Venus Atmospheric Thermal Structure and Radiative Balance

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Sensitivity of net thermal flux to the abundance of trace gases in the lower atmosphere of Venus

We calculated the net thermal flux in the atmosphere of Venus from the surface to 100 km altitude. Our atmospheric model was carefully constructed especially for altitudes below the clouds (2 absorption data. It includes updated collision-induced absorptions in the -1, 1200-1500 cm-1, and 2650-3130 cm-1 wave number ranges. We studied sensitivity of the net thermal flux below the clouds on the abundances of trace gases that were varied within the range reported by observations. Our results reveal a considerable effect of trace gases on radiative budget. We successfully simulate net thermal flux profiles measured in situ by the Night and North probes of Pioneer Venus using 20-50 ppmv H2O, suggesting that the high H2O abundance of 200 ppmv derived in the earlier analysis is not required. Our sensitivity study shows that the trace gases SO2, H2O, and OCS are effective thermal agents, while CO and HCl influences are rather weak. We suggest that the influence of the former three gases should be taken into account to estimate the net radiative energy in the deep atmosphere

Envision M5 Venus orbiter proposal

EnVision [1,2] is a Venus orbiter mission that will determine the nature and current state of geological activity on Venus, and its relationship with the atmosphere, to understand how and why Venus and Earth evolved so differently. Envision is a finalist in ESA’s M5 Space Science mission selection process, and is being developed in collaboration with NASA, with the sharing of responsibilities currently under assessment. It is currently in Phase A study; final mission selection is expected in June 2021. If selected, EnVision will launch by 2032 on an Ariane 6.2 into a six month cruise to Venus, followed by aerobraking, to achieve a near-circular polar orbit for a nominal science phase lasting at least 4 Venus sidereal days (2.7 Earth years)

Mars Express science highlights and future plans

21st EGU General Assembly, EGU2019, proceedings from the conference held 7-12 April, 2019 in Vienna, Austria, id.11100After 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

Progress towards a post-Venus Express Clouds & Haze reference model for Venus

International audienceWith the end of Venus Express in 2014, the focus of the scientific community has gradually moved from the study of Venus Express mono-instrumental data sets to cross-instrumental studies involving pure modeling as well. This is especially true for the clouds and hazes that surround most of the planet between 48 and 70 km. They play a major role at the crossroads of various atmospheric processes among which the radiative budget as well as the dynamical and chemical coupling between the lower and upper atmosphere. In order to support such efforts, ISSI has supported from 2013 to 2015 a "Clouds & Hazes of Venus" scientific team involving Venus Express and ground-based observers as well as microphysical modelers. Together, they compared their results in order to achieve a more unified and consistent view of Venus' clouds and hazes, taking into account its spatial and temporal variability more in detail than previously available VIRA-1 and 2 cloud models. We will review the individual data sets and models that have been used, and then present our strategy towards a unified cloud model. We will first make available some observable parameters to the wider community through a web-based repository. Future steps may involve more advanced techniques (e.g. data assimilation) in order to achieve our objective of a unified Venus clouds & haze model that encompasses its various variabilities as well as possible

Introduction to Icarus special issue “From Mars Express to ExoMars”

Context. In February 2018, the international community working on the investigation and exploration of the atmosphere and surface of Mars met at ESAC near Madrid for a few days conference, organized and funded by the project UPWARDS (“Understanding Planet Mars With Advanced Remote- ensing Datasets and Synergistic Studies”, www.upwards-mars.eu) of the EU Horizon 2020 program. This project, and that conference, were devoted to promote the scientific exploitation of Mars Express data and to revisiting and sharing results from this mission, in preparation for the upcoming new European mission to Mars, the ExoMars-2016. The meeting approximately coincided in time with the end of the aerobraking phase of the Trace Gas Orbiter (TGO), which is the orbital element of ExoMars-2016. The TGO science phase started on 21 April 2018. This special issue of Icarus contains eleven papers which report original research results presented at the meeting or based on those presentations. This is obviously not an exhaustive representation of what was presented in Madrid, as other results have been published elsewhere. But they all share the motto of the meeting - from MEX to TGO - by presenting highlights of almost 15 years of Mars EXpress science legacy and new tools and methods for data analysis, thus paving the way for TGO observations and collaboration between two spacecraft. We think this is a valuable approach which, if properly and timely coordinated, can be very fruitful and should be promoted on every new space mission. The UPWARDS project could be considered as a bridge facilitating transition between two ESA missions, building team connections and enhancing science return from both missions. The second goal of the UPWARDS project, now more in the scientific than in the programmatic realm, was to exploit synergies between different teams in a cross-disciplinary approach, looking for an integral vision of the planet in an attempt to unveil couplings between different regions. In the meeting mentioned above, there were investigations from the subsoil and the surface, to the lower atmosphere's composition and dust, to the water cycle and up to the thermospheric structure and escape to space. In this framework, this issue presents its 11 contributions ordered in this bottom-to-top vision of the atmosphere.We want to acknowledge ESA for successful operations of the Mars Express and the TGO spacecrafts. The project UPWARDS-633127 was funded by the European Union's Horizon 2020 research and innovation Programme.Peer reviewe

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

Variability of the precipitating fluxes during September 2017 event

International audienceWe here study the influence of several solar atmospheric and magnetospheric forcing drivers, during September 2017 solar event. We focus on the fluxes of precipitating heavy ion towards Mars' atmosphere as seen by MAVEN: SWIA (cs product), an energy and angular ion spectrometer and by STATIC (d1 and c6 products), an energy, mass and angular ion spectrometer. [1

Annual survey of water vapor behavior from the OMEGA mapping spectrometer onboard Mars Express

International audience► Analysis of the first years of Mars Express data. ► Extensive comparison with past and simultaneous measurements. ► Agreement between datasets within the uncertainties. ► Significant quantitative discrepancies for the northern summer maximum. ► Limited amplitude of water vapor diurnal fluctuations