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Inert gases (e.g., He and Xe) can exhibit chemical activity at high pressure, reacting with other substances to form compounds of unexpected chemical stoichiometry. This work combines first-principles calculations and crystal structure predictions to propose four unexpected stable compounds of CH4Xe3, (CH4)2Xe, (CH4)3Xe, and (CH4)3Xe2 at pressure ranges from 2 to 100 GPa. All structures are composed of isolated Xe atoms and CH4 molecules except for (CH4)3Xe2, which comprises a polymerization product, C3H8, and hydrogen molecules. Ab initio molecular dynamics simulations indicate that pressure plays a very important role in the different temperature driving state transitions of CH4–Xe compounds. At lower pressures, the compounds follow the state transition of solid–plastic–fluid phases with increasing temperature, while at higher pressures, the stronger Xe–C interaction induces the emergence of a superionic state for CH4Xe3 and (CH4)3Xe2 as temperature increases. These results not only expand the family of CH4–Xe compounds, they also contribute to models of the structures and evolution of planetary interiors. [ABSTRACT FROM AUTHOR]

We report JWST Mid-Infrared Instrument (MIRI) Medium Resolution Spectrograph (MRS) observations of the β Pic moving-group member, η Tel A, along with its brown dwarf binary companion, η Tel B. Following point-spread-function subtraction, we recover the spatially resolved flux from the debris disk around η Tel A, along with the position of the companion exterior to the disk. We present a new 5–26 μ m epoch of spectroscopy for the disk, in which we discover a 20 μ m silicate feature, and the first ever 11–21 μ m spectrum of η Tel B, which indicates a bare photosphere. We derive a new epoch of relative astrometry for the companion, extending the baseline of measurements to 25 yr, and find that it is currently located near the apocenter of an eccentric long-period orbit. The companion's orbit is close enough to the disk that it should significantly perturb the planetesimals within it, resulting in a detectable mid-IR pericenter glow and near alignment with the companion. Contrary to expectations, however, we find that the disk appears to be axisymmetric and potentially misaligned with the companion in the MIRI MRS data. We posit that this may be due to the presence of an additional, as-yet-undetected ∼0.7–30 M J planet orbiting interior to the disk, with a semimajor axis of ∼3–19 au. [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]

Knowing the structure of the crust is critical to understanding a planet's geologic evolution. Crustal thickness inversions rely on bulk density estimates, which are primarily affected by porosity. Due to the absence of high‐resolution gravity data, Mercury's crustal porosity has remained unknown. Here, we use a model that was calibrated to the Moon to relate Mercury's impact crater population and long‐wavelength crustal porosity in the cratered terrains. Therein, porosity is created by large impacts and then decreased as the surface ages due to pore compaction by smaller impacts and overburden pressure. Our models fit independent gravity‐derived porosity estimates in the northern regions, where data is well resolved. Porosity in the cratered terrains is found to be 9%–18% with an average and standard deviation of 13% ± $\pm $ 2%, indicating lunar‐like crustal bulk densities of 2,565 ± $\pm $ 70 kg m−3 ${\mathrm{m}}^{-3}$ from which updated crustal thickness maps are constructed. Plain Language Summary: The crust of a planet is a thermal barrier, which controls how fast heat escapes to space. Depending on its thickness, the crust can strongly insulate the planet's interior preventing efficient cooling. Therefore, knowing the structure of the crust is critical to unraveling the geologic history of planetary bodies. Crustal thickness is typically inverted from gravity and topography data. One critical parameter for these inversions is the bulk density of the crust, which is primarily driven by porosity variations. While high‐resolution gravity field mapping allowed constraining the bulk density and porosity of the lunar crust, crustal porosity on other planetary bodies has remained unknown. In this work, we use a model that was calibrated to the Moon to relate Mercury's impact crater population and long‐wavelength crustal porosity in the cratered terrains. We show that crustal porosity in the cratered terrains ranges from 9% to 18% with an average and standard deviation of 13% ± $\pm $ 2%, indicating lunar‐like low bulk densities of 2,565 ± $\pm $ 70 kg m−3 ${\mathrm{m}}^{-3}$. Key Points: Mercury's crustal porosity estimated from the crater population, assuming porosity formed by large impacts and decreased with surface agingCrustal porosity in the cratered terrains ranges from 9% to 18% with an average and standard deviation of 13% ± 2%The low bulk density of Mercury's crust in the cratered terrain, 2,565 ± 70 kg m−3, is similar to that of the lunar highlands [ABSTRACT FROM AUTHOR]

Context. Atmospheres above lava-ocean planets (LOPs) hold clues related to the properties of their interiors, based on the expectation that the two reservoirs are in chemical equilibrium. Furthermore, such atmospheres are observable with current-generation space- and ground-based telescopes. While efforts have been made to understand how emission spectra are related to the composition of the lava ocean, the influence of oxygen fugacity has yet to be examined in a self-consistent way. Aims. Here, we investigate the sensitivity of atmospheric emission spectra of LOPs to key geochemical parameters, namely, temperature (T), composition (X), and oxygen fugacity (fO2). We also consider the precision involved in recovering these spectra from observations of hot, rocky exoplanets. Methods. We considered 'mineral' atmospheres produced in equilibrium with silicate liquids. We treated fO2 as an independent variable, together with T and X, to compute equilibrium partial pressures (p) of stable gas species at the liquid-gas interface. Above this boundary, the atmospheric speciation and the pressure–temperature structure are computed self-consistently to yield emission spectra. We explored a wide array of plausible compositions, oxygen fugacities (between 6 log10 units below and above the iron-wüstite buffer, IW), and irradiation temperatures (2000, 2500, 3000, and 3500 K) relevant to LOPs. Results. We find that SiO(g), Fe(g) and Mg(g) are the major species below ~IW, ceding to O2(g) and O(g) in more oxidised atmospheres. The transition between the two regimes demarcates a minimum in total pressure (P). Because p scales linearly with X, emission spectra are only modest functions of composition. By contrast, fO2 can vary over orders of magnitude, thereby causing commensurate changes in p. Atmospheres outgassed from reducing melts exhibit intense SiO emission, creating a temperature inversion in the upper atmosphere. Conversely, oxidised atmospheres have lower pSiO and lack thermal inversions, with their resulting emission spectra mimicking that of a black-body. Consequently, the intensity of SiO emission relative to the background, generated by MgO(g), can be used to quantify the fO2 of the atmosphere. Depending on the emission spectroscopy metric of the target, deriving the fO2 of known nearby LOPs is possible with a few secondary occultations observed by JWST. [ABSTRACT FROM AUTHOR]

The stability range of localized three-dimensional convective cells in Rayleigh–Bénard convection is determined across a broad range of viscosity contrasts between the boundaries of the fluid layer, for both free-slip and no-slip boundary conditions. The localized convective cell is generated by a finite-amplitude initial perturbation at subcritical Rayleigh numbers. It appears as a radially symmetric upwelling surrounded by nearly stagnant fluid, which can be characterized as an extremely weak plume. The parameter range in which three-dimensional localized upwellings are stable is slightly larger than that found for two-dimensional rolls. With free-slip boundaries, the lowest viscosity contrast at which the three-dimensional system can exhibit localization is approximately 35, about four times lower than for two-dimensional rolls. The wide range of conditions under which localization occurs in three-dimensional systems due to temperature-dependent viscosity further emphasizes its importance for the understanding of processes within the interiors of planetary bodies and for industrial applications. [ABSTRACT FROM AUTHOR]

