PS4.2 | Venus: models, observations, exoplanet analogue

PS4.2

Venus: models, observations, exoplanet analogue

In June 2021, NASA and ESA selected a fleet of three international missions to Venus. Moreover, the ISRO orbiter mission Shukrayyan-1 is currently in preparation 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. 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 exo-Venus analogues. Moreover, Venus mission concepts, new Venus observations, exoplanet observations, new results from previous observations, and the latest lab and modelling approaches are all welcome to our discussion of solving Venus’ mysteries.

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Co-organized by GD3

Convener: Anna GülcherECSECS | Co-conveners: Cédric Gillmann, Maxence Lefevre, Moa PerssonECSECS, Gregor Golabek

Orals

| Fri, 28 Apr, 08:30–10:15 (CEST)

Room L1

Posters on site

| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)

Hall X4

Posters virtual

| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)

vHall ST/PS

Orals: Fri, 28 Apr | Room L1

The oral presentations are given in a hybrid format supported by a Zoom meeting featuring on-site and virtual presentations. The button to access the Zoom meeting appears just before the time block starts.

Chairpersons: Cédric Gillmann, Gregor Golabek, Maxence Lefevre

08:30–08:35

5-minute convener introduction

Venus: Native and Alien

08:35–08:45

EGU23-8703

solicited

Highlight

Virtual presentation

Venus as a natural laboratory to infer observational prospects of close-in-orbit rocky exoplanets with a 3D model

Gabriella Gilli, Diogo Quirino, Thomas Navarro, Martin Turbet, Lisa Kaltenegger, Thomas Fauchez, Jeremy Leconte, Sebastien Lebonnois, and Luisa Lara

Venus is in the spotlight of the public and scientific community after the selection of 3 missions: DAVINCI and VERITAS by NASA and EnVision by ESA/NASA. It remains an open question how Venus and the Earth started so similar but become such different worlds. Thus, studying Venus is essential for understanding the links between planetary evolution and the habitability of terrestrial planets, including those outside our Solar System. Several Earth-sized exoplanets have been recently detected in short-period orbits of a few Earth days around low-mass stars [1]. Those planets have stellar irradiation levels of several times that of the Earth, suggesting that a Venus-like climate is more likely than an Earth-like [2]. Consequently, the atmosphere of our closest planet Venus represents a relevant case to address observational prospects of rocky close-in orbit exoplanets.

In this work we used the Generic Planetary Climate Model (historically known as the LMD Generic GCM), a 3D model developed for exoplanet and paleoclimate studies ([3], [4], [5], [6], [7]), to simulate the atmosphere of two potential Venus’s analogues: TRAPPIST-1c [1] and LP 890-9c [8], both orbiting M-dwarf stars. We assumed that the planets are tidally-locked, and they have evolved into a modern Venus-like atmosphere (e.g. CO₂-dominated, 92-bar surface pressure), with an H₂SO₄ prescribed cloud layer following Venus Express observations ([9]). Our 3D climate simulations show the presence of an eastward equatorial superrotation jet for Trappist-1c (Quirino et al. in preparation), in agreement with previous prediction of highly irradiated synchronous rotators (e.g., [10]), and an effective day-to-night heat redistribution by three superrotation jets (one equatorial and two high-latitudes) for Speculoos-2c (Quirino et al. MNRAS, submitted).

The results will be shown in terms of simulated temperature/wind fields and the potential characterization of the atmosphere of those planets by JWST and future instrumentations discussed. For instance, under the hypothesis that the planets evolved in a modern Venus, our predicted transmission spectra show that even the strongest CO₂ bands around 4.3 μm will be challenging to be detected by the JWST (10 ppm for LP 890-9c and around 40 ppm for Trappist-1c). Those simulations provide new insights for JWST proposals and highlight the influence of clouds on the spectra of hot rocky exoplanets.

References:

[1] Gillon et al. 2017 Nature 542, [2] Kane et al. 2018 ApJ. 869, [3] Forget & Leconte, 2014 Phil. Trans R. Soc.A372., [4] Turbet et al. 2016 A&A 596. A112, [5] Wordsworth et al. 2011 ApJL 733. L48, [6] Leconte et al. 2013, Nature, 504, 286, [7] Turbet et al. 2020 Space Sci. Rev. 216, 100 [8] Delrez et al. 2022, A&A,Vol.667, id.A59, [9] Haus et al. 2015, PSS, 117, 262, [10] Showman & Polvani 2011, ApJ, 738,71.

Acknowledgments: GG is funded by the Spanish MCIU, the AEI and EC-FEDER funds under project PID2021-126365NB-C21, and IAA’s team acknowledges financial support from the grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033

How to cite: Gilli, G., Quirino, D., Navarro, T., Turbet, M., Kaltenegger, L., Fauchez, T., Leconte, J., Lebonnois, S., and Lara, L.: Venus as a natural laboratory to infer observational prospects of close-in-orbit rocky exoplanets with a 3D model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8703, https://doi.org/10.5194/egusphere-egu23-8703, 2023.

08:45–08:55

EGU23-17505

On-site presentation

Venus as an Exoplanet: Effect of varying stellar, orbital, planetary and atmospheric properties upon composition, habitability and detectability

John Lee Grenfell, Benjamin Taysum, Fabian Wunderlich, Jörn Helbert, Gabriele Arnold, Konstatin Herbst, Miriam Sinnhuber, and Heike Rauer

08:55–09:05

EGU23-8270

Highlight

On-site presentation

Exo-Venus, Exo-Earth, Exo-Dead in the Trappist-1 System?

Michael Way

Venus: Surface and Interior

09:05–09:25

EGU23-8996

solicited

Highlight

On-site presentation

Thermal evolution and interior structure of Venus

Ana-Catalina Plesa, Michaela Walterová, Julia Maia, Iris van Zelst, and Doris Breuer

The dense atmosphere of Venus and the planet’s young surface, dominated by volcanic features, bear witness to its past and potentially ongoing volcanic activity. While unique among the terrestrial planets of our Solar System, Venus is likely similar to a myriad of extrasolar worlds [1]. Thus, investigating Venus’s interior structure, thermal history, and magmatic processes may guide our understanding of the evolution and present-day state of an entire class of exoplanets.

