PS1.3 | Venus: models, observations, (ancient) Earth- and exoplanet analogue
Venus: models, observations, (ancient) Earth- and exoplanet analogue
Co-organized by GD3
Convener: Moa Persson | Co-conveners: Cédric Gillmann, Anna Gülcher, Maxence Lefevre, Gregor Golabek
Orals
| Wed, 17 Apr, 16:15–18:00 (CEST)
 
Room L1
Posters on site
| Attendance Wed, 17 Apr, 10:45–12:30 (CEST) | Display Wed, 17 Apr, 08:30–12:30
 
Hall X3
Posters virtual
| Attendance Wed, 17 Apr, 14:00–15:45 (CEST) | Display Wed, 17 Apr, 08:30–18:00
 
vHall X3
Orals |
Wed, 16:15
Wed, 10:45
Wed, 14:00
In June 2021, NASA and ESA selected a fleet of three international missions to Venus. Moreover, the ISRO orbiter mission Shukrayyan-1 and VOICE (Chinese Academy of Sciences) are currently proposed for launch in the mid 2020s. With the ‘Decade of Venus’ upon us, many fundamental questions remain regarding Venus. Did Venus ever have an ocean? How and when did intense greenhouse conditions develop? How does its internal structure compare to Earth's? How can we better understand Venus’ geologic history as preserved on its surface as well as the present-day state of activity and couplings between the surface and atmosphere? Although Venus is one of the most uninhabitable planets in the Solar System, understanding our nearest planetary neighbor may unveil important lessons on atmospheric and surface processes, interior dynamics and habitability. It may further help us draw important conclusions on the history of our own planet. Beyond the solar system, Venus’ analogues are likely a common type of exoplanets, and we likely have already discovered many of Venus’ sisters orbiting other stars. This session welcomes contributions that address the past, present, and future of Venus science and exploration, and what Venus can teach us about (ancient) Earth as well as exo-Venus analogues. Moreover, Venus mission concepts, new Venus observations, Earth-Venus comparisons, exoplanet observations, new results from previous observations, and the latest lab and modelling approaches are all welcome to our discussion of solving Venus’ mysteries.

Orals: Wed, 17 Apr | Room L1

Chairpersons: Gregor Golabek, Moa Persson, Cédric Gillmann
Venus: Atmosphere
16:15–16:25
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EGU24-22187
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solicited
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Virtual presentation
Franck Selsis, Jérémy Leconte, Martin Turbet, Guillaume Chaverot, and Emeline Bolmont

A planet with a significant water content can give rise to a steam atmosphere (dominated by water vapor) when the incoming stellar flux exceeds the so-called runaway limit or after large impacts or accretion. All steam-atmosphere current models predict that the greenhouse effect of an ocean worth of water vapor is sufficient to generate a surface magma ocean. This has far reaching consequences for the early evolution of warm rocky planets and the coupling of their interior with the atmosphere. In this paradigm, the solidification of the mantle of Venus is believed to have happened only after the escape of its steam atmosphere to space, leaving the mantle desiccated.

However, these conclusions rely on the assumption that atmospheres are fully convective below their photosphere. This hypothesis was introduced in the 80s and is used in a large part of the literature on the subject. Its validity had however not been assessed thoroughly. We will present the results of a climate model that has been specifically designed to model the radiative-convective equilibrium of steam atmospheres without any a priori hypothesis on their convective nature. These results show that steam atmospheres are generally not fully convective, which yields much cooler surfaces than previous models. A runaway greenhouse does not systematically melt the surface. This changes completely our view of the early evolution of Venus', with even more drastic changes for planets around stars redder than the Sun.

The equilibrium thermal structure of a steam atmosphere, which affects observable signatures and mass-radius relationships of warm Earth-like to water-rich planets, becomes strongly dependent on the stellar spectrum and internal heat flow. Our current constraints on the water content of the internal Trappist-1 planets should for example be revisited. For ultracool dwarfs, these results even question the nature of the inner edge of the sometimes called habitable zone.

How to cite: Selsis, F., Leconte, J., Turbet, M., Chaverot, G., and Bolmont, E.: Steam atmospheres and the implications for Venus and Venus-like planets , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22187, https://doi.org/10.5194/egusphere-egu24-22187, 2024.

16:25–16:35
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EGU24-14161
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ECS
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On-site presentation
Stephanie Olson, Jonathan Jernigan, Emilie Lafleche, and Haleigh Brown

Studies of exoplanet habitability involving GCMs typically consider the potential for long-lived surface liquid water—or, in other words, climates that Earth-life may find survivable. However, the presence of life and remotely detectable biosignatures on an exoplanet additionally requires an independent origin of life and that life subsequently thrives rather than simply survives. The origin and proliferation of life are both strongly influenced by climate, and both can therefore be informed by GCM studies in parallel with traditional habitability metrics. 

Wet-dry cycles are thought to be an essential ingredient for the origin of life. Cyclic wetting and drying may arise from either diurnal or seasonal cycles, and thus the likelihood of an origin of life may differ between worlds with very different rotation rates, obliquities, or eccentricities. At the same time, seasonal mixing in aqueous environments can trigger highly productive blooms and amplify biosignatures relative to scenarios lacking temporal variability.  

We used ExoPlaSim (an atmospheric GCM) and cGENIE-PlaSim (a 3D model for ocean dynamics and marine biogeochemistry coupled to a 3D atmospheric GCM) to explore diurnal and seasonal cycles on other worlds—with an eye towards origin of life chemistry and biosignatures. This presentation will ultimately identify the planetary scenarios most conducive to exoplanet life detection. 

How to cite: Olson, S., Jernigan, J., Lafleche, E., and Brown, H.: Exploring origin of life chemistry and exoplanet biosignatures with GCMs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14161, https://doi.org/10.5194/egusphere-egu24-14161, 2024.

16:35–16:45
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EGU24-10478
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ECS
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On-site presentation
Wencheng Shao, Joao Mendonca, and Longkang Dai

Venus has regained great interest from planetary scientists in recent years because of the multiple upcoming Venus missions (e.g., EnVision, DAVINCI+ and VERITAS). Studying Venus is crucial for understanding the evolution of terrestrial planets as well as projecting the Earth’s future. One important component of the Venus climate system, the sulfuric acid clouds, has exhibited spatial and temporal variabilities. These variabilities are closely connected with the interactions between dynamics, photochemistry, radiative transfer and cloud physics. Current modeling studies of the Venus atmosphere have shed light on the underlying physics of the cloud variabilities. However, none of them has resolved the cloud radiative feedback. As an essential step to fully understanding the complex interactions, we develop a state-of-the-art General-Circulation Model (GCM), with cloud condensation/evaporation and radiative feedback processes included. In this talk, I will quantify the radiative forcing caused by the acidic clouds and provide indications of how the radiative forcing can influence the Venus climate evolution.

How to cite: Shao, W., Mendonca, J., and Dai, L.: Cloud radiative feedback on the Venus climate simulated by a General-Circulation Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10478, https://doi.org/10.5194/egusphere-egu24-10478, 2024.

16:45–16:55
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EGU24-7533
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ECS
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On-site presentation
Benjamin Frandsen and Robert Skog

The Venusian atmosphere has rich and diverse chemistry and much of it remains to be explored. Here I present our recent work in identifying new reactions and quantifying their rate constants, along with UV-Vis spectral simulation using quantum chemistry calculations. The research focuses on elemental sulfur allotropes and sulfur oxides. Our UV-Vis spectral simulations are used to narrow the search of the unknown UV absorber by excluding molecules/isomers/conformers without the appropriate absorption and similarly include those with absorption profiles that fit the unknown absorber. Furthermore, we present a mechanism for how substituted sulfuric acid molecules can be formed in the Venusian atmosphere which can impact aerosol formation.

How to cite: Frandsen, B. and Skog, R.: Breaking New Ground in Venusian Atmospheric Sulfur Chemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7533, https://doi.org/10.5194/egusphere-egu24-7533, 2024.