There is growing momentum, as articulated through the visions of space agencies, to establish permanent settlements on planetary bodies such as the Moon and Mars. One key hazard that structures will be subjected to will be hypervelocity impacts of micrometeoroids and orbital debris. Shielding against such impacts is essential to ensure the safety of structures and their human inhabitants. There has, however, been limited research on such shields and no field applications to date. In order to inform the composition and design of protective shields for planetary structures, recourse can be made to protective shields utilised in spacecraft and space stations that have benefitted from years of research and development. This paper reviews the existing shielding practices for spacecraft and space stations as a starting point for the shielding of planetary structures. Shield configurations are firstly introduced. Both experimental tests and numerical simulations required to evaluate the performance of the shields are then discussed. Analytical prediction models for shields are reviewed, and the predictions of these models are compared with test results of corresponding shields from the literature. Finally, the effect of parameters such as projectile diameter, impact velocity, impact angle, and shield geometry on the overall shield performance is analysed. This paper ultimately provides technical knowledge about the shielding systems for spacecraft and space stations that can be used as a point of reference for scientists and engineers to develop shields for structures on planetary bodies. • Review of shielding systems on spacecraft and ISS for MMOD protection. • Analysis of theoretical models for predicting protective shield performance. • Recommendations provided for shielding systems of Lunar and Martian structures. [ABSTRACT FROM AUTHOR]

The immiscibility of hydrogen-helium mixture under the temperature and pressure conditions of planetary interiors is crucial for understanding the structures of gas giant planets (e.g., Jupiter and Saturn). While the experimental probe at such extreme conditions is challenging, theoretical simulation is heavily relied in an effort to unravel the mixing behavior of hydrogen and helium. Here we develop a method via a machine learning accelerated molecular dynamics simulation to quantify the physical separation of hydrogen and helium under the conditions of planetary interiors. The immiscibility line achieved with the developed method yields substantially higher demixing temperatures at pressure above 1.5 Mbar than earlier theoretical data, but matches better to the experimental estimate. Our results suggest a possibility that H-He demixing takes place in a large fraction of the interior radii of Jupiter and Saturn, i.e., 27.5% in Jupiter and 48.3% in Saturn. This indication of an H-He immiscible layer hints at the formation of helium rain and offers a potential explanation for the decrease of helium in the atmospheres of Jupiter and Saturn. The immiscibility of H-He mixtures in gas giants remains poorly understood. Here the authors use large scale machine learning accelerated molecular dynamics simulations to suggest that H-He demixing may occur within large interior radii of Jupiter and Saturn. [ABSTRACT FROM AUTHOR]

Using a nonlinear model of the general circulation of the middle and upper atmosphere (MUAM), spatio-temporal structures of planetary waves (PWs) during boreal winter were studied. Modeling of global atmospheric circulation was performed for January–February. Despite the tropospheric PW sources shaped in the model, the phenomenon of 16-day PW excitation arise out of internal atmospheric sources in the southern lower thermosphere was discovered. To explain the observed phenomenon, a number of numerical experiments were carried out according to different scenarios with a selective turning (on/off) tropospheric sources of PW individual modes (having periods of 4–16 days) in the model. Also, the evolution of perturbed potential enstrophy for a 16-day PW, as well as the contribution of nonlinear interactions between individual PW to it, was studied. This made it possible for the first time to demonstrate explicitly the process of generation a secondary 16-day PW as a result of the nonlinear interconnection of 4-day and 5-day PWs. [ABSTRACT FROM AUTHOR]

We present improved empirical density profiles of Uranus and interpret them in terms of their temperature and composition using a new random algorithm. The algorithm to determine the temperature and composition is agnostic with respect to the temperature gradient in non-isentropic regions and chooses amongst all possible gradients randomly that are stable against convection and correspond to an Equation of State (EoS) compatible composition. Our empirical models are based on an efficient implementation of the Theory of Figures (ToF) up to tenth order including a proper treatment of the atmosphere. The accuracy of tenth order ToF enables us to present accurate calculations of the gravitational moments of Uranus up to J14: J6 = (5.3078 ± 0.3312) 10−7, J8 = (−1.1114 ± 0.1391) 10−8, J10 = (2.8616 ± 0.5466) 10−10, J12 = (−8.4684 ± 2.0889) 10−12, and J14 = (2.7508 ± 0.7944) 10−13. We consider two interior models of Uranus that differ with respect to the maximal number of materials allowed per layer of Uranus (three versus four composition components). The case with three materials does not allow Hydrogen and Helium (H-He) in deeper parts of Uranus and results in a higher water (H2O) abundance which leads to lower central temperatures. On the other hand, the models with four materials allow H-He to be mixed into the deeper interior and lead to rock-dominated solutions. We find that these four composition components' models are less reliable due to the underlying empirical models' incompatibility with realistic Brunt frequencies. Most of our models are found to be either purely convective with the exception of boundary layers, or only convective in the outermost region above ~80% of the planets' radius rU. Almost all of our models possess a region ranging between ~(0.75–0.9) rU that is convective and consists of ionic H2O which could explain the generation of Uranus' magnetic field. [ABSTRACT FROM AUTHOR]

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For the harsh entry environment and higher thermal protection requirements, two structures of three‐dimensional woven gradient thermal protection materials were designed and prepared with the deep space exploration thermal protection system as the object. They are 3D orthogonal woven, 2.5D layer‐to‐layer angle interlock woven, 2.5D layer‐layer angle interlock woven structure(OLL) composite and 3D orthogonal woven, angle 2.5D layer‐to‐layer angle interlock woven, honeycomb structure(OLH) composite. Two materials were prepared and examined by ablation in an oxygen‐acetylene flame. A three‐dimensional macroscopic ablation model was established on the basis of the experiment, and the model was verified to be accurate and effective, which can well respond to the pyrolytic ablation process of the materials. The two designed materials are applied to the outsole of MSL by simulation, and the three‐dimensional response during the entry into Mars is simulated and analyzed in comparison with the thermal protection performance of PICA material. Both materials show better thermal protection than PICA and can be used as a reference in the selection of thermal protection materials. Highlights: Two kinds of 3D gradient woven thermal protection materials are designed.A 3D thermal protection system response model is established.The three‐dimensional response during entry was analyzed.Thermal protection of the material is superior to that of PICA. [ABSTRACT FROM AUTHOR]

Theoretical studies of giant planet formation suggest that substantial quantities of metals—elements heavier than hydrogen and helium—can be delivered by solid accretion during the envelope-assembly phase. This process of metal enhancement of the envelope is believed to diminish as a function of planet mass, leading to predictions for a mass-metallicity relationship. Supporting evidence for this picture is provided by the abundance of CH4 in solar system giant planets, where CH4 abundance, unlike H2O, is unaffected by condensate cloud formation. However, all of the solar system giants exhibit some evidence for stratification of metals outside of their cores. In this context, two fundamental questions are whether metallicity of giant planets inferred from observations of the outer envelope layers represents the bulk metallicity of these planets, and if not, how are metals distributed within giant planets. Comparing the mass-metallicity relationship for solar system giant planets, inferred from the observed CH4 abundance, with various tracers of metallicity in the exoplanet population, has yielded a range of results. There is evidence of a solar-system-like mass-metallicity trend using bulk density estimates of exoplanet metallicity. However, transit-spectroscopy-based tracers of exoplanet metallicity, which probe only the outer layers of the envelope, are less clear about a mass-metallicity trend and raise the question of whether radial composition gradients exist in some giant exoplanets. The large number of known exoplanets enables statistical characterization of planet properties. We develop a formalism for comparing both the metallicity inferred for the outer envelope and the metallicity inferred using the bulk density and show this combination may offer insights into the broader question of metal stratification within planetary envelopes. Our analysis suggests that future exoplanet observations with JWST and Ariel will be able to shed light on the conditions governing radial composition gradients in exoplanets and, perhaps, provide information about the factors controlling stratification and convection in our solar system gas giants. [ABSTRACT FROM AUTHOR]