The present-day geodynamic regime of Venus’s mantle is still debated, but models agree that magmatism played a major role in shaping the atmosphere and surface that we observe today [2]. In this contribution we will summarize the evidence for recent and possibly ongoing magmatic activity in the interior of Venus and show how we can combine current and future observations with thermal evolution models to constrain the planet’s present-day interior structure, dynamics, and magmatic activity.

We calculate the tidal deformation and moment of inertia in our models to provide estimates on deep interior parameters. While the tidal Love number k₂, which is sensitive to the size and state of the core, has been determined from Magellan and Pioneer Venus Orbiter tracking data with large uncertainties [3], the phase lag of the deformation, whose value is particularly sensitive to the thermal state of the interior, has not yet been measured. A rough estimate of the core size of 3500 km with large (>500 km) uncertainties comes from the moment of inertia factor that was determined from Earth-based radar observations [4].

Our models address the recent volcanic activity that was suggested by several observations [e.g., 5]. In particular, we focus on investigating the constraints coming from estimates of the elastic lithosphere thickness, which is linked to the thermal state of the lithosphere at the time of the formation of geological features. Gravity and topography analyses indicate small elastic thicknesses for a variety of locations including coronae [6], steep-sided domical volcanoes [7], and crustal plateaus [8]. The young age of many surface features on Venus suggests a warm lithosphere at present-day, potentially linked to partial melting in the interior. Moreover, a recent study found that the inferred heat flux at 75 locations on Venus associated with recent volcanic and tectonic activity is similar to the values measured on Earth in areas of active extension [9].

Future measurements of the NASA VERITAS and ESA EnVision missions aim to constrain present-day volcanic and tectonic activity as well as the thickness of major layers (crust, mantle, and core) in the interior of Venus. These measurements will provide unprecedented information to address the interior structure and thermal history of our neighbor, who can teach us about the diversity of evolutionary paths that rocky planets around other stars might have followed.

[1] Kane et al., 2019. [2] Rolf et al., 2022. [3] Konopliv and Yodder, 1996. [4] Margot et al., 2021. [5] Smrekar et al., 2010. [6] O’Rourke & Smrekar, 2018. [7] Borrelli et al., 2021. [8] Maia and Wieczorek, 2022. [9] Smrekar et al., 2022.

How to cite: Plesa, A.-C., Walterová, M., Maia, J., van Zelst, I., and Breuer, D.: Thermal evolution and interior structure of Venus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8996, https://doi.org/10.5194/egusphere-egu23-8996, 2023.

09:25–09:35

EGU23-7105

On-site presentation

Venus Atmospheric Structure Investigation (VASI) on the DAVINCI Probe

Ralph Lorenz and the VASI Team

The only near-surface temperature/pressure profile of the atmosphere of our twin planet, Venus, was obtained in 1985 by the VEGA-2 lander. The handful of other probe missions have very limited vertical resolution, or sensor failures in the lowest few km. Unlike altitudes above 40km, which have been relatively well-surveyed by radio occultation profiles from orbiter missions, the fine temperature structure of lowest part of the Venus atmosphere must be interrogated by direct measurement. This structure is important in several respects. First, the structure and composition reflects the interactions between surface and atmosphere of an ‘exoplanet in our back yard’ which may be much more typical than are those of Earth. Secondly, there are indications that particularly interesting phenomena may occur on Venus, not seen in the atmospheres of Earth, Mars or Titan (but analogous to aspects of ocean stratification on Earth): the VEGA-2 profile is impossible to reconcile with a profile that is both convectively stable and compositionally uniform. A favored hypothesis is that the lowest few kilometers are compositionally denser (lower N₂). The supercritical thermodynamics of carbon dioxide add to the rich possibilities in this region.

The exchange of angular momentum between the retrograde, slowly-rotating Venus and its dense atmosphere is reflected in the wind profile, which can now be interpreted by global circulation models. Again, while cloud-top (60-70km) winds are now well-known from Akatsuki and preceding missions, very little data exist on winds in the hidden lowest 40km. Doppler tracking, turbulence measurements, and trajectory reconstruction from descent imaging will shed unprecedented light on the lower atmospheric dynamics.

DAVINCI was selected for flight in 2021 and is presently under development for launch in 2029. This presentation will review how the VASI’s measurements of pressure, temperature and wind, far superior in resolution and/or quantity to those of previous missions, may improve our understanding of Venus and complement DAVINCI’s composition measurements and imaging.

How to cite: Lorenz, R. and the VASI Team: Venus Atmospheric Structure Investigation (VASI) on the DAVINCI Probe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7105, https://doi.org/10.5194/egusphere-egu23-7105, 2023.

09:35–09:45

EGU23-12356

On-site presentation

Conditions for accretion and subduction initiation inside Venus Artemis Coronae

Anne Davaille

According to laboratory experiments and geomorphological observations, it is likely that the very large Artemis coronae is an exemple of plume-induced subduction. As an hot mantle plume breaks the denser lithosphere and flows above it, it forces it to sink. So the subduction trenches are localized along the rim of the plume and strong roll-back is observed. Predicted roll-back velocities are between 1 and 10 cm/yr for Artemis case. Subduction always occurs along partial circles, which is due to the brittle character of the upper part of the lithosphere. As roll-back subduction proceeds, the coronae expands and an accreting ridge system develops inside the coronae.

Laboratory experiments show that the ridge shape is governed primarily by the axial failure parameter \Pi_F , which depends on the spreading velocity, the mechanical strength of the lithospheric material and the axial elastic lithosphere thickness. Experiments with the largest \Pi_F present quite unstable ridge axis with a large lateral sinuosity, transform faults, numerous microplates, and axis jumps. Some of the latter can even cause subduction onset along the abandoned section of the ridge axis. Due to Venus hot surface temperature, this large \Pi_F regime is the most likely inside Artemis. Magellan data indeed shows a large feature, Britomartis Chasma, that has already been proposed to be an accretion ridge. It displays a large sinuosity, comparable to what is predicted by the laboratory experiments. The topography data resolution is not good enough to see transform faults, though. But their presence would explained some of the largest axis offsets. Moreover, the center of Britomartis presents a deep trough, next to a very tall hill. This may be due to core complex formation, but also to the initiation of subduction following an axis jump. Only high-resolution data, such as provided by VERITAS mission, will be able to discriminate between the two options.