16:55–17:05
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EGU24-14689
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On-site presentation
Dmitrij Titov, Igor Khatuntsev, and Marina Patsaeva

Dynamics of the Venus atmosphere is still an unsolved fundamental problem in the planetary physics. ESA’s Venus Express collected long imaging time series in several wavelengths from UV to near-IR. It was later complemented by JAXA’s Akatsuki observations, thus providing the longest almost uninterrupted monitoring of the Venus atmosphere dynamics for about 26 Venus years. Tracking of cloud features allowed determination of wind speed at different levels within the cloud deck thus enabling significant progress in characterization of the mean atmospheric circulation. The analysis revealed wind variability including changes with altitude, latitude, local solar time as well as influence of the surface topography and long term 12.5 years periodicity.

The images also provided morphological evidences of dynamical processes at the cloud level. UV dark low latitudes were found to be dominated by convective mixing that brings UV absorbers from depth, while bright uniform clouds at middle-to-high latitudes are typical for the regions with suppresses vertical mixing. The latter feature correlates with drastic increase of the total cloud opacity poleward from ~60° latitude that likely indicates presence of a dynamical mixing barrier here. Similarity of the global UV cloud morphology at the cloud top (~70 km) and that in the deep cloud (50-55 km) observed in the near-IR on the night side suggested similar morphology shaping processes throughout the cloud deck. Venus Express observed gravity waves poleward of 65°N concentrated at the edges of Ishtar Terra likely indicating their generation by wind interaction with the surface. 

Venus Express performed about 800 radio occultations providing precise measurements of the atmospheric temperature structure and static stability parameter in the altitude range 40-90 km. The Richardson number latitude-altitude field derived from the wind and temperature measurements suggests presence of convection in the cloud deck and stable mesosphere above it with the convective layer extending to greater depth at high latitudes. The talk will present recent results on the atmospheric circulation, supplemented by a summary of the Venus Express observations related to the atmospheric dynamics and an outlook for further analysis of these data.  

How to cite: Titov, D., Khatuntsev, I., and Patsaeva, M.: Venus atmosphere dynamics: digging into the Venus Express observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14689, https://doi.org/10.5194/egusphere-egu24-14689, 2024.

Venus: Surface and Interior
17:05–17:15
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EGU24-9470
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ECS
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On-site presentation
Diogo Louro Lourenço, Paul Tackley, Tobias Rolf, Maria Grünenfelder, Oliver Shah, and Ravit Helled

Venus’ mass and radius are similar to those of Earth. However, Venus’ interior structure and chemical composition are poorly constrained. Seemingly small deviations from the Earth might have important impacts in the long-term evolution and dynamics of Venus when compared to our planet and could help to explain the different present-day surface and atmospheric conditions and geophysical activity between these two planets. Shah et al. (ApJ 2022) presented a range of possible bulk compositions and internal structures for Venus. Their models, designed to fit Venus’ moment of inertia and total mass, predict core radii ranging from 2930-4350 km and include substantial variations in mantle and core composition. In this study, we pick ten different Venus models from Shah et al. (ApJ 2022) that range from a small to a big, and from a S-free to a S-rich core. We run mantle convection evolution models for the different scenarios using the code StagYY (Tackley, PEPI 2008; Armann and Tackley, JGR 2012) and explore how different interior structures and chemical compositions affect the long-term evolution and dynamics of Venus. In our models, the bulk composition of the mantle affects the basalt fraction and the solidus and liquidus temperature profiles. We investigate how the composition and size of the core affects magmatism hence outgassing of water and other volatiles to the atmosphere, the basalt distribution, heat flow, temperature of the mantle and lithosphere, and observables such as the moment of inertia and Love numbers. Since the tectonic regime active on Venus is still unknown, we test different evolution scenarios for a planet covered by a stagnant lid, an episodic lid, and a plutonic-squishy lid. The models produce a range of predictions that can be compared to observations by planned missions to Venus, including EnVision measurements by the VenSpec spectrometers, comprising outgassing of water and other volatiles and surface composition. These can be used to constrain Venus’ interior composition and structure, and reveal key information on the differences between Earth and Venus.

How to cite: Louro Lourenço, D., Tackley, P., Rolf, T., Grünenfelder, M., Shah, O., and Helled, R.: Influence of Possible Bulk Compositions on the Long-Term Evolution and Outgassing of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9470, https://doi.org/10.5194/egusphere-egu24-9470, 2024.

17:15–17:25
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EGU24-5857
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On-site presentation
Scott King

Coronae are crown-like, tectono-volcanic features found on Venus that typically range in diameter from 100-700 km. Diapirs of warm upwelling material impinging on the lithosphere are often invoked to explain coronae formation. With more than 500 coronae identified on the surface of Venus, if these diapirs are individually linked to a mantle plume, Venus must have a very different mantle structure than Earth. I consider three cases designed to assess the potential relationship between large-scale, long-wavelength lower mantle structure and smaller-scale upper mantle structure that could potentially form diapirs consistent with those that are envisioned to interact with the lithosphere and form coronae. I use the geoid and topography to identify the large-scale pattern of convection because the geoid contains and integral of the temperature anomalies over the depth of the mantle. Plume tails—narrow vertical conduits—integrate to give a positive geoid anomaly while small-scale, time-dependent drips or upwellings are minimized in the depth integration. The first case—the reference case—has a small, stepwise decreases in viscosity between the lower mantle (1022 Pa s), transition zone (1021 Pa s), and upper mantle (5x1020 Pa s) with no phase transformations. This led to 20 ~1000-km diameter mantle plumes that remained stationary for more than 1.5 Gyr. This calculation is consistent with a number of geophysical observations it does not support the formation of coronae by plume-lithosphere interaction. To decouple the lower and upper mantle, I further decrease both the upper mantle and transition zone viscosities to 1020 Pa s while leaving all other parameters unchanged. In this calculation the same 20 ~1000-km diameter mantle plumes formed and remained stationary for more than 1.5 Gyr. The geoid and topography are anti-correlated, inconsistent with the observed values on Venus and, the spatial scale, number, and topographic evolution of the plumes are not consistent with coronae. This calculation does not support the formation of coronae by plume-lithosphere interaction. In an attempt to further decouple the upper and lower mantle I add an endothermic phase transformation at the ringwoodite-bridgmanite boundary in addition to the decreased upper mantle and transition zone viscosities while leaving all other parameters unchanged. Unique to this calculation, a very large number of ~100-km diameter small topographic upwellings form some associated with the large-scale geoid high but never associated with the large-scale geoid low. The inclusion of a phase transformation decoupling the upper and lower mantle has the potential to create diapir-like structures in the upper mantle consistent with coronae formation.

How to cite: King, S.: Linking global-scale mantle flow with diapir-like coronae formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5857, https://doi.org/10.5194/egusphere-egu24-5857, 2024.

17:25–17:35
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EGU24-14638
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ECS
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On-site presentation
Michaela Walterová, Ana-Catalina Plesa, Philipp Baumeister, Tina Rückriemen-Bez, Frank W. Wagner, and Doris Breuer

Often termed the twin sister of the Earth, Venus represents an alternative outcome of the evolutionary path taken by large terrestrial planets. Given its extreme surface conditions, lack of surface water, and the absence of plate tectonics, the present-day thermal state of its mantle is likely very different from the Earth. Venus also remains the most enigmatic of terrestrial worlds in terms of interior structure. Both its tidal Love number k2 and the moment of inertia factor, the main sources of information on the core size and interior structure, are known with a large uncertainty of about 10% [1, 2], and the magnitude of tidal dissipation, sensitive to the planet’s thermal state, has only been determined indirectly [e.g., 3]. Yet, the set of observables acquired by the Magellan and Pioneer Venus Orbiter missions can still be used to put constraints on the interior structure.

In this study, we perform a Bayesian inversion of several observational and theoretical constraints (such as the tidal Love number, maximum elastic thickness, or absence of intrinsic magnetic field) to gain insight into the present-day interior structure and thermal state of Venus. This is done by combining the calculation of a global tidal deformation with a 1d parameterised model of mantle convection in the stagnant-lid regime [4,5]. The convection model is based on the thermal boundary layer theory and incorporates partial melting, crustal growth, and inner core crystallization. The elastic structure of the mantle for three selected mineralogical models is obtained from the software Perple_X, based on the minimisation of Gibbs free energy [6]. Finally, to find the tidal parameters, we calculate the deformation of a layered compressible viscoelastic sphere [7]. The mantle is described by the Andrade rheological model, which has proven essential for distinguishing between a fully solid and a fully or partially liquid Venusian core [8]. We vary a large set of rheological, structural, and thermodynamic parameters and predict a range of mantle temperatures consistent with previous stagnant-lid models, average mantle viscosities between 1020-1022 Pa.s, and a tidal quality factor of Q=50+74-24, corresponding to a phase lag of 1.12+1.06-0.67 degrees. Additionally, we discuss how the future measurements of the tidal deformation and the moment of inertia of Venus from EnVision [9] and VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) [10] can improve our understanding of the planet's interior.