The first widespread occurrence of rare Na-, Ca-, and Mg,Mn,Fe-bearing phosphate chladniite was observed in meteorite Graves Nunataks (GRA) 12510, which is a primitive achondrite that sits within the winonaite class. Numerous 1–500 μm chladniite grains were found, often on the margins between silicate clasts and the kamacite portions of the large metal veins that permeated through the sample. The largest chladniite grains are associated with merrillite, kamacite, taenite, troilite, albite, forsterite, diopside, and enstatite, with a few tiny chladniite grains and an apatite grain enclosed within merrillite. GRA 12510s average chladniite composition is Na2.7Ca1.25(Mg10.02Mn0.69Fe0.20)Σ10.91(PO4)9. Electron backscattered diffraction (EBSD) patterns indicate varying degrees of nucleation and growth of chladniite grains. Additionally, the first pure Raman spectrum of chladniite is described here, revealing primary ν1 bands at 954, 974, and especially 984 cm–1. The co-occurrence and close association of merrillite, apatite, chladniite, and P-bearing metallic phases within GRA 12510 suggests that the fO2 of IW-2 to IW-4 is an intrinsic property of the precursor chondritic material, and the phosphatephosphide reaction may have buffered the final winonaite and IAB iron meteorite phase assemblages. Altogether, chladniite appears to form alongside other phosphates, with their chemistries reflecting the diverse environment of their formation. Meteoritic chladniite likely formed through subsolidus oxidation of schreibersite, scavenging Na from albite, Ca from diopside, Mg from enstatite/forsterite, Fe from kamacite/taenite, and Mn from alabandite/chromite when available. A P0-P5+ redox-buffered environment also has implications for thermometry and fast cooling rates, although more experiments are needed to extrapolate powder reaction rates to those of larger crystals. Furthermore, phosphidephosphate buffered experiments may aid in investigating equilibrium chemistry at fO2 values between IW-2 and IW-4, which have been challenging to explore experimentally due to the limited availability of solid metal-metal oxide buffers between IW (Fe-FeO) and IW-5 (Cr-Cr2O3) at temperatures and pressures relevant to planetary interiors. Future investigations of phosphide-phosphate redox-buffered genesis at fO2 values between IW-2 and IW-4 have important implications for primitive meteorite constituents (e.g., CAI values), partially differentiated planetesimals and planets, including Mercury and core formation on Earth. [ABSTRACT FROM AUTHOR]

The Chandler period of Mars is a new parameter determined from observational data that characterizes the properties of the planetary interior. Numerical modeling of the period of the Chandler wobble of Mars was performed for a number of internal structure models that satisfy not only geodetic data (moment of inertia, tidal Love number k2), but also data obtained during a seismic experiment in the years 2019–2022. To reconcile the theoretical and observed values of the Chandler wobble, it is necessary to take into account the inelasticity of the mantle. To take into account the viscoelastic behavior of the interior, the Andrade rheological model was used. It is demonstrated how the value of the Chandler period depends on the rheological model parameters. [ABSTRACT FROM AUTHOR]

The local scale of rotating convection, ℓ, is a fundamental parameter in many turbulent geophysical and astrophysical fluid systems, yet it is often poorly constrained. Here we conduct rotating convection laboratory experiments analogous to convecting flows in planetary cores and subsurface oceans to obtain measurements of the local scales of motion. Utilizing silicone oil as the working fluid, we employ shadowgraph imagery to visualize the flow, from which we extract values of the characteristic cross‐axial scale of convective columns and plumes. These measurements are compared to the theoretical values of the critical onset length scale, ℓcrit, and the turbulent length scale, ℓturb. Our experimentally obtained length scale measurements simultaneously agree with both the onset and turbulent scale predictions across three orders of magnitude in convective supercriticality (102≲Ra∼≲105) $(1{0}^{2}\lesssim \tilde{Ra}\lesssim 1{0}^{5})$, a correlation that is consistent with inferences made in prior studies. We further explore the nature of this correlation and its implications for geophysical and astrophysical systems. Plain Language Summary: Turbulent convection occurs within the liquid metal, water, and gaseous fluid layers of planetary interiors such as Earth's molten iron outer core, the subsurface oceans of icy moons, and the deep atmospheres of gas planets, respectively. The flow in each of these systems is strongly affected by the rotation of the planetary body. This rotation organizes the convecting flow into columnar structures elongated in the direction of the rotation axis. The horizontal width of the columnar flows is known as the local length scale of rotating convection, and is crucially the scale at which important planetary phenomena are driven, such as the induction of Earth's magnetic field. However, this quantity is not well known for geophysical systems. Here we conduct rotating convection laboratory experiments analogous to the convecting flows in planetary interiors, in which the local length scale is measured using a visualization technique called shadowgraph imaging. We compare our measurements to theoretical scaling arguments for laminar and turbulent rotating flows, and find a simultaneous agreement with both. This heretofore unappreciated correlation with both theoretical scales presents difficulties when interpreting laboratory and numerical experimental results in the context of more extreme geophysical flows, a challenge we address in the discussion. Key Points: Laboratory convection experiments simulate turbulent flows within the polar regions of planetary cores and subsurface oceansThe convective flow scale, measured via shadowgraph imaging, agrees with both the critical and turbulent scale predictionsThis agreement cannot be explained without advancement in convection theory, and implies mean field dynamo action occurs in Earth's core [ABSTRACT FROM AUTHOR]

A major challenge in mantle geochemistry is determining the source composition and melt fraction involved in melting. We provide a new Rare‐Earth Element (REE) inverse model that provides source concentration, source and melt mineral modes, and melt fraction based on the difference between separate determinations of bulk distribution coefficients and constrained by boundary conditions. An analytical inverse of the batch melting equation provides expressions for source, Coi ${C}_{o}^{i}$, and bulk distribution coefficient of the mantle, Doi ${D}_{o}^{i}$, with two unknowns, the initial concentration of La in the mantle, CoLa ${C}_{o}^{La}$, and Pi, the bulk distribution coefficient of the melt. We traverse through a range of CoLa ${C}_{o}^{La}$ steps and examine thousands of melt modes, Pi, at each step. Thousands of trial melt modes fail by generating Doi ${D}_{o}^{i}$ that are inconsistent with partition coefficients. Many surviving trials cannot be inverted to estimate a mantle mode. Other boundary conditions eliminate even more trials. Surviving trials are ordered by the difference between Doi ${D}_{o}^{i}$ calculated from the REE data of a lava suite and Dci ${D}_{c}^{i}$ calculated from partition coefficients and mantle mode. We select the solution with the closest fit that passes all the boundary conditions. We tested our new model with lava suites from Hawaii where different lines of evidence suggest that they melted from different mantle sources, Mauna Kea representing shield‐stage lava and submarine Kiekie representing rejuvenated stage lava. Our inverse determination of mantle composition and melting parameters was consistent with earlier models based on assumptions of HREE composition. Plain Language Summary: Determining the composition of our planet's interior is a major goal of geochemistry. The most common approach is to make forward models based on reasonable assumptions about the source composition and the melting process to calculate synthetic compositions that match the observed lava. Successful forward models may be difficult to achieve, but nevertheless remain dependent on initial assumptions. In principle, inverse models make fewer assumptions and achieve more objective results. Even so, most published inverse models for mantle melting require assumptions about the source. The inverse modeling described here relies on boundary conditions and the match between observed and calculated bulk distribution coefficients to determine the behavior of mantle parameters as a function of the initial lanthanum concentration (CoLa ${C}_{o}^{La}$). Certain behavior patterns allow determination of the optimum CoLa ${C}_{o}^{La}$, allowing a complete inverse. Successful inverse models for Hawaiian lava suites define two distinct mantle types, in agreement with past observations about these volcanoes. Key Points: Melt modes and mantle La concentrations generate trial source and bulk distribution profiles, but most solutions fail boundary conditionsTrial solutions are ranked by comparing observed and calculated bulk distribution profiles. The best fit over a range of La is the solutionOptimum source and bulk distribution profiles provide melt extents for shield stage Hawaiian tholeiites and rejuvenated basalts [ABSTRACT FROM AUTHOR]