How to cite: Davaille, A.: Conditions for accretion and subduction initiation inside Venus Artemis Coronae, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12356, https://doi.org/10.5194/egusphere-egu23-12356, 2023.

09:45–09:55

EGU23-9889

Highlight

On-site presentation

EnVision: a Nominal Science Phase Spanning Six Venus Sidereal Days

Thomas Widemann, Anne Grete Straume, Adriana Ocampo, Thomas Voirin, Lynn Carter, Scott Hensley, Lorenzo Bruzzone, Joern Helbert, Ann Carine Vandaele, Emmanuel Marcq, and Caroline Dumoulin

EnVision was selected as ESA’s 5th M-class mission, targeting a launch in the early 2030s. The mission is a partnership between ESA and NASA, where NASA provides the Synthetic Aperture Radar payload. The scientific objective of EnVision is to provide a holistic view of the planet from its inner core to its upper atmosphere. The mission phase B1 started in December 2021 to complete trade-offs, consolidate requirements, interfaces and system specifications. Phase B1 will be concluded with the Mission Adoption Review planned in fall 2023, followed by Mission Adoption in 2024. To meet its science objectives, the EnVision mission needs to return a significant volume of science data to Earth, with a large distance-to-Earth dynamic range (from 0.3 to 1.7 AU), from a low Venus polar orbit, in the hot Venus environment (exacerbated by the operation of highly dissipative units), while operating three spectrometers in an almost cryogenic level environment. This needs to be achieved within constraints on the spacecraft mass as well as Agency programmatic boundaries. Achieving the science objectives under these multiple constraints without oversizing the spacecraft calls for a careful planning of science operations, making the science planning strategy a critical driver in the design of the whole mission, against which the spacecraft and ground segment are then sized.

The payload reference operations scenario simulation demonstrates that all identified surface targets can be imaged with VenSAR, with a performance fully compliant with the science requirements. The first two cycles allow imaging once 80% of the identified Regions of Interest (RoIs) at 30 m resolution. The following two cycles are mostly devoted to 2nd observations of these areas for stereo-topography mapping and the two last cycles to 3rd observations of the “activity” type. Dual polarization and high resolution SAR observations can be performed at any longitude at least once across the 6 cycles. Our strategy is to obtain the widest range of data types that enables us to put the highest resolution datasets into regional and global context. Similarly, understanding atmospheric processes requires a combination of global-scale mapping with targeted observations resolving smaller-scale processes.

How to cite: Widemann, T., Straume, A. G., Ocampo, A., Voirin, T., Carter, L., Hensley, S., Bruzzone, L., Helbert, J., Vandaele, A. C., Marcq, E., and Dumoulin, C.: EnVision: a Nominal Science Phase Spanning Six Venus Sidereal Days, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9889, https://doi.org/10.5194/egusphere-egu23-9889, 2023.

09:55–10:05

EGU23-4231

ECS

On-site presentation

Radar backscattering properties of lava flows on Earth and Venus

Allegra Murra, Marco Mastrogiuseppe, Giovanni Alberti, Letizia Gambacorta, and Roberto Seu

VERITAS mission, recently selected as part of NASA's Discovery program, will allow the investigation of the geological history of Venus, the mapping of its surface to study volcanic and tectonic processes and giving to scientists a unique opportunity to understand its geological activity. The spacecraft will carry the instrument VISAR, an interferometric X-band synthetic aperture radar (SAR) that will provide global 30 m medium resolution imagery of the surface and topographic maps with a spatial resolution of 250 m and a height accuracy of 5 m.

Looking at VERITAS mission, our work combines information obtained both from Digital Elevation Models (DEM) and SAR data acquired over time, in order to study terrestrial lava flows properties. We selected the Pacaya volcano in Guatemala and, supported by the corresponding geological maps, we identified and isolated some of its relevant lava flows. We used SENTINEL-1 SAR data acquired at C band and surface local incidence angle obtained from high resolution DEMs, to study lava flows backscattering coefficient behavior with respect to the incidence angle variation, along with EM formulation. Through fitting theoretical models, scattering laws provided us an estimate for lava flows dielectric properties and roughness. Our research shows a backscattering behavior which changes among different lava flows, in addition we find a seasonal behavior of the backscattering as function of the wet/dry periods of Pacaya. This behavior would not have been detectable without the initial lava flows segmentation, performed before the overall analysis. This selection indeed made possible the study of backscattering coefficient of regions with separately uniform and stationary surface parameters.

How to cite: Murra, A., Mastrogiuseppe, M., Alberti, G., Gambacorta, L., and Seu, R.: Radar backscattering properties of lava flows on Earth and Venus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4231, https://doi.org/10.5194/egusphere-egu23-4231, 2023.

10:05–10:15

EGU23-9086

ECS

On-site presentation

Estimating the seismicity of Venus by scaling Earth’s seismicity

Iris van Zelst, Julia Maia, Moritz Spühler, Ana-Catalina Plesa, Raphaël F. Garcia, Richard Ghail, Anna J. P. Gülcher, Anna Horleston, Taichi Kawamura, Sara Klaasen, Philippe Lognonné, Csilla Orgel, Mark Panning, Leah Sabbeth, and Krystyna Smolinksi

With the selection of multiple missions to Venus by NASA and ESA planned to launch in the coming decade, we will greatly improve our understanding of Venus as a planet. However, the selected missions cannot tell us anything about the seismicity on Venus, which is a crucial observable to constrain the tectonic activity and geodynamic regime of the planet, and its interior structure.

