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Parker Solar Probe (PSP) uses Venus gravity assists (VGA) to achieve the closest orbits to the Sun by a spacecraft. During the third (VGA3) and fourth (VGA4) Venus gravity assists, the PSP entered the Venusian ionosphere. The core electrons could not be detected as they were below the SWEAP/SPAN electrostatic analyzer instrument energy threshold. However, there is another way to estimate the core temperature using quasi‐thermal noise (QTN) data measured by the PSP/FIELDS Radio Frequency Spectrometer instrument. QTN spectroscopy offers an effective tool for measuring electron temperature and density when the electrons are too cold for other instruments to measure, as is the case with VGA3 and VGA4. Low‐frequency plasma wave data from the closest approach during VGA3 and VGA4 was analyzed with the QTN spectroscopy technique to determine the density and first‐ever in‐situ thermal electron temperature of the Venusian ionosphere at solar minimum. Plain Language Summary: Parker Solar Probe is a NASA mission designed to collect solar wind data closer to the Sun than any spacecraft has before. It uses Venus' gravity to achieve its close orbit, collecting data at Venus while doing so. Quasi‐thermal noise spectroscopy was used to determine the thermal electron properties of the Venusian ionosphere during these gravity assists when other instruments could not. This analysis provides insights into how Venus' ionosphere reacts to the solar cycle and how the ionosphere is losing mass. Key Points: Thermal electron properties of Venus' ionosphere can be determined using quasi‐thermal noise spectroscopyVenusian ionospheric electron temperatures are found to be colder at solar minimum than maximumAmbipolar fields, not wave heating, may be the main source of outfield flow in Venusian tail rays [ABSTRACT FROM AUTHOR]

The three largest impact craters, the remains of which have been found on Earth to date, had diameters of about 200 km immediately after formation. The search for traces of larger impact structures continues. This paper presents the results of numerical modeling of the formation of terrestrial impact craters larger than those already found. It is shown that the inferred geothermal gradient significantly influences the initial geometry of the impact melt region, which may facilitate the search for the remains of deeply eroded ancient impact structures. [ABSTRACT FROM AUTHOR]

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Venus' surface and interior dynamics remain largely unconstrained, due in great part to the major obstacles to exploration imposed by its 470°C, 90 bar surface conditions and its thick, opaque atmosphere. Flyby and orbiter‐based thermal emission data provide opportunities to characterize the surface composition of Venus. However, robust interpretations of such data depend on understanding interactions between the planet's surface basaltic rocks and its caustic carbon dioxide (CO2)‐dominant atmosphere, containing trace amounts of sulfur dioxide (SO2). Several studies, using remote sensing, thermodynamic modeling, and laboratory experiments, have placed constraints on basaltic alteration mineralogy and rates. However, constraints on the effects of SO2‐bearing reactions on basalts with diverse compositions remain incomplete. Here, we present new data from a series of gas‐solid reaction experiments, in which samples of two basalt compositions were reacted in an SO2‐bearing CO2 atmosphere, at relevant Venus temperatures, pressure, and oxygen fugacity. Reacted specimens were analyzed by scanning electron microscopy and scanning transmission electron microscopy using sample cross‐sections produced with focused ion beam milling. Surface alteration products were characterized, and their abundances estimated; subsurface cation concentrations were mapped to show the depth of alteration. We demonstrate that the initial development of reaction products progresses rapidly over the course of 30‐day runs. Alkaline basalt samples are coated by Na‐sulfate (likely thenardite, Na2SO4) and amorphous calcium carbonate (CaCO3) alteration products, and tholeiitic basalt samples are primarily covered by anhydrite (CaSO4), Fe‐oxide (FexOy: likely magnetite, Fe3O4), and other minor phases. These mineralogies differ from previous experiments in CO2‐only atmospheres. Plain Language Summary: Surface features on Venus, such as volcanic landforms, and their ages can be studied to infer the planet's interior properties. Venus' thick, opaque atmosphere and extreme temperature and pressure limit a detailed study of its surface. Fortunately, sensors aboard Venus‐orbiting spacecraft can "see" its surface using select wavelengths of light to provide opportunities to interpret the composition of its surface. However, these interpretations rely on understanding how Venus' atmosphere might chemically interact with the surface and what mineral products may result. This is not yet fully understood despite the results of several prior studies with objectives similar to ours. Here, we share the results from experiments that mimic these chemical reactions. We used rock types such as those known to be on the surface of Venus and subjected them to relevant temperatures and pressure and a blend of two reactive gases, carbon dioxide and sulfur dioxide, to model Venus' atmosphere. After the experiments, we examined the rocks with microscopic instruments that allowed us to characterize chemical changes from their surfaces to their interiors. Our interpretations suggest that these reactions occur rapidly and that the compositions of the mineral coatings produced are dictated by the rocks' slightly different compositions. Key Points: Basalts experimentally altered under Venus P‐T conditions and a CO2–SO2 atmosphere produce reaction products of Ca‐ and Na‐sulfates, and Fe‐oxidesAlteration products and the advancement of alteration were strongly dependent upon the compositions of the solid reactantsThe rates at which basalts altered in a CO2–SO2 atmosphere were greater than rates in a CO2‐only atmosphere [ABSTRACT FROM AUTHOR]

Venus preserves ∼1,000 impact craters, yet to date no impact basins larger than 300 km in diameter—common in the oldest terrains on Mercury, Mars and the Moon—are recognized on Venus. The tessera terrain is Venus' oldest recognized terrain. We describe a ∼1,500 km‐diameter concentric ring‐graben complex preserved on Haasttse‐baad Tessera, Venus that we identify as the Haasttse‐baad Tessera Ring Complex (HTRC). Based on geologic relations and numerical modeling, we propose that the HTRC may represent a Valhalla‐type multiring impact basin formed late during the evolution of its host ribbon‐tessera terrain (rtt). Formation of Valhalla‐type impact basins could involve a unique three‐layer target rheology with a thin elastic layer above a low viscosity layer above a deep strong layer. This multi‐layer rheological sandwich is consistent with crustal rheology previously proposed for the formation of Venus' rtt. If the HTRC is a Valhalla‐type impact basin, it would be Venus' oldest, and currently largest, impact structure, providing a rare window into Venus' ancient past and with implications for early crustal processes on Venus. Plain Language Summary: Venus preserves ∼1,000 impact craters, but no craters larger than 300 km—common on Mercury, Mars, and Moon—are recognized. We describe a large circular structure (∼1,500 km‐diameter) that formed on tessera terrain, Venus' oldest recognized surface type. The structure consists of concentric circular troughs that cut the tessera surface; geologic mapping shows that the structure formed late during tessera formation. We discuss the different mechanisms for forming large circular features marked by concentric rings of structures, and propose that it could be an example of a large impact basin named Valhalla‐type impact basin after a structure present in Jupiter's moon Callisto. Previous research suggests that the formation of these impact basins likely involves a distinctive layering in the impact site consisting of a sandwich of layers with different strengths (strong‐weak‐strong), a configuration previously proposed as necessary to form the host tessera terrain. Numerical models show that forming the circular structure as a Valhalla‐type impact basin is possible if a large meteorite crashes into this three‐layer crust. This unique structure, which might represent a very old and large impact structure, could provide a rare window into Venus' ancient past. Key Points: We describe a unique ∼1,500 km‐diameter concentric ring complex and present detailed geologic maps of the structure and its host tesseraWe propose that this structure may represent a Valhalla‐type impact structure, as supported by geologic mapping and numerical modelingIf the hypothesis is valid, the complex is the largest impact structure recognized on Venus, with implications for early planet processes [ABSTRACT FROM AUTHOR]

