Martian dust storm impact on atmospheric H₂O and D/H observed by ExoMars Trace Gas Orbiter

Global dust storms on Mars are rare but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere, primarily owing to solar heating of the dust. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes, as well as a decrease in the water column at low latitudes. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere

No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere, which-given methane's lifetime of several centuries-predicts an even, well mixed distribution of methane. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally

Venus Evolution Through Time: Key Science Questions, Selected Mission Concepts and Future Investigations

In this work we discuss various selected mission concepts addressing Venus evolution through time. More specifically, we address investigations and payload instrument concepts supporting scientific goals and open questions presented in the companion articles of this volume. Also included are their related investigations (observations & modeling) and discussion of which measurements and future data products are needed to better constrain Venus’ atmosphere, climate, surface, interior and habitability evolution through time. A new fleet of Venus missions has been selected, and new mission concepts will continue to be considered for future selections. Missions under development include radar-equipped ESA-led EnVision M5 orbiter mission (European Space Agency 2021), NASA-JPL’s VERITAS orbiter mission (Smrekar et al. 2022a), NASA-GSFC’s DAVINCI entry probe/flyby mission (Garvin et al. 2022a). The data acquired with the VERITAS, DAVINCI, and EnVision from the end of this decade will fundamentally improve our understanding of the planet’s long term history, current activity and evolutionary path. We further describe future mission concepts and measurements beyond the current framework of selected missions, as well as the synergies between these mission concepts, ground-based and space-based observatories and facilities, laboratory measurements, and future algorithmic or modeling activities that pave the way for the development of a Venus program that extends into the 2040s (Wilson et al. 2022)

Keeping the best of two worlds: Linking CGE and microsimulation models for policy analysis

In this paper, we link a CGE model with the tax-benefit microsimulation model EUROMOD for Latvia. The model linkage is done using an iterative top-down bottomup approach, ensuring the convergence of changes in disposable income, employment and wage in both models. We also incorporate the unreported wage payments in CGE and EUROMOD to account for the substantial labour tax non-compliance in Latvia and improve the modelling of the fiscal sector. Several simulations demonstrate the advantages of the joint CGE-EUROMOD system over the individual macro and microsimulation models. The lack of income distribution aspect and the scarcity of fiscal instruments in CGE can be overcome by the features of EUROMOD. The CGE model, on the other hand, provides macroeconomic spillovers that are missing in the simulations of EUROMOD

Gravity waves mapped by the OMEGA/MEX instrument through O-2 dayglow at 1.27 mu m: Data analysis and atmospheric modeling

International audienceWe present the occurrence of waves patterns on the southern polar region of Mars as traced by the O-2 dayglow emission at lambda = 1.27 mu m during late winter/early spring of MY 28. The observations were carried out by the OMEGA (Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite) imaging spectrometer on board Mars Express (MEX). Waves are found preferentially at high incidence angles and latitudes between 55 degrees and 75 degrees S. The dayglow intensity fluctuations are of the order of +/- 3% at incidence angle <88.5 degrees and they can be explained by the propagation of gravity waves in the Martian atmosphere. Mesoscale meteorological modeling predicts gravity wave activity in the same range of latitude as the observed O-2(a(1)Delta(g)) wave patterns with temperature oscillations consistent with existing measurements. Moreover, gravity waves simulated through mesoscale modeling can induce dayglow fluctuations of the same order-of-magnitude as observed in the OMEGA maps. This study confirms that airglow imagery is a powerful method to detect and study the bi-dimensional propagation of gravity waves, as foreseen in previous studies coupling photochemical and dynamical models

Interaction of solar-related effects and stationary gravity wave above Aphrodite Terra according to VMC/Venus Express wind fields

International audienceA set of UV (365 nm) images obtained by the Venus Monitoring Camera onboard Venus Express spacecraft was used to study the circulation of the atmosphere at upper boundary of clouds (70±2 km). 172000 displacement vectors (257 orbits) were obtained by digital wind tracking technique for observation period from 2006 to 2014. This data set allows studying both variation of the wind speed vs. latitude and longitude (correlation with surface topography) and dependence on local time.The zonal speed decrease was found above Aphrodite Terra. It has a solar-related character and strongly connected to the local noon. We studied the shape of the minimum wind speed structure (dependence of wind speed vs. longitude and latitude). It has an elongated shape in latitude. It was found that it repeats a contour of Aphrodite Terra at noon. The shape is conserved at least up to 30°S. In the same time, the wind speed increases by approximately 5 m/s to 30°S, and the area of minimum zonal speed shifts in direction of superrotation. The Sun influence manifests itself in the region of the stationary gravity waveexistence above Aphrodite Terra as the mean zonal flow deceleration in near equatorial latitudes (0-30°S). The zonal speed minimum is observed at noon above highest region of Ovda Regio (western part of Aphrodite Terra). Outside the Aphrodite Terra, the Sun influence does not manifest itself. The structure above highlands of Aphrodite Terra observed at noon may be a result of the stationary wave which generated by Aphrodite Terra and possible higher stability of the atmosphere, as a result of Solar heating, allow gravity waves to reach the upper clouds where they break and decelerate the mean zonal wind.J.-L. Bertaux, I.V. Khatuntsev and M.V. Patsaeva were supported by the Ministry of Education and Science of Russian Federation grant 14.W03.31.0017