Here, we provide new, preliminary estimates of Venus’ global annual seismic budget and the expected frequency of venusquakes per year. We obtain this estimate by scaling the seismicity of the Earth recorded in the CMT catalogue. We test different potential scaling factors based on e.g., the difference in mass, radius, potential seismogenic volume, etc. We also sort the earthquakes into their respective tectonic settings, which allows us to exclude irrelevant tectonic settings present on Earth, but most likely not on Venus from our analysis. This enables us to present a range of potential seismic budgets and venusquake frequencies per tectonic setting on Venus.

This then provides a new estimate of the potential amount of seismicity on Venus. However, it is uncertain how valid this simple scaling approach is from Earth to Venus. Indeed, previous attempts of scaling the volcanism of Earth to Venus (Byrne & Krishnamoorthy, 2022; Van Zelst, 2022) resulted in numbers that aligned with independent estimates, but are still unconstrained and hard to verify until the announced missions fly. Therefore, in order to provide a more robust and holistic view of Venus’ anticipated seismicity, estimates using various different, independent methods should ideally be considered.

To provide exactly that, we set up the ISSI team ‘Seismicity on Venus: Prediction & Detection’. This is an interdisciplinary team of experts in seismology, geology, and geodynamics. Together we aim to assess the seismic activity on Venus from a theoretical and instrumental perspective. In addition to presenting our preliminary seismicity estimates from scaling Earth to Venus, we therefore also use this contribution to briefly introduce the team and its goals and present the preliminary findings from our first, week-long, dedicated in-person meeting aimed at further characterising Venus’ seismicity.

References

Byrne, Paul K., and Siddharth Krishnamoorthy. "Estimates on the frequency of volcanic eruptions on Venus." Journal of Geophysical Research: Planets 127.1 (2022): e2021JE007040.

van Zelst, Iris. "Comment on “Estimates on the Frequency of Volcanic Eruptions on Venus” by Byrne & Krishnamoorthy (2022)." Journal of Geophysical Research: Planets (2022): e2022JE007448.

How to cite: van Zelst, I., Maia, J., Spühler, M., Plesa, A.-C., Garcia, R. F., Ghail, R., Gülcher, A. J. P., Horleston, A., Kawamura, T., Klaasen, S., Lognonné, P., Orgel, C., Panning, M., Sabbeth, L., and Smolinksi, K.: Estimating the seismicity of Venus by scaling Earth’s seismicity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9086, https://doi.org/10.5194/egusphere-egu23-9086, 2023.

Posters on site: Thu, 27 Apr, 16:15–18:00 | Hall X4

The posters scheduled for on-site presentation are only visible in the poster hall in Vienna. If authors uploaded their presentation files, these files are linked from the abstracts below, but only on the day of the poster session.

Chairpersons: Gregor Golabek, Maxence Lefevre

X4.310

EGU23-8312

ECS

On-site presentation

Characterisation of the sensitivity to bias using a gain matrix formulation for the VeSUV/VenSpec-U instrument onboard ESA’s EnVision mission

Lucile Conan, Emmanuel Marcq, Benjamin Lustrement, Ann Carine Vandaele, and Jörn Helbert

Selected in 2021 as the fifth class M mission of ESA’s “Cosmic Vision” programme, EnVision is one the three next exploration mission of Venus, alongside NASA’s VERITAS and DAVINCI. EnVision will bring a holistic approach, by studying the surface and subsurface, different layers of the atmosphere, past and present volcanic activity, as well as coupling processes. To that end, the payload will include a synthetic aperture radar for surface mapping (VenSAR, NASA), a subsurface radar sounder and a radioscience experiment to monitor gravimetric and atmospheric properties.

Finally, the spectrometer suite VenSpec will investigate the surface and atmospheric compositions to analyse their relations with internal activity, using the thermal IR imager VenSpec-M and the high-resolution IR spectrometer VenSpec-H. The UV channel of the suite VenSpec-U, also called VeSUV, will focus on the atmosphere above the clouds, and aims more specifically at characterising the abundance and variability of sulphured gases such as SO and SO₂, and the unidentified UV absorber. To do so, VeSUV will operate in pushbroom mode in the 190-380 nm range with an improved spectral resolution between 205 and 235 nm, and will observe the backscattered sunlight on the dayside of Venus at a spatial sampling ranging from 3 to 24 km.

In order to characterise the instrument’s performances, the sensitivity to bias is analysed using a gain matrix formulation. A perturbation is locally introduced on a synthetic spectrum and a fitting algorithm involving the same radiative transfer model is used to retrieve the atmospheric parameters, for several values of perturbation. As they are small, the assumption of a linear relation between the perturbation and the resulting error on the estimated parameters is made, their ratio corresponding to the matrix element. This method allows a conversion between the measured signal and the atmospheric parameters independently from the bias spectrum (e.g. straylight, calibration error, contamination during mission), as it is computed separately for each wavelength.

How to cite: Conan, L., Marcq, E., Lustrement, B., Vandaele, A. C., and Helbert, J.: Characterisation of the sensitivity to bias using a gain matrix formulation for the VeSUV/VenSpec-U instrument onboard ESA’s EnVision mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8312, https://doi.org/10.5194/egusphere-egu23-8312, 2023.

X4.311

EGU23-14293

ECS

On-site presentation

3D Venusian Ionosphere model: Venus PCM

Antoine Martinez, Jean-Yves Chaufray, and Sébastien Lebonnois

For twenty years, a Planetary Climate Model (PCM) has been developed for the Venus atmosphere at “Institut Pierre-Simon Laplace” (IPSL), in collaboration between LMD and LATMOS, from the surface up to 250 km altitude (Lebonnois et al., 2010; 2016; Martinez et al., 2023). Recently, the Venus PCM (former IPSL Venus GCM) has been updated with the addition of photoionization and ion-neutral chemistry to simulate the Venusian ionosphere at altitudes where the photoequilibrium assumption is valid (below 180-200 km at dayside), based on the Martian ionospheric model described in González-Galindo et al., 2013.