Large topographic rises on Venus are regions thought to be formed in response to the presence of a mantle plume or mantle upwelling, equivalent to hot spots on Earth. In this work, we study the geology and evolution of one of these large topographic rises, Imdr Regio, based on geologic mapping and analysis of geophysical data of the area. Imdr Regio presents a complex structure with two very different areas: (a) an elevated southeast area that is dominated by volcanism associated with Idunn Mons, a large volcano that has been proposed as a site of recent or even active volcanism; (b) another elevated area in the northwest area that also has a large volcano (Arasy Mons), but that is dominated by volcanism and tectonic activity associated with the formation of the Olapa Chasma rift system. These two very differentiated topographically elevated areas also exhibit differences in their geology, volcanic and tectonic style, and geophysical characteristics, which leads us to suggest that more than the classic volcano‐dominated rise classification attributed to Imdr Regio the area could rather be considered as an intermediate or hybrid volcano‐rift dominated large topographic rise. The evaluation of the different genetic scenarios and its correspondence with the observed geology in the area suggests that the complex geology of Imdr Regio could be better explained if we consider models of hot spot evolution that involve the presence of several mantle plumes or secondary upwellings derived from a mantle plume emplaced at a deeper rheological boundary. Plain Language Summary: Large topographic rises on Venus are the equivalent to hot spots like those responsible for the formation of Hawaii on the Earth. We have studied the geologic evolution of one of these large topographic rises, Imdr Regio, and this research shows that Imdr Regio is complex with two differentiated areas. The southeast is dominated by a large volcano, Idunn Mons, that has been proposed as a site of recent or even active volcanism. In the northwest there is also a large volcano Arasy Mons, but the activity is dominated by the Olapa Chasma rift system. The presence of these two areas with differences in their geology, volcanic and tectonic style, and geophysical characteristics, leads us to suggest that, although this large topographic rise was classified as dominated by the volcano, it could indeed be better classified as an intermediate or hybrid volcano‐rift dominated rise. We also evaluate the different scenarios to explain its formation and conclude that the complex geology of Imdr Regio could be better explained if we consider models of hot spot evolution that involve the presence of several mantle plumes or secondary smaller plumes derived from a mantle plume emplaced at a greater depth. Key Points: We have studied the geology of Imdr Regio, a possible active hotspot on Venus, based on geologic mapping and analysis of geophysical dataImdr Regio presents complex geology dominated by Idunn Mons and Olapa Chasma, classifying it as a hybrid volcano‐rift large topographic riseThe complex geology and the topography of Imdr Regio suggest that it could be the result of multiple or secondary plumes in the area [ABSTRACT FROM AUTHOR]

We analyze data from multiple flybys by the Solar Orbiter, BepiColombo, and Parker Solar Probe (PSP) missions to study the interaction between Venus' plasma environment and the solar wind forming the induced magnetosphere. Through examination of magnetic field and plasma density signatures we characterize the spatial extent and dynamics of Venus' magnetotail, focusing mainly on boundary crossings. Notably, we observe significant differences in boundary crossing location and appearance between flybys, highlighting the dynamic nature of Venus' magnetotail. In particular, during Solar Orbiter's third flyby, extreme solar wind conditions led to significant variations in the magnetosheath plasma density and magnetic field properties, but the increased dynamic pressure did not compress the magnetotail. Instead, it is possible that the increased EUV flux at this time rather caused it to expand in size. Key findings also include the identification of several far downstream bow shock (BS), or bow wave, crossings to at least 60 RV ${\mathrm{R}}_{V}$ (1 RV ${\mathrm{R}}_{V}$ = 6,052 km is the radius of Venus), and the induced magnetospheric boundary to at least ∼ ${\sim} $ 20 RV ${\mathrm{R}}_{V}$. These crossings provide insight into the extent of the induced magnetosphere. Pre‐existing models from Venus Express were only constrained to within ∼ ${\sim} $ 5 RV ${\mathrm{R}}_{V}$ of the planet, and we provide modifications to better fit the far‐downstream crossings. The new model BS is now significantly closer to the central tail than previously suggested, by about 10 RV ${\mathrm{R}}_{V}$ at 60 RV ${\mathrm{R}}_{V}$ downstream. Plain Language Summary: We studied data from the missions Solar Orbiter, BepiColombo, and Parker Solar Probe to understand Venus' magnetotail. We focused on how Venus' magnetic environment interacts with the solar wind to create its magnetosphere. By looking at magnetic fields and plasma density, we figured out the size and movement of Venus' magnetotail, and found where its boundaries are. We noticed that these boundaries change a lot between missions, showing that Venus' magnetotail is very dynamic. Our main discoveries include finding boundary crossings like the bow shock 60 times Venus' radius downstream, and the magnetospheric boundary about 20 times Venus' radius downstream. This helps us understand how far the magnetosphere extends and improve our models of its shape. We also saw that the solar wind affects the magnetotail: during one mission, even though the solar wind was strong, it didn't squish the magnetotail; instead, it made it bigger because of increased solar radiation. Key Points: Venus' magnetotail is observed during nine spacecraft flybys revealing a dynamic structure reaching at least 60 RV downstreamAn improved bow shock model is presented for the deep tail regionThe pre‐existing model of the induced magnetospheric boundary is valid downstream to at least 20 RV [ABSTRACT FROM AUTHOR]

The current study explores the dynamic interaction between Interplanetary coronal mass ejections (ICMEs) and the induced magnetosphere of Venus, utilizing measurements from the Venus Express (VEX) mission. We have investigated 16 ICME events during the period 2006–2013. The altitude of the inbound bow shock and ionopause at Venus are comprehensively studied during the passage of these ICMEs. The ionosphere is found to be highly magnetized due to the very high magnetic pressure of the induced magnetosphere. Remarkably, the altitude of the ionopause is found to be significantly changed as compared to the previous quiet day due to the increased solar wind dynamic pressure Pdyn $\left({P}_{\mathit{dyn}}\right)$. The ratio of the altitude of ionopause and magnitude of the magnetic field (∣B∣) $(\vert B\vert)$ at ionopause on the event days to the quiet days shows a strong anti‐correlation which indicates the ionopause height is inversely related to the magnetic field. Intriguingly, the position of the bow shock exhibited minimal deviations compared to typical quiet days, underscoring that, during ICME events, the ionopause location is more responsive to solar wind pressure fluctuations than the bow shock location. Additionally, the heavy‐ion density near and above the ionopause is found to be significantly higher than that observed on previous quiet days. This substantial increase implies that ICMEs can induce atmospheric loss in Venus's atmosphere and also cause a significant reduction in the ionopause location. Key Points: The ionopause is found to be significantly changed during the passage of ICMEs compared to the quiet time valuesThe bow shock position exhibited minimal deviations during the event compared to typical quiet daysThe heavy‐ion density near and above the ionopause is significantly higher during ICMEs compared to previous quiet days [ABSTRACT FROM AUTHOR]

Stagnant lid planets are characterized by a globe-encircling, conducting lid that is thick and strong, which leads to reduced global surface heat flows. Consequently, the mantles of such planets can have warmer interiors than Earth, and interestingly, a pyrolitic mantle composition under warmer conditions is predicted to have a distinctly different mantle transition zone compared to the present-day Earth (Hirose, 2002; Stixrude and Lithgow-Bertelloni, 2011; Ichikawa et al., 2014; Dannberg et al, 2022). Instead of olivine primarily transforming into its higher-pressure polymorphs such as wadsleyite and then ringwoodite, at pressures corresponding to 410 km and 520 km depth in Earth, respectively, it instead transforms into a mineral assemblage of wadsleyite, majorite, and ferropericlase (WMF), and then to majorite + ferropericlase (MF), before finally transforming into bridgmanite at pressures corresponding to 660 km depth in Earth (Stixrude and Lithgow-Bertelloni, 2011; Ichikawa et al., 2014). Convective motions in stagnant lid planets are dominated by small-scale instabilities (cold drips) forming within the mobile rheological sublayer under the rigid lid. Using ASPECT and a thermodynamic model of a pyrolitic mantle composition generated by HeFESTo, we show that under certain conditions, the small drips can pond atop the WMF-MF mineral phase transition. The barrier to convective flow arises from the WMF mineral phase assemblage having an effective negative thermal expansivity (Stixrude and Lithgow-Bertelloni, 2022). Although large-scale downwellings that typically occur within mobile lid planets are able to pass through the WMF zone without difficulty (Dannberg et al., 2022; Li RP et al., 2024), the smaller and less negatively buoyant nature of downwelling drips in stagnant lid planets are more susceptible to these effects, which leads to an ephemeral layering of the mantle. Our numerical models show that in stagnant lid planets with mantle potential temperatures that exceed 1900 K, the smaller, cold drips from the lid continue to pile up until enough of them have coalesced that they collectively avalanche as a larger instability into the deeper interior.

