Fournier, R., et al. (1999). JGR, 104, 24155. Gierasch, P., & Goody, R. (1968). P&SS, 16, 615. Guerlet, S., Ignatiev, N., Fouchet, T., et al. (2018). EPSC, 2018-223. Hess, S. L., Henry, R. M., Leovy, C. B., et al. (1977). JGR, 82, 4559. KleinböHl, A., John Wilson, R., Kass, D., et al. (2013). GRL, 40, 1952. Korablev, O., Montmessin, F., Trokhimovskiy, A., et al. (2018). SSW, 214, 7. Lee, C., Lawson, W. G., Richardson, M. I., et al. (2009). JGR: Planets, 114, E03005. Svedhem, H., Korablev, O., Mitrofanov, I., et al. (2020). EPSC, 2020-802. Zurek, R. W. (1976). JAS, 33, 321.

HDO and the D/H ratio are important in order to understand Mars past and present climate, in particular regarding the evolution through ages of the Martian water cycle. We present simulations of the HDO cycle with the LMD Mars GCM and compare the retrieved cycle with observations provided by the Atmospheric Chemistry Suite (ACS) on board the ESA/Roscosmos Trace Gas Orbiter (TGO). This work is a companion study of Vals et al. presented in session TP12, which presents the evolutions of the model since Rossi et al, (2021), and explores the behaviour of the D/H ratio cycle when taking into account the microphysics and radiative effect of clouds, as well as the effect of kinetics on fractionation during condensation. Introduction Mars is known to have had a significant liquid water reservoir on the surface and the D/H ratio derived from the HDO/H2O abundance ratio is a sensitive tool to constrain the primordial abundance of the water reservoir on Mars and its evolution with time. The current ratio is at least five times that of the Vienna Standard Mean Ocean Water (SMOW) (Owen et al. 1988 , Encrenaz et al. 2018, Krasnopolsky 2015, Villanueva et al. 2015). H and D atoms in the upper atmosphere come from H2O and HDO, their sole precursor in the lower atmosphere. The lower mass of H over D atoms and the fact that H2O is preferentially photolysed over HDO (Cheng et al. 1999) explain the differential escape of these two elements. Also, the heavier isotope, HDO, has a lower vapor pressure than H2O, which results in an enrichment of the deuterated isotope in the solid phase of water. This effect is known as the Vapor Pressure Isotope Effect (VPIE) and can reduce the D/H ratio above the condensation level to values as low as 10% of the D/H ratio near the surface (Bertaux et al. 2001, Fouchet et al. 2000). Fractionation should affect the amount of HDO depending on latitude, longitude, altitude and season (Montmessin et al. 2005, Rossi et al. 2021). Modeling HDO We present here the results from our (re)integration of the HDO cycle into the LMD Mars GCM, taking into account HDO in its vapour and ice phases in the atmosphere, and as surface ice. In Rossi et al. (2021), we presented first results with a dust annual scenario mimicking the dust seasonal and spatial evolution observed during Martian Year 34 (MY34) and including the occurrence of the Global Dust Storm (GDS). The simulations illustrated the effect of the dust on the temperature field, and therefore on the circulation and the cloud formation. Since clouds are forming at higher altitude (if at all), the deuterium is less constrained vertically and can extend to higher altitudes. A similar effect being observed for water vapour (Fedorova et al., 2020). In Rossi et al. (2021) we used a simplified cloud formation scheme, without condensation nuclei, and didn't include the radiative effect of clouds. Figure 1: Zonally averaged meridional profiles of the D/H ratio in the vapour phase, as predicted by the updated GCM for MY34. Each subplot shows the beginning of each month. Here we present results of a new version of the model, this time including the microphysics of cloud formation, the radiative effect of clouds but also the effect of kinetics on the fractionation factor (see companion abstract of Margaux Vals in TP12). As shown in Fig 1, the effect of the dust storm of MY34 is still quite visible, with a D/H ratio relatively constant in higher parts of the atmosphere (up to 1 Pa). With this updated model, we are able to make comparisons with the HDO profiles observed by ACS onboard TGO. Preliminary results In order to be comparable with the solar occultations from ACS, the GCM output is interpolated at a solar zenith angle of 90° and at the coordinates (latitude, longitude, local time and solar longitude) of each solar occultation. In particular, we