While fascinating in its own, Venus offers a unique window into the processes shaping other planets. In stark contrast to Earth, Venus is an inhospitable world, yet it serves as an important early-Earth analogue that may shed light on our planet’s history. Beyond the Solar System, Venus-like exoplanets are likely common, and many may already have been discovered orbiting other stars. More broadly, studying Venus can provide key insights into atmospheric evolution, interior dynamics, surface processes, and planetary habitability. This session aims to address the past, present, and future of Venus science and exploration, and what Venus can teach us about Earth as well as exo-Venus analogues. We invite contributions on a wide range of topics, including mission concepts, analyses of new and legacy observations, Earth-Venus comparisons, exoplanet observations, and the latest laboratory and modeling approaches to solving Venus' mysteries.
Gravity data from Magellan revealed Venus's excited spin state: the planet does not rotate around its axis of symmetry (principal axis of inertia), but instead, the spin axis is offset from this principal axis by 0.48° [1]. As a consequence, Venus's spin pole is expected to move across the planet's surface (polar motion), but this motion has not yet been detected, since currently available images of Venus's surface lack the resolution necessary to resolve it.
Anticipating the exploration of Venus by ESA's EnVision and NASA's VERITAS, we show in this study how a future measurement of polar motion, combined with a refined measurement of the precession (the spin axis's motion in inertial space), could improve our knowledge of Venus's interior structure by helping to reveal essential properties such as the state and size of its core.
We used a distribution of plausible interior density profiles[2] and GCM-simulated atmospheric dynamics[3] to derive Venus's expected polar motion. At a timescale of a few years, the spin pole is expected to drift across the surface at a rate of 21.7 (±2.6) meters per year[4]. This rate depends largely on the moment of inertia of Venus (for models with a fully solidified core) or that of the mantle only (for models with a liquid core).
This polar drift is the short-term expression of a slow wobble (called the Chandler wobble) of the spin axis around the principal axis, with a period of 13,000-19,000 years. We characterized the wobble's damping, caused by dissipation in Venus's solid tides (pole tide and solar tide). From a range of plausible tidal responses[5], the damping timescale ranges from 0.8 to 13 million years. Combined with the Chandler frequency acting here as a resonant frequency, we derived the transfer function characterizing how Venus's polar motion responds to an excitation, thus providing a basis for further investigations of long-term excitation processes that could explain the currently observed excited spin state.
[1] Konopliv et al. (1999), Icarus, doi:10.1006/icar.1999.6086
[2] Shah et al. (2022), The Astrophysical Journal, doi:10.3847/1538-4357/ac410d
[3] Lai et al. (2024), JGR Planets, doi:10.1029/2023je008253
[4] Phan and Rambaux (2025), Astronomy & Astrophysics, doi:10.1051/0004-6361/202553658
[5] Musseau et al. (2024), Icarus, doi:10.1016/j.icarus.2024.116245
How to cite: Phan, P.-L. and Rambaux, N.: Venus's Polar Drift as a Probe of its Interior Structure, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1048, https://doi.org/10.5194/egusphere-egu26-1048, 2026.
Most of the current knowledge regarding the interior of Venus is derived from Magellan gravity and topography datasets collected three decades ago. While this mission provided the first high-resolution global gravity field, the computational limitations of the 1990s necessitated compromises that impacted the accuracy of the gravity solutions. We report on a reanalysis of the Magellan Doppler tracking data, leveraging modern computational capabilities to improve the Venus gravity field, orientation, and rotational dynamics.
Most significantly, modern computing power allows us to achieve a spherical harmonic degree-and-order 180 solution via a single inversion, eliminating the need for the multi-step approach that previously affected the solution. We observe a reduction in high-frequency noise (ringing) in the solution, leading to more coherent spatial structures in the solution which is beneficial for localized analyses of near-subsurface features. The single-step solution, additionally, removes the discontinuities in the uncertainty estimates of the gravity field coefficients, enabling more coherent and robust uncertainty quantification on derived products.
Using this new field, we investigate the elastic properties of the lithosphere taking advantage of improved polar resolution and robust uncertainty quantification. Additionally, we assess the sensitivity of the dataset to length-of-day variations which were previously not explicitly solved-for, but whose magnitudes as observed from Earth would have had a measurable influence on the probe.
How to cite: Cascioli, G., Goossens, S., and Mazarico, E.: A new look at Venus gravity and rotation from a reanalysis of Magellan Doppler tracking, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19152, https://doi.org/10.5194/egusphere-egu26-19152, 2026.
Cryptic degassing is the release of volatiles from a magmatic intrusion independent of extrusive volcanic activity. On Earth, rheological transitions within the crust can throttle magma ascent, leading to the cryptic release of volatiles and the decoupling of the CO2 flux from the rate of extrusive volcanism (Black et al., 2024). This process is particularly significant for large igneous province (LIP) events, where high magma influx rates may sustain CO2 release and lead to greenhouse warming for > 1 Myr after eruption ceases (Black et al., 2024).
On Venus, higher surface temperatures and lower eruption efficiencies (Lourenço et al., 2020) suggest that this rheologic transition can occur for even lower magmatic influx rates than on Earth. Venus’s surface exhibits numerous volcanic features associated with intrusive magmatism, including coronae and steep-sided domes, where shallow intrusions may continuously outgas volatiles to the atmosphere. However, the role of cryptic degassing on Venus and its potential for influencing the atmosphere has not been previously explored.
We will present a model of rheologic throttling of magmas within Venus’s crust and assess the potential for cryptic degassing of CO2 and other volatiles. Our results will have implications for understanding how outgassing has contributed to Venus’s atmosphere and the interpretation of noble gas signatures such as argon and helium isotopes (Namiki & Solomon, 1998).
References
Black, B. A., Karlstrom, L., Mills, B. J. W., Mather, T. A., Rudolph, M. L., Longman, J., & Merdith, A. (2024). Cryptic degassing and protracted greenhouse climates after flood basalt events. Nature Geoscience, 17(11), 1162–1168. https://doi.org/10.1038/s41561-024-01574-3
Lourenço, D. L., Rozel, A. B., Ballmer, M. D., & Tackley, P. J. (2020). Plutonic-Squishy Lid: A New Global Tectonic Regime Generated by Intrusive Magmatism on Earth-Like Planets. Geochemistry, Geophysics, Geosystems, 21(4), e2019GC008756. https://doi.org/10.1029/2019GC008756
Namiki, N., & Solomon, S. C. (1998). Volcanic degassing of argon and helium and the history of crustal production on Venus. Journal of Geophysical Research: Planets, 103(E2), 3655–3677. https://doi.org/10.1029/97JE03032
How to cite: Trussell, A., O'Rourke, J., Black, B., and Mukhopadhyay, S.: Modeling Cryptic Degassing From Intrusive Magmatism on Venus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15675, https://doi.org/10.5194/egusphere-egu26-15675, 2026.
Venus' dense atmosphere prevents optical surface observation, making radar the only geological analysis method. Without ground truth on Venus, terrestrial analogues provide the only means to validate radar interpretation techniques.
Venus' surface is dominated by volcanic terrain [2] and understanding what changes the new missions may ‘see’ requires analysis of radar signatures at barren, volcanic terrains on Earth. The Askja volcanic area provides an ideal natural laboratory [1] basaltic composition, diverse flows (historical to >6100 years), minimal vegetation cover, and accessibility for validation [5,6]. Key questions include: (1) Can we differentiate volcanic surfaces using radar backscatter? (2) Can we date flows based on radar characteristics? (3) Can we identify flow emplacement and modification processes?
Methodology and Data Acquisition
This research analyses ten lava flow units from the 1961 Vikrahraun eruption to >6100-year-old flows using multi-scale radar data: high-resolution F-SAR (2m), which was collected by the DLR for the VERITAS mission in Aug 2023, at X-band (3.1 cm), S-band (9.4 cm), and L-band (23.8 cm) with full polarimetry [3,4], and Sentinel-1 C-band (30m) [7]. Flow units are mapped using radar imagery, stratigraphic relationships, and field data.
Key Findings
Backscatter curves as a function of incidence angle for individual lava flows show a strong decrease in backscatter with increasing incidence angle (10-15 dB decrease from 10° to 80°), consistent with typical radar scattering behaviour from rough surfaces.
S-band HH analysis reveals systematic changes in backscatter with increasing age: youngest flows (1961) show highest mean backscatter (-7.9 dB), and the oldest flows (>6100 years) show lowest (-16.8 dB); ca 10 dB backscatter decrease over 6000 years. This marked decrease with flow age is caused by post-emplacement weathering, smoothing and mantling.
The age-backscatter correlations across X, C, S, and L bands reflect systematic changes in lava flow surface characteristics over time. Young flows with original emplacement textures produce high backscatter, while older flows develop smoother surfaces through weathering, resulting in lower backscatter. Surface roughness and backscatter decrease with age, enabling relative dating using multi-parameter radar data.
Wavelength comparison reveals progressive decrease in contrast and dynamic range from L-band through S-band to X-band, with enhanced discrimination at longer wavelengths. L-band with cross-polarized (HV) channel provides the highest dynamic range, optimal for flow differentiation.
Polarimetric analysis successfully differentiates surface scattering mechanisms and flow morphologies. High HH and HH/HV ratios indicate smooth pāhoehoe flows and mantled surfaces, while high HV backscatter indicates rough a'ā flows and steep terrain slopes. Decomposition analysis further enhances morphological discrimination capabilities.
Implications and Conclusions
This study demonstrates that multi-parameter radar data enables discrimination of flow morphologies and ages through wavelength-scale roughness analysis. Age-backscatter correlations provide quantitative dating frameworks, while polarimetric analysis enables morphological and textural discrimination. These findings provide ground truth for interpreting radar signatures of volcanic terrains on Venus, supporting upcoming VERITAS and EnVision missions.