Based on the successful landings of landing modules (LM) on the surface and the introduction of aerostat probes (AP) into the air, the feasibility of exploring Venus by an AP drifting in the cloud layer of its atmosphere using short-term descents and landings on its surface has been substantiated. Mathematical modeling was performed to confirm the feasibility of short-term AP drops with a scientific package (SP) in a thermostatted compartment for sampling soil, aerosols and gases and remote sensing (RS) in various regions remote from each other near the surface of the planet Venus for their analysis during a long drift at the height of the cloud layer. Using the example of individual SP devices for geochemical and geophysical studies of Venusian rocks, the scenario and capabilities of AP are shown, which significantly expand both the range of scientific tasks to be solved and the capabilities of the scientific equipment itself. [ABSTRACT FROM AUTHOR]

Based on the PREM Earth model, more than a thousand models of the internal structure of Venus have been built, differing in the radius and density of the core, the density of the mantle, the viscosity distribution and rheology. The core radius varies from 2800 to 3600 km, and the density in the mantle and core varies within a few percent of the PREM model values. When calculating tidal Love numbers, Andrade rheology is used to take into account the inelasticity of the mantle. Specifically the values of the Andrade rheological model parameters that best describe the tidal deformation of the Earth are used. This significantly reduces the error when calculating Love numbers. It has been shown that Venus can have an internal solid core only if the composition of the planet is very different from that of Earth. Comparison of the observed values of the moment of inertia and tidal Love number k2 with model values allowed us to conclude that the radius of the core of Venus is with a high probability in the range of 3288 ± 167 km. [ABSTRACT FROM AUTHOR]

The Chandler wobble of Venus has been analyzed on the basis of the Earth-like models of the planet. The method for calculating the Chandler wobble period of Venus was tested on the example of the Earth. To take into account the inelasticity of the interior of a planet, the Andrade rheology was used; and the values of the rheologic model parameters, which can explain the observed period of the Chandler wobble of the Earth, were determined. Projections on the Chandler wobble period of Venus were obtained. For the most plausible models of the internal structure of Venus, in which the core radius is assumed to be within an interval of 3288 ± 167 km, the Chandler wobble period is 30–48 thousand years. A large error in the results is mainly caused by a wide range of probable values for the constant of precession of Venus. [ABSTRACT FROM AUTHOR]

This study analyzes H2O and HDO vertical profiles in the Venus mesosphere using Venus Express/Solar Occultation in the InfraRed data. The findings show increasing H2O and HDO volume mixing ratios with altitude, with the D/H ratio rising significantly from 0.025 at ~70 km to 0.24 at ~108 km. This indicates an increase from 162 to 1,519 times the Earth's ratio within 40 km. The study explores two hypotheses for these results: isotopic fractionation from photolysis of H2O over HDO or from phase change processes. The latter, involving condensation and evaporation of sulfuric acid aerosols, as suggested by previous authors [X. Zhang et al., Nat. Geosci. 3, 834-837 (2010)], aligns more closely with the rapid changes observed. Vertical transport computations for H2O, HDO, and aerosols show water vapor downwelling and aerosols upwelling. We propose a mechanism where aerosols form in the lower mesosphere due to temperatures below the water condensation threshold, leading to deuterium-enriched aerosols. These aerosols ascend, evaporate at higher temperatures, and release more HDO than H2O, which are then transported downward. Moreover, this cycle may explain the SO2 increase in the upper mesosphere observed above 80 km. The study highlights two crucial implications. First, altitude variation is critical to determining the Venus deuterium and hydrogen reservoirs. Second, the altitude-dependent increase of the D/H ratio affects H and D escape rates. The photolysis of H2O and HDO at higher altitudes releases more D, influencing long-term D/H evolution. These findings suggest that evolutionary models should incorporate altitude-dependent processes for accurate D/H fractionation predictions. [ABSTRACT FROM AUTHOR]

Induced magnetospheres form around planetary bodies with atmospheres through the interaction of the solar wind with their ionosphere. Induced magnetospheres are highly dependent on the solar wind conditions and have only been studied with single spacecraft missions in the past. Without simultaneous measurements of solar wind variations and phenomena in the magnetosphere, establishing a link between both can only be done indirectly, using statistics over a large set of measurements. This gap in knowledge could be addressed by a multi-spacecraft plasma mission, optimized for studying global spatial and temporal variations in the magnetospheric system around Venus, which hosts the most prominent example of an induced magnetosphere in our solar system. The MVSE mission comprises four satellites, of which three are identical scientific spacecraft, carrying the same suite of instruments probing different regions of the induced magnetosphere and the solar wind simultaneously. The fourth spacecraft is the transfer vehicle which acts as a relay satellite for communications at Venus. In this way, changes in the solar wind conditions and extreme solar events can be observed, and their effects can be quantified as they propagate through the Venusian induced magnetosphere. Additionally, energy transfer in the Venusian induced magnetosphere can be investigated. The scientific payload includes instrumentation to measure the magnetic field, electric field, and ion–electron velocity distributions. This study presents the scientific motivation for the mission as well as requirements and the resulting mission design. Concretely, a mission timeline along with a complete spacecraft design, including mass, power, communication, propulsion and thermal budgets are given. This mission was initially conceived at the Alpbach Summer School 2022 and refined during a week-long study at ESA's Concurrent Design Facility in Redu, Belgium. • Multi-spacecraft plasma physics mission concept to Venus. • Dynamics of induced magnetospheres due to variations in the solar wind. • Magnetospheric reaction due to extreme solar events. [ABSTRACT FROM AUTHOR]

The clouds have a great impact on Venus's energy budget and climate evolution, but its three‐dimensional structure is still not well understood. Here we incorporate a simple Venus cloud physics scheme into a flexible GCM to investigate the three‐dimensional cloud spatial variability. Our simulations show good agreement with observations in terms of the vertical profiles of clouds and H2SO4 vapor. H2O vapor is overestimated above the clouds due to efficient transport in the cloud region. The cloud top decreases as latitude increases, qualitatively consistent with Venus Express observations. The underlying mechanism is the combination of H2SO4 chemical production and meridional circulation. The mixing ratios of H2SO4 at 50–60 km and H2O vapors in the main cloud deck basically exhibit maxima around the equator, due to the effect of temperature's control on the saturation vapor mixing ratios of the two species. The cloud mass distribution is subject to both H2SO4 chemical production and dynamical transport and shows a pattern that peaks around the equator in the upper cloud while peaks at mid‐high latitudes in the middle cloud. At low latitudes, H2SO4 and H2O vapors, cloud mass loading and acidity show semidiurnal variations at different altitude ranges, which can be validated against future missions. Our model emphasizes the complexity of the Venus climate system and the great need for more observations and simulations to unravel its spatial variability and underlying atmospheric and/or geological processes. Plain Language Summary: On Venus, highly reflective clouds cover the surface entirely. This means that the clouds greatly impact Venus's current and, very likely, past energy budget. Therefore, understanding the Venus clouds is essential to constructing a full paradigm of the Venus climate and evolution. However, due to the lack of both three‐dimensional, long‐term observations and comprehensive climate models, the cloud spatial structure and its impact on atmospheric processes remain elusive. Here, we construct a three‐dimensional climate model that includes cloud physics and simple chemistry as the first step toward fully understanding the Venus clouds. Our simulated vertical profiles of the Venus clouds agree well with observations. We find that the condensable gases, sulfuric acid and water vapors in the cloud region become more abundant in the lower latitudes due to the temperature difference over different latitudes. The cloud top becomes lower as it approaches the polar region, and the underpinning processes are related to sulfuric acid chemical production and meridional circulation. The equatorial cloud structure shows semidiurnal features, which are related to the excited thermal tides in the Venus atmosphere. Our study is preparing for future Venus missions like EnVision, to maximize their science returns. Key Points: We construct a Venus climate model with cloud physics, and the cloud vertical structure agrees with observationsH2SO4 and H2O vapors in the middle cloud basically follow their SVMRs and show higher concentrations at low latitudesThe semidiurnal thermal tide affects H2SO4 and H2O vapors, cloud mass loading and acidity at different altitudes [ABSTRACT FROM AUTHOR]

There is a growing consensus that Venus is seismically active, although its level of seismicity could be very different from that of Earth due to the lack of plate tectonics. Here, we estimate upper and lower bounds on the expected annual seismicity of Venus by scaling the seismicity of the Earth. We consider different scaling factors for different tectonic settings and account for the lower seismogenic thickness of Venus. We find that 95–296 venusquakes equal to or bigger than moment magnitude (Mw) 4 per year are expected for an inactive Venus, where the global seismicity rate is assumed to be similar to that of continental intraplate seismicity on Earth. For the active Venus scenarios, we assume that the coronae, fold belts, and rifts of Venus are currently seismically active. This results in 1,161–3,609 venusquakes ≥Mw4 annually as a realistic lower bound and 5,715–17,773 venusquakes ≥Mw4 per year as a maximum upper bound for an active Venus. Plain Language Summary: Venus could be seismically active at the moment, but it is uncertain how many earthquakes (or to use the proper term: venusquakes) there could be in a year. Here, we calculate the minimum and maximum number of venusquakes we could expect in a given year on Venus based on different assumptions. If we assume there is not much seismic activity on Venus (comparable to the interior of tectonic plates on Earth), we find that we could expect about a few hundred venusquakes per year with a magnitude bigger than or equal to 4. For an estimate of the maximum amount of venusquakes, we assume that Venus has regions with more seismic activity: the so‐called coronae, fold belts, and rifts. Depending on our assumptions, we then find that more than 17,000 venusquakes with a magnitude bigger than or equal to 4 could occur in a year. Key Points: An inactive Venus with global background seismicity like Earth's continental intraplate seismicity has a few hundred quakes ≥Mw4 per yearA lower bound on an active Venus where fold belts, coronae, and rifts are seismically active predicts a few thousand quakes ≥Mw4 annuallyThe upper bound for an active Venus results in thousands (∼5,000–18,000) venusquakes ≥Mw4 per year [ABSTRACT FROM AUTHOR]

