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.

The newly selected Venus missions EnVISION and VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) by ESA and NASA offer new opportunities for studying Venus but will also contribute to furthering our knowledge of Venus as an exoplanet. Hot, rocky planets are favoured exoplanet targets due to generally more frequent transits than cooler Earth-like objects. In our work presented here, we simulate Venus as an exoplanet using our coupled climate-photochemical model 1D-TERRA. In the simulations, we vary stellar, orbital, planetary and atmospheric parameters and study the effect of these parameters upon atmospheric composition, climate and spectral detectability with forthcoming missions. 

How to cite: Grenfell, J. L., Taysum, B., Wunderlich, F., Helbert, J., Arnold, G., Herbst, K., Sinnhuber, M., and Rauer, H.: Venus as an Exoplanet: Effect of varying stellar, orbital, planetary and atmospheric properties upon composition, habitability and detectability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17505, https://doi.org/10.5194/egusphere-egu23-17505, 2023.

Since the discovery of the Trappist-1 system a number of studies have explored which of these planets are within the canonical habitable zone with Trappist-1e the most likely Exo-Earth-like of the bunch [e.g. 1,2,3,4]. At the same time they also tend to indicate that Trappist-1d is likely an exo-Venus.  Using the ROCKE-3D General Circulation Model [5] we investigate whether Trappist-1d is likely to be an Exo-Venus, an Exo-Earth, or is a bare rock (Exo-Dead). We apply our previous approach to understand the climate history of Venus [6] to explore Trappist-1d.

[1] Wolf, E.T. (2017) ApJ 839:L1

[2] Turbet et al. (2018) A&A 612, A86

[3] Krissansen-Totton, J. and Fortney, J.J. (2022) PSJ 933:115

[4] Kane, S.R. et al. (2021) AJ 161:53 

[5] Way, M.J. et al. (2017) ApJS 213:12

[6] Way, M.J. and Del Genio, A.D. (2020) JGR Planets, 125, e2019JE006276

How to cite: Way, M.: Exo-Venus, Exo-Earth, Exo-Dead in the Trappist-1 System?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8270, https://doi.org/10.5194/egusphere-egu23-8270, 2023.

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.

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.

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.

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.

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.

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.