By simulating the ionosphere and comparing the results with observations from spacecraft missions, we have been able to better understand the processes at work in the Venusian ionosphere. Here, we will focus on the main ion species (O⁺, CO₂⁺, O₂⁺, H⁺, CO⁺) and on the modeling of the Venusian ionosphere by Venus PCM through the comparison of the ionosphere composition with Pioneer Venus observation (PV-OIMS, PV-OETP). We also explore the effects of the addition of ambipolar diffusion on the vertical density profile of the main ions, based on the work of Chaufray et al., 2014 for the Martian ionosphere.

References:

Chaufray, J.-Y., Gonzalez-Galindo, F., Forget, F., Lopez-Valverde, M., Leblanc, F., Modolo, R., Hess, S., Yagi, M., Blelly, P.-L., and Witasse, O. (2014), Three-dimensional Martian ionosphere model: II. Effect of transport processes due to pressure gradients, J. Geophys. Res. Planets, 119, 1614– 1636, doi:10.1002/2013JE004551.
Lebonnois, S., Hourdin, F., Eymet, V., Crespin, A., Fournier, R., Forget, F., 2010. Superrotation of Venus’ atmosphere analyzed with a full general circulation model. J. Geophys. Res. (Planets) 115, 6006. https://doi.org/10.1029/2009JE003458.
Lebonnois, S., Sugimoto, N., Gilli, G., 2016. Wave analysis in the atmosphere of Venus below 100-km altitude, simulated by the LMD Venus GCM. Icarus 278, 38–51. https://doi.org/10.1016/j.icarus.2016.06.004.
González-Galindo, F., J.-Y. Chaufray, M. A. López-Valverde, G. Gilli, F. Forget, F. Leblanc, R. Modolo, S. Hess, and M. Yagi (2013), Three-dimensional Martian ionosphere model: I. The photochemical ionosphere below 180 km, J. Geophys. Res. Planets, 118, 2105–2123, doi:10.1002/jgre.20150.
Martinez, A., Lebonnois, S., Millour, E., Pierron, T., Moisan, E., Gilli, G., Lefèvre, F., Exploring the variability of the Venusian thermosphere with the IPSL Venus GCM, Icarus, 2023, 115272, 0019-1035, https://doi.org/10.1016/j.icarus.2022.115272

How to cite: Martinez, A., Chaufray, J.-Y., and Lebonnois, S.: 3D Venusian Ionosphere model: Venus PCM, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14293, https://doi.org/10.5194/egusphere-egu23-14293, 2023.

X4.312

EGU23-16340

On-site presentation

VERITAS gravity investigations: measuring Venus’ rotational state, moment of inertia, Love numbers, and atmospheric tides

Luciano Iess, Fabrizio de Marchi, Gael Cascioli, Erwan Mazarico, Joseph Renaud, Daniele Durante, Sander Goossens, and Suzanne Smrekar

The key scientific objective of the NASA/JPL Discovery-class mission VERITAS (Venus Emissivity, Radio science, INSAR, Topography And Spectroscopy) is understanding the links between the interior, surface, and atmospheric evolution.

After a 6-months cruise and a 11-months aerobraking phases, VERITAS is planned to operate during four Venus cycles (4x243 Earth days) in a near circular polar orbit (180x255km in altitude at 85.4 deg. inclination) providing gravity science data thanks to the 2-way X/Ka band Doppler link and VISAR (Venus Interferometric Synthetic Aperture Radar) instrument.

The radio science data and VISAR landmark features (tie points) will allow a precise determination of the rotational state of Venus: we show that the precession rate can be measured with an accuracy of 13’’/cy. From this result, the moment of inertia factor (MOIF) C/MR², can be estimated with a 0.3% accuracy (10x improvement). Moreover, the expected accuracy of the tidal Love number measurement is 0.2%: this will allow to resolve the ambiguity of the core state (solid/liquid) and to distinguish between different interior models (core radius, mantle viscosity) [1].

The atmosphere of Venus is subject to a time-dependent mass redistribution due to pressure and temperature variations induced by solar heating. This phenomenon is called “thermal tide" and it moves eastward along the Venus’ surface with a 117d period (i.e. about a Venus solar day).

Thermal tides can be detected as a time-variable perturbation to the Venus gravity field due to 1) the moving atmospheric masses (direct effect) and to 2) the planet’s response to the variations of the surface loading (indirect effect, parametrized through the load Love numbers).

We show that VERITAS radio science and VISAR data can also be used to measure the load Love numbers up to degree 4 with good accuracy (4% for degree 2). In particular, the degree 2 coefficient can provide independent, and complementary, information on the mantle viscosity and composition.

Moreover, a simultaneous measurement of the degree 2 tidal (k₂, h₂) and loading (k₂') Love numbers can be used to provide finer bounds on the mantle viscosity and possibly to constrain the mantle rheology.

[1] G. Cascioli, S. Hensley, F. De Marchi, D. Breuer, D. Durante, P. Racioppa, L. Iess, E. Mazarico and S. E. Smrekar (2021) Planet. Sci. J. 2 220

How to cite: Iess, L., de Marchi, F., Cascioli, G., Mazarico, E., Renaud, J., Durante, D., Goossens, S., and Smrekar, S.: VERITAS gravity investigations: measuring Venus’ rotational state, moment of inertia, Love numbers, and atmospheric tides, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16340, https://doi.org/10.5194/egusphere-egu23-16340, 2023.