This paper introduces the new Venus global ionosphere‐thermosphere model (V‐GITM) which incorporates the terrestrial GITM framework with Venus‐specific parameters, ion‐neutral chemistry, and radiative processes in order to simulate some of the observable features regarding the temperatures, composition, and dynamical structure of the Venus atmosphere from 70 to 170 km. Atmospheric processes are included based upon formulations used in previous Venus GCMs, several augmentations exist, such as improved horizontal and vertical momentum equations and tracking exothermic chemistry. Explicitly solving the momentum equations allows for the exploration of its dynamical effects on the day‐night structure. In addition, V‐GITM's use of exothermic chemistry instead of a strong heating efficiency accounts for the heating due to the solar EUV while producing comparable temperatures to empirical models. V‐GITM neutral temperatures and neutral‐ion densities are compared to upper atmosphere measurements obtained from Pioneer Venus and Venus Express. V‐GITM demonstrates asymmetric horizontal wind velocities through the cloud tops to the middle thermosphere and explains the mechanisms for sustaining the wind structure. In addition, V‐GITM produces reasonable dayside ion densities and shows that the neutral winds can carry the ions to the nightside via an experiment advecting O2+ ${\mathrm{O}}_{2}^{+}$. Plain Language Summary: We present a new, state‐of‐the‐art Venus global circulation model, the Venus global ionosphere thermosphere model. The new model will be useful for answering unknown questions about Venus' atmosphere, the physics of CO2 rich planets, and Venus missions utilizing the aerobraking maneuver. We performed many model simulations and compared the results to some of the existing Venus data sets to assess the accuracy of the model. The results showed that the dayside extreme ultraviolet heating can be captured using the dominant ion‐neutral chemistry rather than relying on simplified legacy methods. Furthermore, the cloud layer below the thermosphere has a unique wind pattern and its impact on the thermospheric temperatures and winds were explored. This work also revealed that the thin nightside ionosphere forms as a result of the transport of a single ion species. Key Points: A new, non‐hydrostatic Venus ionosphere‐thermosphere model is introduced with new physics not previously included in Venus GCMsSimulations during solar minimum conditions are used for data‐model comparisons of the temperatures, plasma, and neutral densitiesThe influence of the retrograde superrotating zonal flow is explored in relation to how it affects the neutral temperature and velocities [ABSTRACT FROM AUTHOR]

The Venusian atmosphere hosts a 10 km deep convective layer that has been studied by various spacecrafts. However, the impact of the strong vertical mixing on the chemistry of this region is still unknown. This study presents the first realistic coupling between resolved small‐scale turbulence and a chemical network. The resulting vertical mixing is different for each species: those with longer chemical timescales will tend to be well‐mixed. Vertical eddy diffusion due to resolved convection motions was estimated, ranging from 102 to 104 m2/s for the 48–55 km convective layer, several orders of magnitude above the typically used value. In the 48–55 km convective layer, the impact of the small‐scale turbulence on the cloud layer boundaries was between 200 m and 1 km. The impact of turbulence on cloud chemistry is consistent with Venus Express/Visible and Infrared Thermal Imaging Spectrometer observations. The observability at the cloud‐top of small‐scale turbulence by VenSpec‐U spectrometer would be challenging. Plain Language Summary: Venus hosts a global sulfuric acid cloud layer between 45 and 70 km. A convective layer is present between roughly 50 and 60 km, with its variability in latitude and local time assessed by observation, with a thicker layer at high latitude and at night. One question that remains unclear is how this turbulence mixes momentum, heat, and chemical species. Especially, the impact of the strong vertical mixing on the chemistry of this region is still unknown. To investigate this topic, we use a convection‐resolving model coupled for the first time with a realistic chemical network. The resulting vertical mixing is different for each species: those with longer chemical timescales will tend to be well‐mixed. 1D and global circulation models use the so‐called vertical eddy diffusion approach to represent turbulent motion, quantified in our model and underestimated in chemistry models. The small‐scale turbulence in the cloud layer causes a variation in the altitude of the top and bottom boundaries of the cloud. Our model shows that the impact of turbulence on cloud chemistry corresponds well to what has been observed by satellites. In the future, the EnVision mission will be able to observe chemical species at the small turbulence scales. Key Points: Estimation for the first time of the spatial and temporal variability of chemical species due to vertical mixingQuantification of the vertical eddy diffusion coefficient, order of magnitude above typical used valuesCloud‐top altitudes change by 0.2–1 km due to vertical convective mixing and gravity waves [ABSTRACT FROM AUTHOR]

The collisionless nature of planetary magnetospheres means that electromagnetic forces are fundamental in controlling the flow of energy and momentum through these systems. We use Pioneer Venus Orbiter (PVO) observations to demonstrate that the magnetic pumping process can be active at Venus, in analogy to its recent discovery at Mars. The presented case study demonstrates the framework for how the process can work at Venus, and the results of a statistical analysis show that the ambient plasma conditions support the process being active. Magnetic pumping enables low frequency magnetosonic waves to heat ambient ionospheric electrons and provides a mechanism that couples the solar wind to the Venusian ionosphere. This is the first time the magnetic pumping process has been discussed at Venus. Plain Language Summary: Our Sun emits a stream of particles outward into our solar system, known as the solar wind. When these particles encounter planets and other bodies (such as comets), they either collide with the body (as happens with our Moon) or are deflected around the obstacle, similar to how water in a stream flows around a rock (this happens at most planets, including Earth, Venus and Mars). Understanding the physical forces that control this deflection enable us to understand how the Sun interacts with the planets in our solar system. We use in situ measurements made by the Pioneer Venus Orbiter spacecraft, which orbited the planet Venus, to investigate one specific process, known as "magnetic pumping." This process allows energy from the solar wind to flow into the Venusian atmosphere. We provide a case study demonstrating how this process can operate at Venus, and show that the average conditions in the near Venus space environment can support this process in a more general sense. Key Points: A case study demonstrates how the magnetic pumping process operates at VenusStatistical analysis of the plasma conditions at Venus support the notion that magnetic pumping can operate thereMagnetic pumping provides an avenue for the solar wind to couple to the Venusian ionosphere and heat ionospheric electrons [ABSTRACT FROM AUTHOR]

Surface geologic features form a detailed record of Venus' evolution. Venus displays a profusion of volcanic and tectonics features, including both familiar and exotic forms. One challenge to assessing the role of these features in Venus' evolution is that there are too few impact craters to permit age dates for specific features or regions. Similarly, without surface water, erosion is limited and cannot be used to evaluate age. These same observations indicate Venus has, on average, a very young surface (150–1000 Ma), with the most recent surface deformation and volcanism largely preserved on the surface except where covered by limited impact ejecta. In contrast, most geologic activity on Mars, the Moon, and Mercury occurred in the 1st billion years. Earth's geologic processes are almost all a result of plate tectonics. Venus' lacks such a network of connected, large scale plates, leaving the nature of Venus' dominant geodynamic process up for debate. In this review article, we describe Venus' key volcanic and tectonic features, models for their origin, and possible links to evolution. We also present current knowledge of the composition and thickness of the crust, lithospheric thickness, and heat flow given their critical role in shaping surface geology and interior evolution. Given Venus' hot lithosphere, abundant activity and potential analogues of continents, roll-back subduction, and microplates, it may provide insights into early Earth, prior to the onset of true plate tectonics. We explore similarities and differences between Venus and the Proterozoic or Archean Earth. Finally, we describe the future measurements needed to advance our understanding of volcanism, tectonism, and the evolution of Venus. [ABSTRACT FROM AUTHOR]