Interaction of solar-related effects and stationary gravity wave above Aphrodite Terra according to VMC/Venus Express wind fields

International audienceA set of UV (365 nm) images obtained by the Venus Monitoring Camera onboard Venus Express spacecraft was used to study the circulation of the atmosphere at upper boundary of clouds (70±2 km). 172000 displacement vectors (257 orbits) were obtained by digital wind tracking technique for observation period from 2006 to 2014. This data set allows studying both variation of the wind speed vs. latitude and longitude (correlation with surface topography) and dependence on local time.The zonal speed decrease was found above Aphrodite Terra. It has a solar-related character and strongly connected to the local noon. We studied the shape of the minimum wind speed structure (dependence of wind speed vs. longitude and latitude). It has an elongated shape in latitude. It was found that it repeats a contour of Aphrodite Terra at noon. The shape is conserved at least up to 30°S. In the same time, the wind speed increases by approximately 5 m/s to 30°S, and the area of minimum zonal speed shifts in direction of superrotation. The Sun influence manifests itself in the region of the stationary gravity waveexistence above Aphrodite Terra as the mean zonal flow deceleration in near equatorial latitudes (0-30°S). The zonal speed minimum is observed at noon above highest region of Ovda Regio (western part of Aphrodite Terra). Outside the Aphrodite Terra, the Sun influence does not manifest itself. The structure above highlands of Aphrodite Terra observed at noon may be a result of the stationary wave which generated by Aphrodite Terra and possible higher stability of the atmosphere, as a result of Solar heating, allow gravity waves to reach the upper clouds where they break and decelerate the mean zonal wind.J.-L. Bertaux, I.V. Khatuntsev and M.V. Patsaeva were supported by the Ministry of Education and Science of Russian Federation grant 14.W03.31.0017

Need for Updates to the Venus International Reference Model (VIRA)