References: [1] Adeli et al., 2023; [2] Brossier et al., 2020; [3] Horn et al., 2017; [4] Keller et al., 2024; [5] Mason et al., 2024; [6] Raguso et al., 2025; [7] Torres et al., 2012.
How to cite: Davidova, N., Moreira, A., Ghail, R., Gallardo i Peres, G., and Mason, P.: Multi-wavelength Polarimetric Radar Analysis of Lava Flows at Askja, Iceland: A Venus Analogue Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8132, https://doi.org/10.5194/egusphere-egu26-8132, 2026.
The detection of surface changes on Venus is fundamental to understanding its ongoing volcanic activity and geological evolution. The upcoming EnVision and VERITAS missions, equipped with advanced SAR systems (VenSAR and VISAR), will image Venus more than 40 years after Magellan. This presents an unprecedented opportunity to detect active surface processes by comparing future high-resolution images with Magellan data. However, reliable inter-mission SAR change detection faces significant challenges due to differences in spatial resolution, wavelength, polarization, and viewing geometry.
A critical issue is the difference in spatial resolution between SAR images, which invalidates classical statistical models that assume identical equivalent number of looks (ENL) and leads to unreliable change detection results. In this work, we propose a novel change detection method by integrating the generalized beta prime (GB2) distribution into the Kittler-Illingworth (KI) minimum error thresholding framework, termed GB2KI. A modified criterion function is derived for optimal threshold selection. To address the class imbalance problem, we introduce an entropy-weighted maximum likelihood estimation method for robust parameter estimation. Additionally, a multiscale post-processing technique is developed to suppress noise patches and reduce false alarms in the final change detection map.
The proposed method is validated using both simulated and real SAR datasets. Simulations are conducted on Magellan Cycle 1 and Cycle 3 images by adding artificial changes with varying intensities, extents, and types to test the algorithm’s robustness. Further validation is performed using Earth observation data from the Holuhraun lava flow-field in Iceland. Two distinct datasets are analyzed, including Sentinel-1 images from different imaging modes (1-year interval) and Radarsat-1/Sentinel-1 images (15-year interval). Results demonstrate that our method achieves higher overall accuracy with significantly reduced false alarm rates compared to existing approaches.
This work provides a robust framework for inter-mission SAR change detection applicable to future Venus missions, enabling reliable identification of volcanic activity and other surface processes.
How to cite: Gao, Y., Gallardo i Peres, G., Awasthi, S., Ghail, R., and Mason, P. J.: Detecting Surface Changes on Venus: A GB2KI Thresholding Approach for Inter-mission SAR Images, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21046, https://doi.org/10.5194/egusphere-egu26-21046, 2026.
Upcoming Venus missions will feature a range of radar and multispectral instruments to image and map the surface, which is inaccessible to optical sensors due to the thick Venus atmosphere. Of these missions, the X-band VISAR synthetic aperture radar (SAR) instrument on the VERITAS spacecraft will be used to create a global, high-resolution Digital Elevation Map (DEM) with a posting of less than 250 m and a vertical accuracy of better than 10 m. How can the VERITAS mission achieve such performance if the Venus atmosphere, with its high pressure and temperature, introduces consequent apparent range delays to the radar measurements of several hundreds of meters, and only limited in-situ measurements of the deep atmosphere from earlier missions are available?
Our answer to this problem is a Venus atmospheric model that combines available data on the atmospheric constituents with wave propagation physics of X-band signals under such conditions. Based on previous work by Duan et al. (2010), we have built a Python-based toolkit to compute the signal delay and attenuation for given atmospheric composition, refraction and absorption models, and instrument viewing geometries. We investigate using simulations how the mismodeling of the atmospheric parameters can lead to an inaccurate georegistration of the SAR imagery (based on work by Gisinger et al., 2015, 2017), which in turn would significantly degrade the quality of the derived DEMs.
We perform our investigations on a global scale and over the entire VERITAS science phase of approx. 3 years, and compare our results with analytical expressions. We also show that the expected variability of temperature, pressure, and ionospheric density with latitude and solar time only plays a negligible role in the performance degradation. Finally, we aim to share our atmospheric modeling code with the community, such that we may incorporate improvements to the model, and to help sensitize future users of radar (or multispectral) data from the VERITAS, EnVision, or other missions, to the importance of atmospheric corrections.
How to cite: Köhne, T., Gisinger, C., Duan, X., Hensley, S., and Peral, E.: The Importance of Atmospheric Modeling for Next-Generation Venus Mapping Missions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9253, https://doi.org/10.5194/egusphere-egu26-9253, 2026.
On Earth, infrasound can travel vast distances through waveguides formed by changes in the sound speed and wind structure. While propagating, these waves retain valuable information about the source and the propagation medium, making infrasound suitable to monitor explosive events, including from volcanic sources.
In contrast to Earth, extreme conditions on the surface rule out conventional ground-based sensors for infrasound recording on Venus. A more practical alternative is to use atmospheric balloons equipped with acoustic sensors. Such balloons can be deployed in the middle atmosphere, where conditions allow for longer mission durations.
However, to explore the existence of prospective explosive volcanism on Venus, such deployments will only be valuable if there exist waveguides to duct the infrasound from these sources to the balloons. But do such waveguides exist? To address this question, we performed an extensive set of wave-propagation simulations to map the global morphology of infrasound ducting on Venus, with the Venus Climate Database as the atmospheric model. We considered volcanic sources and assessed how effectively infrasound is guided to balloon altitudes.
We find persistent waveguides in both zonal and meridional directions, driven by the strong superrotational and subsolar-to-antisolar winds in the middle and upper atmosphere. We find that these waveguides enable ground-to-balloon propagation, indicating that the conditions are suitable for detecting long-range infrasound. Our discovery strengthens the case for future balloon-based missions to Venus.
How to cite: Gullbekk, S. B., Brissaud, Q., Froment, M., and Näsholm, S. P.: Infrasound waveguides on Venus enable exploration of explosive volcanism using balloons, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-804, https://doi.org/10.5194/egusphere-egu26-804, 2026.
EnVision is ESA’s next mission to Venus in partnership with NASA, where NASA provides the VenSAR instrument and mission support to critical phases. ASI, DLR, BelSPO, and CNES lead the procurements of the SRS, VenSpec-M, VenSpec-H and VenSpec-U instruments and the Radio Science Experiment (RSE), respectively. The mission was adopted in January 2024, and Thales Alenia Space (TAS) was awarded the contract to build the spacecraft in January 2025. The launch is scheduled for 2031, and the start of the science operations at Venus is expected in mid-2034, 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 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 perform novel sounding of the upper crust in search of material boundaries. The three spectrometers, VenSpec-U, VenSpec-H and VenSpec-M, operating in the UV and Near-IR, will map trace gases, search for volcanic gas plumes above and below the clouds, and map surface emissivity and composition. The Radio Science Experiment (RSE) 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 cloud layer in radio occultation. All instruments have Venus heritage and robust margins relative to the requirements, allowing the mission to meet its scientific objectives. The EnVision science teams will adopt an open data policy, with public release of the scientific data after validation and verification. Public calibrated data availability is <6 months after data downlink.
The Envision Science Working Team (SWT) have recently compiled a list of prioritized Venus targets used to create the Regions of Interest (ROIs) to be observed by the mission. The missions scientific objectives, instrumentation, and status will be presented together with a first version of the ROIs, on-going scientific and technical maturity activities, and the next steps in the mission preparation.
How to cite: Straume-Lindner, A. G. and Pacros, A. and the Envision Science Working Team (SWT): Objectives and status of the Envision Venus mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4511, https://doi.org/10.5194/egusphere-egu26-4511, 2026.
Geochemical models of atmospheric formation and evolution predict that Venus-like atmospheres, dominated by CO2 and thicker than a few bars pressure, are among the most common secondary volcanic atmospheres to be produced on rocky exoplanets. Meanwhile, astronomical detection biases toward short period planets ensure than rocky exoplanets are commonly found orbiting their host stars within the hypothetical 'Venus Zone' - a zone bounded by the cosmic shoreline at its inner edge and the CO2-condensation line at its outer edge. In this talk, I will present the chemical diversity of Venus-like atmospheres from both of these perspectives: the diversity of Venus-like atmospheres predicted via geochemistry, and the diversity of photochemical disequilibrium processes reshaping these atmospheres across the range of planet-hosting stars that we observe via astronomy.
How to cite: Jordan, S., Rungger, G., Bower, D., and Sossi, P.: The Diversity of Venus-like Atmospheres on Exoplanets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12411, https://doi.org/10.5194/egusphere-egu26-12411, 2026.
Next-generation instruments will provide the first opportunity to characterize temperate rocky exoplanets orbiting Sun-like stars. Because the surface conditions of rocky exoplanets are much more difficult to constrain than their bulk parameters, these observations will be very challenging. Furthermore, there is a broad range of possible climates for such exoplanets due to difficult-to-constrain parameters like atmosphere mass and composition, surface composition, water abundance, rotation, and obliquity. For example, Venus and Earth have similar bulk parameters but very different climate regimes. Therefore, characterizing a temperate rocky exoplanet means being able to distinguish between Venus-like and Earth-like climates from the planet’s spectrum. I will compare synthetic reflected light spectra of Venus constructed from climate simulations and empirical data. I will discuss the sensitivity of these spectra to model, instrument, and observation parameters, and the conditions required to identify an exoplanet as Venus-like or Earth-like.
How to cite: Macdonald, E., Kislyakova, K., Van Looveren, G., Müller, L., and Raorane, A.: Venus as an analogue for exoplanet observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20571, https://doi.org/10.5194/egusphere-egu26-20571, 2026.