Multiplanetary systems spanning the radius valley are ideal testing grounds for exploring the different proposed explanations for the observed bimodality in the radius distribution of close-in exoplanets. One such system is HIP 29442 (TOI-469), an evolved K0V star hosting two super-Earths and one sub-Neptune. We observed HIP 29442 with CHEOPS for a total of 9.6 days, which we modelled jointly with two sectors of TESS data to derive planetary radii of 3.410 ± 0.046, 1.551 ± 0.045, and 1.538 ± 0.049 R⊕ for planets b, c, and d, which orbit HIP 29442 with periods of 13.6, 3.5, and 6.4 days, respectively. For planet d this value deviates by more than 3σ from the median value reported in the discovery paper, leading us to conclude that caution is required when using TESS photometry to determine the radii of small planets with low per-transit signal-to-noise ratios and large gaps between observations. Given the high precision of these new radii, combining them with published RVs from ESPRESSO and HIRES provides us with ideal conditions to investigate the internal structure and formation pathways of the planets in the system. We introduced the publicly available code plaNETic, a fast and robust neural network-based Bayesian internal structure modelling framework. We then applied hydrodynamic models to explore the upper atmospheric properties of these inferred structures. Finally, we identified planetary system analogues in a synthetic population generated with the Bern model for planet formation and evolution. Based on this analysis, we find that the planets likely formed on opposing sides of the water iceline from a protoplanetary disk with an intermediate solid mass. We finally report that the observed parameters of the HIP 29442 system are compatible with a scenario where the second peak in the bimodal radius distribution corresponds to sub-Neptunes with a pure H/He envelope and with a scenario with water-rich sub-Neptunes. [ABSTRACT FROM AUTHOR]

A novel wave energy harvester (WEH) that can recover energy in the direction of heave, sway, and surge is designed under the background of low recovery efficiency and complex installation of the existing wave energy harvester. The harvester consisted of four main components: energy input module, energy transfer module, energy conversion module, and energy store module. In the paper, to convert more wave energy into electrical energy and improve the energy conversion efficiency of WEH, the motion transfer module is divided into vertical and horizontal motion transfer modules, which are used to harvest vertical and horizontal wave energy, respectively. The vertical motion transfer module combined with the ball screw structure, planetary gear structure, and one-way gear units ensure the generator has high speed. The horizontal motion transfer module is mainly composed of three uniformly distributed one-way gear units, ensuring collect the wave energy in all horizontal directions. The dynamic model of the harvester is established, and the simulation experiment is carried out under wave conditions with periods of 2 s, 2.5 s, and 3 s, respectively. The simulation results show that when the wave period is 2 s, 2.5 s, and 3 s, the corresponding energy conversion efficiency of the WEH is 66.7%, 60.9%, and 57.1%, respectively. The proposed study provides a theoretical reference for modeling similar WEHs and can effectively balance energy supply and demand and further support the global agenda of UN-2030 for sustainable development, especially SDG-7. [ABSTRACT FROM AUTHOR]

SUMMARY: A 3-D finite-difference solver has been developed and implemented for Boussinesq convection in a spherical shell. The solver transforms any complex curvilinear domain into an equivalent Cartesian domain using Jacobi transformation and solves the governing equations in the latter. This feature enables the solver to account for the effects of the non-spherical shape of the convective regions of planets and stars. Apart from parallelization using MPI, implicit treatment of the viscous terms using a pipeline alternating direction implicit scheme and HYPRE multigrid accelerator for pressure correction makes the solver efficient for high-fidelity direct numerical simulations. We have performed simulations of Rayleigh–Bénard convection at two Rayleigh numbers Ra = 105 and 107 while keeping the Prandtl number fixed at unity (Pr = 1). The average radial temperature profile and the Nusselt number match very well, both qualitatively and quantitatively, with the existing literature. Closure of the turbulent kinetic energy budget, apart from the relative magnitude of the grid spacing compared to the local Kolmogorov scales, ensures sufficient spatial resolution. [ABSTRACT FROM AUTHOR]

SUMMARY: Thermal convection in planetary solid (rocky or icy) mantles sometimes occurs adjacent to liquid layers with a phase equilibrium at the boundary. The possibility of a solid–liquid phase change at the boundary has been shown to greatly help convection in the solid layer in spheres and plane layers and a similar study is performed here for a spherical shell with a radius-independent central gravity subject to a destabilizing temperature difference. The solid–liquid phase change is considered as a mechanical boundary condition and applies at either or both horizontal boundaries. The boundary condition is controlled by a phase change number, Φ, that compares the timescale for latent heat exchange in the liquid side to that necessary to build a topography at the boundary. We introduce a numerical tool, available at https://github.com/amorison/stablinrb, to carry out the linear stability analysis of the studied setup as well as other similar situations (Cartesian geometry, arbitrary temperature and viscosity depth-dependent profiles). Decreasing Φ makes the phase change more efficient, which reduces the importance of viscous resistance associated to the boundary and makes the critical Rayleigh number for the onset of convection smaller and the wavelength of the critical mode larger, for all values of the radii ratio, γ. In particular, for a phase change boundary condition at the top or at both boundaries, the mode with a spherical harmonics degree of 1 is always favoured for Φ ≲ 10−1. Such a mode is also favoured for a phase change at the bottom boundary for small (γ ≲ 0.45) or large (γ ≳ 0.75) radii ratio. Such dynamics could help explaining the hemispherical dichotomy observed in the structure of many planetary objects. [ABSTRACT FROM AUTHOR]