[1] Konopliv & Yoder (1995), doi:10.1029/96GL01589.

[2] Margot et al. (2021), doi:10.1038/s41550-021-01339-7.

[3] Correia & Laskar (2003), doi:10.1016/S0019-1035(03)00043-5.

[4] Morschhauser et al. (2011), doi:10.1016/j.icarus.2010.12.028.

[5] Baumeister et al. (2023), doi:10.1051/0004-6361/202245791.

[6] Connolly (2009), doi:10.1029/2009GC002540.

[7] Takeuchi & Saito (1972), doi:10.1016/B978-0-12-460811-5.50010-6.

[8] Dumoulin et al. (2017), doi:10.1002/2016JE005249.

[9] Rosenblatt et al. (2021), doi:10.3390/rs13091624.

[10] Cascioli et al. (2023), doi:10.3847/PSJ/acc73c.

How to cite: Walterová, M., Plesa, A.-C., Baumeister, P., Rückriemen-Bez, T., Wagner, F. W., and Breuer, D.: Constraining the interior structure and thermal state of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14638, https://doi.org/10.5194/egusphere-egu24-14638, 2024.

17:35–17:45
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EGU24-3129
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ECS
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On-site presentation
Yann Musseau, Caroline Dumoulin, Gabriel Tobie, Cédric Gillmann, Alexandre Revol, and Emeline Bolmont

Venus' rotation is the slowest of all planetary objects in the solar system and the only one in the retrograde direction. It is commonly admitted that such a rotation state is the result of the balance between the torques created by the gravitational and atmospheric thermal tides1. The internal viscous friction associated with gravitational tides drive the planet into synchronization (deceleration) while the bulge due to atmospheric thermal tides tend to accelerate the planet out of this synchronization1,6. Other torque components (related to the two first one) also affect the rotation2. This work first provide an estimate of the viscosity of Venus' mantle explaining the current balance with thermal atmospheric forcing. Second, this study quantify the impact of the internal structure and its past evolution on the gravitational tides and thus on the rotation history of Venus. Using atmospheric pressure simulations from the Venus climate database4,5,7, we first estimated the atmospheric thermal torque and showed that topography and interior response to atmospheric loading, usually ignored in previous studies, have a strong influence on the amplitude of thermal atmospheric torque. Computing the viscoelastic response of the interior to gravitational tides and atmospheric loading3, we showed that the current viscosity of Venus' mantle must range between 2.3x1020 Pa.s and 2.4x1021 Pa.s to explain the current rotation rate as an equilibrium between torques. We then evaluated the possible past evolution of the viscosity profile of the mantle considering different simple thermal evolution scenarios.  We showed that in absence of additional dissipation processes, viscous friction in the mantle cannot slowdown the rotation to its current state for an initial period shorter than 2-3 days, even for an initially very hot mantle. Beyond Venus, these results has implications for Earth-size exoplanets indicating that their current rotation state could provide key insights on their atmosphere-interior coupling.

1Correia, A. C. M. and J. Laskar (2001), Nature.
2Correia, A. C. M. (2003), Journal of Geophysical Research.
3Dumoulin, C., G. Tobie, O. Verhoeven, P. Rosenblatt and N. Rambaux (2017), Journal of Geophysical Research.
4Lebonnois, S., F. Hourdin, V. Eymet, A. Crespin, R. Fournier and F. Forget (2010),  Journal of Geophysical Research.
5Lebonnois, S., N. Sugimoto and G. Gilli (2016), Icarus.
6Leconte, J., H. Wu, K. Menou and N. Murray (2015), Science.
7Martinez, A., S. Lebonnois, E. Millour, T. Pierron, E. Moisan, G. Gilli and F. Lefèvre (2023), Icarus.

How to cite: Musseau, Y., Dumoulin, C., Tobie, G., Gillmann, C., Revol, A., and Bolmont, E.:  Viscosity of Venus' mantle as inferred from its rotational state, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3129, https://doi.org/10.5194/egusphere-egu24-3129, 2024.

17:45–17:55
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EGU24-18247
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On-site presentation
Anne Grete Straume-Lindner, Mitch Schulte, Anne Pacros, Thomas Voirin, Lorenzo Bruzzone, Paul Byrne, Lynn Carter, Caroline Dumoulin, Gabriella Gilli, Joern Helbert, Scott Hensley, Kandis Lea Jessup, Walter Kiefer, Emmanuel Marcq, Philippa Mason, Alberto Moreira, Ann Carine Vandaele, and Thomas Widemann

EnVision is ESA’s next mission to Venus, in partnership with NASA, where NASA provides the Synthetic Aperture Radar payload and mission support. The ESA mission adoption is scheduled for January 2024, and the launch for 2031. The start of the science operations at Venus is early 2035 following the mission cruise, and aerobraking phase around Venus to achieve a low Venus polar orbit. The scientific objective of EnVision is to provide a holistic view of the planet from its inner core to its upper atmosphere, studying the planets history, activity and climate. EnVision aims to establish the nature and current state of Venus’ geological evolution and its relationship with the atmosphere. EnVision’s overall science objectives are to: (i) characterize the sequence of events that formed the regional and global surface features of Venus, as well as the geodynamic framework that has controlled the release of internal heat over Venus history; (ii) determine how geologically active the planet is today; (iii) establish the interactions between the planet and its atmosphere at present and through time. Furthermore, EnVision will look for evidence of past liquid water on its surface.

The nominal science phase of the mission will last six Venus cycles (~four Earth years), and ~210 Tbits of science data will be downlinked using a Ka-/X-band communication system. The science objectives will be addressed by five instruments and one experiment, provided by ESA memberstates and NASA. The VenSAR S-band radar will perform targeted surface imaging as well as polarimetric and stereo imaging, radiometry, and altimetry. The high-frequency Subsurface Radar Sounder (SRS) will sound the upper crust in search of material boundaries. Three spectrometers, VenSpec-U, VenSpec-H and VenSpec-M, operating in the UV and Near- and Short Wave-IR, respectively, will map trace gases, search for volcanic gas plumes above and below the clouds, and map surface emissivity and composition. A Radio Science Experiment (RSE) investigation will exploit the spacecraft Telemetry Tracking and Command (TT&C in Ka-/X bands) system to determine the planet’s gravity field and to sound the structure and composition of the middle atmosphere and the cloud layer in radio occultation. All instruments have substantial heritage and robust margins relative to the requirements, with designs suitable for operation in the Venus environment, and were chosen to meet the broad range of measurement requirements needed to support the EnVision scientific objectives. The EnVision science teams will adopt an open data policy, with public release of the scientific data after verification and validation. Public calibrated data availability is <6 months after data downlink.

The mission phase B1 was concluded in December 2023 following the successful Mission Adoption Review and positive science review and recommendations by the ESA Solar System and Exploration Working Group (SSEWG) and Space Science Advisory Committee (SSAC). The mission adoption is scheduled for 25 January 2024. The scientific objectives and status of the EnVision mission preparations will be presented, including an overview of the scientific topics being studied and the next steps in the mission preparation.

How to cite: Straume-Lindner, A. G., Schulte, M., Pacros, A., Voirin, T., Bruzzone, L., Byrne, P., Carter, L., Dumoulin, C., Gilli, G., Helbert, J., Hensley, S., Jessup, K. L., Kiefer, W., Marcq, E., Mason, P., Moreira, A., Vandaele, A. C., and Widemann, T.: Science objective and status of the EnVision Mission to Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18247, https://doi.org/10.5194/egusphere-egu24-18247, 2024.