The extreme conditions in Venus’s lower atmosphere make robust calibration of in situ observations challenging. Consequently, measurements from past entry probes provided mixed evidence regarding the existence of a near-surface particulate layer (NSPL). Although the Venera 11 (1978) and Venera 13 and 14 (1982) landers performed in situ spectrophotometric observations during descent, the original datasets were later lost. However, a subset has been reconstructed by digitising graphical outputs produced during the missions’ initial data-processing phase [1]. Following careful analysis to identify and mitigate errors and other artefacts, the reconstructed dataset retains the reliable downward-looking spectra acquired by the three landers from ~62 km altitude to the surface.
Previous retrievals from the reconstructed Venera 13 indicated an NSPL centred at ~3.5–5 km, with particulate optical properties consistent with a basaltic composition [2]. Following the methodology of [2], we use NEMESIS, a radiative transfer and retrieval code [3], to perform near-surface retrievals from the reconstructed Venera 11 and Venera 14 datasets. The results from Venera 11, 13, and 14 retrievals are compared with reported detections and non-detections from other instruments on earlier in situ missions, to explore potential formation pathways for the NSPL in light of the combined observational record.
References:
[1] Ignatiev, N. I., Moroz, V. I., Moshkin, B. E., Ekonomov, A. P., Gnedykh, V. I., Grigor’ev, A. V., and Khatuntsev, I. V. Cosmic Research 35(1), 1–14 (1997).
[2] Kulkarni, S. V., Irwin, P. G. J., Wilson, C. F., & Ignatiev, N. I. Journal of Geophysical Research: Planets, 130, e2024JE008728, (2025).
[3] Irwin, P. G., Teanby, N. A., de Kok, R., Fletcher, L. N., Howett, C. J., Tsang, C. C., Wilson, C. F., Calcutt, S. B., Nixon, C. A., and Parrish, P. D. Journal of Quantitative Spectroscopy and Radiative Transfer 109(6), 1136–1150 (2008).
How to cite: Kulkarni, S., Irwin, P., Wilson, C., and Ignatie, N.: Comparative analysis of Venera 11, 13, and 14 spectrophotometric data: implications for the near-surface particulate layer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22501, https://doi.org/10.5194/egusphere-egu26-22501, 2026.
We present the first N2 profile for Venus’ deep lower atmosphere (<15 km) and a constrained isotopic composition for cloud N2 [1]. This work directly addresses unresolved questions for Venus using legacy observations. Prior to this work, there were no reported measurements for N2 abundances at <15 km and the isotopic composition remained unconstrained [2]. The N2 parameters are critical to understanding the evolution and thermal properties of the atmosphere [3-7]. Our N2 results were obtained by re-analysis of data acquired in 1978 by the Pioneer Venus Large Probe Neutral Mass Spectrometer (LNMS) [8]. The archived mass spectra from 64.2 to 0.2 km were treated using the analytical procedures specifically developed for the LNMS [9-11]. Judicious peak fitting permitted disambiguation of (A) N2+ and CO+ at 28 u and (B) 14N15N+, 13CO+, and C2H5+ at 29 u. Quality controls included comparing the (A) LNMS CO+/CO2+ ratios to the NIST database and literature and (B) fitted counts for CO+ to the expected counts of CO+ calculated from C18O+ and 13CO+ using the LNMS 16O/18O and 12C/13C ratios (obtained from CO2). Our results show that N2 is uniformly mixed across the deep lower atmosphere between ~0.2 and 15 km (2.49 ± 0.10 v%). In contrast, N2 is non-uniformly mixed across the sub-cloud atmosphere and clouds (~15–59 km), where N2 abundances increase by ~ 2-fold between ~15 km (2.45 ± 0.32 v%) and ~59-51 km (5.21 ± 0.18 v%). Using the cloud data, we also obtained a constrained 15N/14N ratio (2.93×10-3 ± 0.13×10-3) and δ15N value (-204 ± 35‰). Thus, the LNMS results [1] suggest that (A) the atmosphere is unstable at <15 km, (B) N2 is not well-mixed >15 km, and (C) the cloud δ15N falls between Earth and the solar wind [12, 13]. Comparisons of the N2 abundances and isotopic compositions for nitrogen, carbon, and oxygen to other Venus measurements will be discussed.
References:
[1] Mogul R. et al. (2025) GRL 52.
[2] Hoffman J. H. et al. (1979) Science 205.
[3] Moroz V. et al. (1997) Adv. Space Res. 19.
[4] Avice G. et al. (2022) Space Sci. Rev. 218.
[5] Vandaele A. C. et al. (2016) Adv. Space Res. 57.
[6] Morellina S. et al. (2020) Icarus 350.
[7] Limaye S. S. et al. (2017) Icarus 294.
[8] Hoffman J. H. et al. (1980) JGR Space Sci. 85.
[9] Mogul R. et al. (2023) Icarus 392.
[10] Mogul R. et al. (2023) MethodsX 11.
[11] Mogul R. et al. (2025) JGR Planets 130.
[12] Marty B. et al. (2011) Science 332.
[13] Füri E. et al. (2015) Nature Geosci. 8.
How to cite: Mogul, R., Limaye, S., and Way, M.: First N2 Profile for Venus’ Deep Lower Atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2276, https://doi.org/10.5194/egusphere-egu26-2276, 2026.
The existing measurements of the lower atmosphere provided little information about the spatiotemporal distributions and variations of temperature and sulfur compounds profiles. An improved understanding of temperature and sulfur compounds in the Venusian lower atmosphere is required to investigate the mechanisms which maintain the atmospheric super-rotation, the surface-atmosphere interactions, and the origin and evolution of the Venusian atmosphere and climate. In the present study, we demonstrate that a passive microwave sounder placed in low Venus orbit could provide the required high-precision, high-resolution and vertically-resolved observations of temperature, sulfur dioxide (SO2) and gaseous sulfuric acid (H2SO4(g)). By model simulations, the frequency channel selection and performance simulation for the sounder are completed. The simulation results show that temperature can be measured from the Venus surface to ~61 km with a precision of 1-3.5 K and a vertical resolution of 6-15 km. Precision of 10-35% is expected for SO2 in the ~12-64 km altitude range and with a vertical resolution of 8-19 km. H2SO4(g) can be measured in the altitude range ~36-54 km with a precision of 10-30% and a vertical resolution of 6-13 km.
How to cite: Zhang, Z. and Dong, X.: Simulation Study on Passive Microwave Remote Sensing of the Venusian Lower Atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3313, https://doi.org/10.5194/egusphere-egu26-3313, 2026.
Observations of Venus' night-side disc in the transparency windows of the CO2 atmosphere (spectacular at 1.74 and 2.3 μm near-infrared wavelengths) allow us to study various morphology and dynamics in the middle to lower cloud layers of Venus. For such studies, Akatsuki, Japan's Venus Orbiter was equipped with the IR2 2-μm camera (Satoh, et al., 2017). A sharp and large discontinuity of cloud opacities was imaged in the night-side of Venus by IR2 (Peralta et al., 2020). This feature was best observed by IR2 in 4 occasions, 9 August, 18 August, 27August, and 5 September in 2016. Since the faint night-side emission features receive contamination from intense light from the day crescent, we have developed image restoration techniques which successfully recovered the "true" contrast between this enormous cloud cover (ECC) and the adjacent background cloud (BC) regions. From such restored images, the radiance from pixels in BC and ECC from each image were extracted. By conducting a series of radiative transfer computations, we compare the observed brightness changes (from BC to ECC) in two filters of IR2 (1.735 and 2.26 μm). It is found that an increase of Mode 3 particles near the cloud base (∼48 km altitude) can reproduce the decreasing radiance from BC to ECC for 9 August and 27 August data. On the other hand, the 18 August data require both the increase of Mode 3 particles AND decrease of smaller particles at the same time to explain the observation. Finally, the 5 September data do not need the increase of Mode 3 particles but slight increase of smaller particles explains the data. Although these are not a unique explanation of how the cloud structure changes from BC to ECC region, this seems to be a favorable characterization of its lifecycle. Implications to the possible mechanism will also be discussed.
How to cite: Satoh, T., Sato, T., Imamura, T., and Kuroda, T.: Radiative Transfer Analysis of Gigantic Discontinuity in Venus Cloud Layer and ItsLifecycle, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15629, https://doi.org/10.5194/egusphere-egu26-15629, 2026.
In the context of future Venusian missions, it is crucial to improve our understanding of Venus upper atmosphere through 3D modelling, notably for spacecraft orbit computation. This study compares three General Circulation Models (GCMs) of the Venusian atmosphere up to the exosphere: The Venus Planetary Climate Model (Venus PCM; Lebonnois et al., 2010; Martinez et al. 2024), the Venus Thermospheric Global Model (VTGCM; Brecht et al., 2021) and the Tohoku University GCM (TUGCM; Hoshino et al., 2013), focusing on their nominal simulations (e.g. composition, thermal & dynamic structures and heating/cooling rates).
Similarities and discrepancies among them are deeply discussed in Martinez et al. (2026), together with data-models comparison. Despite similar large-scale features, significant differences are identified among the models (see Figure 1). All three GCMs reproduce a warm dayside thermosphere and a cold nightside cryosphere, driven by a balance between solar extreme ultraviolet heating, near-infrared heating, radiative cooling by CO2 at 15-μm, thermal conduction, and dynamical effects. However, the magnitude and vertical distribution of temperatures differ substantially, particularly in the upper thermosphere. Comparisons with Pioneer Venus, Venus Express, and Magellan observations reveal that the nominal simulations systematically overestimate daytime exospheric temperatures. This bias is consistently linked to an underestimation of atomic oxygen densities, which reduces radiative cooling efficiency at high altitudes.