International audienceThe Venus International Reference Model (VIRA) was developed after the results from the data collected by Venera 13 and 14 as well as the Pioneer Venus Orbiter and Multi-Probe missions became available (Kliore et al. 1985). The model included (i) Atmospheric circulation, (ii) Atmospheric composition, (iii) Thermal structure, (iv) Neutral upper atmosphere, (v) Particulate matter, (vi) Solar and thermal radiation, and (vii) Venus ionosphere. Since then, there have been some updates proposed for the thermal structure after the Venera 11, 13, 14, Venera 15 and 16 orbiters, VeGa 1 and VeGa 2 lander and balloon data (Moroz and Zasova 1997; Limaye 2016; Limaye et al. 2017; Limaye et al. 2018a). Updates to the composition of the upper atmosphere were proposed from Solar Occultation Infrared Radiometer on Venus Express (Vandaele et al. 2016). Venus Express has provided some results on the ionosphere but no specific model updates have been proposed. One of the key recent results is that the troposphere of Venus does not appear to be well-mixed in the two major constituents - carbon dioxide and nitrogen. The nitrogen abundance appears to vary from 5% between 60-100 km (Peplowski et al. 2020) to about 2.6 % at 22 km (Oyama et al. 1980), and hypothesized to be zero near the surface (Lebonnois and Schubert 2017). The resulting vertical gradient in the atmospheric molecular weight affects the precise altitude/pressure level of all atmospheric measurements, remote as well as in-situ. There are some new results on the Venus cloud properties from Venus Monitoring Camera (Markiewicz et al. 2014; Wilson et al. 2015; Limaye et al. 2018b; Marcq et al. 2018; Markiewicz et al. 2018; Petrova 2018; Titov et al. 2018; Marcq et al. 2020) and questions about trace species indicating chemical disequilibrium are arising (Florenskii et al. 1978; Florenskij et al. 1978; Donahue and Hodges 1993; Bains et al. 2020; Greaves et al. 2020; Mogul et al. 2020). In addition, questions about the nature and identity of the absorbers of incident solar radiation persist with hypotheses for biological contributions (Limaye et al. 2018c; Seager et al. 2020). For these reasons, it would be useful to initiate a process to update the VIRA model components. References Bains W., Petkowski J. J., Seager S., Ranjan S., Sousa-Silva C., Rimmer P. B., Zhan Z., Greaves J. S., and Richards A. M. S. (2020) Phosphine on Venus Cannot be Explained by Conventional Processes. pp arXiv:2009.06499. Donahue T. M., and Hodges R. R. (1993) Venus methane and water. Geophysical Research Letters, 20: 591-594 Florenskii C. P., Volkov V. P., and Nikolaeva O. V. (1978) A geochemical model of the Venus troposphere. Icarus, 33: 537.10.1016/0019-1035(78)90189-6 Florenskij K. P., Volkov V. P., and Nikolaeva O. V. (1978) The geochemical process of daily variations of the cloud cover of Venus. Geokhimiia, 3: Greaves J. S., Richards A. M. S., Bains W., Rimmer P. B., Sagawa H., Clements D. L., Seager S., Petkowski J. J., Sousa-Silva C., Ranjan S., Drabek-Maunder E., Fraser H. J., Cartwright A., Mueller-Wodarg I., Zhan Z., Friberg P., Coulson I., Lee E. l., and Hoge J. (2020) Phosphine gas in the cloud decks of Venus. Nature Astronomy.10.1038/s41550-020-1174-4 Kliore A. J., Moroz V. I., and Keating G. M. (1985) The Venus International Reference Atmosphere. Advances in Space Research, 5: Lebonnois S., and Schubert G. (2017) The deep atmosphere of Venus and the possible role of density-driven separation of CO2 and N2. Nature Geoscience, 10: 473-477.10.1038/ngeo2971 Limaye S. (2016) Comparison of Thermal Structure Results from Venus Express and Ground Based Observations since Vira, 41st COSPAR Scientific Assembly, http://adsabs.harvard.edu/abs/2016cosp...41E1166L Limaye S., Zasova L., and Bocanegra Bahamon T. (2018a) Updating the Venus Atmospheric Structure for VIRA.https://ui.adsabs.harvard.edu/abs/2018cosp...42E2017L Limaye S. S., Lebonnois S., Mahieux A., Pätzold M., Bougher S., Bruinsma S., Chamberlain S., Clancy R. T., Gérard J.-C., Gilli G., Grassi D., Haus R., Herrmann M., Imamura T., Kohler E., Krause P., Migliorini A., Montmessin F., Pere C., Persson M., Piccialli A., Rengel M., Rodin A., Sandor B., Sornig M., Svedhem H., Tellmann S., Tanga P., Vandaele A. C., Widemann T., Wilson C. F., Müller-Wodarg I., and Zasova L. (2017) The thermal structure of the Venus atmosphere: Intercomparison of Venus Express and ground based observations of vertical temperature and density profiles&#10032;. Icarus, 294: 124.10.1016/j.icarus.2017.04.020 Limaye S. S., Grassi D., Mahieux A., Migliorini A., Tellmann S., and Titov D. (2018b) Venus Atmospheric Thermal Structure and Radiative Balance. Space Science Reviews, 214: 102.10.1007/s11214-018-0525-2 Limaye S. S., Mogul R., Smith D. J., Ansari A. H., Słowik G., and Vaishampayan P. (2018c) Venus' Spectral Signatures and the Potential for Life in the Clouds. Astrobiology, 18: 1181-1198.10.1089/ast.2017.1783 Marcq E., Mills F. P., Parkinson C. D., and Vandaele A. C. (2018) Composition and Chemistry of the Neutral Atmosphere of Venus. Space Science Reviews, 214: 10 Marcq E., Lea Jessup K., Baggio L., Encrenaz T., Lee Y. J., Montmessin F., Belyaev D., Korablev O., and Bertaux J.-L. (2020) Climatology of SO2 and UV absorber at Venus' cloud top from SPICAV-UV nadir dataset. Icarus, 335: 113368.https://doi.org/10.1016/j.icarus.2019.07.002 Markiewicz W. J., Petrova E., Shalygina O., Almeida M., Titov D. V., Limaye S. S., Ignatiev N., Roatsch T., and Matz K. D. (2014) Glory on Venus cloud tops and the unknown UV absorber. Icarus, 234: 200-203 Markiewicz W. J., Petrova E. V., and Shalygina O. S. (2018) Aerosol properties in the upper clouds of Venus from glory observations by the Venus Monitoring Camera (Venus Express mission). Icarus, 299: 272-293.https://doi.org/10.1016/j.icarus.2017.08.011 Mogul R., Limaye S. S., Way M. J., and Cordova J. A., Jr. (2020) Is Phosphine in the Mass Spectra from Venus' Clouds? , pp arXiv:2009.12758. Moroz V. I., and Zasova L. V. (1997) VIRA-2: a review of inputs for updating the Venus International Reference Atmosphere. Advances in Space Research, 19: 1191-1201 Oyama V. I., Carle G. C., Woeller F., Pollack J. B., Reynolds R. T., and Craig R. A. (1980) Pioneer Venus gas chromatography of the lower atmosphere of Venus. Journal of Geophysical Research, 85: 7891.10.1029/JA085iA13p07891 Peplowski P. N., Lawrence D. J., and Wilson J. T. (2020) Chemically distinct regions of Venus's atmosphere revealed by measured N2 concentrations. Nature Astronomy.10.1038/s41550-020-1079-2 Petrova E. V. (2018) Glory on Venus and selection among the unknown UV absorbers. Icarus, 306: 163-170.https://doi.org/10.1016/j.icarus.2018.02.016 Seager S., Petkowski J. J., Gao P., Bains W., Bryan N. C., Ranjan S., and Greaves J. (2020) The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere. Astrobiology.10.1089/ast.2020.2244 Titov D. V., Ignatiev N. I., McGouldrick K., Wilquet V., and Wilson C. F. (2018) Clouds and Hazes of Venus. Space Science Reviews, 214: 126.10.1007/s11214-018-0552-z Vandaele A. C., Chamberlain S., Mahieux A., Ristic B., Robert S., Thomas I., Trompet L., Wilquet V., Belyaev D., Fedorova A., Korablev O., and Bertaux J. L. (2016) Contribution from SOIR/VEX to the updated Venus International Reference Atmosphere (VIRA). Advances in Space Research, 57: 443-458.https://doi.org/10.1016/j.asr.2015.08.012 Wilson C. F., Marcq E., Markiewicz W. J., Montmessin F., Fedorova A., Wilquet V., Petrova E. V., Ignatiev N. I., Shalygina O. S., Maattanen A. E., McGouldrick K. M., Hashimoto G. L., Imamura T., Rossi L., Luginin M., Oschlisniok J., Haus R., Parkinson C. D., Titov D. V., Zasova L. V., and Limaye S. S. (2015) The clouds of Venus - an overview of Venus Express results. European Planetary Science Congress 2015, held 27 September - 2 October, 2015 in Nantes, France, Online at http://meetingorganizer.copernicus.org/EPSC2015, id.EPSC2015-762, 10