17:55–18:00

Posters on site: Wed, 17 Apr, 10:45–12:30 | Hall X3

Display time: Wed, 17 Apr 08:30–Wed, 17 Apr 12:30
Chairpersons: Gregor Golabek, Moa Persson, Cédric Gillmann
X3.29
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EGU24-16898
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ECS
Joanna Egan, Wuhu Feng, Alexander James, James Manners, Daniel R. Marsh, and John M. C. Plane

The cause of the inhomogeneous near-ultraviolet absorption observed in the upper clouds of Venus remains a key question in Venusian research. One possible candidate in the literature is ferric chloride. The absorption spectrum of ferric chloride currently in use by models uses ethyl acetate as a solvent and does not reproduce the absorption features observed on Venus. The study of the optical properties and chemistry of ferric chloride in the sulphuric acid cloud droplets is required to draw valid conclusions regarding its suitability as a candidate for the near-UV absorption.

In this study, we measure the absorption spectrum of ferric chloride in sulphuric acid from 200 – 600 nm at a range of temperatures and measure the rate of conversion of the ferric chloride ions into ferric sulphate ions. We then use the resulting ferric chloride absorption coefficients in a 1D radiative transfer model and estimate the required concentration of ferric chloride in the clouds to be 0.6 – 0.9 wt% in the mode 1 (~0.3 µm radius) cloud droplets to match observations. We also predict the atmospheric concentrations of ferric chloride formed from the reaction of iron ablating from cosmic dust entering Venus’ atmosphere around 120 km with hydrogen chloride emitted by volcanic activity, and estimate the accumulation timescale of ferric chloride to produce the required concentrations in the clouds.

How to cite: Egan, J., Feng, W., James, A., Manners, J., Marsh, D. R., and Plane, J. M. C.: Laboratory studies and modelling of ferric chloride as the cause of the anomalous UV absorption in the Venusian atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16898, https://doi.org/10.5194/egusphere-egu24-16898, 2024.

X3.30
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EGU24-16505
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ECS
Peng Han and Sébastien Lebonnois

Until now, the Venus PCM (Planetary Climate Model) was using precomputed tables for the distribution of the solar heating rates in the atmosphere of Venus. A new scheme is now implemented to compute online the radiative transfer of the solar flux, which allows more flexibility to study sensitivity to opacity sources. We have investigated the sensitivity of the temperature and circulation of the Venusian cloud region to the distribution of the UV absorber. Different vertical distributions of the UV absorber, as well as variations of this along latitudes, have been tested, and comparison is discussed of the vertical profile of computed solar heating rates, temperature distribution in the cold collar region, as well as the resulting mean zonal wind field.

How to cite: Han, P. and Lebonnois, S.: Influence of the UV absorber distribution on the temperature and circulation ofthe Venusian cloud region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16505, https://doi.org/10.5194/egusphere-egu24-16505, 2024.

X3.31
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EGU24-13314
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ECS
Anna Maria Gargiulo, Antonio Genova, Flavio Petricca, Edoardo Del Vecchio, Simone Andolfo, Tommaso Torrini, Pascal Rosenblatt, Sébastien Lebonnois, Jean-Charles Marty, and Caroline Dumoulin

EnVision radio science investigation will deepen our understanding of Venus’ gravity, interior structure and atmospheric properties. To address these scientific questions, a two-way link communication (configuration X/X/Ka-band) is established with the ESA ESTRACK ground stations enabling precise orbit determination (POD) during the science phase. An accurate modeling of the spacecraft’s dynamics, including the atmospheric drag acceleration, is key for retrieving EnVision’s trajectory and constraining Venus’ gravity field, tides and orientation parameters.

Dedicated radio occultation campaigns are designed to characterize electron density profiles in the ionosphere and atmospheric density, pressure and temperature in the mesosphere and upper troposphere of Venus. Furthermore, an accurate POD of the spacecraft also provides complementary information on the atmospheric density at the altitudes crossed by the probe, extending the science return of the EnVision mission.

The atmospheric drag perturbation strongly affects spacecraft trajectories that are characterized by a pericenter altitude above Venus’ surface of less than 220 km. By accounting for different Venus’ atmospheric models, e.g., the Venus Climate Database (VCD) and the Venus Global Reference Atmospheric Model (Venus-GRAM), we investigate the impact of potential errors and uncertainties in the predicted atmospheric properties on the orbit evolution of the spacecraft. We note significant inconsistencies between Venus’ atmospheric models at the spacecraft altitudes including atmospheric density differences of more than 200%. These discrepancies may be representative of the current knowledge of Venus’ upper atmosphere and thermosphere. Thus, we carried out a perturbative analysis of the dynamical forces by introducing a mismodeling in the atmospheric density profiles. We assumed the VCD for the simulation of the radio tracking measurements and we included as a priori model in the estimation process the Venus-GRAM. By developing a batch sequential filter that adjusts a set of atmospheric density scale factors, we compensated for the mismodeling and improved the quality of the dynamical model and of the orbit determination. The proposed approach enables an estimation of the atmospheric density at the spacecraft altitudes with an accuracy of 25% and accuracies in the orbit reconstruction of 1-2 m, 30-40 m and 20-30 m in the radial, transverse and normal directions.

How to cite: Gargiulo, A. M., Genova, A., Petricca, F., Del Vecchio, E., Andolfo, S., Torrini, T., Rosenblatt, P., Lebonnois, S., Marty, J.-C., and Dumoulin, C.: Estimation of Venus' atmospheric density through EnVision precise orbit determination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13314, https://doi.org/10.5194/egusphere-egu24-13314, 2024.

X3.32
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EGU24-17524
Dexin Lai, Sebastien Lebonnois, and Tao Li

High-resolution runs of the Venus PCM (1.25° in longitude and latitude) successfully simulated Venus atmospheric superrotation. The results show a clear spectrum and structure of atmospheric waves, primarily with periods of 5.65 days and 8.5 days. The simulation successfully reproduces long-term quasi-periodic oscillation of the zonal wind and primary planetary-scale wave seen in observations. These oscillations are obtained with a period of about 163-222 days close to the observations. The Rossby waves show robustness in wave characteristics and angular momentum transport due to Rossby-Kelvin instability by comparing the 5.65-day wave with the 5.8-day wave simulated by another Venus GCM, AFES-Venus. Similarities are also evident between the 8.5-day wave in our simulation and the 7-day wave obtained in AFES-Venus. Furthermore, the long-term variations in angular momentum transport indicate that the 5.65-day wave is the dominant factor of the oscillation on the superrotation, and the 8.5-day wave is the secondary. When the 5.65-day wave grows, its angular momentum transport is enhanced and accelerates (decelerates) the lower-cloud equatorial jet (cloud-top mid-latitude jets). Meanwhile, the 8.5-day wave weakens, reducing its deceleration effect on the lower-cloud equator region. Consequently, this flattens the background wind and weakens instability, leading to the decay of the 5.65-day wave. And vice versa when the 5.65-day wave is weak.

How to cite: Lai, D., Lebonnois, S., and Li, T.: Planetary-scale wave study in Venus cloud layer, simulated by the Venus PCM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17524, https://doi.org/10.5194/egusphere-egu24-17524, 2024.

X3.33
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EGU24-10655
|
ECS
Ting-Juan Liao, Eliot Young, Mark Bullock, dave crisp, and Yuk Yung

The investigation into Venus's atmosphere has highlighted deficiencies in photochemical models when it comes to explaining the distribution of trace gas species, particularly crucial elements like CO and OCS, which play a vital role in Venus's sulfur cycle and cloud formation.

To gain a comprehensive understanding of the abundance and variability of these trace gases ahead of the DaVinci probe's descent, we initiated an observational study using NASA's IRTF telescope equipped with the high-resolution ISHELL spectrometer. Conducted from June 11 to June 30, 2023, our study involved capturing K, H, and J-band spectra of Venus's night side. We employed the SMART software to calculate synthetic spectra, considering various gas abundances and emission angles.

With our high-resolution spectral data (R=λ/Δλ~25,000), we successfully mapped the abundances of CO, H2O, and OCS in the equatorial region, revealing both daily and latitudinal variations. Our focus was on examining the delicate balance between chemistry and transport, evident in the observed anti-correlation between OCS and CO abundance with cloud opacity.