We explore the potential for repeat‐pass SAR Interferometry (InSAR) correlation to track volcanic activity on Venus' surface motivated by future SAR missions to Earth's sister planet. We use Hawai'i as a natural laboratory to test whether InSAR can detect lava flows assuming orbital and instrument parameters similar to that of a Venus mission. Hawai'i was chosen because lava flows are frequent, and well documented by the United States Geological Survey, and because Hawai'i is a SAR supersite, where space agencies have offered open radar data sets for analysis. These data sets have different wavelengths (L, C, and X bands), bandwidths, polarizations, look angles, and a variety of orbital baselines, giving opportunity to assess the suitability of parameters for detecting lava flows. We analyze data from ALOS‐2 (L‐band), Sentinel‐1 (C‐band), and COSMO‐SkyMed (X‐band) spanning 2018 and 2022. We perform SAR amplitude and InSAR correlation analysis over temporal baselines and perpendicular baselines similar to those of a Venus mission. Fresh lava flows create a sharp, noticeable decrease in InSAR correlation that persists indefinitely for images spanning the event. The same lava flows are not always visible in the corresponding amplitude images. Moreover, noticeable decorrelation persists in image pairs acquired months after the events due to post‐emplacement contraction of flows. Post‐emplacement effects are hypothesized to last longer on the Venusian surface, increasing the likelihood of detecting Venus lava flows using InSAR. We argue for further focus on repeat‐pass InSAR capabilities in upcoming Venus missions, to detect and quantify volcanic activity on Earth's hotter twin. Plain Language Summary: Scientists are still unsure whether volcanic activity is presently occurring on Venus. Future missions to Venus may have the opportunity to detect new lava flows on Venus' surface using a process called interferometry, in which two radar images of a planet's surface over time are compared to see what's changed between them. Interferometry has been used to detect lava and volcanic activity on Earth in the past. We use Hawai'i as a natural laboratory, measuring lava flows there with interferometry, under simulated conditions of a Venus mission, to test whether it will be possible for future Venus missions to track lava flows with interferometry. From the results of our case study, we believe that future missions to Venus such as NASA's VERITAS will be able to do exactly that. Key Points: Under favorable mission and instrument conditions, SAR Interferometry (InSAR) can detect lava flows on VenusInSAR correlation effects from thermal subsidence can be seen for several months post‐lava‐flow‐emplacementLava flows are more easily visible in InSAR correlation maps than in differenced SAR amplitude maps [ABSTRACT FROM AUTHOR]

We present here a numerical analysis of planetary and calendric cycles of planet Venus showing how Mayas could have known about Maximum Common Divisor and least common multiples concepts. Venus cycles were of capital importance for them as shown in the Dresden Codex. We will learn about Ring numbers and read several pages related to various astronomical Venus facts. [ABSTRACT FROM AUTHOR]

We have studied energy-low-cost ballistic trajectories of a spacecraft flight to Venus with asteroid flyby. It is shown that when using schemes including a gravitational maneuver required to deliver the lander to a given area on the surface of Venus, the passing of at least one asteroid is possible. A total of 39 asteroids were discovered, whose passage can occur when launching in 2029–2050. An analysis of the attainable landing areas during the flight of a spacecraft to Venus along trajectories of this type has been performed. It is shown that in each launch window in the period from 2029 to 2050, it is possible to find an asteroid whose passage is possible during the time period between two approaches of the spacecraft to Venus. [ABSTRACT FROM AUTHOR]

Sapas Mons is a large shield volcano in Atla Regio on Venus. Its summit region is partially encircled by a system of pits and extensional faults (graben). The existence and configuration of this system have been attributed to stresses generated above the margin of a magma chamber spanning the region beneath the summit. The proposed stress‐generating mechanism includes either withdrawal of magma from or solidification of magma within such a chamber (Keddie & Head, 1994, https://doi.org/10.1007/bf00644896). To explore these hypotheses, we calculate Finite Element Method models of stresses and deformations resulting from magma chamber depressurization beneath a Sapas Mons‐sized edifice with axisymmetric geometry. For a range of magma chamber depths and vertical thicknesses, we determine the minimum under pressure that produces a stress state predicting failure in circumferential normal mode at the observed position of the graben system. We also determine maximum under pressure under two conditions: (1) no failure (thrust fault mode) predicted at the summit, and (2) predicted failure (thrust fault mode) limited to within 10 km of the summit. We find that successful models require sill‐like chamber geometry with vertical thicknesses <1.5 km (diameter to thickness aspect ratios >66:1), and chamber depth <8 km beneath the summit. Calculated reductions in chamber volume are comparable to volumes of late‐stage eruptive units mapped at Sapas Mons, favoring the magma withdrawal hypothesis for graben system formation. Evidence that unit 5 of Keddie and Head (1994, https://doi.org/10.1007/bf00644896) overlapped in time with, but largely postdated, the graben forming event renders it the most likely destination for magma removed from the chamber. Plain Language Summary: Sapas Mons is a large volcanic mountain on Venus, with lava flows that extend outwards for 100s of kilometers. Its distinctive summit region is partially encircled by a narrow ring of faults, which are most prominent on the east side. It has been proposed that a very wide but short chamber full of molten rock (magma) exists beneath the center of Sapas Mons, and that the faulting occurs when the top of the chamber moves downward, which can happen in two ways: (1) magma cools and solidifies within the chamber or (2) the magma leaves the chamber, presumably to erupt at the surface in lava flows. We calculated computer models of the process by which the magma chamber would contract in order to figure out the conditions under which the observed faults could happen (and also under which other types of faults, not seen, are avoided). The chambers must be less than 8 km below the summit and thinner than 1.5 km tall. We determined that the volume lost by the chamber is about the same as that estimated for a specific group of lava flows near the summit, a finding that favors scenario 2 above. Key Points: Sapas Mons volcano on Venus exhibits a partial ring of extensional faults that results from depressurization of an oblate magma chamberNumerical models of magma chamber deflation require extremely oblate chambers at shallow depths to explain observed fault patternsModeled chamber volume changes are comparable to volumes of the youngest mapped volcanic units, pointing to a magma withdrawal mechanism [ABSTRACT FROM AUTHOR]

Abstract Parker Solar Probe (PSP) uses Venus gravity assists (VGA) to achieve the closest orbits to the Sun by a spacecraft. During the third (VGA3) and fourth (VGA4) Venus gravity assists, the PSP entered the Venusian ionosphere. The core electrons could not be detected as they were below the SWEAP/SPAN electrostatic analyzer instrument energy threshold. However, there is another way to estimate the core temperature using quasi‐thermal noise (QTN) data measured by the PSP/FIELDS Radio Frequency Spectrometer instrument. QTN spectroscopy offers an effective tool for measuring electron temperature and density when the electrons are too cold for other instruments to measure, as is the case with VGA3 and VGA4. Low‐frequency plasma wave data from the closest approach during VGA3 and VGA4 was analyzed with the QTN spectroscopy technique to determine the density and first‐ever in‐situ thermal electron temperature of the Venusian ionosphere at solar minimum.

It has recently been suggested that deformed crustal plateaus on Venus may be composed of felsic (silica-rich) rocks, possibly supporting the idea of an ancient ocean there. However, these plateaus have a tendency to collapse owing to flow of the viscous lower crust. Felsic minerals, especially water-bearing ones, are much weaker and thus lead to more rapid collapse, than more mafic minerals. We model plateau topographic evolution using a non-Newtonian viscous relaxation code. Despite uncertainties in the likely crustal thickness and surface heat flux, we find that quartz-dominated rheologies relax too rapidly to be plausible plateau-forming material. For plateaus dominated by a dry anorthite rheology, survival is possible only if the background crustal thickness is less than 29 km, unless the heat flux on Venus is less than the radiogenic lower bound of 34 [Formula: see text]. Future spacecraft determinations of plateau crustal thickness and mineralogy will place firmer constraints on Venus's heat flux.

We show that the nucleic acid bases adenine, cytosine, guanine, thymine, and uracil, as well as 2,6-diaminopurine, and the "core" nucleic acid bases purine and pyrimidine, are stable for more than one year in concentrated sulfuric acid at room temperature and at acid concentrations relevant for Venus clouds (81% w/w to 98% w/w acid, the rest water). This work builds on our initial stability studies and is the first ever to test the reactivity and structural integrity of organic molecules subjected to extended incubation in concentrated sulfuric acid. The one-year-long stability of nucleic acid bases supports the notion that the Venus cloud environment—composed of concentrated sulfuric acid—may be able to support complex organic chemicals for extended periods of time. [ABSTRACT FROM AUTHOR]

The surface of Venus is in contact with a hot (~470 °C), high pressure (92 bars), and caustic (CO2 with S, but little H2O) atmosphere, which should cause progressive alteration of the crust in the form of sulfate and iron-oxide coatings; however, the exact rate of alteration and mineral species are not well constrained. Different experimental approaches, each with its own limitations, are currently being used to constrain mineralogy and alteration rates. One note is that no experimental approach has been able to fully replicate the necessary conditions and sustain them for a significant length of time. Furthermore, geochemical modeling studies can also constrain surface alteration mineralogy, again with different assumptions and limitations. Here, we review recent geochemical modeling and experimental studies to constrain the state of the art for alteration mineralogy, rate of alteration, open questions about the surface mineralogy of Venus, and what can be constrained before the fleet of missions arrives later this decade. Combining the new results confirms that basalt on the surface of Venus should react quickly and form coatings of sulfates and iron-oxides; however, the mineralogy and rate of alteration are dependent on physical properties of the protolith (including bulk composition, mineralogy, and crystallinity), as well as atmospheric composition, and surface temperature. Importantly, the geochemical modeling results show that the mineralogy is largely controlled by atmospheric oxygen fugacity, which is not well constrained for the near-surface environment on Venus. Therefore, alteration experiments run over a range of oxygen and sulfur fugacities are needed across a wide range of Venus analog materials with varying mineralogy and crystallinity. [ABSTRACT FROM AUTHOR]