A total solar eclipse provides an unparalleled opportunity to study the changes in the atmosphere's planetary boundary layer (PBL) due to changes in radiative heating. Although previous eclipse studies have demonstrated that significant changes occur, few studies have explored the evolution of these changes. To better understand the changes in the lowest layers of the PBL during an eclipse, a multi-sensor sampling approach was taken. Radiosonde launches were used to explore the depth of the column, while Unmanned Aerial Vehicles (UAVs) were used to document with high-resolution the brief changes in the vertical structure of the PBL caused by the eclipse. These changes highlighted differences from previous studies that relied solely on radiosonde and/or mesonet data alone. Higher-resolution sampling of the lower PBL showed a delay in the local vertical mixing as well as changes in the PBL height from pre- to post-eclipse. Slow responses were noted at the top of the PBL while very rapid changes to the PBL profile were captured in the near-surface layer. These changes highlighted differences from previous studies that relied solely on radiosonde and/or mesonet data alone. A preliminary analysis of the collected data highlighted a slow response to the eclipse near the top of the planetary boundary layer (radiosonde data) with very rapid changes noted in the near surface layer (UAV data). Preliminary results show that PBL heights remained nearly constant until well after third contact when a 35 hPa lowering of the PBL heights was observed and were limited to the lowest 25 hPa. The UAV soundings demonstrated the development of a strong inversion where the air below 990 hPa rapidly cooled with a nearly 1 °C drop in temperature observed. These observed changes raise interesting questions about how the lower and upper parts of the planetary boundary layer interact. [ABSTRACT FROM AUTHOR]

We present ionization structures of IC 2003, a planetary nebula with [WR] central star, using a 1-D dusty photo-ionization code: "CLOUDY 17.03". The photo-ionization model is constrained by archival UV emission line fluxes, medium-resolution optical spectroscopy, IRAS 25 μ m flux, absolute H β flux, and the mean angular size of the nearly spherical optical nebula. To constrain the carbon abundance and the effect of photo-electric heating in the ionized gas, we used UV emission lines. We considered an amorphous carbon dust grain with MRN and KMH size distributions to address the importance of photo-electric heating in the ionized nebula. We show that KMH grain size distribution with quantum dust heating reproduces the observations quite well. We construct the ionization structures of different elements at their different ionization stages in the nebula. We derive the physical properties of the planetary nebula and its chemical composition, as well as the parameters of its central star. The estimated nebular dust-to-gas mass ratio is 2.37 × 10 - 3 , and the enhanced photo-electric heating yielded by small dust grains is 9.4 % of the total heating. We considered the H-poor model atmosphere for the central star; the effective temperature of the central star is 177 kK, the specific gravity log(g) is 6, and its luminosity ( L ∗ ) is 6425 L ⊙ . The derived central star parameters plotted on stellar evolutionary tracks correspond to a central star mass of 0.636 M ⊙ and to a progenitor mass of 3.26 M ⊙ . [ABSTRACT FROM AUTHOR]

The characterization of super-Earth- to Neptune-sized exoplanets relies heavily on our understanding of their formation and evolution. In this study, we link a model of planet formation by pebble accretion to the planets' long-term observational properties by calculating the interior evolution, starting from the dissipation of the protoplanetary disk. We investigate the evolution of the interior structure in 5–20 M⊕ planets, accounting for silicate redistribution caused by convective mixing, rainout (condensation and settling), and mass loss. Specifically, we have followed the fate of the hot silicate vapor that remained in the planet's envelope after planet formation as the planet cools. We find that disk dissipation is followed by a rapid contraction of the envelope from the Hill or Bondi radius to about one-tenth of that size within 10 Myr. Subsequent cooling leads to substantial growth of the planetary core through silicate rainout accompanied by inflated radii, in comparison to the standard models of planets that formed with core-envelope structure. We examined the dependence of rainout on the planet's envelope mass, on the distance from its host star, on its silicate mass, and on the atmospheric opacity. We find that the population of planets that formed with polluted envelopes can be roughly divided into three groups based on the mass of their gas envelopes: bare rocky cores that have shed their envelopes, super-Earth planets with a core-envelope structure, and Neptune-like planets with diluted cores that undergo gradual rainout. For polluted planets that formed with envelope masses below 0.4 M⊕, we anticipate that the inflation of the planet's radius caused by rainout will enhance the mass loss by a factor of 2–8 compared to planets with unpolluted envelopes. Our model bridges the gap between the predicted composition gradients in massive planets and the core-envelope structure in smaller planets. [ABSTRACT FROM AUTHOR]

The dependence of seismic wave speeds on propagation or polarization direction, called seismic anisotropy, is a relatively direct indicator of mantle deformation and flow. Mantle seismic anisotropy is often inferred from measurements of shear-wave splitting. A number of standard techniques to measure shear-wave splitting have been applied globally; for example, *KS splitting is often used to measure upper mantle anisotropy. In order to obtain robust constraints on anisotropic geometry, it is necessary to sample seismic anisotropy from different directions, ideally using different seismic phases with different incidence angles. However, many standard analysis techniques can only be applied for certain epicentral distances and source–receiver geometries. To search for new ways to detect mantle anisotropy, instead of focusing on the sensitivity of individual phases, we investigate the wavefield as a whole: we apply a 'wavefield differencing' approach to (systematically) understand what parts of the seismic wavefield are most affected by splitting due to seismic anisotropy in the mantle. We analyze differences between synthetic global wavefields calculated for isotropic and anisotropic input models, incorporating seismic anisotropy at different depths. Our results confirm that the seismic phases that are commonly used in splitting techniques are indeed strongly influenced by mantle anisotropy. However, we also identify less commonly used phases whose waveforms reflect the effects of anisotropy. For example, PS is strongly affected by splitting due to seismic anisotropy in the upper mantle. We show that PS can be used to fill in gaps in global coverage in shear-wave splitting data sets (for example, beneath ocean basins). We find that PcS is also a promising phase, and present a proof-of-concept example of PcS splitting analysis across the contiguous United States using an array processing approach. Because PcS is recorded at much shorter distances than *KS phases, PcS splitting can therefore fill in gaps in backazimuthal coverage. Our wavefield differencing results further hint at additional potential novel methods to detect and characterize splitting due to mantle seismic anisotropy. [ABSTRACT FROM AUTHOR]

We assess the accuracy of common hybrid exchange-correlation (XC) functionals (PBE0, PBE0-1/3, HSE06, HSE03, and B3LYP) within the Kohn–Sham density functional theory for the harmonically perturbed electron gas at parameters relevant for the challenging conditions of the warm dense matter. Generated by laser-induced compression and heating in the laboratory, the warm dense matter is a state of matter that also occurs in white dwarfs and planetary interiors. We consider both weak and strong degrees of density inhomogeneity induced by the external field at various wavenumbers. We perform an error analysis by comparing with the exact quantum Monte Carlo results. In the case of a weak perturbation, we report the static linear density response function and the static XC kernel at a metallic density for both the degenerate ground-state limit and for partial degeneracy at the electronic Fermi temperature. Overall, we observe an improvement in the density response when the PBE0, PBE0-1/3, HSE06, and HSE03 functionals are used, compared with the previously reported results for the PBE, PBEsol, local-density approximation, and AM05 functionals; B3LYP, on the other hand, does not perform well for the considered system. Additionally, the PBE0, PBE0-1/3, HSE06, and HSE03 functionals are more accurate for the density response properties than SCAN in the regime of partial degeneracy. [ABSTRACT FROM AUTHOR]

Acoustic waves generated by seismic waves contain information on the internal structure of planets, and can be sensed by pressure sensors onboard high-altitude balloons. To identify the various contributions (infrasound signal, noise, balloon response, etc.) in such pressure records, a full waveform modeling is implemented and completed by infrasound ray tracing and additional data analysis. Here, we analyze the Stratéole-2 pressure data associated with two earthquakes (Garcia et al. Geophys. Res. Lett. 49(15):e98844, 2022) and compared these to full waveform simulations by SPECFEM2D-DG-LNS software. Even if our simulations do not precisely reproduce the waveform observed in the frequency range [0.05, 0.3] Hz, we show that the waveform presents more sensitivity to quake and internal structure parameters than to atmospheric structure, and that seismic surface wave dispersion is observed in balloon pressure records. The long-duration pressure oscillations observed after the main infrasonic signal cannot be fully reproduced by our one-dimensional input model even when source time function complexity and aftershocks are considered. These features are ascribed mainly to the complex vertical ground movements below the balloon and partly to late secondary infrasound arrivals excited by the interactions of seismic waves with the topography. These results enhance the advantages and limitations of quake-related infrasound observations on board terrestrial and planetary balloon platforms. [ABSTRACT FROM AUTHOR]