Figure 1: Diurnal structure of the temperatures for equatorial latitude (30°S–30°N) for Venus PCM, VTGCM and TUGCM at high solar activity (leftside) and at low solar activity (rightside). The approximate altitude of each model for each solar period is marked in white for pressure levels of 10, 1, 0.1, 10−2, 10−3, 10−4 and 10−5 Pa.
Based on the findings of the article, a list of recommendations is proposed aiming at improving the modelling of Venus’ upper atmosphere, among them: 1. Standardize the EUV-UV solar spectrum input. 2. Update the near-infrared heating scheme with Venus Express-Era data. 3. Reassess Radiative cooling schemes. 4. Investigate the underestimated atomic Oxygen abundance.
References:
Brecht, A. S., Bougher, S. W., Shields, D., Liu, H.‐L., & Lee, C. (2021). Planetary‐Scale Wave Impacts on the Venusian Upper Mesosphere and Lower Thermosphere. In Journal of Geophysical Research: Planets (Vol. 126, Issue 1). American Geophysical Union (AGU). https://doi.org/10.1029/2020je006587
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.
Martinez, A., Chaufray, J.-Y., Lebonnois, S., Gonzàlez-Galindo, F., Lefèvre, F., & Gilli, G. (2024). Three-dimensional Venusian ionosphere model. In Icarus (Vol. 415, p. 116035). Elsevier BV. https://doi.org/10.1016/j.icarus.2024.116035
Martinez A., Karyu H., Brecht A., Gilli G., Lebonnois S., Kuroda T., Stolzenbach A., Gonzalez-Galindo F., Bougher S. and Fujiwara H. (2026). Comparison of General Circulation Models of Venus upper atmosphere. Icarus, 116901, 0019-1035, https://doi.org/10.1016/j.icarus.2025.116901
Hoshino, N., Fujiwara, H., Takagi, M., Kasaba, Y., (2013), Effects of gravity waves on the day-night difference of the general circulation in the Venusian lower thermosphere, J. Geophys. Res. (Planets), 118, pp. 2004-2015, doi:10.1002/jgre.20154
How to cite: Martinez, A., Karyu, H., Brecht, A., Gilli, G., Lebonnois, S., Kuroda, T., Stolzenbach, A., Gonzalez-Galindo, F., Bougher, S., Fujiwara, H., and M. Lara, L.: Comparison of General Circulation Models of the Venus upper atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9887, https://doi.org/10.5194/egusphere-egu26-9887, 2026.
Thermal tides dominate Venus’ middle atmosphere, exhibiting a semidiurnal signature at low latitudes and a diurnal one at mid-to-high latitudes. However, their full three-dimensional structure and dynamical influence remain only partially characterized. Past studies have primarily relied on cloud-level temperatures from radio occultation and horizontal winds from cloud tracking. Recent analyses of Akatsuki radio-occultation profiles at low latitudes revealed both upward and downward propagation of the semidiurnal component, pointing to an excitation region within the cloud deck (50–65 km). It remains unclear whether this mechanism extends to higher latitudes or how it couples to the broader three-dimensional flow.
Here, we present a new analysis of over 1,000 radio-occultation soundings from Akatsuki (2016–2024) and Venus Express (2006–2014), spanning 90°S to 90°N and altitudes from 40 to 95 km. This combined dataset enables a detailed reconstruction of Venus' thermal structure across the solar day cycle, capturing the transition from semidiurnal to diurnal tides, their evolving vertical propagation, and how the altitude of peak tidal signatures varies with latitude. We also derive the zonal flow field via cyclostrophic balance, both in the time-mean state and over the solar day. Compared with cloud-level measurements, our results provide new insight into the tidal modulation of zonal winds and associated energy transport.
How to cite: Navon, R., Galanti, E., Imamura, T., Tellmann, S., Ando, H., and Kaspi, Y.: The latitudinal and vertical structure of Venus’ thermal tides as inferred from radio occultations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16911, https://doi.org/10.5194/egusphere-egu26-16911, 2026.
Venus at ultraviolet (UV) wavelengths exhibits distinct light and dark markings (Rossow et al., JAS ,1980). The discovery of sulfur dioxide (SO2) using a ground-based high resolution spectrometer explained Venus’ albedo at wavelengths < 320 nm but not these dark markings at 320-500 nm (Esposito et al. GRL, 1979; Pollack et al., JGR , 1980; Pérez-Hoyos et al., JGR , 2018). So at least one other absorber must be important at these wavelengths. Radiative balance simulations suggest this unidentifed absorber is responsible for absorbing about half of the solar energy absorbed by Venus’ atmosphere (Titov et al., Space Sci Rev, 2018). Polysulfur species (Sx) have been suggested but a sufficiently fast pathway to form these polysulfur species hasn’t been identified (Mills et al., Planet Space Sci, 2007). One pathway that has received minimal attention since it was proposed by Halstead and Thrush (Proc. R. Soc. Lond. A Math. Phys. Sci., 1966) is the reaction SO+OCS→CO2+S2. This reaction was proposed by Halstead and Thrush (1966) to explain the disagreement between their inferred upper limit rate for 2SO{+M} →SO2+S {or (SO)2} and the rate inferred by Sullivan and Warneck (Ber. Bunsenges. Phys. Chem., 1965). Baulch et al. (Butterworths, 1976) included the Halstead and Thrush (1966) rate for SO+OCS→CO2+S2 in their assessment of high temperature gas kinetic data but noted it should be used with caution. This reaction potentially enhances the rates of formation of both CO2 and Sx, and, thus, it potentially contributes to two long-standing issues in Venus atmospheric chemistry: the overprediction of mesospheric column O2 and the requirement for faster production of S2 (if Sx contributes significantly to the unidentified UV absorption). When included in a 1-D photochemical model with the Halstead and Thrush (1966) rate coefficient, this reaction dominates production of S2 in the upper cloud layer. This occurs for both the Pinto et al. (Nature Comm., 2021) and Francés-Monerris et al. (Nature Comm., 2022) schemes for enhanced S2 production. The resultant SO2 profile differs significantly from previous simulations (Zhang et al., Icarus, 2012) but remains marginally compatible with existing observations (Jessup et al., Icarus, 2015). Similar behaviour is found when the volume mixing ratio for OCS at 58 km is increased to 4x10-6 and SO2 is reduced to 1.2x10-6, even if the SO+OCS reaction rate is set to zero. The results from a suite of simulations exploring this new region of parameter space and the potential implications for the Venus upper cloud will be discussed.
How to cite: Katrivesis Brown, G., Mills, F., and Croke, B.: An Exploration of Polysulfur Chemistry in a Simulated Venus Atmosphere , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1286, https://doi.org/10.5194/egusphere-egu26-1286, 2026.
Despite decades of exploration by multiple space missions, the history of water on Venus remains uncertain, limiting our understanding of the planet’s evolution and its potential for habitability. The atmospheric deuterium-to-hydrogen (D/H) ratio is a key tracer of past water loss and atmospheric escape processes. To date, measurements of this ratio have been largely confined to altitudes at or below the exobase level, derived from remote sensing and in situ observations of water vapor. In this work, we revisit magnetic field observations from Venus Express to analyze pick-up ion cyclotron waves generated by freshly ionized hydrogen, so called proton cyclotron waves (PCWs). We further extend this approach to investigate pick-up ion cyclotron waves associated with deuterium ion pick-up, providing the first altitude-resolved density profile of deuterium in Venus’ extended exosphere. We find that the hydrogen escape rate is consistent with previous observations, while the inferred deuterium escape rates are higher than expected, indicating a limited Venusian water inventory with implications for the planet’s atmospheric and planetary evolution (see EGU Abstract from Scherf+).
How to cite: Weichbold, F., Lammer, H., Scherf, M., Schmid, D., Simon-Wedlund, C., Mazelle, C., Volwerk, M., Constantinou, T., Woitke, P., Emminger, P., Ferrus, M., and Rimmer, P.: Probing Venus’ Extended Exosphere through Deuterium and Hydrogen generated Pick-Up Ion Cyclotron Waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17869, https://doi.org/10.5194/egusphere-egu26-17869, 2026.
The three rocky planets of our Solar System, Earth, Venus, and Mars, each once had the potential to sustain habitable conditions, yet today only Earth remains habitable. A key factor governing planetary habitability is the ability to retain an atmosphere. At present, atmospheric loss from all three terrestrial planets is dominated by non-thermal escape processes driven by interactions between planetary atmospheres and the solar wind. In the absence of a strong intrinsic magnetic field, Venus is particularly vulnerable to such interactions.
In this presentation, I will focus on the role of non-thermal escape processes on present-day and early Venus, with particular emphasis on ion pickup. Neutral atmospheric species ionized by solar UV radiation and charge exchange are continually picked up by the magnetized solar wind, resulting in the loss of planetary volatiles. While present-day escape rates are too low to substantially cause thinning of atmosphere, these processes were likely far more efficient under the enhanced solar activity conditions of the early Solar System. I aim to explore how non-thermal escape drives the long-term evolution of Venus and contributed to the development of its present CO₂-dominated atmosphere. The possible existence of an early Venusian magnetic dynamo and its implications on non-thermal escape may also provide context for Venus as an analogue for early Earth and rocky exoplanets.
How to cite: Raorane, A., Kislyakova, K., Van Looveren, G., Guedel, M., Mueller, L., and Macdonald, E.: Non-thermal Escape in Venus Atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6985, https://doi.org/10.5194/egusphere-egu26-6985, 2026.