On Venus, radar observations of the surface have highlighted two categories of craters: bright‐floored, interpreted as pristine, and dark‐floored, interpreted as being partially filled by lava. While volcanic resurfacing occurs within and outside craters in the plains, it seems mainly concentrated within the interior of dark‐floored craters in the crustal plateaus, suggesting that the magma is negatively buoyant there. Indeed, crater unloading may facilitate vertical ascent of a negatively buoyant magma by decompressing the underlying crust. However, the crater topography also generates a shear stress which would tend to horizontalize the vertical propagation of a dyke. We use numerical simulations of magma ascent in an axisymmetric crater stress field to demonstrate that, depending on the crust thickness and the magma‐crust density contrast, a negatively buoyant magma can indeed erupt only in the crater interior while remaining stored in the crust elsewhere. In particular, we identify four different behaviors depending on if and where a magma‐filled crack ascending below a crater reaches the surface. We draw a regime diagram as a function of two characteristic dimensionless numbers. For eruption to occur only in the crater interior requires a crust thinner than 45 km and a limited range of magma‐crust density contrasts, between 40 and 280 kg m−3 for crust thicknesses between 20 and 45 km, the permissible range decreasing for increasing crustal thicknesses. These results suggest that the crustal plateaus may not be particularly thick and could be slightly differentiated, but probably not very felsic. Plain Language Summary: The Magellan mission revealed two categories of impact craters at the surface of Venus: the pristine bright‐floored and the dark‐floored craters, which are interpreted as craters partially filled by smooth lava after their formation. In the crustal plateaus of Venus, the magma reaches the surface mainly within craters, suggesting that it is denser than the crust. Because of the crater negative topography, the underlying crust is decompressed relative to its surroundings, which, in turn, facilitates magma ascent below the crater despite its negative buoyancy. We first gather surface observations on a set of craters located in the crustal plateaus of Venus to construct a characteristic fresh crater topography. We then use a model of magma ascent below a crater in the crust of Venus to constrain the magma and crust densities as well as the initial magma storage depth that allow for magma eruption within the crater interior only. We show that magma reaches the surface only in the interior of the crater if the crust is slightly less dense than the magma and if it is not too thick (≤45 km in thickness). Key Points: We identify four different behaviors for magma‐filled crack propagation below cratersWe draw a behavior diagram as a function of two dimensionless numbers characterizing dyke propagation below a craterMagma infilling of dark‐floored craters in Venus' plateaus requires a crustal thickness ≤45 km and a small crust‐magma density contrast [ABSTRACT FROM AUTHOR]

Venus boasts an abundance of volcanoes and volcano‐like structures. Synthetic aperture radar images of the surface have revealed extensive evidence of volcanism, including lava flows and edifices. Volcanic activity is further supported by crater statistics, and analysis of topography and gravity data. Unique to Venus, coronae are quasi‐circular volcano‐tectonic features exhibiting diverse volcanic characteristics. Despite this, volcanism is often under‐represented in formation models. We identify a new subset of coronae that display topographic changes subsequent to the emplacement of lava flows within their fracture annuli, pointing to the critical role of volcanic and magmatic processes in the formation of these coronae. Through spherical‐harmonic distribution analysis, we find that this new subset is spatially related to the full coronae database, pointing to an intrinsic process of coronae formation. Furthermore, coronae exhibit strong correlations and similar spectral shapes at low spherical harmonic degrees with large volcanoes, suggesting a shared geodynamic origin. Our findings underscore the pivotal role of volcanism in coronae formation and highlight the need for future research to integrate magmatic and volcanic processes more comprehensively into geophysical models. Such models would better capture the complex interactions between volcanic emplacement, magmatic activity, and lithospheric dynamics on Venus. Plain Language Summary: Venus's surface has a large number of volcanoes and features with characteristics similar to volcanoes. Radar imagery of the surface reveals signs of volcanism such as lava flows and volcanically built mountains. A unique volcanic feature, found only on Venus, are coronae, which have circular fractures and various types of associated volcanic activity. Explanations of how coronae form often do not consider the role of volcanic activity. In our study, we identify a new group of coronae that have undergone changes in topography after lava erupted and flowed over them, which has been interpreted as volcanism having a central role in corona formation. The locations of this subset of coronae on the surface fit well with all other coronae, suggesting that the processes that caused this topographic change occur throughout the corona population and are a basic part of how all coronae form. Additionally, we find that coronae have a similar pattern on the surface to large volcanoes, which indicates a shared volcanically based origin. Our work shows that in order to better understand coronae, we need to consider the role of volcanism in their formation. Key Points: A new subset of coronae shows topographic changes post‐lava flow emplacementSpectral analysis reveals strong long‐wavelength similarities between coronae and large volcanoesVolcanism plays a crucial role in corona formation and should be considered central in future models of formation [ABSTRACT FROM AUTHOR]

The tentative detection of ppb levels of phosphine (PH[sub 3]) in the clouds of Venus was extremely surprising, as this reduced gas was not expected to be a component of Venus' oxidized atmosphere. Despite potential confirmation in legacy Pioneer Venus mass spectrometry data, the detection remains controversial. Here we review the potential production of phosphine by gas reactions, surface and sub-surface geochemistry, photochemistry, and other nonequilibrium processes. None of these potential phosphine production pathways is sufficient to explain the presence of phosphine in Venus atmosphere at near the observed abundance. The source of atmospheric PH[sub 3] could be unknown geo- or photochemistry, which would imply that the consensus on Venus' chemistry is significantly incomplete. An even more extreme possibility is that a strictly aerial microbial biosphere produces PH[sub 3]. The detection of phosphine adds to the complexity of chemical processes in the Venusian environment and motivates better quantitation of the gas phase chemistry of phosphorus species and in situ follow-up sampling missions to Venus. [ABSTRACT FROM AUTHOR]

Venus is Earth's closest neighbor, hosting a similar size, density, and location in the Solar System. Due to these similarities, Venus has been suggested as a premier location for particular mission sets to include: near-Venus communications and positioning, navigation, and timing (PNT); planetary science; heliophysics; space weather monitoring; and planetary defense. This paper, for the first time in literature, presents 37 unique planar periodic orbits discovered in the Sun–Venus system that may be used for such missions. The Circular Restricted Three-Body Problem (CR3BP) is the primary dynamical model utilized to generate all periodic orbits in the Sun–Venus system. The discovered orbits are grouped into four categories based on their shape: Near-Venus periodic orbits, Sun–Venus touring periodic orbits, Sun–Venus touring periodic orbits featuring near-Sun flybys, and Sun–Venus touring periodic orbits featuring near-Mercury flybys. Each orbit is discussed in terms of its respective Jacobi constant and stability within the context of the CR3BP. The stability of the orbits provides a preliminary analysis of station-keeping costs related to propellant expenditure, thereby determining the feasibility of implementing these trajectories. Specifically, this research shows that most of the identified orbits possess stability indices below 2, suggesting that minimal propellant is necessary for station-keeping maneuvers to sustain the preferred trajectory. For all orbits, specific initial position and velocity states conditions are provided, accompanied by recommendations for their potential mission applications. This research aims to advance ongoing astrodynamics research by filling a catalog hole and providing a Sun–Venus CR3BP orbit baseline. [ABSTRACT FROM AUTHOR]

Scientists have long speculated about the potential habitability of Venus, not at the 700K surface, but in the cloud layers located at 48–60 km altitudes, where temperatures match those found on Earth's surface. However, the prevailing belief has been that Venus' clouds cannot support life due to the cloud chemical composition of concentrated sulfuric acid—a highly aggressive solvent. In this work, we study 20 biogenic amino acids at the range of Venus' cloud sulfuric acid concentrations (81% and 98% w/w, the rest water) and temperatures. We find 19 of the biogenic amino acids we tested are either unreactive (13 in 98% w/w and 12 in 81% w/w) or chemically modified in the side chain only, after 4 weeks. Our major finding, therefore, is that the amino acid backbone remains intact in concentrated sulfuric acid. These findings significantly broaden the range of biologically relevant molecules that could be components of a biochemistry based on a concentrated sulfuric acid solvent. [ABSTRACT FROM AUTHOR]

Recent ground-based observations of Venus have detected a single spectral feature consistent with phosphine (PH3) in the middle atmosphere, a gas which has been suggested as a biosignature on rocky planets. The presence of PH3 in the oxidized atmosphere of Venus has not yet been explained by any abiotic process. However, state-of-the-art experimental and theoretical research published in previous works demonstrated a photochemical origin of another potential biosignature—the hydride methane—from carbon dioxide over acidic mineral surfaces on Mars. The production of methane includes formation of the HC · O radical. Our density functional theory (DFT) calculations predict an energetically plausible reaction network leading to PH3, involving either HC · O or H· radicals. We suggest that, similarly to the photochemical formation of methane over acidic minerals already discussed for Mars, the origin of PH3 in Venus' atmosphere could be explained by radical chemistry starting with the reaction of ·PO with HC·O, the latter being produced by reduction of CO2 over acidic dust in upper atmospheric layers of Venus by ultraviolet radiation. HPO, H2P·O, and H3P·OH have been identified as key intermediate species in our model pathway for phosphine synthesis. [ABSTRACT FROM AUTHOR]