We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a bright (V  = 12.6 mag, K  = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors 42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory, as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of 12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy. [ABSTRACT FROM AUTHOR]

Abundant carbon was identified on Mercury by MESSENGER, which is interpreted as the remnant of a primordial graphite flotation crust, suggesting that the magma ocean and core were saturated in carbon. We re-evaluate carbon speciation in Mercury's interior in light of the high pressure-temperature experiments, thermodynamic models and the most recent geophysical models of the internal structure of the planet. Although a sulfur-free melt would have been in the stability field of graphite, sulfur dissolution in the melt under the unique reduced conditions depressed the sulfur-rich liquidus to temperatures spanning the graphite-diamond transition. Here we show it is possible, though statistically unlikely, that diamond was stable in the magma ocean. However, the formation of a solid inner core caused diamond to crystallize from the cooling molten core and formation of a diamond layer becoming thicker with time. A diamond layer that becomes thicker with time is generated from carbon exsolution at the core-mantle boundary of Mercury, owing to cooling of its metallic core and potentially the silicate magma ocean. [ABSTRACT FROM AUTHOR]

The Grüneisen parameter is an important parameter for the thermal state and evolution of the core, but its uncertainties and their implications are sometimes overlooked. Several formalisms using different parameters values have been used in different studies, making comparison between studies difficult. In this paper, we use previously published data sets to test the sensitivity of modelling the thermal state of the early core to the different formalisms and parameter values used to describe the evolution of the Grüneisen parameter with density. The temperature of the core obtained in our models is less sensitive to the uncertainties of the parameters used in Al'Tshuler et al. formalism than the uncertainties of the parameters used in Anderson formalism. [ABSTRACT FROM AUTHOR]

The dynamics of an inertial confinement fusion capsule, or of a stellar or planet interior, obey a very similar set of equations: magneto-radiative-hydrodynamic equations. The solutions of these equations, however, depend entirely on the transport properties associated with the different materials at play. To properly model the dynamics of these systems, it is necessary to determine with high accuracy the transport coefficients of several materials over a large range of thermodynamic conditions. Experimental capabilities in this respect are still limited due to the nature of the microphysics at play and the extreme conditions involved. Numerical simulations are thus necessary, and in this respect, molecular dynamics simulations based on density functional theory offer exquisite possibilities to constrain the transport properties in the warm to hot dense matter regime. In this paper, we report the methodology used to extract different transport properties based on molecular dynamics performed with the software Abinit. The examples shown are based on the specific cases identified for the purpose of the second charged-particle transport code comparison workshop. [ABSTRACT FROM AUTHOR]

The mass transport of volatiles on Mars represents a seasonally changing load on the surface of the planet. Like on Earth, as mass is redistributed across the planet, the surface responds in a complex manner becoming displaced downwards or upwards. The magnitude and extent of displacement depend on the properties of the load and mechanical properties of the planetary interior. Based on new estimates of the height variation of the seasonal polar caps (SPCs), we predict local surface displacements of up to tens of millimeters with a strong degree 1 signal throughout the Martian year. The long‐wavelength portion of the displacement is potentially observable, with a magnitude of a few millimeters, located away from the SPC where one could realistically measure it with a landed or orbital mission. We also model the direct contribution of this process to observable time variable gravity, where we find the zonal coefficients to be in line with previous measurements, although with a smaller magnitude. Future measurements of this displacement could be used to help elucidate the composition of the interior of Mars using this process as a probe into the Martian interior. Furthermore, more refined measurements of time‐variable gravity would be a powerful tool in constraining the pole‐to‐pole volatile cycle present on Mars. Plain Language Summary: Mars has seasons that are similar to Earth's because of its axial tilt. This causes the CO2 polar caps of Mars to grow and shrink depending on the time of year. This change in mass causes the surface of Mars to physically displace in response to the change in mass. The magnitude of this displacement is based upon the change in the height of the polar caps and the interior properties of Mars, as a more rigid planet would resist this displacement more. Using new estimates of the height variations, we model what the magnitude and pattern of the displacement look like across Mars. We find displacements of up to tens of millimeters at the poles and a few millimeters closer to the equator. Measurement of this displacement and changes in gravity could help determine the interior structure of Mars and alleviate conflicting models of how Mars formed. Modern landed instruments, such as a geodetic station, and orbital instruments, such as altimeters and interferometric synthetic aperture radar, have the capability to do this. Key Points: Global seasonal displacements of the surface of Mars are caused by the deposition and sublimation of CO2 at the polesWe find its magnitude to be as high as centimeters and evaluate the needed measurement precision to constrain the interior of MarsThis reported displacement and gravity perturbation could be measured by a dedicated geodetic instrument or time‐variable gravity mission [ABSTRACT FROM AUTHOR]

Determining compositions of low-mass exoplanets is essential in understanding their origins. The certainty by which masses and radius are measured affects our ability to discern planets that are rocky or volatile rich. In this study, we aim to determine sound observational strategies to avoid diminishing returns. We quantify how uncertainties in mass, radius, and model assumptions propagate into errors in inferred compositions of rocky and water planets. For a target error in a planet's iron-mass fraction or water content, we calculate the corresponding required accuracies in radius and mass. For instance, a rocky planet with a known radius error of 2 per cent (corresponding to TESS detection best errors) demands mass precision to be at 5–11 per cent to attain an 8 wt% precision in iron-mass fraction, regardless of mass. Similarly, a water world of equal radius precision requires 9–20 per cent mass precision to confine the water content within a 10 wt% margin. Lighter planets are more difficult to constrain, especially water-rich versus water-poor worlds. Studying Earth as an exoplanet, we find an ∼±5 point 'error floor' in iron-mass fraction and ∼±7 in core-mass fraction from our lack of knowledge on mineralogy. The results presented here can quickly guide observing strategies to maximize insights into small exoplanet compositions while avoiding overobserving. [ABSTRACT FROM AUTHOR]

With the advent of toroidal and double-stage diamond anvil cells (DACs), pressures between 4 and 10 Mbar can be achieved under static compression, however, the ability to explore diverse sample assemblies is limited on these micron-scale anvils. Adapting the toroidal DAC to support larger sample volumes offers expanded capabilities in physics, chemistry, and planetary science: including, characterizing materials in soft pressure media to multi-megabar pressures, synthesizing novel phases, and probing planetary assemblages at the interior pressures and temperatures of super-Earths and sub-Neptunes. Here we have continued the exploration of larger toroidal DAC profiles by iteratively testing various torus and shoulder depths with central culet diameters in the 30–50 µm range. We present a 30 µm culet profile that reached a maximum pressure of 414(1) GPa based on a Pt scale. The 300 K equations of state fit to our P–V data collected on gold and rhenium are compatible with extrapolated hydrostatic equations of state within 1% up to 4 Mbar. This work validates the performance of these large-culet toroidal anvils to > 4 Mbar and provides a promising foundation to develop toroidal DACs for diverse sample loading and laser heating. [ABSTRACT FROM AUTHOR]