Through near-infrared observations, this study aims to unravel the intricate interplay between atmospheric dynamics and chemical reactions in Venus's cloud formation. By providing insights into observed cloud patterns and elucidating the relationship between atmospheric chemistry, dynamics, and cloud creation on Venus, we contribute crucial parameters to refine existing photochemical models.

How to cite: Liao, T.-J., Young, E., Bullock, M., crisp, D., and Yung, Y.: Unraveling Venus's Atmospheric Composition: Insights into CO, H2O, and OCS Abundances through Observations and Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10655, https://doi.org/10.5194/egusphere-egu24-10655, 2024.

X3.34
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EGU24-8798
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ECS
Robert Skog, Benjamin Frandsen, and Theo Kurtén

The Venusian atmosphere has everything to be an exciting natural sulfur laboratory. In addition to relatively high concentrations of sulfur dioxide, suitable conditions in the atmosphere make both thermo- and photochemical reactions possible, allowing for complex chemical reactions and the formation of new sulfur containing compounds. These compounds could explain or contribute to the enigmatic 320-400 nm absorption feature in the atmosphere. One of the proposed absorbers is polysulfur compounds. While some experimentally obtained UV-VIS spectra have been published, studying the different polysulfur species individually is extremely difficult due to the reactive nature of sulfur. In this work UV-VIS spectra for polysulfur species S2 to S8 were simulated using the nuclear ensemble approach to determine if they fit the absorption profile of the unknown absorber.

Geometries were optimized at the ωB97X-D/aug-cc-pV(T+d)Z level of theory, with the S2, S3, and S4 structures also being optimized at the CCSD(T)/aug-cc-pV(T+d)Z level of theory. For the lowest energy isomers UV-VIS spectra were simulated using a nuclear ensemble of 2000 geometries, with vertical excitations calculated at the EOM-CCSD/def2-TZVPD or the ωB97X-D/def2-TZVPD levels of theory.

The simulated UV-VIS spectra for the smaller species were in quite good agreement with experimental results. Two different molecules were identified with substantial absorption cross sections in the range of the unknown absorber: The open chain isomer of S3, and the trigonal isomer of S4 However, the mixing ratios of these species in the Venusian atmosphere are also needed to make a more conclusive statement. Other polysulfur compounds have insignificant absorption cross sections in the 320-400 nm range and can therefore be excluded.

The calculated absorption cross sections can be used to calculate photolysis rates, which can be straight away added to atmospheric models of Venus. In addition, this work will help future space missions to Venus, for example by focusing their search for the unknown absorber.

How to cite: Skog, R., Frandsen, B., and Kurtén, T.: Simulating UV-VIS Spectra for Polysulfur Species in the Venusian Atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8798, https://doi.org/10.5194/egusphere-egu24-8798, 2024.

X3.35
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EGU24-18366
Arianna Piccialli, Davide Grassi, Alessandra Migliorini, Romolo Politi, Giuseppe Piccioni, and Pierre Drossart

Venus is a natural laboratory to study the atmospheric circulation on a slowly rotating planet. The dynamics of its upper atmosphere (60-120 km) is a combination of retrograde zonal wind found in the lower mesosphere and solar-to-antisolar winds that characterize the thermosphere, and it is subject to a strong turbulence and a dramatic variability both on day-to-day as well as longer timescales. Moreover, several wavelike motions with different length scales have been detected at these altitudes within and above the clouds and they are supposed to play an important role in the maintenance of the atmospheric circulation. The basic processes maintaining the super-rotation (an atmospheric circulation located at the clouds level and being 80 times faster than the rotation of the planet itself) and other dynamical features of Venus circulation are still poorly understood [1].

Different techniques have been used to obtain direct observations of wind at various altitudes: tracking of clouds in ultraviolet (UV) and near infrared (NIR) images give information on wind speed at cloud top (~70 km altitude) [2] and within the clouds (~61 km, ~66 km) [3], while ground-based measurements of doppler-shift in CO2 band at 10 μm [4] and in several CO (sub-)millimeter lines [5,6] sound thermospheric and upper mesospheric winds, showing a strong variability.

In the mesosphere, at altitudes where direct observations of wind are not possible, zonal wind fields can be derived from the vertical temperature structure using the thermal wind equation. Previous studies [7,8,9] showed that on slowly rotating planets, like Venus and Titan, the strong zonal winds at cloud top can be successfully described by an approximation of the Navier–Stokes equation, the cyclostrophic balance in which equatorward component of centrifugal force is balanced by meridional pressure gradient.

We will present zonal thermal winds derived by applying the cyclostrophic approximation from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) temperature retrievals. VIRTIS was one of the experiments on board the European mission Venus Express [10]. For this study, we will analyze the complete VIRTIS dataset acquired between December 2006 and January 2010 [11,12].

References

[1] Sanchez-Lavega, A. et al. (2017) Space Science Reviews, Volume 212, Issue 3-4, pp. 1541-1616.

[2] Goncalves R. et al. Atmosphere, 12:2., 2021. doi: 10.3390/atmos12010002.

[3] Hueso, R. et al. (2012) Icarus, Volume 217, Issue 2, p. 585-598.

[4] Sornig, M. et al. (2013) Icarus 225, 828–839.

[5] Rengel, M. et al. (2008) PSS, 56, 10, 1368-1384.

[6] Piccialli, A. et al. A&A, 606, A53 (2017) DOI: 10.1051/0004-6361/201730923

[7] Newman, M. et al. (1984) J. Atmos. Sci., 41, 1901-1913.

[8] Piccialli A. et al. (2008) JGR, 113,2, E00B11.

[9] Piccialli A. et al. (2012) Icarus, 217, 669–681

[10] Drossart, P. et al. (2007) PSS, 55:1653–1672

[11] Grassi D. et al. (2008) JGR., 113, 2, E00B09.

[12] Migliorini, A. et al. (2012) Icarus 217, 640–647.

How to cite: Piccialli, A., Grassi, D., Migliorini, A., Politi, R., Piccioni, G., and Drossart, P.: Zonal winds in Venus mesosphere from VIRTIS/VEx temperature retrievals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18366, https://doi.org/10.5194/egusphere-egu24-18366, 2024.

X3.36
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EGU24-16442
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ECS
Lucile Conan, Emmanuel Marcq, Benjamin Lustrement, Nicolas Rouanet, Ann Carine Vandaele, and Jörn Helbert

The next ESA mission to Venus, EnVision, aims to study the planet as a whole, including its various constituting parts as well as their interactions and coupling processes. Several instruments will therefore compose the payload: a synthetic aperture radar (VenSAR, NASA), a subsurface radar sounder and a suite of three spectrometers (VenSpec) will be embedded, and a radioscience experiment will be implemented. Among them, the UV channel of the spectrometer suite, VenSpec-U, will observe the atmosphere above the clouds and will focus on the characterisation of the sulphured gases SO2 and SO, the monitoring of the unknown UV absorber and dynamical processes. These four topics have been identified as the main science objectives of the instrument and have driven the elaboration of a preliminary design based on the requirements (e.g. spectral range, spectral and spatial resolution) that were formulated with respect to these goals.

The compliance of the current design with respect to these requirements, regarding in particular the precision of the retrieved science data, can then be assessed. Sensitivity studies are therefore performed using the Radiative Transfer Model (RTM), updated from the one used for SPICAV-UV/Venus Express retrievals (Marcq et al., 2020), that allows to link atmospheric features and UV reflectance spectra. Two types of perturbations are considered : errors of random nature arising from the presence of noise on the signal, or systematic errors caused by various effects that induce biases on the measurements. The first ones can be characterised through the influence of the Signal-to-Noise Ratio (SNR) on the uncertainties associated to each retrieved parameter through the fitting algorithm. Limits in terms of SNR can then be defined in order to ensure the compliance with the specifications. The second ones are referring to the impact of biases on the retrievals’ accuracy, and evaluate more specifically the effects of the similarities between the spectral characteristics of these biases and those of the atmospheric components aiming to be detected. The implemented method is based on the Effective Spectral Radiometric Accuracy (ESRA) requirement, previously defined within the framework of the ESA Sentinel missions. It allows to study biases independently as well as potential compensations, so that allowable envelopes of residual errors can then be estimated for each of the considered biases.