The possible existence of a microbial community in the venusian clouds is one of the most intriguing hypotheses in modern astrobiology. Such a community must be characterized by a high survivability potential under severe environmental conditions, the most extreme of which are very low pH levels and water activity. Considering different scenarios for the origin of life and geological history of our planet, a few of these scenarios are discussed in the context of the origin of hypothetical microbial life within the venusian cloud layer. The existence of liquid water on the surface of ancient Venus is one of the key outstanding questions influencing this possibility. We link the inherent attributes of microbial life as we know it that favor the persistence of life in such an environment and review the possible scenarios of life's origin and its evolution under a strong greenhouse effect and loss of water on Venus. We also propose a roadmap and describe a novel methodological approach for astrobiological research in the framework of future missions to Venus with the intent to reveal whether life exists today on the planet. [ABSTRACT FROM AUTHOR]

The recent and still controversial claim of phosphine detection in the venusian atmosphere has reignited consideration of whether microbial life might reside in its cloud layers. If microbial life were to exist within Venus' cloud deck, these microorganisms would have to be multi-extremophiles enclosed within the cloud aerosol particles. The most straightforward approach for resolving the question of their existence is to obtain samples of the cloud particles and analyze their interior. While developing technology has made sophisticated in situ analysis possible, more detailed information could be obtained by examining samples with instrumentation in dedicated ground-based facilities. Ultimately, therefore, Venus Cloud-level Sample Return Missions will likely be required to resolve the question of whether living organisms exist in the clouds of Venus. Two multiphase mission concepts are currently under development for combining in situ analyses with a sample return component. The Venus Life Finder architecture proposes collection of cloud particles in a compartment suspended from a balloon that floats for weeks at the desired altitude, while the Novel solUtion for Venus explOration and Lunar Exploitation (NUVOLE) concept involves a glider that cruises within the cloud deck for 1200 km collecting cloud aerosol particles through the key regions of interest. Both architectures propose a rocket-driven ascent with the acquired samples transported to a high venusian orbit as a prelude to returning to Earth or the Moon. Both future conceptual missions with their combined phases will contribute valuable information relative to the habitability of the clouds at Venus, but their fulfillment is decades away. We suggest that, in the meantime, a simplification of a glider cloud-level sample collection scenario could be accomplished in a shorter development time at a lower cost. Even if the cloud particles are not organic and show no evidence of living organisms, they would reveal critical insights about the natural history and evolution of Venus. [ABSTRACT FROM AUTHOR]

Venus is Earth's sister planet, with similar mass and density but an uninhabitably hot surface, an atmosphere with a water activity 50–100 times lower than anywhere on Earths' surface, and clouds believed to be made of concentrated sulfuric acid. These features have been taken to imply that the chances of finding life on Venus are vanishingly small, with several authors describing Venus' clouds as "uninhabitable," and that apparent signs of life there must therefore be abiotic, or artefactual. In this article, we argue that although many features of Venus can rule out the possibility that Earth life could live there, none rule out the possibility of all life based on what we know of the physical principle of life on Earth. Specifically, there is abundant energy, the energy requirements for retaining water and capturing hydrogen atoms to build biomass are not excessive, defenses against sulfuric acid are conceivable and have terrestrial precedent, and the speculative possibility that life uses concentrated sulfuric acid as a solvent instead of water remains. Metals are likely to be available in limited supply, and the radiation environment is benign. The clouds can support a biomass that could readily be detectable by future astrobiology-focused space missions from its impact on the atmosphere. Although we consider the prospects for finding life on Venus to be speculative, they are not absent. The scientific reward from finding life in such an un-Earthlike environment justifies considering how observations and missions should be designed to be capable of detecting life if it is there. [ABSTRACT FROM AUTHOR]

This work reviews possible signatures and potential detectability of present-day volcanically emitted material in the atmosphere of Venus. We first discuss the expected composition of volcanic gases at present time, addressing how this is related to mantle composition and atmospheric pressure. Sulfur dioxide, often used as a marker of volcanic activity in Earth's atmosphere, has been observed since late 1970s to exhibit variability at the Venus' cloud tops at time scales from hours to decades; however, this variability may be associated with solely atmospheric processes. Water vapor is identified as a particularly valuable tracer for volcanic plumes because it can be mapped from orbit at three different tropospheric altitude ranges, and because of its apparent low background variability. We note that volcanic gas plumes could be either enhanced or depleted in water vapor compared to the background atmosphere, depending on magmatic volatile composition. Non-gaseous components of volcanic plumes, such as ash grains and/or cloud aerosol particles, are another investigation target of orbital and in situ measurements. We discuss expectations of in situ and remote measurements of volcanic plumes in the atmosphere with particular focus on the upcoming DAVINCI, EnVision and VERITAS missions, as well as possible future missions. [ABSTRACT FROM AUTHOR]

The Sandal-Binder Aphrodite, a witty variation on Praxiteles' Aphrodite of Knidos, is one of the most frequently reproduced sculptural types in Greco-Roman art. Created in a variety of materials throughout the Mediterranean, extant versions of this iconography show the goddess in the act of tying (or possibly untying) her sandal. Although a large number of these works of art date between the first and fourth century CE, most studies on the Sandal-Binder have approached it primarily as an expression of Hellenistic Greek artistic trends. The present study shifts our attention away from the cultural milieu of the Sandal-Binder's creation to that of its reception. Two well-preserved examples--one from a house in Pompeii and the other from London--attest to the process of translating or adapting this sensual image of Aphrodite to a Roman ideological framework. In both cases, it is through the language of body adornment that this transformation is achieved: while the example from Pompeii (a marble statuette adorned with gold paint) shows the goddess wearing contemporary jewelry and clothing, the diminutive silver figurine from London is part of a fashionable hairpin that points to the dissemination of imperial hairstyles in Rome's remotest province. By calling attention to their design and function, this essay highlights the complex polysemy of Roman Sandal-Binders and the powerful messages they communicated to a diverse audience of viewers both at the heart of the empire and in the provinces. [ABSTRACT FROM AUTHOR]

Series of consecutive UV (365 nm) images of Venus cloud coverage provide a way to investigate dynamics of the mesosphere. An unprecedented series of such images was obtained by the VMC/Venus Express (ESA) and UVI/Akatsuki (JAXA) cameras from 2006 to 2022. At 10°S long-term variations in the mean zonal and meridional wind speed are observed with a period of 12.5 ± 0.5 years. Analysis of the of the mean zonal wind behavior around noon (12 ± 1 h) at phase angles of 60°–90° in limited observation time intervals shows that near the minimum of the long-term dependence the deceleration of the horizontal flow is observed above the highest part of Aphrodite Terra, Ovda Regio, for both VMC and UVI. Conversely, acceleration is observed above the Ovda Regio near the maximum of the long-term dependence. The considered longitudinal variations of the zonal wind speed extend from the equator to middle latitudes (0°–40°). The meridional wind speed shows longitudinal variations associated with the topography of the underlying surface, regardless of whether the horizontal flow is slowing down or accelerating above the highlands of Aphrodite Terra. [ABSTRACT FROM AUTHOR]

Venus' thick atmosphere is capable of destroying kilometer-sized bodies such as asteroids, creating various types of traces on the surface. While larger cosmic bodies are able to reach the surface, creating impact craters or crater dispersion fields, smaller bodies effectively transfer the initial kinetic energy into the atmosphere, resulting in an "atmospheric explosion" at some altitude. In these cases, the most visible marks on the surface of Venus are created by atmospheric shock waves and the flow of gas behind the shock fronts reflected from the solid surface. The transitional sizes of impactors that break up in the atmosphere but reach the surface give rise to clusters of craters. The paper presents the first results of three-dimensional calculations of the destruction of rocky asteroids in the atmosphere of Venus, indicating significant differences from simple two-dimensional axisymmetric calculations. [ABSTRACT FROM AUTHOR]

The idea for Reymont's Venus was most likely connected with his stay in Strzelce Małe near Przedbórz, where he spent his vacation in 1897, and the direct inspiration could have been the storms that hit the area. The writer had already planned a sketch devoted to Venus de Milo. Venus was originally published by a Munich publishing house and has several later editions. It interpretations range from sociological to axiological. The article describes the circumstances of the creation of the work, introduces its context, and offers a philosophical reading. [ABSTRACT FROM AUTHOR]