Context. Out of the more than 5000 detected exoplanets, a considerable number belong to a category called "mini-Neptunes". Interior models of these planets suggest that they have primordial H–He-dominated atmospheres. As this type of planet is not found in the Solar System, understanding their formation is a key challenge in planet formation theory. Unfortunately, quantifying how much H–He planets have, based on their observed mass and radius, is impossible due to the degeneracy of interior models. Aims. Another approach to estimating the range of possible primordial envelope masses is to use formation theory. As different assumptions in planet formation can heavily influence the nebular gas accretion rate of small planets, it is unclear how large the envelope of a protoplanet should be. We explore the effects that different assumptions regarding planet formation have on the nebular gas accretion rate, particularly by exploring the way in which solid material interacts with the envelope. This allows us to estimate the range of possible post-formation primordial envelopes. Thereby, we demonstrate the impact of envelope enrichment on the initial primordial envelope, which can be used in evolution models. Methods. We applied formation models that include different solid accretion rate prescriptions. Our assumption is that mini-Neptunes form beyond the ice line and migrate inward after formation; thus, we formed planets in situ at 3 and 5 au. We considered that the envelope can be enriched by the accreted solids in the form of water. We studied how different assumptions and parameters influence the ratio between the planet's total mass and the fraction of primordial gas. Results. The primordial envelope fractions for low- and intermediate-mass planets (total mass below 15 M⊕) can range from 0.1% to 50%. Envelope enrichment can lead to higher primordial mass fractions. We find that the solid accretion rate timescale has the largest influence on the primordial envelope size. Conclusions. Rates of primordial gas accretion onto small planets can span many orders of magnitude. Planet formation models need to use a self-consistent gas accretion prescription. [ABSTRACT FROM AUTHOR]

Fluids and melts in planetary interiors significantly influence geodynamic processes from volcanism to global‐scale differentiation. The roles of these geofluids depend on their viscosities (η). Constraining geofluid η at relevant pressures and temperatures relies on laboratory‐based measurements and is most widely done using Stokes' Law viscometry with falling spheres. Yet small sample chambers required by high‐pressure experiments introduce significant drag on the spheres. Several correction schemes are available for Stokes' Law but there is no consensus on the best scheme(s) for high‐pressure experiments. We completed high‐pressure experiments to test the effects of (a) the relative size of the sphere diameter to the chamber diameter and (b) the top and bottom of the chamber, that is, the ends, on the sphere velocities. We examined the influence of current correction schemes on the estimated viscosity using Monte Carlo simulations. We also compared previous viscometry work on various geofluids in different experimental setups/geometries. We find the common schemes for Stokes' Law produce statistically distinct values of η. When inertia of the sphere is negligible, the most appropriate scheme may be the Faxén correction for the chamber walls. Correction for drag due to the chamber ends depends on the precision in the sinking distance and may be ineffective with decreasing sphere size. Combining the wall and end corrections may overcorrect η. We also suggest the uncertainty in η is best captured by the correction rather than propagated errors from experimental parameters. We develop an overlying view of Stokes' Law viscometry at high pressures. Plain Language Summary: Liquids and vapors, collectively known as fluids, occur throughout the Earth and other planets. Compared to solid rock, fluids can move rapidly due to their lower viscosities and hence influence and promote important geologic processes. The large span of pressures and temperatures inside planets influences the viscosities of fluids. Measuring a fluid viscosity at relevant pressures is most often done by tracking a sphere that sinks in the fluid. The sinking speed of the sphere is converted to the fluid viscosity by balancing forces which cause and oppose the sinking, known as Stokes' Law. To create the right pressures, unique devices are used which require small chambers to house the fluid and sphere. The small chambers affect the sinking speeds and hence Stokes' Law becomes inaccurate. There are several corrections for the chamber effects on the sphere. However, there is no consensus on which correction should be used for high‐pressure measurements. We examined the chamber effects on the sinking speeds in high‐pressure experiments. We calculated the fluid viscosity using each correction and considered the uncertainties. We find that the corrections produce unique values of viscosity and are not equal. Future work should carefully consider the choice in correction. Key Points: We performed high‐pressure experiments to evaluate drag acting on falling spheres in Stokes' Law viscometryWe evaluated different correction schemes for Stokes' Law and used Monte Carlo simulations to evaluate the uncertainties in each schemeThe best correction may be for drag due to the chamber walls, while other corrections may be ineffective or over‐correct the viscosity [ABSTRACT FROM AUTHOR]

An understanding of the rheological behavior of the solid Earth is fundamental to provide a quantitative description of most geological and geophysical phenomena. The continuum mechanics approach to describing large-scale phenomena needs to be informed by a description of the mechanisms operating at the atomic scale. These involve crystal defects, mainly vacancies and dislocations. This often leads to a binary view of creep reduced to diffusion creep or dislocation creep. However, the interaction between these two types of defects leading to dislocation climb plays an important role, and may even be the main one, in the high-temperature, low strain rate creep mechanisms of interest to the Earth sciences. Here we review the fundamentals of dislocation climb, highlighting the specific problems of minerals. We discuss the importance of computer simulations, informed by experiments, for accurately modeling climb. We show how dislocation climb increasingly appears as a deformation mechanism in its own right. We review the contribution of this mechanism to mineral deformation, particularly in Earth's mantle. Finally, we discuss progress and challenges, and we outline future work directions. Dislocations can be sources or sinks of vacancies, resulting in a displacement out of the glide plane: climb. Dislocation climb can be a recovery mechanism during dislocation creep but also a strain-producing mechanism. The slow natural strain rates promote the contribution of climb, which is controlled by diffusion. In planetary interiors where dislocation glide can be inhibited by pressure, dislocation climb may be the only active mechanism. [ABSTRACT FROM AUTHOR]

The Earth is no longer the only known celestial body containing one or more liquid phases. The Cassini spacecraft has discovered seas of hydrocarbons at the surface of Titan, while a series of corroborating evidences argue in favor of the existence of an aqueous ocean beneath the icy crust of several moons. Capillarity embraces a family of physical processes occurring at the free surface of a liquid. These phenomena depend on the liquid properties and on the local planetary conditions. Capillarity may have important direct or indirect implications on the geoscientific and astrobiological points of view. In this paper, we discuss capillarity physics among solar system objects and expected consequences for planetary science. Plain Language Summary: The formation of raindrops, the production of tiny liquid droplets by bubble bursting at the surface of an ocean, or even the floatation of small solid particles at this surface, are examples of capillarity effects, physical processes which can be observed in everyday life. In this work, we discuss such phenomena in extraterrestrial contexts where large amount of liquids have be detected during past decades by space exploration. Key Points: Capillarity is involved in numberless natural processesDuring past decades, the presence of liquid phase of different nature has been detected on several extraterrestrial bodies of the solar systemWe review and discuss physical processes that may have important consequences in planetary science like the transport of organic material between planetary interior and the atmosphere [ABSTRACT FROM AUTHOR]