Today, Venus is a dry planet with an atmosphere that contains very little water. The bulk D/H ratio in its atmosphere is enriched by a factor of ~120 compared to the Earth. This suggests that more of the lighter hydrogen escaped into space over time compared to the heavier deuterium, leading to the conclusion that the planet once hosted a much larger water reservoir than today. Recent climate studies even suggest that Venus could have hosted a temperate period with a liquid water ocean and habitable conditions up to ~0.7 Gyr ago [1]. If so, (i) the ocean must have evaporated afterwards with H and D being lost into space and O being either lost into space or sequestered into the surface, and (ii) the D/H ratio likely needed to fractionate from its initially low, Earth-like value toward its present bulk value since the time of ocean evaporation. Recent analysis of Venus Express data, however, suggest that the D/H ratio in Venus’ atmosphere increases with altitude, reaching values of D/H~0.2 in the mesosphere [2] and even ~0.4 in the exosphere [3]. Photochemical escape rates for D and H based on the analysis of exospheric ion cyclotron waves (see EGU abstract by Weichbold et al.) further suggest lower loss rates for H but higher ones for D, as expected before Venus’ unexpectedly high upper atmosphere D/H ratio was revealed. Based on these novel results, we re-evaluate the evolution of Venus’ water inventory and D/H ratio over time. Our study indicates that only a comparatively small amount of H and D could have been lost since the last resurfacing event (contributing to less than 1 m global equivalent layer of water) and that the D/H ratio likely has been fractionated toward high values already relatively early in Venus’ history, potentially during an early phase when the atmospheric escape of H transitioned from hydrodynamic toward Jeans escape indicating an early loss of most of Venus’ water reservoir. A habitable ocean, as late as 0.7 Gyr ago, can therefore hardly be compatible with the new findings on Venus’ upper atmosphere D/H ratio and the therewith connected escape rates of H and D. This supports recent findings that Venus has never been liquid-water habitable [4].
References:
[1] Way, M. J. and Del Genio, Anthony D., Venusian Habitable Climate Scenarios: Modeling Venus Through Time and Applications to Slowly Rotating Venus-Like Exoplanets, Journal of Geophysical Research (Planets), 125, 5, e06276, 2020, doi:10.1029/2019JE00627610.1002/essoar.10501118.3.
[2] Mahieux, A., Viscardy, S., Yelle, R.V. et al., Unexpected increase of the deuterium to hydrogen ratio in the Venus mesosphere, Proceedings of the National Academy of Science, 121, 34, e2401638121, 2024, doi:10.1073/pnas.2401638121.
[3] Weichbold, F., Lammer, H., Scherf, M. et al., First Detection of Deuterium in Venus's Extended Exosphere, 2025, preprint (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-7720153/v1]
[4] Constantinou, T., Shorttle, O., and Rimmer, P. B., A dry Venusian interior constrained by atmospheric chemistry, Nature Astronomy, 9, 189, 2025, doi:10.1038/s41550-024-02414-5.
How to cite: Scherf, M., Weichbold, F., Erkaev, N., Lammer, H., Constantinou, T., Woitke, P., Simon-Wedlund, C., Ferus, M., Eminger, P., Rimmer, P., Kačina, J., and Němečková, K.: What does the unexpectedly high D/H ratio in Venus’ upper atmosphere imply for the existence of a late ocean?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19284, https://doi.org/10.5194/egusphere-egu26-19284, 2026.
Venus’ regios are large surface structures characterized by both elevated topography and geoid, as well as presence of extensive lava flows that overlie the surrounding terrains. These regios are the youngest surface features observed on Venus, and are interpreted as the manifestations of mantle plumes and related melting. Our goal is to infer the subsurface structure of Venus that is consistent with the observation of these structures. Using the finite-element open-source code ASPECT, we set up a 3D thermochemical incompressible model with melting to calculate the convection in the upper mantle and related lithospheric evolution. The assumed material rheology includes thermal and melt-induced chemical buoyancy, as well as diffusion creep with water-dependent stiffening. We perform a parametric study independently varying rheological properties, plume size, and plume temperature. For each set of parameters, we analyze the melting distribution, surface topography, and the generated geoid, and compare these predictions with available observations of Venus’ regios. Our results demonstrate that the plume models are mostly consistent with the geophysical signature of Venus’ regios. Additionally, we provide constraints on the upper-mantle structure beneath the regios, and show the diversity of the melting patterns that may explain various systems of tectonic features observed on Venus.
How to cite: Dizov, A., Čadek, O., Maierová, P., Dumoulin, C., Choblet, G., and Tobie, G.: Regios as a manifestation of upper-mantle dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-499, https://doi.org/10.5194/egusphere-egu26-499, 2026.
Increasing observational evidence and recent geodynamical modelling indicate that Venus may have experienced or may still experience tectonic-like processes (Sulcanese et al., 2024; Gülcher et al., 2025). In fact, surface deformation is believed to be driven primarily by mantle convection and plume-lithosphere interactions, producing a wide range of tectono-volcanic features (Smrekar et al., 2023). A key expression of this deep dynamics is the global network of rifts (chasmata), which extends for thousands of kilometres (Graff et al., 2018; Brossier et al., 2022). However, their driving mechanisms, temporal evolution, and lithospheric structure remain poorly constrained as a result of limited observational data. Therefore, constraining the evolution of Venusian chasmata is essential to understanding the interior dynamics of the planet and its evolution.
In this study, we used forward 2D numerical models to constrain the rates, durations, and lithospheric structures of extensional processes, integrating observational evidence from topography and gravity anomalies to improve our understanding of Venusian rifting. In particular, we tested different extensional velocities and lithospheric and crustal thicknesses.
For comparison with topographic and gravity observation, we extracted 12 topographic cross-sections along 28 Venusian rift axis. To minimize 3D effects when compared with our 2D numerical models, we evaluated the longitudinal variability of topography by grouping three or more adjacent cross-sections and computing their mean profiles. Only portions of the rifts that did not show statistically significant variations in topography were considered for our comparison. We then compared the mean topography of these rift portions with the topography predicted by the models. Finally, we compared the gravity anomalies derived from the selected rift portions with the gravity anomalies extracted by the models.
We observed that extensional velocities between 0.5 and 2 cm/yr reproduce the observed topography well, while lower velocities often do not allow for the development of rifting structures. In addition, models with a lithospheric thickness of 100 km and a crustal thickness of 15 km show the best topographic fit with observations. Finally, comparing the observations with the evolution of the models at different times allows us to recognize an asynchronous evolution in the Diana chasma, with differences of approximately 1 Myr along its axis.
J. Brossier, M. S. Gilmore, and J. W. Head. Extended rift-associated volcanism in ganis chasma, venus detected from magellan radar emissivity. Geophysical Research Letters, 49 (15):e2022GL099765, 2022. doi:10.1029/2022GL099765.
J. Graff, R. Ernst, and C. Samson. Evidence for triple-junction rifting focussed on local magmatic centres along parga chasma, venus. Icarus, 306:122–138, 2018. doi:10.1016/j.icarus.2018.02.010.
A. J. Gülcher, M. Gurnis, and S. E. Smrekar. Dynamics of venusian rifts and their interactions with plumes and intrusions. Earth and Planetary Science Letters, 667:119514, 2025. doi:10.1016/j.epsl.2025.119514.
S. E. Smrekar, C. Ostberg, and J. G. O’Rourke. Earth-like lithospheric thickness and heat flow on Venus consistent with active rifting. Nature Geoscience, 16:13–18, 2023. doi:10.1038/s41561-022-01068-0.
D. Sulcanese, G. Mitri, and M. Mastrogiuseppe. Evidence of ongoing volcanic activity on Venus revealed by Magellan radar. Nature Astronomy, 8:973–982, 2024. doi:10.1038/s41550-024-02272-1.
How to cite: Thieulot, C., Regorda, A., van Zelst, I., Maia, J., and Erdős, Z.: Constraining the evolution of Venusian rifts: an integrated observation and modelling approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5892, https://doi.org/10.5194/egusphere-egu26-5892, 2026.
Venus and Earth exemplify two divergent evolutionary pathways of rocky planets despite their similar sizes, bulk densities and orbital distances. Today, Earth maintains a thin N2- and O2-dominated atmosphere, regulated by efficient volatile and crustal recycling, while Venus hosts a CO2-dominated, 92 bar atmosphere that results in extreme surface temperatures. The origin of Venus’ massive atmosphere is likely a combination of processes including early magma ocean degassing, impact delivery and long-term mantle outgassing, with possibly one or more catastrophic outgassing events (Gillmann et al., 2022). The efficiency and composition of long-term mantle outgassing is still poorly constrained for Venus. Previous studies have shown that pressure is the primary control on volatile solubility, regulating whether degassing occurs at all and the elemental sequence of volatility e.g. C-bearing species degass predominantely at higher pressures, while the redox state of the mantle controls primary the chemical speciation of outgassed volatiles e.g. wheather CH4 or CO or CO2 is degassed (Gaillard and Scaillet, 2014, Gaillard et al. 2020).
In contrast to Ortenzi et al. (2020), who have focused on the redox-dependence of volatile partitioning and gas speciation for various planetary masses, this study investigates the pressure-dependence of volcanic outgassing for varying redox states and its implications for Venus’ atmospheric evolution. First, Atmodeller (Bower et al., 2025) is used to calculate the pressure-dependent volatile solubility and gas speciation for erupted lava. Then, the findings are linked to 2D mantle convection models of Venus with varying surface temperatures and rheological parameters. These models use the numerical mantle convection code StagYY (Tackley, 2008) including partial melting with prescribed intrusion efficiencies to quantify melt production, lithospheric thickness as well as the tectonic regime. By explicitly accounting for volatile degassing as a function of surface pressure, our study aims to constrain total outgassing and the role of pressure-buffered volatile retention in shaping Venus’ atmosphere.
How to cite: Murzakhmetov, L., Gillmann, C., Bower, D., Gülcher, A., Sossi, P., and Tackley, P.: Pressure-Dependent Mantle Outgassing and the Evolution of Venus’ atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20754, https://doi.org/10.5194/egusphere-egu26-20754, 2026.