compare the model with ACS observations presented in Alday et al. (2021). Figure 2 presents some early results of such comparison. Figure 2: Profiles of the D/H ratio from the GCM (in orange) and from ACS data (in blue). Profiles are averaged over bins of solar longitude (covering the end of MY34 and the beginning of MY35) and latitude. Error bars indicate the standard deviation within the bin. The altitude is given in kilometers above the areoid. The comparison shows a good agreement between the GCM profiles and the observations for the D/H ratio in several bins in latitude and solar longitude. This indicates that the model is capable of representing the process of isotopic fractionation and its effect on the D/H ratio. A more detailed comparison between the observations and the GCM, in particular with respect to the distribution of water vapour is ongoing. Acknowledgements ExoMars is the space mission of ESA and Roscosmos. The ACS experiment is led by IKI Space Research Institute in Moscow. The project acknowledges funding by Roscosmos and CNES. Science operations of ACS are funded by Roscosmos and ESA. Science support in IKI is funded by Federal agency of science organizations (FANO). L.R. acknowledges support from CNES and from the Excellence Laboratory "Exploration Spatiale des Environnements Planétaires (ESEP)".

Introduction This study focuses on the water cycle around the Northern seasonal polar cap from the end of autumn to the following spring season, and more precisely on the progression and retreat of CO2 and H2O frost. The CO2 and water cycle has been modeled by Martian global climate models (GCMs). At high latitudes, its main components are the permanent polar ice cap, humidity in the atmosphere (water vapor), clouds in abundance in winter (forming the polar hood), locally formed ice and frost. Other components, CO2 ice and frost, and dust, may also have an impact on the water cycle. Starting with Mariner-9, several satellites have observed (water) frost in particular at high latitudes and in the vicinity of polar caps. The OMEGA imaging spectrometer (on Mars Express) has made numerous observations of the northern high latitudes of Mars since 2004. Based on a series of observations from the end of autumn of MY 27 (Ls ~260°) to the end of spring of MY 28, Appéré et al. (2011) described the temporal evolution of H2O and CO2 deposits, constantly evolving northwards through sublimation and deposition of the corresponding ice/frost. This ends just before the summer solstice (around Ls ~70°) after the complete disappearance of CO2 ice. At high latitudes, the sublimation of frost then contributes to an abundant emission of water vapor. Current Martian GCMs include the water and CO2 cycles. In the past decade, the modeling of the water cycle has been improved in the LMD GCM (Navarro et al., 2014 ; Pottier et al. 2017 ; Vals, 2019). The LMD Martian GCM is able to reproduce the global and seasonal water cycle during the winter-spring seasons. However, it releases excessive humidity in the polar region. In order to improve the model, we examined and compared the southernmost position of water frost and its poleward progression on Martian GCM data and on spectral images from OMEGA. Data and Method In OMEGA data, frost can be detected by an absorption band of H2O at 1.5 mm (Langevin et al., 2007). Similarly, when the depth of the absorption band falls below a chosen value, the frost is considered as having disappeared. On one orbit-segment image, the southernmost pixels form a (more or less continuous) line corresponding to the limit of frost (“crocus”-type line). In the model simulation, we use the surface water ice content provided by the LMD GCM (Forget et al., 1999) in order to detect the frost dissipation. Water ice content values (in kg/m2) have been calculated on a regular grid (5.625° longitude x 3.75° latitude) 4 times every sol (at 0, 6, 12 and 18 h LT) over one Martian year. Starting at the end of the northern autumn (Ls ~ 260°), the evolution of the water ice content can be examined at every grid point. In most cases, all these pixels are observed at the same local time. We calculate an average GCM frost dissipation time Lsfd_GCM from the 4 closest GCM neighbor grid points, weighted by the distance between each GCM grid point and the OMEGA frost limit. Then the time interval between the dissipation of frost in OMEGA water ice absorption depth profile