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

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

Twelve-Year Cycle in the Cloud Top Winds Derived from VMC/Venus Express and UVI/Akatsuki Imaging

We present joint analysis of the UV (365 nm) images captured by the cameras on board ESA’s Venus Express and JAXA’s Akatsuki spacecraft. These observations enabled almost continuous characterization of the cloud top circulation over the longest period of time so far (2006–2021). More than 46,000 wind vectors were derived from tracking the UV cloud features and revealed changes in the atmospheric circulation with the period of 12.5 ± 0.5 years. The zonal wind component is characterized by an annual mean of −98.6 ± 1.3 m/s and an amplitude of 10.0 ± 1.6 m/s. The mean meridional wind velocity is −2.3 ± 0.2 m/s and has an amplitude of 3.4 ± 0.3 m/s. Plausible physical explanations of the periodicity include both internal processes and external forcing. Both missions observed periodical changes in the UV albedo correlated with the circulation variability. This could result in acceleration or deceleration of the winds due to modulation of the deposition of the radiative energy in the clouds. The circulation can be also affected by the solar cycle that has a period of approximately 11 years with a large degree of deviation from the mean. The solar cycle correlated with the wind observations can probably influence both the radiative balance and chemistry of the mesosphere. The discovered periodicity in the cloud top circulation of Venus, and especially its similarity with the solar cycle, is strongly relevant to the study of exoplanets in systems with variable “suns”

Twelve-Year Cycle in the Cloud Top Winds Derived from VMC/Venus Express and UVI/Akatsuki Imaging

We present joint analysis of the UV (365 nm) images captured by the cameras on board ESA’s Venus Express and JAXA’s Akatsuki spacecraft. These observations enabled almost continuous characterization of the cloud top circulation over the longest period of time so far (2006–2021). More than 46,000 wind vectors were derived from tracking the UV cloud features and revealed changes in the atmospheric circulation with the period of 12.5 ± 0.5 years. The zonal wind component is characterized by an annual mean of −98.6 ± 1.3 m/s and an amplitude of 10.0 ± 1.6 m/s. The mean meridional wind velocity is −2.3 ± 0.2 m/s and has an amplitude of 3.4 ± 0.3 m/s. Plausible physical explanations of the periodicity include both internal processes and external forcing. Both missions observed periodical changes in the UV albedo correlated with the circulation variability. This could result in acceleration or deceleration of the winds due to modulation of the deposition of the radiative energy in the clouds. The circulation can be also affected by the solar cycle that has a period of approximately 11 years with a large degree of deviation from the mean. The solar cycle correlated with the wind observations can probably influence both the radiative balance and chemistry of the mesosphere. The discovered periodicity in the cloud top circulation of Venus, and especially its similarity with the solar cycle, is strongly relevant to the study of exoplanets in systems with variable “suns”

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

High latitude gravity waves at the Venus cloud tops as observed by the Venus Monitoring Camera on board Venus Express

International audienceHigh resolution images of Venus Northern hemisphere obtained with the Venus Monitoring Camera (VMC/VEx) allow studying small-scale dynamical phenomena at the cloud tops (∼62-70 km altitude) including features like wave trains. A systematic visual search of these waves was performed; more than 1500 orbits were analyzed and wave patterns were observed in more than 300 images. Four types of waves were identified in VMC images on the base of their morphology: long, medium, short and irregular type waves. With the aim to characterize the wave types and their possible excitation source, we retrieved wave properties such as location (latitude and longitude), local time, solar zenith angle, packet length and width, orientation, and wavelength of each wave. The long type waves appear as long and narrow straight features extending more than a few hundreds kilometers and with wavelengths between 7 and 17 km. Medium type waves exhibit irregular wavefronts extending more than 100 km and with wavelengths in the range 8-21 km. Short wave packets have a width of several tens of kilometers and extend to few hundreds kilometers and are characterized by smaller wavelengths (3-16 km). Irregular wave fields appear to be the result of wave interference. The waves are often identified in all VMC filters and are mostly found in the cold collar region at high latitudes (60-80°N) and are concentrated above Ishtar Terra, a continental size highland that includes the highest mountain belts of the planet. The high speed of the Venus Express spacecraft close to the pericentre does not allow to measure phase speed of waves due to the short temporal interval between image pairs. The lack of information on phase velocities does not allow us to establish with absolute confidence the nature of these waves. However, by comparing the morphology and properties of the wave features observed in VMC images to those seen by previous observations it is reasonable to assume that the waves studied here are gravity waves