Reconstructing Venus’s early evolution and determining whether it once had Earth-like, temperate conditions remain challenging because its surface is geologically young. Climate models suggest that Venus may have maintained mild temperatures and even liquid water until <1 Ga (Way et al., 2016), while other work suggests that Venus might have had high surface temperature over most of its history, with values possibly even higher than today (Noack et al., 2012). At the same time, the surface temperature is strongly linked to the volcanic and outgassing history, and thus to the presence of volatiles in the interior. Some studies suggest that the interior is intrinsically dry (Constantinou et al., 2024), while others indicate that at least the lower mantle might still contain volatiles (Smrekar & Sotin, 2012). The presence of volatiles can substantially affect the mantle viscosity that, in turn, affects the thermal, magmatic, and outgassing history.
Venus’s geodynamic regime is heavily debated (Rolf et al., 2022), but recent evidence of ongoing volcanic activity (Herrick & Hensley, 2023) indicates that magmatic processes could still play a key role today. Early geodynamic models that included magmatism considered only extrusive magmatism, known as heat-pipe regime (Moore & Webb, 2013). Recent studies investigated scenarios where magmatic intrusions dominate, known as plutonic-squishy regime (Lourenco et al., 2020). Although current surface and lithospheric conditions suggest a highly intrusive magmatic style (Maia et al., 2025), the relative roles of intrusive and extrusive magmatism in regulating mantle cooling for different surface temperature scenarios and rheological conditions remain unexplored.
We test different surface temperature and mantle viscosity values and model their effect on the long-term cooling on Venus and Venus-like planets, using the geodynamic code GAIA in a 2D spherical annulus geometry (Hüttig et al., 2013; Fleury et al., 2024). We assume a temperature- and depth-dependent viscosity following an Arrhenius law (Hirth & Kohlstedt, 2003), and pressure- and temperature-dependent thermal conductivity and expansivity (Tosi et al., 2013). We model the decay of radioactive heat-producing elements and cooling of the core. Melting occurs when mantle temperatures exceed the solidus (Stixrude et al., 2009).
Our results show that surface temperature and mantle viscosity are key factors in determining the efficiency of planetary cooling for different magmatic styles (intrusive or extrusive). A high surface temperature, like Venus’s current 737 K, shows a more efficient cooling when intrusive magmatism is considered, while cooler surfaces (~500 K) lead to stronger mantle cooling for an extrusive magmatism scenario, for cases assuming a reference viscosity of ~1021 Pa s. Mantle viscosity modulates this behavior: lower viscosities (~1020 Pa s) allow planets with cold surfaces to cool more efficiently if intrusions are present, while higher viscosities (~1022 Pa s) with hot surfaces cool more efficiently if extrusive magmatism dominates. These findings suggest that Venus’s surface conditions and mantle properties over time play a crucial role in its thermal and magmatic evolution, offering insights into the potential habitability of Venus-like exoplanets, where the balance between intrusive and extrusive magmatism likely governs long-term surface-mantle interactions and volatile cycling.
How to cite: Herrera, C., Plesa, A.-C., Maia, J., and Breuer, D.: Surface temperature and mantle viscosity influence the cooling efficiency of magmatic styles on Venus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1018, https://doi.org/10.5194/egusphere-egu26-1018, 2026.
Giant impacts were common in the early evolution of the Solar System. Such an impact has been suggested to have affected the rotation of Venus and possibly its thermal evolution, causing long-lived volcanic activity.
Here, we explore a range of possible giant impacts using smoothed particle hydrodynamics (SPH). We analyse the post-impact rotation and debris disc masses to identify scenarios that can reproduce Venus’ present-day characteristics. We model post-impact interior dynamics evolution using the StagYY convection code, by transferring the thermal field obtained through SPH simulations into a 2D spherical annulus geometry. We account for the low viscosity of molten volumes of the mantle above 35% melt fraction by using an effective "eddy" thermal conductivity of 1010 W/(m.K) following Lourenço et al. (2020), and the heat flux is parametrized following Abe (1993, 1997). The evolution of the core uses a 1D parameterized model to track the temperature profile and the growth of the inner core.
We observe that a wide range of impact scenarios are consistent with Venus’ current rotation for both head-on collisions on a non-rotating Venus and oblique, hit-and-run impacts on a rotating Venus. Collisions that match consistent rotation rates typically produce minimal debris discs residing within Venus’ synchronous orbit (Bussmann et al., 2025). We select these favourable scenarios to model their long-term interior evolution.
In the simulations, giant impacts expectedly produce surface magma oceans. Their relative depths vary between different simulations depending on impact properties: from a shallow melt layer in the order of 100 km thick to a fully molten mantle from surface to core-mantle boundary for the most energetic impacts (high impactor mass and velocity). If the surface is able to radiate heat to space efficiently, the magma ocean cools down quickly and first reaches the rheological transition (35% melt fraction) in a few 100-1000 yrs. Full solidification (0% melt fraction) can take longer because of the effects of the impact on the deep interior.
Indeed, as highlighted by Marchi et al. (2023), giant impacts also deposit a considerable amount of energy in the upper layers of the core, which translates into temperatures reaching up to 104 K. This causes the base of the mantle to fully melt. The resulting liquid layers (in the core and the mantle) convect vigorously and cool the core rapidly (~104 years). The very hot mantle melt is buoyant and rises toward the surface through the solid mantle on timescales of 104-105 yrs. Plumes formed in such a way persist until the excess of heat is extracted from the core and the lower mantle reaches the rheological transition. Solidification of the surface can be delayed by plumes, but models indicate that a fully solid state is reached in a few 1-10 Myr.
After a few hundred million years, the thermal evolution of a Venus-like planet that experienced a giant impact becomes similar to that of cases devoid of impacts. The characteristics of the convection regime in both cases do not substantially differ at present-day (after 4.5 Gyr).
How to cite: Gillmann, C., Tackley, P., Bussmann, M., Lourenço, D., Reinhardt, C., Meier, T., Stadel, J., and Helled, R.: Giant impacts on Venus: lasting consequences on interior dynamics and volcanism, or the lack thereof., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10551, https://doi.org/10.5194/egusphere-egu26-10551, 2026.
Often referred to as the Earth’s twin, Venus represents today one of the most extreme places in the Solar System, with a dense atmosphere and a young surface dominated by volcanic features at all spatial scales (Hahn & Byrne, 2023). While the present-day interior structure and geodynamic regime is still debated, models agree that magmatism played a major role during the entire thermal history (Rolf et al., 2022).
Limited constraints for the deep interior of Venus are available from measurements of the tidal Love number k2 = 0.295±0.066 (Konopliv & Yoder, 1996), which is sensitive to the size and state of the core, and moment of inertia factor (MoIF), which describes the distribution of mass in the interior suggesting a core radius of 3500±500 km (Margot et al., 2021). The phase lag of the deformation, whose value is particularly sensitive to the thermal state of the interior, has not yet been measured but will be constrained by future missions.
Venus has a higher correlation of gravity and topography for long wavelengths and a globally large apparent depth of compensation (Sjogren et al., 1980). Recently, Maia et al. (2023) showed that a viscosity jump at 700 km depth (corresponding to ringwoodite-bridgmanite phase transition) is inconsistent with the observations, while a 250-km-thick low-viscosity layer at the base of the lithosphere is favored by the data.
In this study, we use the mantle convection code GAIA (Hüttig et al., 2013) to compute the thermal evolution of Venus. We use a pressure- and temperature-dependent viscosity, and allow for surface mobilization. Our models are compatible with the so-called plutonic squishy lid regime (Lourenco et al., 2020), in which magmatic intrusions can considerably affect the thermal state of the lithosphere (Herrera et al., this meeting). The thermal expansivity and conductivity are pressure- and temperature-dependent (Tosi et al., 2013), and we consider core cooling and radioactive decay as appropriate for thermal evolution modeling. We vary the core radius (3025–4000 km), mantle viscosity (1020–1022 Pa s), and the viscosity increases with depth (up to three orders of magnitude). Based on the assumed core size and on the thermal state, temperature variations, and viscosity structure obtained from our models we calculate the tidal deformation, the MoIF, and evaluate the dynamic topography and geoid signatures.
We find that models with a core radius ≥4000km are incompatible with current estimates of the tidal Love number k2. Our models also show a lower tidal quality factor for Venus compared to solid Earth, which suggests a hotter interior. The increase of viscosity with depth needs to be lower than two orders of magnitude to avoid a significant decrease of the spectral correlation and admittance, at odds with observations.
Future measurements of the NASA VERITAS (Smrekar et al., 2022) and ESA EnVision (Straume-Lindner et al., 2022) missions will provide unprecedented information to address the interior structure and thermal history of Venus, and will help refine models of the interior evolution.
How to cite: Plesa, A.-C., Maia, J., Walterova, M., and Breuer, D.: The thermal state and interior structure of Venus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14324, https://doi.org/10.5194/egusphere-egu26-14324, 2026.
Although several lines of evidence suggest that substantial water was lost from the atmosphere of Venus, it remains unclear whether surface oceans ever existed. One possible proxy for past water–basalt interactions, which are most easily accomplished within oceans, is the occurrence of abundant felsic rocks. Venus’s crustal plateaus share some characteristics with Earth’s continental crust and have been suggested to be composed of granitoids or other felsic rocks based on infrared emissivity anomalies. Future missions will continue to investigate this possibility, which is considered critical for assessing the planet’s past habitability.
The growth of Earth’s continental crust is associated with the hydrous alteration of basalts, which can either melt directly to produce felsic melts (e.g., Archean TTGs) or generate modern calc-alkaline granitoids through extensive differentiation of hydrous silicate melts at subduction zones. Anhydrous
igneous processes, on the other hand, are generally thought to produce only minute amounts of felsic material (<10%) and only under very specific conditions, such as extreme fractional crystallization.