X4.313

EGU23-3592

On-site presentation

Magma oceanography of the dense, ultrashort-period sub-Earth GJ 367b

Gregor Golabek, Tim Lichtenberg, and Paul Tackley

The dawn of high-resolution observations with the James Webb Space Telescope will enable spatially resolved observations of ultrashort-period rocky exoplanets. Some of these planets orbit so closely to their star that they lack an atmosphere [1], which gives direct access to their surfaces and opens a window to infer their geodynamics [2]. The physical parameters of the ultrashort-period sub-Earth GJ 367b have been observationally constrained to a planetary radius of about 0.72 to 0.75 Earth-radii and a mass between 0.48 and 0.55 Earth-masses, implying a density of 6200 to 8500 kg/m³[3, 4], which puts this planet in a Mercury-like interior regime with a thin mantle overlying a fractionally large core.
The dayside temperature ranges between 1500 to 1800 K, thus suggesting the presence of a permanent magma ocean or dayside magma pond on the surface, induced by stellar irradiation. The large uncertainty on the age of the stellar system, between 30 Myr [4] and about 8 Gyr [3], however, introduce severe uncertainties related to the compositional and thermal evolution of the planetary mantle. In this study we perform global 2D spherical annulus StagYY simulations [5, 6] of solid state mantle convection and surface melting with the goal to constrain the geometric and compositional properties of
the planet. Constraining the spatial dimensions of thermodynamic properties of partially molten, atmosphere-less planets like GJ 367b offers unique opportunities to constrain the compositional fractionation during magma ocean epochs and provides avenues to constrain the delivery and loss cycle of atmophile elements on strongly irradiated exoplanets.

References:
[1] L. Kreidberg and 18 co-authors. Absence of a thick atmosphere on the terrestrial exoplanet LHS 3844b. Nature, 573:87–90, August 2019.
[2] T. G. Meier, D. J. Bower, T. Lichtenberg, P. J. Tackley, and B.-O. Demory. Hemispheric Tectonics on LHS 3844b. Astrophys. J. Lett., 908:L48, February 2021.
[3] K.W.F. Lam and 78 co-authors. GJ 367b: A dense, ultrashort-period sub-earth planet transiting a nearby red dwarf star. Science, 374:1271–1275, 2021.
[4] W. Brandner, P. Calissendorff, N. Frankel, and F. Cantalloube. High-contrast, high-angular resolution view of the GJ367 exoplanet system. Mon. Notices Royal Astron. Soc., 513:661–669, June 2022.
[5] J. W. Hernlund and P. J. Tackley. Modeling mantle convection in the spherical annulus. Phys. Earth Planet. Int., 171:48–54, 2008.
[6] P. J. Tackley. Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid. Phys. Earth Planet. Int., 171:7–18, 2008.

How to cite: Golabek, G., Lichtenberg, T., and Tackley, P.: Magma oceanography of the dense, ultrashort-period sub-Earth GJ 367b, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3592, https://doi.org/10.5194/egusphere-egu23-3592, 2023.

X4.314

EGU23-7619

On-site presentation

First long-term study of the Venus' Cloud Discontinuity with uninterrupted observations

Javier Peralta, António Cidadão, Luigi Morrone, Clyde Foster, Mark Bullock, Eliot F. Young, Itziar Garate-Lopez, Agustín Sánchez-Lavega, Takeshi Horinouchi, Takeshi Imamura, Emmanuel Kardasis, Atsushi Yamazaki, and Shigeto Watanabe

The discontinuity/disruption is a recurrent atmospheric wave observed to propagate during decades at the deeper clouds of Venus (47-56 km above the surface), while its absence at the top of the clouds (~70 km) suggests that it might dissipate at the upper clouds and contribute to the puzzling atmospheric superrotation through wave-mean flow interaction.

Thanks to a campaign of ground-based observations performed in coordination with JAXA's Akatsuki mission since December 2021 until July 2022, we aimed to undertake the longest uninterrupted monitoring of the cloud discontinuity up to date to obtain a pioneering long-term characterization of its main properties and better constrain its recurrence and lifetime. The dayside upper, middle and nightside lower clouds were studied with images taken with suitable filters acquired by Akatsuki/UVI, amateur observers and NASA's IRTF/SpeX, respectively. Hundreds of images were inspected in search of discontinuity events and to measure properties like its dimensions, orientation or rotation period.

We succeeded in tracking the discontinuity at the middle clouds during 109 days without interruption. The discontinuity exhibited properties nearly identical to measurements in 2016 and 2020, with an orientation of 91º±8º, length of 4100±800, width of 500±100 km and a rotation period of 5.11±0.09 days. Ultraviolet images during 13-14 June 2022 suggest that we have witnessed for the first time a manifestation of the discontinuity at the top of the clouds during ~21 hours, facilitated by an altitude change in the critical level for this wave due to slower zonal winds.

How to cite: Peralta, J., Cidadão, A., Morrone, L., Foster, C., Bullock, M., Young, E. F., Garate-Lopez, I., Sánchez-Lavega, A., Horinouchi, T., Imamura, T., Kardasis, E., Yamazaki, A., and Watanabe, S.: First long-term study of the Venus' Cloud Discontinuity with uninterrupted observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7619, https://doi.org/10.5194/egusphere-egu23-7619, 2023.

X4.315

EGU23-8806

ECS

On-site presentation

The effects of water and intrusive magmatism on the evolution and dynamics of Venus

Marla Metternich, Paul Tackley, Diogo L. Lourenço, and Cedric Thieulot

Observations of Venus reveal tectonic expressions and recent volcanism, showing that the planet is still active. Tectonically deformed areas such as ridges or tesserae indicate surface mobility, however, no signs of active plate tectonics like on Earth have been found. The tectonics and volcanism of Venus and other terrestrial planets are defined by the active mantle convection mode. A key component of tectonics is rheology, which is affected by water as shown by numerous studies^[1]. However, the effects of water have been mostly ignored when studying Venus because its interior has been assumed to be dry. This notion is being challenged by indications of strong hydrodynamic escape to space that requires volcanic replenishment^[2]. Therefore, water should be present in Venus’ interior, even if its content is not known. Importantly, the potential effects of water in the dynamics and evolution of Venus are poorly understood. This calls for the consideration of complex dynamic thermo-magmatic models that track water and take into account intrusive and extrusive magmatism.

In this study, we use the code StagYY to perform state-of-the-art 2D numerical models in a spherical annulus geometry to assess the effects of water on the tectono-magmatic evolution of Venus^[3]. Particular attention will be given to changes in mantle viscosity, melt generation and crustal properties such as thickness and surface age. We explore model settings related to melting, intrusive magmatism, and water presence. Results show that intrusion depth influences the thermal evolution and related magmatism. Moreover, preliminary results show that the rate of water outgassing is directly related to changes in the thermo-magmatic evolution of Venus. Water outgassing rates have further implications on surface conditions and atmospheric compositions over time. In the future, coupling these improved mantle convection models to atmospheric evolution models may unveil new insights into the thermal and tectonic history that has shaped Venus into the planet we observe today.