and in the collocated (interpolated) water ice disappearance on the GCM can be determined. Results With a perfect GCM and well-chosen frost-detection thresholds on both datasets, the dissipation of frost should be simultaneous for collocated data in both datasets. Otherwise, when the frost time dissipation interval DLsfd = Lsfd_OMEGA - Lsfd_GCM is positive (respectively negative), the model is late (in advance) w.r.t. observation. We will present results of the evolution of the frost time dissipation during the winter-spring season. Conclusion and prospects Determining the time interval between the frost dissipation line observed by OMEGA and by a GCM can help to understand the behavior of the model at high latitudes, to detect its limits and to improve it. On the other hand, the systematic presence of a non-negligible time interval could reveal a systematic bias, which can be related to the detection thresholds used for the detection of frost. Acknowledgements Thomas Appéré provided a part of the OMEGA water ice imagery and ancillary data. The other part of OMEGA data was extracted from the database on the PSUP portal (http://psup.ias.u-psud.fr/ ). References - Appéré, T., Schmitt, B., Langevin, Y., Douté, S., Pommerol, A., Forget, F., Spiga, A., Gondet, B., and Bibring, J.-P. (2011). Winter and spring evolution of northern seasonal deposits on Mars from OMEGA on Mars Express. Journal of Geophysical Research (Planets), 116(E15):5001. - Forget, F., Hourdin, F., Fournier, R., Hourdin, C., Talagrand, O., Collins, M., Lewis, S. R., Read, P. L., and Huot, J.-P. (1999). Improved general circulation models of the Martian atmosphere from the surface to above 80 km. J. Geophys. Res., 104:24,155–24,176. - Langevin, Y., Bibring, J.-P., Montmessin, F., Forget, F., Vincendon, M., Douté, S., Poulet, F., and Gondet, B. (2007). Observations of the south seasonal cap of Mars during recession in 2004-2006 by the OMEGA visible/near-infrared imaging spectrometer on board Mars Express. J. Geophys. Res., 112:E08S12. - Navarro, T., Madeleine, J.-B., Forget, F., Spiga, A., Millour, E., Montmessin, F., and Määttänen, A. (2014). Global Climate Modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds. Journal of Geophysical Research (Planets), 119:1479–1495. - Pottier, A., Forget, F., Montmessin, F., Navarro, T., Spiga, A., Millour, E., Szantai, A., and Madeleine, J.-B. (2017). Unraveling the martian water cycle with high-resolution global climate simulations. Icarus, 291:82–106. - Vals, M. (2019). Modélisation numérique des cycles de l’eau et des poussières de la planète Mars et de leurs couplages. PhD thesis. Université Pierre et Marie Curie, Paris, Fr.

International audience

21st EGU General Assembly, EGU2019, proceedings from the conference held 7-12 April, 2019 in Vienna, Austria, id.11100, After 15 years in orbit Mars Express remains one of ESA's most scientifically productive Solar System missions whose publication record now exceeds 1200 papers. Characterization of the geological processes on a local-to-regional scale by HRSC, OMEGA and partner experiments on NASA spacecraft has allowed constraining land-forming processes in space and time. Recent results suggest episodic geological activity as well as the presence of large bodies of liquid water in several provinces (e.g. Eridania Planum, Terra Chimeria) in the early and middle Amazonian epoch and formation of vast sedimentary plains north of the Hellas basin. Mars Express observations and experimental teams provided essential contribution to the selection of the Mars-2020 landing sites. Recent discovery of subglacial liquid water underneath the Southern polar cap has proven that the mission science potential is still not exhausted. More than a decade-long record of the atmospheric parameters such as temperature, dust loading, water vapor and ozone abundance, water ice and CO2 clouds distribution, collected by SPICAM, PFS, OMEGA, HRSC and VMC together with subsequent modeling have provided key contributions to our understanding of the martian climate. Recent spectroscopic monitoring of the 2018 dust storm revealed dust properties, their spatial and temporal variations and atmospheric circulation. More than 10,000 crossings of the bow shock by Mars Express allowed ASPERA-3 to characterize complex behavior of the magnetic boundary topology as function of the solar EUV flux. Observations of the ion escape during complete solar