We performed thermodynamic calculations showing that, while anhydrous processes are indeed inefficient at producing felsic melts at low pressure, abundant felsic melts (≈25%) can be generated by melting dry metabasalts at sufficiently high pressures (>1.5 GPa; depths >60 km). Such conditions were likely met on Venus, either within the roots of several crustal plateaus or during resurfacing events accompanied by crustal recycling. Although these melts are felsic (dacitic) in composition, their viscosity should be low enough to allow them to rise to the surface, implying that extensive felsic crust on Venus could be compatible with a water-poor planet that never experienced oceans.
How to cite: Collinet, M., Maia, J., Plesa, A.-C., Klemme, S., and Wieczorek, M.: Could felsic crustal plateaus have formed on a Water-Poor Venus?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22898, https://doi.org/10.5194/egusphere-egu26-22898, 2026.
When we look at Earth’s surface, we can identify a wide range of crustal deformation patterns associated with the planet’s underlying geodynamic processes. This approach can be adapted to the surfaces of other planetary bodies, enabling the understanding of the origin and evolution of the structures they host.
Venus is considered Earth’s sister planet due to their similarities in size and composition; however, they exhibit different tectonic regimes, resulting in distinct surface features. The deformation of the surface of Venus is characterized by numerous patterns of lineaments that are notably distinct from those on Earth, but with some similarities that allow for establishing parallelisms.
In this work, we map tectonic lineaments across key areas of Venus's surface using Magellan Synthetic Aperture Radar (SAR) imagery in ArcGIS Pro. We selected a few areas that host fault systems with some degree of analogy to those found on Earth. These faults are divided into different families based on their orientation, spatial distribution and cross-cutting relationships. The objective is to establish a relative chronology of tectonic events and to gain insights into the stress regimes responsible for their formation.
The analysis of these deformation patterns aims to better understand the geodynamic processes that shape the Venusian surface and to explain why and how these structures differ from those observed on Earth. Such results will be important when preparing for future space missions to Venus.
This work is supported by FCT, I.P./MCTES through national funds (PIDDAC): LA/P/0068/2020 - https://doi.org/10.54499/LA/P/0068/2020 , UID/50019/2025, https://doi.org/10.54499/UID/PRR/50019/2025, UID/PRR2/50019/2025
How to cite: Fandinga, I., Duarte, J. C., Machado, P., Quirino, D., and Rosas, F. M.: Mapping Tectonic Lineaments in Venus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10668, https://doi.org/10.5194/egusphere-egu26-10668, 2026.
One of the biggest open questions about Venus is the degree and extent of present-day volcanism [1]. Despite having a similar size and density to Earth, Venus underwent distinct geodynamic evolution. The planet hosts a wide diversity of tectonic and volcanic landforms, as revealed by NASA/Magellan global imagery (1990 – 1994) [2].
One prominent feature is the extensive, widespread rifts on Venus (e.g., [3]), covering about 8% of the planetary surface [4]. These are extensional structures [5], among the youngest geological features on the planet according to stratigraphic interpretation [6]. Evidence of recent rift volcanism has been suggested for Olapa Chasma [7 – 9] and Ganis Chasma [10 – 11]. However, the mechanisms of rift formation, age, and relationships with other structural features remain poorly understood, yet crucial for supporting modelling studies [12].
In this study, we analyse the tectonovolcanic activity of a few selected rifts on Venus using microwave emissivity as a proxy to constrain the weathering degree, relative age, and composition [11, 13 – 14], assuming the presence of ferroelectric minerals [13, 15 – 16]. We use Synthetic Aperture Radar (SAR), microwave emissivity, and elevation datasets collected from NASA/Magellan. Site selection, radar emissivity, and elevation extraction are performed in ArcGIS Pro to examine emissivity excursion with altitude. Complementary analyses based on stratigraphic relationships with structural features, such as lava flows, rift structures, and lineaments, provide relative chrono-stratigraphy and conceptual interpretation of tectonovolcanic activation processes. Thus, the objective is to provide a conceptual model for tectonovolcanic rift activation by combining microwave emissivity excursions, stratigraphic relationships, and stress patterns. These results are relevant to upcoming accepted and potential missions to Venus in the coming decade, which will yield extensive new data.
References: [1] Filiberto, J., et al., 2025. Geochemistry, 85; [2] Saunders, R. S., & Pettengill, G. H., 1991. Science, 252, 247; [3] Masursky, H., et al., 1980, J. Geophys. Res., 85, A13; [4] Price, M., & Suppe, J., 1995. EM&P, 71, 99; [5] Magee, K. P., & Head, J. W., 1995. J. Geophys. Res., 103, B1; [6] Ivanov, M. A., & Head, J. W., 2011. P&SS, 59, 1559; [7] D’Incecco, P., et al., 2020. EPSL, 546, 116410; [8] D’Incecco, P., et al., 2021. PSJ, 2, 5; [9] López, I., et al., 2022. J. Volcanol. Geotherm. Res., 421, 107428; [10] Shalygin, E. V., et al., 2015. GRL, 42, 12; [11] Brossier, J., et al., 2022. GRL, 49, e2022GL099765; [12] Regorda, A., et al., 2023. JGR: Planets. 128, e2022JE007588; [13] Brossier, J. F., et al. 2020. Icarus. 343. 113693; [14] Brossier, J., et al., 2021. JGR: Planets. 126, e2020JE006722; [15] Shepard, M. K., et al., 1994. GRL, 21, 6; [16] Treiman, A. H., et al., 2016. Icarus, 280, 172.
Funding: DQ acknowledges this work to be supported by FCT - Fundação para a Ciência e Tecnologia, I.P. by project reference and DOI identifier 10.54499/2023.05220.BD. This work is supported by FCT, I.P./MCTES through national funds (PIDDAC): LA/P/0068/2020 - https://doi.org/10.54499/LA/P/0068/2020 , UID/50019/2025, https://doi.org/10.54499/UID/PRR/50019/2025, UID/PRR2/50019/2025
How to cite: Quirino, D., Duarte, J. C., Machado, P., Green, M., Rosas, F. M., and Fandinga, I.: Exploring Rift Tectonovolcanism in Venus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20866, https://doi.org/10.5194/egusphere-egu26-20866, 2026.
Current models of Venus’ volcanic activity and evolution largely rely on maps of volcanic edifices and features, most notably on an extensive human survey of Magellan data that produced a catalog of ~85,000 volcanic features with sizes ranging from ~1 km (~7 SAR pixels) to ~100 km [1]. Our goal is to use a supervised deep learning-driven approach to address some of the limitations of the catalog provided by [1], specifically by 1) suppressing or removing (human) observer expectancy and fatigue effects, 2) complementing the catalog with edifices smaller than ~5 km (making up 99 % of the [1] catalog), and 3) adding accurate morphometric information for all volcanic features. Ultimately, we seek to create a reference catalog of volcanic features on Venus that can enable investigations of volcanic activity and evolution at an unprecedented level of scale as well as form the backbone for the systematic identification of surface change using new data returned by upcoming Venus missions.
We previously trained EVA, the Extractor Vulcanis Aedificiis (Volcanic Edifice Extractor) [2]. The current version of EVA identifies ~200,000 shield volcanoes (shields) and calderas across Venus, scanning through both left-look (LL) and right-look (RL) SAR data in only ~4 hours. EVA detects ~90 % of all surface-visible edifices in a small, dedicated testset, where ~90 % of all testset detections are correct. Globally, we find that the number of detected shields increases by up to ~5x in regions mapped as shield plains [3] and more than 10x in more heavily tectonized regions. Qualitative inspection suggests that in tectonized regions, false detections are more prevalent. To further scrutinize EVA’s performance, we examine 22 regions across the planet covered by LL data, each with at least ~50 EVA detections, that span all major geologic units. Nine regions are also covered by RL images. For each region we manually map shields and calderas to provide a second “ground truth” data set (in addition to that of [1]) against which EVA detections can be compared. Preliminary results indicate that in regions of higher shield density [1], the two ground truth data sets differ in number of detections by a factor of 1.5-2, with excellent overlap (i.e. most features in the smaller data set are contained in the larger one), and EVA results in another ~2x as many detections. There is also very good agreement between the two ground-truth data sets in more tectonized areas, and we are currently using results from these areas to understand and refine EVA performance.
We will present EVA’s current performance and solicit community feedback, to ensure that EVA can be a reliable, well-understood, and comprehensive inventory of volcanic features on Venus.
[1] Hahn & Byrne (2023). A Morphological and Spatial Analysis of Volcanoes on Venus. JGR Planets 128 (4).
[2] Bickel et al. (2025). Revisiting Volcanism on Venus with Deep Learning. Lunar and Planetary Science Conference 2025, Abstract ID #1387.
[3] Ivanov & Head (2011). Global Geological Map of Venus. Planetary and Space Science 59 (1559–1600).
How to cite: Bickel, V. T., Johnson, C. L., Russell, M. B., and Rossmann, F. M.: EVA – Towards a Comprehensive Inventory of Small Volcanic Features on Venus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12049, https://doi.org/10.5194/egusphere-egu26-12049, 2026.