How to cite: Metternich, M., Tackley, P., Lourenço, D. L., and Thieulot, C.: The effects of water and intrusive magmatism on the evolution and dynamics of Venus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8806, https://doi.org/10.5194/egusphere-egu23-8806, 2023.

X4.316

EGU23-12463

On-site presentation

Correlations between minor species in the Venus mesosphere from the SOIR/Venus Express spectrograph

Arnaud Mahieux, Aaron Yangambi Libote, Séverine Robert, Ariana Piccialli, Loïc Trompet, and Ann Carine Vandaele

The Solar Occultation in the Infrared (SOIR) instrument was an infrared echelle grating spectrometer on board the Venus Express spacecraft of ESA that sounded the Venus mesosphere using the solar occultation technique [1] from 2006 to 2014. Working at very high resolution, it performed 500+ solar occultations during which many species could be targeted, wherein CO [1], H₂O [2], HDO [3], HCl, HF [4], SO₂ [5], OCS, SO₃, H₂S, CS [6], etc., aside from CO₂ [7], the main atmosphere constituent. From the measured spectra, we could derive vertical profiles covering the 65 to 160 km region at maximum extent, each species being detected in specific altitude ranges, depending on the strength of their respective spectral absorption bands and concentrations. Temperature profiles were also derived considering the CO₂ vertical profiles and the hydrostatic equation [7]. During each solar occultation, SOIR could measure up to four spectral intervals corresponding to the diffraction orders of the echelle grating, allowing us to simultaneously target specific species in different altitude regions.

In this work, we are seeking correlations between the concentrations of the minor species, and between the minor species and the temperature profiles, that were measured simultaneously. We will summarize those possible concentration dependencies focusing on possible latitude or time trends. We will also report on possible temperature dependence on the concentrations of those species.

[1] Vandaele , A.C., et al. (2016), Icarus, 272.

[2] Chamberlain, S., et al. (2020), Icarus, 346.

[3] Fedorova, A., et al. (2008), J. Geophys. Res., 113.

[4] Mahieux, A., et al. (2015), Planet. Space Sci., 113-114.

[5] Mahieux, A., et al. (2015), Planet. Space Sci., 113-114.

[6] Mahieux, A., et al. (2023), Icarus, Under review.

[7] Mahieux, A., et al. (2015), Planet. Space Sci., 113-114.

How to cite: Mahieux, A., Yangambi Libote, A., Robert, S., Piccialli, A., Trompet, L., and Vandaele, A. C.: Correlations between minor species in the Venus mesosphere from the SOIR/Venus Express spectrograph, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12463, https://doi.org/10.5194/egusphere-egu23-12463, 2023.

X4.317

EGU23-15108

ECS

On-site presentation

Evolution of Venusian rifts: Insights from Numerical Modeling

Alessandro Regorda, Cedric Thieulot, Iris van Zelst, Zoltán Erdös, Julia Maia, and Susanne Buiter

Venus is a terrestrial planet with dimensions similar to the Earth and, although it is generally assumed that it does not host plate-tectonics, there are indications that Venus might have experienced, or still does experience, some form of tectonics. In fact, there are widespread observations of rifts on Venus called ‘chasma’ (plural ‘chasmata’), from radar-image interpretation of normal-fault-bounded graben structures (Harris & Bédard, 2015).

The rifts on Venus have been likened to continental rifts on Earth such as the East African (e.g., Basilevsky & McGill, 2007) and Atlantic rift system prior to ocean opening (Graff et al., 2018), even if they are commonly wider than their terrestrial equivalent (e.g., Foster & Nimmo, 1996). However, despite being a prominent feature on its surface, little is known about the mechanisms responsible for creating rifts on Venus beyond the assumption that they are extensional features (Magee & Head, 1995).

Since rifting on Earth in both continental and oceanic settings has been extensively studied through modeling, we adapted 2D thermo-mechanical numerical models of rifting on Earth to Venus in order to study how rifting structures observed on the Venusian surface could have been formed. More specifically, we investigated how rifting evolves under the high pressure and temperature conditions of the Venusian surface and the lithospheric structure proposed for Venus.

Our results show that a strong crustal rheology such as diabase is needed to localize strain and to develop a rift under the harsh surface conditions of Venus. The evolution of the rift formation is predominantly controlled by the crustal thickness, with a 25 km-thick diabase crust required to produce mantle upwelling and melting. Lastly, we compared the surface topography produced by our models with the topography profiles of different Venusian chasmata. We observed a good fit between models characterised by different crustal thicknesses and the Ganis and Devana Chasmata, suggesting that differences in rift features on Venus could be due to different crustal thicknesses.

References

Basilevsky, A. T., & McGill, G. E. (2007). Surface evolution of Venus. In Exploring Venus as a terrestrial planet (p. 23-43). American Geophysical Union. doi: 10.1029/176GM04

Foster, A., & Nimmo, F. (1996). Comparisons between the rift systems of East Africa, Earth and Beta Regio, Venus. Earth and Planetary Science Letters, 143 (1), 183-195. doi: 10.1016/0012-821X(96)00146-X

Graff, J., Ernst, R., & Samson, C. (2018). Evidence for triple-junction rifting focussed on local magmatic centres along Parga Chasma, Venus. Icarus, 306 , 122-138. doi: 10.1016/j.icarus.2018.02.010

Harris, L. B., & Bédard, J. H. (2015). Interactions between continent-like ‘drift’, rifting and mantle flow on Venus: gravity interpretations and Earth analogues. In: Volcanism and Tectonism Across the Inner Solar System. Geological Society of London. doi: 10.1144/SP401.9

Magee, K. P., & Head, J. W. (1995). The role of rifting in the generation of melt: Implications for the origin and evolution of the Lada Terra-Lavinia Planitia region of Venus. Journal of Geophysical Research: Planets, 100 (E1), 1527-1552. doi: 10.1029/94JE02334

How to cite: Regorda, A., Thieulot, C., van Zelst, I., Erdös, Z., Maia, J., and Buiter, S.: Evolution of Venusian rifts: Insights from Numerical Modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15108, https://doi.org/10.5194/egusphere-egu23-15108, 2023.