cycle revealed important dependencies of the atmospheric erosion rate on parameters of the solar wind and EUV flux and established global energy balance between the solar wind and escaping ion flow. The observations showed that ion escape can be responsible for removal of about 10 mbar over the Mars history that implies existence of other more effective escape channels. The structure of the ionosphere sounded by the MARSIS radar and the MaRS radio science experiment was found to be significantly affected by the solar activity, the crustal magnetic field, as well as by the influx of meteorite and cometary dust. MARSIS and ASPERA-3 observations suggest that the sunlit ionosphere over the regions with strong crustal fields is denser and extends to higher altitudes as compared to the regions with no crustal anomalies. Several models of the upper atmosphere and plasma environment are being developed based on and in support of the collected experimental data. The models aim at creating user-friendly data base of plasma parameters similar to the Mars Climate Database that would be of great service to the planetary community. A significant recent achievement was the flawless transition to the >gyroless> attitude control and operations mode on the spacecraft, that would allow mitigating the onboard gyros aging and extending the mission lifetime. In November 2018 ESA's Science Programme Committee (SPC) confirmed the mission operations till the end of 2020 and notionally approved its extension till the end of 2022. The talk will give the Mars Express status, review the recent science highlights, and outline future plans focusing on synergistic science with TGO.

The Martian atmosphere (from the surface up to the outer layers) is a very dynamic system, quickly responding to strong radiative forcing coming from the absorption of solar radiation from dust particles lofted during dust storms. So far, such dynamical phenomena at short time scales and large spatial scales have been observed mainly from spacecraft in polar or quasi-polar orbits, which cannot provide continuous and simultaneous observations over fixed, large regions. This limitation can be bypassed using spacecraft in equatorial, circular, planet-synchronous (i.e. areostationary) orbit at an altitude of 17,031.5 km above the Martian surface. Besides their possible use as communication relays for ground-based assets, for space weather monitoring (they orbit outside Mars' bow shock), and for the study of surface properties (e.g. thermal inertia and albedo), the unique scientific advantages of areostationary satellites for weather monitoring are comparable to those provided by geostationary satellites. These platforms greatly increase the temporal resolution and coverage of single events, and are ideally suited for data assimilation in global climate models. Thanks to NASA PSDS3 program, we have elaborated a mission concept to put a low-cost, low-weight, ESPA-class SmallSat in areostationary orbit, which is capable of supporting various tank sizes in order to provide a wide range of ΔV for three different Mars arrival scenarios. ExoTerra Resource LLC adapted its "Electrically Propelled Interplanetary CubeSat" bus as part of the mission design. Despite the optimization of the flight trajectories and the use of machine learning algorithms to prioritize data downlink, the conclusions of the concept study clearly point towards the current challenges represented by propulsion, communication, and possibly radiation tolerance for scientific SmallSat missions to Mars. Such conclusions are generally common among all low-cost interplanetary SmallSat concepts. Furthermore, a single areostationary satellite is enough to provide a full-disk view to monitor regional dust storms and water ice clouds at specific locations, but cannot provide the global coverage required to understand extreme phenomena such as Martian planetary-scale dust events. For this reason, we have recently started to study a more advanced mission concept involving the use of at least three areostationary satellites. This new study is carried out in collaboration with the Jet Propulsion Laboratory within the scope of a wider NASA-funded project (PMCS program) looking at a constellation concept. The challenge is to keep the areostationary satellite configuration within the ESPA class limits, in order to take advantage of possible future rideshare opportunities.