All known life on Earth inhabits environments that maintain conditions between certain extremes of temperature, chemical composition, energy availability, and so on (Chapter 6). Life may have emerged in similar environments elsewhere in the Solar System and beyond. The ongoing search for life elsewhere mainly focuses on those environments most likely to support life, now or in the past—that is, potentially habitable environments. Discussion of habitability is necessarily based on what we know about life on Earth, as it is our only example. This chapter gives an overview of the known and presumed requirements for life on Earth and discusses how these requirements can be used to assess the potential habitability of planetary bodies across the Solar System and beyond. We first consider the chemical requirements of life and potential feedback effects that the presence of life can have on habitable conditions, and then the planetary, stellar, and temporal requirements for habitability. We then review the state of knowledge on the potential habitability of bodies across the Solar System and exoplanets, with a particular focus on Mars, Venus, Europa, and Enceladus. While reviewing the case for the potential habitability of each body, we summarize the most prominent and impactful studies that have informed the perspective on where habitable environments are likely to be found. [ABSTRACT FROM AUTHOR]

In this paper, the object of analysis is a votive relief found on the territory of the Roman road station Carassura. The plate is a part of the collection of the National Archaeological Museum and it has not been published previously. The iconography of the image is examined, and an attempt is made to attribute and date the object. The discussion on the votive relief places it in the broader context of artifacts with Greco-Roman iconography and clearly detectable Egyptian influences. [ABSTRACT FROM AUTHOR]

Since December 2015, Ultraviolet Imager (UVI) onboard Akatsuki has been observing Venus clouds at the wavelengths of 283 and 365 nm. Horizontal winds near the cloud top derived from the UVI images over ∼7 earth years are analyzed to elucidate spatial and temporal variability of the superrotation and planetary‐scale waves. Zonal winds averaged over the analysis period are asymmetric with respect to the equator, being faster in the southern hemisphere. This asymmetry varied temporarily and was occasionally reverted. Comparison of the winds from the two wavelengths suggests that it is uncertain whether the asymmetry is in the wind distribution or in the sensing altitude for winds. Mean zonal winds representing the superrotation exhibited broad low‐frequency variability with spectra resembling the red noise spectra. This is indicative of the presence of internal variability rather than responses to periodical external forcing. Planetary‐scale waves with zonal‐wavenumber 1 at periods around 4 and 5 days, which have been interpreted as equatorial Kelvin and Rossby waves, respectively, are quantified. While the ∼5‐day waves have nearly constant frequencies, the ∼4‐day waves have variable phase speeds that follow the superrotation speed. This result indicates that the ∼5‐day waves are likely to extend over a large depth below the cloud top and that the ∼4‐day waves are likely to be confined near the cloud top. Their possible generation mechanism through the coupling of Kelvin and Rossby waves is discussed. This study further reports wind variability of 10 to 15‐day periodicity, thermal‐tide structure, and comparison with minor species observations. Plain Language Summary: Akatsuki is the only currently operational artificial satellite of Venus. It has been conducting imaging observations at two ultraviolet wavelengths since December 2015. By measuring the movement of cloud features in the images, we obtain horizontal winds near the cloud‐top altitude where the famous superrotation is maximized. By using wind data over ∼7 earth years, we show that the superrotation speed varies over time, showing a broad spectrum. This is indicative of internally created variability rather than periodic variability created by external forcing. We also reveal that mean westward winds that characterize the superrotation have some differences between the northern and southern hemispheres and that these differences vary over time. However, the data do not allow us to conclude whether the asymmetry is in the winds or in the sensing altitude. Venus has long been known for having two kinds of planetary‐scale waves with periods around 4 and 5 days, but their vertical distributions are unknown. We indicate that the 5‐day waves have a deeper vertical distribution than the 4‐day waves from the differences in the long‐term changes in their frequencies. We further characterize the thermal tides excited by solar heating and suggest wind variability at periods of 10–15 days. Key Points: Venus' superrotation as measured near the cloud top exhibits rich low frequency variations indicating internal variabilityPlanetary‐scale ∼4‐ and ∼5‐day waves are suggested to reside in different altitude rangesTemporally varying hemispheric asymmetry is found in zonal winds, which might partly be due to the sensing altitude asymmetry [ABSTRACT FROM AUTHOR]

Mars and Venus have atmospheres but lack intrinsic dipole magnetic fields. Consequently, the solar wind interaction at each planet results in the formation of an induced magnetosphere. Our work aims to compare the low‐altitude (< 250 km) component of the induced magnetic field at Venus and Mars using observations from Pioneer Venus Orbiter and Mars Atmosphere and Volatile EvolutioN. We restrict the in‐situ data from Mars to regions of weak crustal magnetism. At Venus, it has long been known the vertical structure of the induced magnetic field profiles have recurring features that enable them to be classified as either magnetized or unmagnetized. We find the induced field profiles at Mars are more varied, lack recurring features, and are unable to be classified in the same way. The solar zenith angle dependence of the low‐altitude field strength at both planets is controlled by the shape of the magnetic pileup boundary. Also, because the ionospheric thermal pressure at Venus is often comparable to the solar wind dynamic pressure, the induced fields are weaker than required to balance the solar wind by themselves. By contrast, induced fields at Mars are stronger than required to achieve pressure balance. Lastly, we find the induced fields in the magnetized ionosphere of Venus have a weaker dependence on solar wind dynamic pressure than the induced fields at Mars. Our results point to planetary properties, such as planet‐Sun distance, having a major effect on the properties of induced fields at nonmagentized planets. Key Points: Unlike Venus, the induced magnetic field profiles at Mars are unable to be categorized into magnetized and unmagnetized statesAt both planets, the solar zenith angle dependence of the induced field strength is controlled by the shape of the magnetic pileup boundaryInduced fields at Mars are stronger than expected if assuming the fields form to achieve pressure balance with the oncoming solar wind [ABSTRACT FROM AUTHOR]

Abstract We explore the potential for repeat‐pass SAR Interferometry (InSAR) correlation to track volcanic activity on Venus' surface motivated by future SAR missions to Earth's sister planet. We use Hawai'i as a natural laboratory to test whether InSAR can detect lava flows assuming orbital and instrument parameters similar to that of a Venus mission. Hawai'i was chosen because lava flows are frequent, and well documented by the United States Geological Survey, and because Hawai'i is a SAR supersite, where space agencies have offered open radar data sets for analysis. These data sets have different wavelengths (L, C, and X bands), bandwidths, polarizations, look angles, and a variety of orbital baselines, giving opportunity to assess the suitability of parameters for detecting lava flows. We analyze data from ALOS‐2 (L‐band), Sentinel‐1 (C‐band), and COSMO‐SkyMed (X‐band) spanning 2018 and 2022. We perform SAR amplitude and InSAR correlation analysis over temporal baselines and perpendicular baselines similar to those of a Venus mission. Fresh lava flows create a sharp, noticeable decrease in InSAR correlation that persists indefinitely for images spanning the event. The same lava flows are not always visible in the corresponding amplitude images. Moreover, noticeable decorrelation persists in image pairs acquired months after the events due to post‐emplacement contraction of flows. Post‐emplacement effects are hypothesized to last longer on the Venusian surface, increasing the likelihood of detecting Venus lava flows using InSAR. We argue for further focus on repeat‐pass InSAR capabilities in upcoming Venus missions, to detect and quantify volcanic activity on Earth's hotter twin.

Abstract The Venusian atmosphere hosts a 10 km deep convective layer that has been studied by various spacecrafts. However, the impact of the strong vertical mixing on the chemistry of this region is still unknown. This study presents the first realistic coupling between resolved small‐scale turbulence and a chemical network. The resulting vertical mixing is different for each species: those with longer chemical timescales will tend to be well‐mixed. Vertical eddy diffusion due to resolved convection motions was estimated, ranging from 102 to 104 m2/s for the 48–55 km convective layer, several orders of magnitude above the typically used value. In the 48–55 km convective layer, the impact of the small‐scale turbulence on the cloud layer boundaries was between 200 m and 1 km. The impact of turbulence on cloud chemistry is consistent with Venus Express/Visible and Infrared Thermal Imaging Spectrometer observations. The observability at the cloud‐top of small‐scale turbulence by VenSpec‐U spectrometer would be challenging.

Abstract The collisionless nature of planetary magnetospheres means that electromagnetic forces are fundamental in controlling the flow of energy and momentum through these systems. We use Pioneer Venus Orbiter (PVO) observations to demonstrate that the magnetic pumping process can be active at Venus, in analogy to its recent discovery at Mars. The presented case study demonstrates the framework for how the process can work at Venus, and the results of a statistical analysis show that the ambient plasma conditions support the process being active. Magnetic pumping enables low frequency magnetosonic waves to heat ambient ionospheric electrons and provides a mechanism that couples the solar wind to the Venusian ionosphere. This is the first time the magnetic pumping process has been discussed at Venus.