Posters virtual: Thu, 27 Apr, 16:15–18:00 | vHall ST/PS

The posters scheduled for virtual presentation are visible in Gather.Town. Attendees are asked to meet the authors during the scheduled attendance time for live video chats. If authors uploaded their presentation files, these files are also linked from the abstracts below, but only on the day of the poster session. The button to access Gather.Town appears just before the time block starts.

Chairperson: Cédric Gillmann

vSP.29

EGU23-9112

ECS

Virtual presentation

The effect of a climatic thermal runaway on the tectonic regime of Venus

Antonio Manjón-Cabeza Córdoba and Tobias Rolf

The origin of the observed differences between Earth and Venus remains a mystery. On Earth, surface deformation is focused at narrow plate margins resulting in plate tectonics (or a mobile-lid regime). On Venus, a global network of connected plate margins is absent, but the surface is young and has preserved evidence of at least regional crustal mobility. Therefore, the planet must be in a yet-to-be-defined regime distinct from plate tectonics, for example an episodic-lid regime. The array of Venus missions planned for the next decade provides us with an unprecedented chance to refine our knowledge of this tectonic regime, but to use the upcoming data, we need hypotheses to test and a physical framework in which to contextualize the data. To explain the discrepancy on the tectonic regime, a popular hypothesis is that Venus’ higher surface temperatures foster a stiffer lithosphere due enhanced grain growth. Thermally assisted grain growth is supposed to increase the lithospheric viscosity, since diffusion creep depends on grain size, and therefore subduction becomes less efficient. In a previous work [Manjón-Cabeza Córdoba, A., Rolf, T., and Arnould, M: Feasibility of the mobile-lid regime controlled by grain size evolution. EGU General Assembly 2022], we showed that high grain reduction can decrease the interval of yield stresses for which the episodic regime applies, but the results on grain growth were not too conclusive. Here, we present a new set of convection models in spherical annulus geometry using different surface temperatures to specifically address the differences between Earth and Venus. Our results suggest that the effect of the climate thermal runaway depends on the strength of the lithosphere. For yield stresses that yield Earth-like behaviors at lower surface temperatures, an increase in surface temperature does not result in the episodic regime, but rather a sluggish-dripping regime with relatively low plateness. We conclude that either Venus is not in an episodic-regime, or a different explanation must be put forward for the tectonic regime of Venus (e.g., lack of liquid water at the surface).

How to cite: Manjón-Cabeza Córdoba, A. and Rolf, T.: The effect of a climatic thermal runaway on the tectonic regime of Venus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9112, https://doi.org/10.5194/egusphere-egu23-9112, 2023.

Discussion

vSP.30

EGU23-9783

ECS

Virtual presentation

Constraining Venus’ convection regime from Baltis Vallis topography

Nathan McGregor, Francis Nimmo, Cedric Gillmann, Gregor Golabek, Alain Plattner, and Jack Conrad

Baltis Vallis (BV) is a 6,800-km long lava channel on Venus with a present-day uphill flow direction. The apparently uphill flow must be a consequence of deformation changing the topography after flow emplacement. The topography of BV thus retains a record of Venus’ convection history, as mantle convection causes time-dependent surface deformation. Venus’ mean surface age is likely in the range 300-500 Ma. The observed deformation of BV indicates that mantle convection was active over the past ∼400 Myr and provides constraints on the length scales and vertical amplitudes involved. We place constraints on Venus’ present-day internal structure and dynamics by comparing dynamical topography produced by numerical convection codes with the topography of BV.

We simulate time-dependent stagnant-lid mantle convection on Venus with a suite of coupled interior-surface evolution models for a range of assumed mantle properties. We compare the simulated topographies of model BV profiles to the actual topography of BV using two metrics. The first metric is the root-mean-square (RMS) height. A model is considered successful if its RMS height is similar to the RMS height of BV. The second metric is the “decorrelation time”. Given a particular model time τ, the correlation between model BV topography at a later time τ₂ and an earlier time τ₁ is calculated. When this correlation first falls to zero, the decorrelation time is then τ₂ – τ₁. The decorrelation time is inspired by the observation of BV’s present-day uphill flow and the inference that the present-day topography must be uncorrelated with the original topography when BV formed flowing downhill. We compare this decorrelation time to the surface age of Venus (∼400 Ma). A model is considered successful if the decorrelation time is less than the surface age of Venus.

From 14 mantle convection models, each initialized with different parameters, we identified two convection models that best fits our metrics. These models have a viscosity contrast ∆η of 10⁸and 10⁷, respectively, and both have a Rayleigh number Ra of 10⁸. Although Venus’ heat flux is highly uncertain, our model fluxes are consistent with some inferred heat fluxes. Models with higher total surface heat fluxes tend to yield lower decorrelation times; our favored models have some of the highest heat fluxes. We also find that models with a higher Ra tend to have a lower RMS height, in agreement with Guimond et al. (2022).

Our favored models have vigorous convection beneath a stagnant lid, and high surface heat fluxes. The viscosity of the lower mantle in these models is ∼10²⁰ Pa s, roughly two orders of magnitude lower than that of Earth’s. The majority of the surface heat flux is due to melt advection, indicating high rates of volcanic resurfacing. While current data are insufficient to test these predictions, once paired with forthcoming observations from several new Venus missions, our work will be able to bring Venus’ interior into sharper focus.

How to cite: McGregor, N., Nimmo, F., Gillmann, C., Golabek, G., Plattner, A., and Conrad, J.: Constraining Venus’ convection regime from Baltis Vallis topography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9783, https://doi.org/10.5194/egusphere-egu23-9783, 2023.