Introduction The thermal profile of Pluto’s atmosphere has been measured from ground-based observations and from the REX instrument on-board New Horizons [1,2]. From the surface to the top of the atmosphere, the profiles show a 3-km deep ~37 K cold layer above the N2 ice-covered surface, a strong positive gradient below 50 km, warming the stratosphere up to 110 K, and a 40 K negative gradient cooling the upper atmosphere to 70 K. Our objective is to study the radiative balance of Pluto’s atmosphere in 1D with a radiative-convective model, and in 3D with the full Pluto Global Climate Model (GCM), taking into account the radiative impact of haze particles. We focus on three aspects of the thermal profile with the GCM: (1) It has been suggested that the organic haze has a significant radiative impact and is responsible for the cooling of the upper atmosphere [3]. However, this has not been explored yet in details in a GCM and remains to be tested against JWST observations of Pluto’s atmosphere thermal emission. (2) The depth of the near-surface cold layer in the GCM is currently only 1 km, versus 3 km in the observations [4,5]. (3) The significant temperature gradient between the equator and the north pole tentatively indicated by recent ALMA observations (PI Lellouch) is not predicted by current models, because the long radiative timescale of Pluto’s atmosphere should prevent horizontal temperature gradients. However, by radiating in the infrared, haze particles could shorten the radiative timescale and trigger significant temperature gradients. The Pluto GCM The GCM is described in detail in [4,5]. It takes into account the sublimation and condensation cycles of N2, CH4, and CO [4], their thermal and dynamical effects, the cloud formation, the vertical turbulent mixing, molecular thermal conduction, and a detailed surface thermal model with different thermal inertia for various timescales (diurnal, seasonal). It also includes a parameterization of the formation of organic haze [6]. We use the 1D radiative-convection version of the GCM to explore the radiative impact of haze depending on the haze properties. We then use the 3D GCM to explore the effect in a climatic context, with consistent 3D predictions for haze formation and methane abundance, which are used as an input for our radiative transfer calculation. At the conference we will present the results obtained with our model for different types of haze particles (spheres, fractal aggregates) and different datasets of laboratory-generated optical constants. We will reveal if the radiative haze can solve the three mysteries mentioned in Section 1, and how it impacts Pluto’s atmosphere dynamics. Acknowledgements T.B. was supported for this research by an appointment to the National Aeronautics and Space Administration (NASA) Post-doctoral Program at the Ames Research Center administered by Universities Space Research Association (USRA) through a contract with NASA. References [1] Hinson, D. P., et al., Radio occultation measurements of Pluto’s neutral atmosphere with New Horizons, Icarus, 290, 96–111, 2017. [2] A. Dias-Oliveira et al., Pluto's atmosphere from stellar occultations in 2012 and 2013, ApJ 811, 53, 2015. [3] Zhang, X., et al, Haze heats Pluto's atmosphere yet explains its cold temperature, Nature, 2017. [4] Forget, F., et al., A post-new horizons global climate model of Pluto including the N2, CH4 and CO cycles, Icarus, 287, 54–71, 2017. [5] Bertrand, T., et al., Pluto’s Beating Heart Regulates the Atmospheric Circulation: Results From High-Resolution and Multiyear Numerical Climate Simulations. JGR: Planets, 125(2), 1–24, 2020. [6] Bertrand, T. and Forget, F.: 3D modeling of organic haze in Pluto’s atmosphere, Icarus, 287:72, 2017.