How to cite: Conan, L., Marcq, E., Lustrement, B., Rouanet, N., Vandaele, A. C., and Helbert, J.: Sensitivity studies for the VeSUV/VenSpec-U instrument onboard ESA’s EnVision mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16442, https://doi.org/10.5194/egusphere-egu24-16442, 2024.

X3.37
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EGU24-4022
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Therese Encrenaz, Thomas Greathouse, Rohini Giles, Thomas Widemann, Bruno Bezard, Franck Lefevre, Maxence Lefevre, Wencheng Shao, Hideo Sagawa, Emmanuel Marcq, and Anicia Arredondo

As part of a long-term monitoring program, full disk thermal maps of HDO (near 7 microns) and SO2 (near 7 and 19 microns) have been obtained at the cloud top of Venus in 2023, using the TEXES(Texas Echelon Cross-Echelle Spectrograph)  imaging spectrometer at the Infrared Telescope Facility (IRTF) at Mauna Kea Observatory. Assuming a constant D/H isotopic ratio, the water abundance has been more or less constant since 2018, at about half its value in 2012-2016. In contrast, the SO2 abundance, which was very high in 2018-2019 and very low between July 2021 and March 2023, has increased by a factor of about 5 between February and July 2023 (close to its maximum level of 2018-2019), and has remained at its high level in September 2023. The origin of these long-term variations is still unclear. In addition, stringent upper limits of NH3 (at 927-931 cm-1), PH3 (at 1161-1164 cm-1) and HCN at 744-748 cm-1) at the cloud top have been obtained in July 2023. These results will be presented and discussed.

How to cite: Encrenaz, T., Greathouse, T., Giles, R., Widemann, T., Bezard, B., Lefevre, F., Lefevre, M., Shao, W., Sagawa, H., Marcq, E., and Arredondo, A.: Ground-based thermal mapping of Venus:  HDO and SO2 monitoring and upper limits of NH3, PH3 and HCN at the cloud top, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4022, https://doi.org/10.5194/egusphere-egu24-4022, 2024.

X3.38
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EGU24-8135
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ECS
Davide Sulcanese, Giuseppe Mitri, and Marco Mastrogiuseppe

Previous studies have inferred volcanic activity on Venus from indirect evidence, including variations in atmospheric composition and thermal emissivity data [1, 2, 3]. More recently, a study hypothesized ongoing volcanic activity on Venus, evidenced by a volcanic vent that collapsed between two different Magellan observing cycles [4]. Expanding upon this premise, we are investigating the surface geology of Venus using the extensive radar and altimetric data acquired by the Magellan spacecraft.

In particular, by properly processing the SAR images, we are conducting a detailed geomorphological analysis of Venus' surface, in order to identify and characterize various surface morphologies. Additionally, the altimetric data provided valuable insights into the topographical variations across Venus, further contributing to the geomorphological assessment.

Our research not only enhances the understanding of the geology of Venus but also underscores the significance of radar imaging in the study of planetary surfaces, where no other imaging techniques are available. The findings highlight the crucial role of continued exploration of Venus, which could be greatly advanced by upcoming missions such as VERITAS and EnVision [5, 6]. Equipped with superior radar technology, these missions are expected to provide images of Venus's surface at an unprecedented resolution and signal-to-noise ratio, far surpassing that of the Magellan SAR, thus enabling a more detailed characterization of Venus's surface morphology.

 

References

1. Truong, N. & Lunine, J. Volcanically extruded phosphides as an abiotic source of Venusian phosphine. Proceedings of the National Academy of Sciences 118, e2021689118 (2021).

2. Esposito, L. W. Sulfur dioxide: Episodic injection shows evidence for active Venus volcanism. Science 223, 1072-1074 (1984).

3. Smrekar, S. E. et al. Recent hotspot volcanism on Venus from VIRTIS emissivity data. Science 328, 605-608 (2010).

4. Herrick, R. R. & Hensley, S. Surface changes observed on a Venusian volcano during the Magellan mission. Science, eabm7735 (2023).

5. Hensley, S. et al. VISAR: Bringing Radar Interferometry to Venus. In Proceedings of International EnVision Venus science workshop, Berlin, Germany (2023).

6. Ghail, R. C. et al. VenSAR on EnVision: Taking earth observation radar to Venus. International journal of applied earth observation and geoinformation 64, 365-376 (2018).

Acknowledgments

G.M., D.S., and M.M. acknowledge support from the Italian Space Agency (2022-15-HH.0).

How to cite: Sulcanese, D., Mitri, G., and Mastrogiuseppe, M.: Investigating the volcanic activity on Venus with Magellan data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8135, https://doi.org/10.5194/egusphere-egu24-8135, 2024.

X3.39
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EGU24-14443
Katherine Boggs, Jordan Shackman, Jerry Demorcy, Christine Pendleton, Jess Hall, Mahdi Chowdhury, Holly Bley, Ember Varga, Julia Shustova, Bridgette Dear, Parke Fontaine, Lovleen Dhami, Shane Herrington, Richard Ernst, Hafida El Balil, Erin Bethell, and Simon Hamner

The NASA Magellan Mission (1990 to 1994) produced a valuable resource that planetary geologists continue to use three decades later to unravel the geological characteristics of Venusian Large Igneous Provinces. The ability to be the first to map the surface of Venus is a powerful engagement tool to inspire the next generation of planetary geologists, as illustrated by the size of the Mount Royal University (MRU) Venus geological mapping team (now 25, nearly ¼ of the MRU Geology Major program). MRU is a public undergraduate university. Students are recruited out of 1st and 2nd year courses. In year one (Y1) of the research program students learn how to use the ArcGIS software while being introduced to the geological features of Venus as they map their quadrant, in Y2 or Y3 the students present a poster at an internal research day. The goal by Y4 is for these students to publish a peer-reviewed journal article. Currently one student who ran into pandemic roadblocks through high school could be published while she upgrades her marks, before she is in the MRU Geology Major Program. Such opportunities could prove to be incentives to guide other students past similar roadblocks (we will start working with local junior and high school students in the near future). Collectively we are working towards completing the geological map of the Henie Quadrangle (V-58, south Venus). Detailed mapping (at 1:500,000) revealed that lava canali extend across the entire quadrangle, with evidence for at least three generations of canali. Three canali originate from corona features (e.g. the circumferential dykes around Fotla Corona) suggesting that some canali may be linked to corona formation. The orientation of compressional wrinkle ridges (WR) in northern Henie suggest that these WRs were formed due to strain associated with the formation of the Artemis tectonomagmatic feature which is directly north of Henie. Artemis is possibly the largest such feature in the Solar System. The extent of the Artemis influence is being constrained across the Henie Quadrangle. The source of strain that formed a differently oriented WR swarm to the south of Henie is unknown. There is no evidence for the strain localization into master faults that we see on Earth. More work is needed to develop a model for the formation of the paired Latmikaik-Xacau Coronae and the associated Tellervo Chasma, Sunna-Laverna Dorsae and the Sonmunde-Mdeb-Arubani Flucti. A fissure eruption out of the Sunna Dorsa is proposed as the origin for the surrounding Arubani Fluctus.      

How to cite: Boggs, K., Shackman, J., Demorcy, J., Pendleton, C., Hall, J., Chowdhury, M., Bley, H., Varga, E., Shustova, J., Dear, B., Fontaine, P., Dhami, L., Herrington, S., Ernst, R., El Balil, H., Bethell, E., and Hamner, S.: Henie Quadrangle (V-58, Southern Venus); Large Igneous Province Features, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14443, https://doi.org/10.5194/egusphere-egu24-14443, 2024.