Winds in the Lower Cloud Level on the Nightside of Venus from VIRTIS-M (Venus Express) 1.74 μm Images

The horizontal wind velocity vectors at the lower cloud layer were retrieved by tracking the displacement of cloud features using the 1.74 µm images of the full Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS-M) dataset. This layer was found to be in a superrotation mode with a westward mean speed of 60–63 m s−1 in the latitude range of 0–60° S, with a 1–5 m s−1 westward deceleration across the nightside. Meridional motion is significantly weaker, at 0–2 m s−1; it is equatorward at latitudes higher than 20° S, and changes its direction to poleward in the equatorial region with a simultaneous increase of wind speed. It was assumed that higher levels of the atmosphere are traced in the equatorial region and a fragment of the poleward branch of the direct lower cloud Hadley cell is observed. The fragment of the equatorward branch reveals itself in the middle latitudes. A diurnal variation of the meridional wind speed was found, as east of 21 h local time, the direction changes from equatorward to poleward in latitudes lower than 20° S. Significant correlation with surface topography was not found, except for a slight decrease of zonal wind speed, which was connected to the volcanic area of Imdr Regio

Winds from visible (513 nm) images obtained by the Venus Express Monitoring Camera

International audienceLong-term observations of Venus by the Venus monitoring camera (VMC) [4] onboard Venus Express in the visible range (513 nm) allowed to obtain information on circulation in the middle of Hadley cell. Here we present preliminary results of wind tracking of visible images obtained by VMC in the period 2007/07/01-2013/01/29. The mean zonal speed in middle latitudes (30-65ºS) is monotonously changing with latitude-76.5 to-61.5 m/s. In low latitudes (10-20ºS) zonal speed is about-82 m/s. Differences in the behavior of the meridional component in low and middle latitudes indicate that different cloud layers are observed in the visible range (513 nm). The mean horizontal flow demonstrates a dependence on local solar time. Moreover, the nature of diurnal variations is different for low and middle latitudes. Following Bertaux et al. [1] the mean horizontal flow in the middle of Hadley cell show a connection with the underlying topography