The atmospheres of Venus and Mars are primarily CO2 which photolyses at wavelengths ∼<200 nm to CO and O. Direct recombination via CO+O+M → CO2+M is very slow so the rate of production of CO2 to balance its loss via photolysis is controlled by the abundances of trace radicals that catalyse production of CO2 (e.g., Yung and DeMore, Icarus 51, 199, 1982). These trace radicals, such as OH and ClCO, are derived directly or indirectly from photolysis of H2O and HCl. Previous large uncertainties in the rates of some of the key reactions that comprise these catalytic processes have been significantly reduced (eg., Mills and Allen, PSS 55, 2007; Marcq et al., Space Sci Rev 214, 10, 2018; Chao et al., AGU Fall Mtg Abst P11B-2985, 2024). In addition, several studies in the past 15 years have refined our understanding of the UV cross sections of CO2 and H2O (e.g., Archer et al., JQSRT 117, 88, 2013; Schmidt et al., PNAS 110, 17691, 2013; Ranjan et al., Astrobio 17, 687, 2017; Venot et al., A & A 609, A34, 2018; Ranjan et al., Ap J 896, 148, 2020). Consequently, it is appropriate to examine again the impact on mesospheric simulations of the remaining uncertainties in the photolysis and extinction cross sections for CO2, HCl, and H2O.
How to cite: Mills, F.: Impact of uncertainties in CO2, HCl, and H2O cross sections on simulations of Venus mesospheric chemistry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4927, https://doi.org/10.5194/egusphere-egu26-4927, 2026.
The rate of injection of cosmic dust into the Earth’s atmosphere is estimated to be 28 ± 16 tonnes per day. As this dust ablates between altitudes of 80 and 105 km, it generates neutral and ionized metal layers. These layers have been characterized through space-based spectroscopy, ground-based lidar observations, and rocket-borne mass spectrometry. A cosmic dust input rate of 31 ± 18 t d−1 is estimated for Venus [Carrillo-Sanchez et al., 2020]; this material should ablate and form metal layers between 105 and 120 km. However, these layers have not yet been observed on Venus.
In this study, we model the latitudinal and diurnal variability of the Venusian metal layers (mainly Na, Mg, Fe and SiO), and assess the probability of their spectroscopic detection. For the simulations, the whole atmosphere Venus Planetary Climate (PCM) Model was used, with the metals being injected into the upper atmosphere through an orbitally varying Meteoric Input Function (MIF). The model also incorporates detailed neural and ion-molecule atmospheric chemistry networks for Fe, Mg, Na and Si, and was run for over two Venus years.
A pronounced diurnal variability in the Venusian metal layers is predicted: the neutral metal atom layers peak on the night side, with maxima occurring around the morning terminator, when neutral metals have had the longest time to build up through the neutralization of their corresponding metal ions. Latitudinal variability in metal column density is highly correlated with Venusian circulation, driven by strong meridional and zonal winds. The Fe, Na, Mg and SiO layers peak at different altitudes, which results in species-dependant latitudinal distributions shaped by the horizontal winds.
The metal layers are potentially observable in the atmosphere of Venus. In particular, the predicted Na layer should be detectable from terrestrial telescopes, either via solar-pumped resonance fluorescence or via occultation at 589 nm. Venusian Na should produce a particularly strong signal at the morning terminator in the northern hemisphere, consistent with the variability highlighted above. Different observational techniques will be discussed.
Finally, we emphasize the significance of detecting metal layers in Venus’s CO2-rich atmosphere, in contrast to Earth’s O2–rich atmosphere. Knowledge of the metal layers on Venus should provide a useful framework for probing the atmospheres of Venus-like exoplanets. In general, the distribution and behaviour of meteoric sodium in exoplanetary atmospheres merits further exploration, as indicated by the growing number of sodium detections in the atmospheres of Hot Jupiters and Hot Neptunes.
How to cite: Ceragioli, B., Plane, J., Marsh, D., Feng, W., Egan, J., Carrillo-Sánchez, J. D., Janches, D., Christou, A., Stolzenbach, A., Lebonnois, S., and Lefèvre, F.: Exploring the variability of the meteoric metal layers in the Venusian atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1157, https://doi.org/10.5194/egusphere-egu26-1157, 2026.
The early evolution of the atmospheres of Venus, Earth, and Mars, and hence their potential habitability, is strongly linked to the early evolution of the Sun, which was significantly more active during the first ~1 billion years than it is at present. The high solar X-ray and extreme ultraviolet (XUV) surface flux received by the three planets during this time heated their upper atmospheres, inducing thermal and non-thermal atmospheric escape rates that are assumed to be significantly higher than at present. However, whether an atmosphere is stable against escape into space depends not only on the incident solar/stellar XUV surface flux but also on planetary size and atmospheric composition. CO2 and other infrared coolants, for instance, cool the thermosphere, making atmospheres with larger CO2 mixing ratios less susceptible to atmospheric erosion. This implies that atmospheres with certain compositions (e.g., CO2-dominated atmospheres) were more likely to survive the harsh conditions of the early Solar System than others (e.g., N2-dominated atmospheres). This, in turn, has implications for prebiotic chemistry and the origin of life since different atmospheric compositions, but also the therewith connected tropospheric temperature and the hydrology of a planet, further affect the photochemical production and rainout of prebiotic molecules into ancient oceans or shallow ponds. This highlights the importance of considering both the upper atmosphere/thermosphere to evaluate atmospheric stability and the lower atmosphere/homosphere to evaluate prebiotic chemistry and climatic conditions if we want to better understand the habitability and evolution of the rocky planets in the Solar System and beyond. We first discuss atmospheric stability on early Venus, Earth, and Mars and investigate the atmospheric compositions needed for the three planets to host stable atmospheres. By investigating the photochemical production and rainout of prebiotic molecules (with a focus on formaldehyde) within thermally stable atmospheres, we finally assess the prebiotic potential and early habitability of the three planets.
How to cite: Scherf, M., Weichbold, F., Lammer, H., Woitke, P., Constantinou, T., Rimmer, P., and Ferus, M.: Atmospheric stability and its implication on prebiotic chemistry on early Venus, Earth, and Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19506, https://doi.org/10.5194/egusphere-egu26-19506, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 4
EGU26-3726 | Posters virtual | VPS27
Reproduction of Long-Term Variability of Super-Rotation Using Akatsuki Horizontal Wind Data AssimilationMon, 04 May, 14:00–14:03 (CEST) vPoster spot 4
In Fujisawa et al. (2022) [1], we previously produced an objective analysis of the Venusian atmosphere by assimilating horizontal winds derived from cloud tracking of the UVI camera onboard the Venus orbiter Akatsuki. To produce objective analysis, we used the Venus atmospheric data assimilation system ALEDAS-V (Sugimoto et al., 2017) [2], which is based on the Venus general circulation model AFES-Venus (Sugimoto et al., 2014) [3]. This dataset appropriately corrects both the phase bias of thermal tides and the super-rotation speed in AFES-Venus to be closer to those observed in the real Venusian atmosphere. The dataset was produced by assimilating observations from September to December 2018, a period that includes an intensive observation period of Akatsuki.
Akatsuki has accumulated observational data over a long period from 2015 to 2024, and it has been revealed that the super-rotation speed exhibits both faster and slower periods (Horinouchi et al., 2024) [4]. In this study, we selected five epochs during the Akatsuki observation period that exhibit characteristic super-rotation speeds and performed data assimilation for each epoch. As a result, we confirmed that distinct super-rotation speeds corresponding to each epoch, including their meridional asymmetry, are reproduced. In the presentation, we will show the relationship between the reproduced super-rotation speeds and the structure of the atmospheric circulation.
- [1] Fujisawa, Y., et al. (2022) Sci. Rep. 12, 14577.
- [2] Sugimoto, N., et al. (2017) Sci. Rep. 7(1), 9321.
- [3] Sugimoto, N., et al. (2014) J. Geophys. Res. Planets 119, 1950–1968.
- [4] Horinouchi, T., et al. (2024) J. Geophys. Res. Planets 129, e2023JE008221.
How to cite: Fujisawa, Y., Sugimoto, N., Komori, N., Murakami, S., Ando, H., Takagi, M., Imamura, T., Horinouchi, T., Hashimoto, G. L., Ishiwatari, M., Enomoto, T., Miyoshi, T., Kashimura, H., and Hayashi, Y.-Y.: Reproduction of Long-Term Variability of Super-Rotation Using Akatsuki Horizontal Wind Data Assimilation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3726, https://doi.org/10.5194/egusphere-egu26-3726, 2026.
EGU26-22816 | Posters virtual | VPS27
Simultaneous mapping of CO, SO2 and HDO on the night side of VenusMon, 04 May, 14:57–15:00 (CEST) vPoster spot 4
In order to better understand the photochemical and dynamical processes which drive the atmosphere of Venus, we have started in January 2012 an observing campaign to monitor the behavior of sulfur dioxide and water near the cloud top of Venus, using the TEXES (Texas Echelon Cross-Echelle Spectrograph) imaging spectrometer at the NASA InfraRed Telescope Facility (IRTF, Mauna Kea Observatory ; Encrenaz et al. Astron. Astrophys. 703, id.A219, 2025). These data have shown evidence for drastic changes in the SO2 abundance, both on the short term and the long term, the origin of which is unclear, as well as a strong spatial variability at low latitudes. In February 2025, data have been obtained at 4.7 and 7.4 microns on the night side of Venus (49 arcsec in diameter), allowing us for the first time to map simultaneously CO, SO2 and H2O (through its proxy HDO) near the cloud top of Venus. The data seem to show a slight enhancement of CO around midnight, consistent with the results previously reported from millimeter/submillimeter observations in the upper mesosphere (Clancy et al. Icarus 217, 779, 2012). The TEXES data will be used in an attempt to constrain coupled dynamical-chemical GCM simulations of the Venus atmosphere (e.g. Shao et al., AGU General Conference, New Orleans, USA, December 2025).
How to cite: Encrenaz, T., Greathouse, T., Marcq, E., Shao, W., Lefèvre, F., Giles, R., Lefèvre, M., Widemann, T., Bézard, B., and Sagawa, H.: Simultaneous mapping of CO, SO2 and HDO on the night side of Venus , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22816, https://doi.org/10.5194/egusphere-egu26-22816, 2026.