X3.40
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EGU24-16255
Anne Davaille

The dynamic regime prevailing in the mantle of present-day Venus is still unknown. The surface of Venus seems uniformly quite young; it has  been proposed that it was due to a catastrophic resurfacing 150-700 Ma, and that the planet was in a stagnant lid regime since. Indeed, Magellan observations have failed to reveal a continuous set of accretion ridges and subduction zones, signatures of plate tectonics. But subduction features (trench, elastic bulge) are present in a number of localized spots, for exemple around two of the largest coronae, Artemis and Quetzelpetlal. There, subduction would be mainly by roll-back and could have been induced by the impingement of a mantle plume under the lithosphere, as predicted by our recent fluid dynamics laboratory experiments. Further analysis of our experiments suggest that subduction would be facilitated by the presence of a few % of a liquid phase in the asthenosphere. Melt would be most likely for the Venusian case, as anyway hinted by the amount of volcanic features on the surface of the planet. The experimental scaling laws further suggest that roll-back and subduction could be quite fast (10 cm/yr) because of the old age of the subducting lithosphere and the transformation to eclogite of the basaltic crust. This is turn would generate the rapid opening of a back-arc basin. Laboratory experiments show that for Venus temperature conditions, the produced crust and lithosphere could be quite disorganized with a contorted spreading center, large transforms and microplates. Moreover, the buoyancy of the newly created plate would cause it to remain quite elevated compared to the surrounding plains. Hence, inspection of the topography of Venus suggests several new plates created by subduction: beside the interior of Artemis coronae, Enyo Fossae and Asthik Planum could be plausible candidates. 

How to cite: Davaille, A.: Signatures of a regime of episodic localized subduction: from laboratory experiments to Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16255, https://doi.org/10.5194/egusphere-egu24-16255, 2024.

X3.41
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EGU24-12790
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ECS
Iris van Zelst, Barbara De Toffoli, Raphaël F. Garcia, Richard Ghail, Anna J. P. Gülcher, Anna Horleston, Taichi Kawamura, Sara Klaasen, Maxence Lefevre, Philippe Lognonné, Julia Maia, Sven Peter Näsholm, Mark Panning, Ana-Catalina Plesa, Leah Sabbeth, Krystyna Smolinski, Celine Solberg, and Simon Stähler

With the selection of multiple missions to Venus by NASA and ESA that are planned to launch in the coming decade, we will greatly improve our understanding of Venus. However, none of these missions have determining the seismicity of the planet as one of their primary objectives. Nevertheless, constraints on the seismicity remain crucial to understand the tectonic activity and geodynamic regime of the planet and its interior structure. 

Funded by the International Space Science Institute (ISSI) in Bern, Switzerland, we have gathered an interdisciplinary team of experts in seismology, geology, and geodynamics to assess the potential seismicity of Venus, specific regions that could be seismically active at present, and the methods to detect them.

Here, we present the findings from our second ISSI team meeting (January 29 - February 2, 2024), aiming to review knowledge on Venus's seismicity and interior and identify the best approaches for future missions. We present the feasibility, advantages, and disadvantages of different seismic observation techniques on the surface (e.g., broadband seismometers, distributed acoustic sensing methods), from a balloon (acoustic sensors), and from orbit (airglow imagers). We make a recommendation for the instrumentation of a future seismology-focused mission to Venus. 

We also suggest target regions with a high likelihood of significant surface deformation and/or seismicity. These targets are useful for the upcoming VERITAS (Venus Emissivity, Radio Science, InSAR, Topography and Spectroscopy) and EnVision missions and would specifically benefit from the repeat pass interferometry of VERITAS, which detects surface deformation and can therefore in principle constrain the maximum displacement of surface faulting at locations that are visited twice during the mission. 

How to cite: van Zelst, I., De Toffoli, B., Garcia, R. F., Ghail, R., Gülcher, A. J. P., Horleston, A., Kawamura, T., Klaasen, S., Lefevre, M., Lognonné, P., Maia, J., Näsholm, S. P., Panning, M., Plesa, A.-C., Sabbeth, L., Smolinski, K., Solberg, C., and Stähler, S.: Seismicity on Venus: optimal detection methods and target regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12790, https://doi.org/10.5194/egusphere-egu24-12790, 2024.

X3.42
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EGU24-19372
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ECS
Marla Metternich, Paul J. Tackley, Nickolas Moccetti Bardi, and Diogo L. Lourenço

Observations of Venus imply ongoing tectonic and volcanic activity, suggesting the planet is dynamically active[1,2]. Tectonically altered regions, such as ridges or tesserae, indicate surface mobility. However, unlike Earth, no evidence of active plate tectonics has been identified. The tectonics and volcanism of terrestrial planets are closely tied to active mantle convection modes. Rheology, a crucial element in tectonics, is influenced by the presence of water[3]. Despite this, the impact of water has largely been overlooked in Venus studies, as its interior is typically assumed to be dry. This assumption is being challenged by indications of significant hydrodynamic escape into space, requiring volcanic replenishment. Consequently, water is likely still present in Venus' interior, even if the concentrations are unknown. Importantly, the potential effects of water on Venus' dynamics and evolution remain poorly understood. The interplay between water, mantle dynamics, and volcanic activity would likely contribute to a more comprehensive understanding of Venus' evolution.  This underlines the need to consider complex dynamic thermo-magmatic models that account for water, including composition-dependent finite water solubilities.

 

In this study, we use the numerical code StagYY to perform state-of-the-art 2D models in a spherical annulus geometry to assess the effects of water on the tectono-magmatic evolution of Venus[4,5]. Particular attention will be given to the way water influences mantle convection and tectonics. Indeed, results show that the presence of water can dramatically change the geodynamic regime through the rheology, melting and outgassing. With the introduction of composition-dependent water solubility maps, dehydration processes will redistribute water throughout the mantle[6]. Since water content is directly related to the viscosity structure, the convective regime is expected to change as well. The main question we want to address is how dehydration processes and water distribution influence the convective and tectonic regimes of Venus. Studying the impact of water on Venus's interior may not only unveil insights into its tectonic evolution but also sets the stage for crucial future research, advancing our broader understanding of planetary processes and habitability.

 

[1] Smrekar, S. E., Stofan, E. R., Mueller, N., Treiman, A., Elkins-Tanton, L., Helbert, J., ... & Drossart, P. (2010). Recent hotspot volcanism on Venus from VIRTIS emissivity data. Science, 328(5978), 605-608.

[2]Gülcher, A. J., Gerya, T. V., Montési, L. G., & Munch, J. (2020). Corona structures driven by plume–lithosphere interactions and evidence for ongoing plume activity on Venus. Nature Geoscience13(8), 547-554.

[3]Karato, S. I. (2015). Water in the evolution of the Earth and other terrestrial planets. Treatise on Geophysics, 9, 105-144.

[4] Tackley, P. J. (2008). Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid. Physics of the Earth and Planetary Interiors, 171(1-4), 7-18.

[5]Tian, J., Tackley, P. J., & Lourenço, D. L. (2023). The tectonics and volcanism of Venus: New modes facilitated by realistic crustal rheology and intrusive magmatism. Icarus, 399, 115539.

[6]Nakagawa, T. (2017). On the numerical modeling of the deep mantle water cycle in global-scale mantle dynamics: The effects of the water solubility limit of lower mantle minerals. Journal of Earth Science, 28(4), Article 4. https://doi.org/10.1007/s12583-017-0755-3

How to cite: Metternich, M., Tackley, P. J., Moccetti Bardi, N., and Lourenço, D. L.: Water and the tectonic regime of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19372, https://doi.org/10.5194/egusphere-egu24-19372, 2024.

X3.43
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EGU24-5946
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ECS
Carianna Herrera, Ana-Catalina Plesa, Julia Maia, Stephan Klemme, and Lauren Jennings

The recent analysis of radar data from NASA’s Magellan mission suggests that volcanic activity is ongoing on Venus [1], providing unprecedented evidence that Venus’s evolution and present day state has been dominated by volcanic processes. Venus’s geodynamics and tectonics seem to be well characterized by the so-called “plutonic squishy lid” regime, where part of the melt that is formed in the interior rises to the surface but a significant part remains trapped in the crust and lithosphere forming intrusions [2]. These intrusions strongly influence the mantle’s thermal evolution, heat flow, and the present-day thermal state of the subsurface.

This study focuses on the effects of intrusive magmatism on the lithosphere thickness and thermal gradient. The latter is used to evaluate our models by comparing our results to estimates based on studies of the elastic lithosphere thickness [3,4,5]. We use the geodynamic code Gaia in a 2D spherical annulus geometry [6]. Our models vary the intrusive to extrusive ratio from a fully intrusive case to a fully extrusive one and the intrusive melt depth from 10 km to 90 km.