Introduction: Remnants of glacial and periglacial geomorphological features are visible up to mid-latitudes on Mars. Notably, an out-of-equilibrium “latitude-dependant mantle” extends to 30° latitude in both hemispheres [1]. These patches were likely deposited as snowfall in the recent past (less than ~2Myr) in response to climate change driven by shift in obliquity, similar to Earth glacial/interglacial periods [2]. However, martian climate models usually struggle to reproduce environmental conditions required to form LDM under recent paleoclimatic orbital forcing. We present a new set of simulations with refined description of surface and sub-surface water processes and their relevance regarding the deposition and above all stability of large ice patches up to mid-latitudes in both martian hemispheres. Water-ice clouds in recent paleoclimates: As present-day martian atmosphere is extremely dry, water ice clouds have second-order effects in global climate models [6]. Modeling higher obliquity episodes, ie shifts from 25° up to 35°, atmospheric humidity is enhanced by polar warming and water-ice cloud become a key element of martian climate [7,8]. Their radiative effect strongly warms the atmosphere, amplifies meridional circulation and water transport toward tropical latitudes. Previous work showed that radiatively active water-ice clouds allow for the transportation and deposition of water ice patches up to mid-latitudes [7]. However, these deposits can only be perennial under extreme atmospheric dust scenarios, in order to limit summertime sublimation. Frost and ice albedo: Surface water ice has a typical albedo of 0.35 in our present-day Mars model [9]. Mid-latitude ice patches resulting from an intensified water cycle at higher obliquity would rather have a 0.7 albedo, due to less dust content and fresh snowfall. By limiting solar heating, this albedo parametrization favors the persistence of mid-latitude ice throughout summer. Latent heat of sublimation: The latent heat of water sublimation has been neglected in present-day climate models, because of the low amount of water and thus energy flux involved. The sublimation of water was hitherto simply computed using surface temperature and water vapor equilibrium. Similarly to the frost albedo effect, taking into account the latent heat of water becomes relevant when the water cycle, and thus the energy flux involved, is intensified at higher obliquity. It also favors the year-long persistence of mid-latitude ice by adding an energy cost to sublimation, which decreases surface heating. Nudging subsurface thermal inertia: Martian soil’s thermal inertia is driven by the presence of subsurface perennial water ice, regulated by long-term equilibrium with water vapor [10]. This equilibrium is modified with the water cycle at higher obliquity. Instead of waiting for natural equilibrium to occur, we artificially accelerate the relocation of subsurface water ice, and accordingly increase subsurface thermal inertia. Subsurface ice inventory is computed each year using annual mean water vapor, as proposed in [10]. Conclusions with idealized orbital forcing: The recent excursions to 35° obliquity are thought to be the main drivers of martian glaciations. We use our new parametrizations along with idealized orbital forcing, that is a 35° obliquity and a null-excentricity, to show that the effect of water-ice clouds, frost albedo and latent heat of sublimation allow for the preservation of mid-latitude ice deposits when equilibrium is reached. In the last ~2 Myr on Mars, obliquity has reached 35° a dozen times, for approximately 1000 years each time [11]. Under our idealized hypothesis, the accumulation rate is compatible with hundreds of meters thick latitude-dependent mantle of ice-rich deposits. References: [1] Head, J. W., J. F. Mustard, M. A., Kreslavsky, R. E. Milliken, and D. R. Marchant (2003), Nature, 426 (6968), 797–802. [2] Forget, F., Byrne, S., Head, J. W., Mischna, M. A., & Schörghofer, N. (2017), The Atmosphere and Climate of Mars, Haberle et al. Editors, Cambridge University Press [3] Forget, F., Haberle, R. M., Montmessin, F., Levrard, B., & Head, J. W. (2006), 311(5759), 368-371. [4] Levrard, B., Forget, F., Montmessin, F and Laskar, J. (2004), Nature, 431 (7012), 1072-1075. [5] Madeleine, J. B., Forget, F., Head, J. W., Levrard, B., Montmessin, F., & Millour, E. (2009), Icarus, 203(2), 390-405. [6] Madeleine, J. B., Forget, F., Millour, E., Navarro, T., & Spiga, A. (2012), GRL, 39(23).[7] Madeleine, J. B., Head, J. W., Forget, F., Navarro, T., Millour, E., Spiga, A., ... & Dickson, J. L. (2014), GRL, 41(14), 4873-4879. [8] Kahre, M. A., Haberle, R. M., Hollingsworth, J. L. and Wilson, R. J. (2019), Ninth International Conference on Mars, held 22-25 July, 2019 in Pasadena, California. LPI Contribution No. 2089, id.6303. [9] Navarro, T., Madeleine, J. B., Forget, F., Spiga, A., Millour, E., Montmessin, F., & Määttänen, A. (2014), JGR: Planets, 119(7), 1479-1495. [10] Schorghofer, N. (2007). Theory of ground ice stability in sublimation environments. Physical Review E, 75(4), 041201. [11] Laskar, J., Correia, A. C. M., Gastineau, M., Joutel, F., Levrard, B., & Robutel, P. (2004), Icarus, 170(2), 343-364.