Venus' atmosphere: an overview before next exploration missions

International audienceDuring the last 15 years, our knowledge about the atmosphere of Venus has expanded greatly, mainly due to the contribution of two dedicated orbiters: Venus Express from ESA (2006-2014) and Akatsuki from JAXA (2015-present). Both missions included a comprehensive payload (imagers and/or spectrometers operating in the UV and/or IR range) which enabled them to measure key parameters about the atmosphere from the surface to the topmost layers. Among their discoveries are a much greater than anticipated spatial and temporal variability, in terms of minor species composition, cloud layers, dynamics and thermal structure. Most surprisingly, part of this variability was due to unsuspected coupling between the surface and the upper atmospheric layers at cloud top level. They also highlighted gaps in our knowledge, some of them long standing like the nature of the unknown UV absorber, that they could not solve. Undoubtedly, all these results contributed to the renewed interest for the planet Venus that was confirmed by the selection, in June 2021, of three space exploration missions targeting the planet in the 2030s. The science case of all these missions (DAVINCI and VERITAS from NASA, EnVision from ESA) include, to some extent, atmospheric characterization based on the aforementioned discoveries. This review talk will summarize our current knowledge about the atmosphere of Venus after Akatsuki and Venus Express, including some key outstanding questions. It will then proceed in a review of the planned atmospheric investigations from the above mentioned selected missions, as well as others from e.g. ISRO and Roscosmos

Venus' atmosphere: an overview before next exploration missions

International audienceDuring the last 15 years, our knowledge about the atmosphere of Venus has expanded greatly, mainly due to the contribution of two dedicated orbiters: Venus Express from ESA (2006-2014) and Akatsuki from JAXA (2015-present). Both missions included a comprehensive payload (imagers and/or spectrometers operating in the UV and/or IR range) which enabled them to measure key parameters about the atmosphere from the surface to the topmost layers. Among their discoveries are a much greater than anticipated spatial and temporal variability, in terms of minor species composition, cloud layers, dynamics and thermal structure. Most surprisingly, part of this variability was due to unsuspected coupling between the surface and the upper atmospheric layers at cloud top level. They also highlighted gaps in our knowledge, some of them long standing like the nature of the unknown UV absorber, that they could not solve. Undoubtedly, all these results contributed to the renewed interest for the planet Venus that was confirmed by the selection, in June 2021, of three space exploration missions targeting the planet in the 2030s. The science case of all these missions (DAVINCI and VERITAS from NASA, EnVision from ESA) include, to some extent, atmospheric characterization based on the aforementioned discoveries. This review talk will summarize our current knowledge about the atmosphere of Venus after Akatsuki and Venus Express, including some key outstanding questions. It will then proceed in a review of the planned atmospheric investigations from the above mentioned selected missions, as well as others from e.g. ISRO and Roscosmos

Serverless Architecture for Data Processing and Detecting Anomalies with the Mars Express MARSIS Instrument

The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express has been sampling the topside ionosphere of Mars since mid-2005. The analysis of the main reflection (nadir) of the ionosphere through the ionograms provided by the MARSIS instrument is typically performed manually due to the high noise level in the lower frequencies. This task, which involves pattern recognition, turns out to be unfeasible for the >2 million ionograms available at the European Planetary Science Archive. In the present contribution, we propose a modular architecture based on serverless computing (a paradigm that stands on the cloud) for optimal processing of these ionograms. In particular, we apply serverless computing to detect oblique echoes in the ionosphere, which are nonnadir reflections produced when MARSIS is sounding regions above or nearby crustal magnetic fields, where the ionosphere loses the spherical symmetry. Oblique echoes are typically observed at similar frequencies to the nadir reflections but at different times delays, sometimes even overlaying the nadir reflection. Oblique echoes are difficult to analyze with the standard technique due to their nonconstant and highly variable appearance, but they harbor essential information on the state of the ionosphere over magnetized regions. In this work we compare the proposed serverless architecture with two local alternatives while processing a representative data subset and finally provide a study by means of cost and performance