Our models show that depending on the percentage of extrusive melt and the depth of magmatic intrusions, the maximum thermal gradient varies from a few K/km up to almost 40 K/km at present day, with higher values obtained for higher percentages of intrusive melt and shallower the magmatic intrusions. Moreover, our results show that the thermal gradients have remained similar during the last 750 Myr. Models in which the extrusive magmatism is higher than 60% and the depth of magmatic intrusions lies deeper than 50 km cannot explain high local thermal gradients as suggested by studies of elastic lithosphere thickness [3,4,5].

In a recent study [7], the presence of a low viscosity layer (LVL) in the shallow Venusian mantle has been suggested to be related to the presence of partial melt. The LVL starts beneath the lithosphere at depths shallower than 200 km. This places constraints on the depth of melting that we can use to select successful models. Models that are compatible with partial melting starting at depth of 200 km or less beneath the surface require less than 40% extrusive magmatism and an intrusive melt depth strictly higher than 10 km.

We use our models to estimate ranges for melting conditions in the interior at present day. The range of melt temperatures lies between 2000 and 2250 K and the depth of melting between ~200 and 360 km. These estimations serve as a starting point for and will be compared with high-pressure-high-temperature laboratory experiments that will be performed at the University of Münster to select the most likely mantle compositions of Venus that can explain the Venera and Vega data.

References:

[1] Herrick & Hensley, Science, 2023. [2] Rolf et al., SSR, 2023. [3] Smrekar et al., Nature Geoscience, 2023. [4] Borelli et al., JGR, 2021. [5] Maia et al., JGR, 2022. [6] Hüttig et al., PEPI, 2013. [7] Maia et al., GRL, 2023.

How to cite: Herrera, C., Plesa, A.-C., Maia, J., Klemme, S., and Jennings, L.: Thermal evolution and magmatic history of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5946, https://doi.org/10.5194/egusphere-egu24-5946, 2024.

X3.44
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EGU24-12316
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ECS
Vojtěch Patočka, Julia Maia, and Ana-Catalina Plesa

The spin period of Venus is anomalously large. With one Venusian day being 243 Earth days, the rotational bulge of
Venus has the amplitude of only tens of centimetres, making the Earth’s hotter twin the least rotationally stable planet in
the Solar System. Being a slow-rotator creates a unique link between internal and rotational dynamics. This is because,
on a slow-rotator, convection driven redistribution of mass may produce perturbations of the body’s inertia tensor that
are comparable in amplitude with the inertia of the rotational bulge. Venus thus may respond to mantle convection by
wobbling (Spada et al., 1996), and wobbling is detectable when both the rotational and the figure axes are measured
accurately. The present-day estimate of the angle between the two axes is 0.5°, but it is based on gravity models with a
limited resolution (Konopliv et al., 1999). Future missions to Venus, namely VERITAS and EnVision, are likely to provide
a more robust measurement.

The geodynamic regime of Venus’ mantle remains enigmatic. Observational data does not support the existence of
continuous plate tectonics on its surface, but some recent evidence of ongoing tectonic and volcanic activity (e.g. Herrick
and Hensley, 2023) and crater statistics analyses (e.g. O'Rourke et al., 2014) indicate that the planet is unlikely to be in a
stagnant lid regime (see also Rolf et al., 2022). Here we perform 3D spherical mantle convection simulations of the different
possible tectonic scenarios and compute the resulting reorientation of Venus. The reorientation is accompanied by a wobble
whose average amplitude we evaluate and compare to the present day estimate of 0.5° (Konopliv et al., 1999). Since the
different convective regimes predict vastly different rotational dynamics, the comparison provides a useful constraint on
the interior dynamics of Venus. This work was supported by the Czech Science Foundation through project No. 22-20388S.

References
Herrick, R., Hensley, S., 2023. Surface changes observed on a venusian volcano during the magellan mission. Science
doi:10.1126/science.abm7735.

Konopliv, A., Banerdt, W., Sjogren, W., 1999. Venus gravity: 180th degree and order model. Icarus 139, 3–18.
doi:10.1006/icar.1999.6086.

O'Rourke, J.G., Wolf, A.S., Ehlmann, B.L., 2014. Venus: Interpreting the spatial distribution of volcanically modified
craters. Geophys. Res. Lett. 41, 8252–8260. doi:10.1002/2014gl062121.

Rolf, T., Weller, M., Gulcher, A., Byrne, P., O’Rourke, J.G., Herrick, R., Bjonnes, E., Davaille, A., Ghail, R., Gillmann,
C., Plesa, A.C., Smrekar, S., 2022. Dynamics and evolution of venus’ mantle through time. Space Science Reviews 218,
70. doi:10.1007/s11214-022-00937-9.

Spada, G., Sabadini, R., Boschi, E., 1996. Long-term rotation and mantle dynamics of the Earth, Mars, and Venus.
J. Geophys. Res. Planets 101, 2253–2266. doi:10.1029/95JE03222.

How to cite: Patočka, V., Maia, J., and Plesa, A.-C.: The link between internal and rotational dynamics of Venus: The amplitude of mantle convection-driven wobble, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12316, https://doi.org/10.5194/egusphere-egu24-12316, 2024.

Posters virtual: Wed, 17 Apr, 14:00–15:45 | vHall X3

Display time: Wed, 17 Apr 08:30–Wed, 17 Apr 18:00
Chairpersons: Gregor Golabek, Moa Persson, Cédric Gillmann
vX3.6
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EGU24-13391
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ECS
Blair McGinness, Giles Harrison, Karen Aplin, Martin Airey, and Keri Nicoll

The electrical environment of Venus has been investigated through extensive considerations of whether lightning has been detected in the atmosphere [1]. Although an important process, the presence or absence of lightning does not completely describe Venus’ electrical environment. Little consideration has been made of other related aspects, such as the possible presence of a global atmospheric electric circuit, as is present on Earth. In this context, lightning would be regarded as the source in a possible global circuit, which distributes charge across a planet. New arguments for and against a global electric circuit in Venus’ atmosphere are presented here which arise from re-analysis of data from the Venera 13 & 14 landers.

On Earth, the global atmospheric electric circuit connects regions of disturbed weather to distant regions of fair weather, by current flow between the conducting ionosphere and surface. Disturbed weather regions produce the potential difference between these conducting layers, which drives the current flow. The presence of a similar global circuit on other planets has been proposed, but their existence remains an open question, which motivates further work [2].

The Venera 13 & 14 landers descended through Venus’ atmosphere carrying a wealth of instrumentation. Each lander carried a point discharge sensor, which recorded electrical discharges between the spacecraft and the atmosphere [3]. The discharges recorded were difficult to explain using existing models of Venus’ environment, so it was previously proposed that low atmosphere haze layers could have caused them [4]. Further evidence for these haze layers has been provided by spectroscopic data from the Venera landers, which showed significant atmospheric extinction in the same region [5]. We have attempted to investigate whether it would be plausible for haze layers to cause both the electrical and extinction effects, and whether this favours a global electric circuit in Venus’ atmosphere.

To investigate this, a model describing electrical interactions in Venus’ atmosphere has been produced. The effects of different haze layers on Venus’ electrical environment were able to be studied, via different inputs to the model. The haze layer properties have been constrained by the spectroscopic observations. Results from the electrical modeling were compared with the electrical discharges recorded by the landers, allowing us to determine the conditions which best recreate these observations. Our investigations show that similar results to the observed Venera data can be produced by the electrical model when the effects of a global atmospheric electric circuit are included, but not when they are neglected. These findings are not definitive, but they do provide supporting evidence for the presence of a global electric circuit in Venus’ atmosphere.

References:
[1] R.D. Lorenz (2018). Progress in Earth and Planetary Science, 5. [2] K.L. Aplin (2006). Surveys in Geophysics 27. 63-108. [3] L. Ksanfomality et al. (1982). Soviet Astronomy Letters, 8. 230–232. [4] R.D. Lorenz (2018). Icarus, 307. 146-149. [5] B. Grieger (2003). Proceedings of the International Workshop Planetary Probe Atmospheric Entry and Descent Trajectory Analysis and Science. 63–70.

How to cite: McGinness, B., Harrison, G., Aplin, K., Airey, M., and Nicoll, K.: New Evidence for a Global Atmospheric Electric Circuit on Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13391, https://doi.org/10.5194/egusphere-egu24-13391, 2024.