International audience; Solar tides are responsible for much of the spatial‐temporal variability of Mars' upper atmosphere (100–∼200 km). However, the tidal spectrum, its latitude versus Ls variability, and its vertical evolution remain uncertain. In this paper, Mars Climate Sounder temperature measurements at 76 km above Mars' areoid are used to construct a multiyear latitude versus Ls climatology of the tidal spectrum. The most important spectral components include the solar‐synchronous (“migrating”) components DW1, SW2, and the solar‐asynchronous (“nonmigrating”) tides DE3, DE2, DE1, SE1, S0, and SW1. The Mars Climate Database (MCD), which provides predictions from the Laboratoire de Météorologie Dynamique Global Climate Model, captures particularly well the amplitudes and key structural features of the solar‐asynchronous tides at 76 km that furthermore underly the large longitudinal structures in density that are observed between 100 and 200 km. Height‐latitude and latitude‐Ls structures of MCD density perturbations are therefore examined between 76 and 172 km and interpreted in terms of mean wind and dissipation effects. In particular, due to the smaller radius and more intense zonal‐mean zonal winds at Mars compared to Earth, Doppler‐shift effects are significantly exaggerated compared to Earth. Evidence is also provided for nonnegligible contributions to density variability from stationary planetary waves which arise from tide‐tide nonlinear interactions. It is moreover shown that MCD captures the salient amplitude and phase characteristics of the ∼±30–60% longitudinal density perturbations measured by the Mars Global Surveyor accelerometer. This, and the excellent MCD‐MCS agreement at 76 km, lends credibility to the ability of MCD to provide new insights into thermosphere density variability at Mars due to vertical coupling by solar tides.

The researchers studied the Tcheonzamun (The Thousand Character Essay) poem of 769 to 784th characters. The poem is composed of dialogues between an aged man and a young man, or between a husband and wife of a family. The main theme of the poem is ‘recovering from defeat’. The aged man praises the young man, ‘You are magnifique, Maeg’s descendants!’. In another interpretation, there is a matrimonial expression, and there is an opinion that the ancient Chinese people had only little theological knowledge. Here, the author of Tcheonzamun expressed his deep belief in the Lord. Key words: Dialogue, Tcheonzamun (The Thousand Character Essay), aged man and young man, husband and wife.

International audience; We have completed our seasonal monitoring of hydrogen peroxide and water vapor on Mars using ground-based thermal imaging spectroscopy, by observing the planet in March 2014, when water vapor is maximum, and July 2014, when, according to photochemical models, hydrogen peroxide is expected to be maximum. Data have been obtained with the Texas Echelon Cross Echelle Spectrograph (TEXES) mounted at the 3 m–Infrared Telescope Facility (IRTF) at Maunakea Observatory. Maps of HDO and H2O2 have been obtained using line depth ratios of weak transitions of HDO and H2O2 divided by CO2. The retrieved maps of H2O2 are in good agreement with predictions including a chemical transport model, for both the March data (maximum water vapor) and the July data (maximum hydrogen peroxide). The retrieved maps of HDO are compared with simulations by Montmessin et al. (2005, J. Geophys. Res., 110, 03006) and H2O maps are inferred assuming a mean martian D/H ratio of 5 times the terrestrial value. For regions of maximum values of H2O and H2O2, we derive, for March 1 2014 (Ls = 96°), H2O2 = 20+/−7 ppbv, HDO = 450 +/−75 ppbv (45 +/−8 pr-nm), and for July 3, 2014 (Ls = 156°), H2O2 = 30+/−7 ppbv, HDO = 375+/−70 ppbv (22+/−3 pr-nm). In addition, the new observations are compared with LMD global climate model results and we favor simulations of H2O2 including heterogeneous reactions on water-ice clouds.