Meteorite paleomagnetism is fundamental to understanding planetary dynamo processes and the evolution of the early Solar System. However, due to the extraterrestrial and ancient origins of meteorites, their paleomagnetic recording fidelity remains uncertain, which can be tested from a planetary sample formed in a known field. On Earth, historic lavas are used to examine paleomagnetic recording fidelity through the Thellier‐series experiment and other paleointensity methods, which can produce paleointensity estimates to test against the known field strength. But natural terrestrial rocks have different magnetic mineralogy from planetary samples, so they cannot faithfully infer the recording fidelity of meteorites. Here, we used an iron‐particle‐bearing sample from the Syracuse University Lava Project (SULP), which is analogous to the lunar basalts and howardite‐eucrite‐diogenite meteorites and forms in the present‐day Earth's field, to investigate the recording fidelity of these meteorites. No remanence has been identified in the high coercivity range with alternating field (AF) demagnetization due to the sample's low coercivity and AF noise, which produces underestimated paleointensities. Two accurate thermal paleointensities indicate that we may acquire accurate paleointensities from non‐ideal multidomain (MD) iron grains with the Thellier‐Coe and RESET methods, but the success rate is low due to the MD effect and thermal alteration in the experiments. Our results imply that MD iron‐bearing meteorites have the potential to provide accurate paleointensities that can be used to constrain planetary processes. Plain Language Summary: The strength of ancient magnetic fields retrieved from meteorites provides quantitative estimates of the dynamics of the planetary core. It is essential to acquire accurate strength to study the evolution of planetary interiors. However, the accuracy of the recovered magnetic strength of meteorites has not been fully tested because we previously lacked a sample that was similar to the meteorites and formed in a known field. Here, we use an iron‐bearing sample produced by the Syracuse University Lava Project (SULP), which is analogous to lunar basalts and howardite‐eucrite‐diogenite meteorites and forms in the present‐day Earth's field, to test the accuracy of the recovered magnetic strength of meteorites. Although coarse iron grains (>1 μm) in the SULP sample and some meteorites are not ideal magnetic carriers, our results show that we may acquire accurate magnetic field strength from them with a new method. Key Points: An iron‐bearing sample formed in the Earth's magnetic field is used to test the paleomagnetic fidelity of meteoritesThermal paleointensity experiments have the potential to acquire accurate paleointensities from non‐ideal multidomain iron grainsThe low temperatures in extraterrestrial environments may lead to paleointensity underestimation of mission‐returned samples [ABSTRACT FROM AUTHOR]

The present-day climate (the recent 100–150 years) obviously constitutes the structure of a global intra-system rhythmic process with an individual rhythm of about 60 years. In turn, each of the rhythms is presented by the two climate phases of about 25–35 years characterized by qualitative differences: one phase is relatively continental, while the other is humid. Globality and quasi-synchronism of environmental changes are accompanied by planetary structures: the Global Atmospheric Oscillation (GAO) in the atmosphere and the Multidecadal Oscillation of the Heat content in the Ocean (MOHO) discovered relatively recently. Unexpected and rapid qualitative phase changes in the climate, which first focused attention in the mid-1970s of the last century, were titled "climate shifts". The revealed features of the present-day climate are of exceptional scientific and practical interest and deserve the development of methods for predicting the timing of the forthcoming climate shift. Arising unexpectedly and accompanied by rapid significant changes, these shifts identified the problem of understanding the nature and establishing the processes and mechanisms causing them. First of all, of interest are phase changes in the thermodynamic state of the climate system components: the ocean, atmosphere, and continents. As a result of the World Ocean (WO) thermohydrodynamics numerical modelling, it is shown that MOHO is localized in the layer of the main thermocline, where the most important elements of the WO circulation are located. The performed study based on observational data allows us to conclude that, during the phase of the WO thermal discharge (1975–1999), the two key systems of currents, the Kuroshio and the Gulf Stream, were under similar thermodynamic conditions. [ABSTRACT FROM AUTHOR]

We are interested in the influence of cloudy atmospheres on the thermal radius evolution of warm exoplanets from an interior modelling perspective. By applying a physically motivated but simple parametrized cloud model, we obtain the atmospheric P – T structure that is connected to the adiabatic interior at the self-consistently calculated radiative–convective boundary. We investigate the impact of cloud gradients, with the possibility of inhibiting superadiabatic clouds. Furthermore, we explore the impact on the radius evolution for a cloud base fixed at a certain pressure versus a subsiding cloud base during the planets' thermal evolution. We find that deep clouds clearly alter the evolution tracks of warm giants, leading to either slower/faster cooling than in the cloudless case (depending on the cloud model used). When comparing the fixed versus dynamic cloud base during evolution, we see an enhanced behaviour resulting in a faster or slower cooling in the case of the dynamic cloud base. We show that atmospheric models including deep clouds can lead to degeneracy in predicting the bulk metallicity of planets, Z P. For WASP-10b, we find a possible span of |$\approx {Z_\mathrm{P}}_{-0.06}^{+0.10}$|⁠. For TOI-1268b, it is |$\approx {Z_\mathrm{P}}_{-0.05}^{+0.10}$|⁠. Further work on cloud properties during the long-term evolution of gas giants is needed to better estimate the influence on the radius evolution. [ABSTRACT FROM AUTHOR]

Magnesium oxide is one of many important materials that comprise the mantles of terrestrial planets. In this regard, its properties at high temperatures and pressures reflect the nature of the planetary interior. Shock wave loading of magnesium oxide with account for polymorphic phase transition in a pressure range of 325–400 GPa is numerically simulated using a thermodynamic equilibrium model. The parameters of the consistent equation of state for high- and low-pressure magnesium oxide phases (MgO I and MgO II) are determined. The thermodynamic parameters of these phases are simulated. The Hugoniots of single and double compression are constructed in a range of 1–1000 GPa, and the following parameters are calculated: heat capacity along the normal isobar, entropy as a function of temperature, and temperature along the Hugoniot. The simulation results are verified using data from experiments and calculations of other authors. [ABSTRACT FROM AUTHOR]

Metal carbides are known to contain small carbon units similar to those found in the molecules of methane, acetylene, and allene. However, for numerous binary systems ab initio calculations predict the formation of unusual metal carbides with exotic polycarbon units, [C6] rings, and graphitic carbon sheets at high pressure (HP). Here we report the synthesis and structural characterization of a HP-CaC2 polymorph and a Ca3C7 compound featuring deprotonated polyacene-like and para-poly(indenoindene)-like nanoribbons, respectively. We also demonstrate that carbides with infinite chains of fused [C6] rings can exist even at conditions of deep planetary interiors (~ 140 GPa and ~3300 K). Hydrolysis of high-pressure carbides may provide a possible abiotic route to polycyclic aromatic hydrocarbons in Universe. The authors demonstrate that carbides with infinite chains of fused [C6] and [C5] rings are synthesized at deep planetary pressures and temperatures. Hydrolysis of these carbides may lead to polycyclic aromatic hydrocarbons in the Universe. [ABSTRACT FROM AUTHOR]

First-principles calculations and analysis of the thermodynamic, structural, and electronic properties of liquid SiO 2 characterize the bonded-to-atomic transition at 0.1–1.6 TPa and 10 4 – 10 5 K (1–9 eV), the high-energy-density regime relevant to understanding planetary interiors. We find strong ionic bonds that become short-lived due to high kinetics during the transition, with sensitivity of the transition temperature to pressure, and our calculated Hugoniots agree with past experimental data. These results reconcile previous experimental and theoretical findings by clarifying the nature of the bond dissociation process in early Earth and "rocky" (oxide) constituents of large planets. [ABSTRACT FROM AUTHOR]

The radii of planets serve as significant constraints for their internal structure. Despite the complexity of planetary internal structure compared to stars, substantial advancements have been made in this field. The most critical uncertainties stem from the chemical composition and equation of state of planetary material. Using the MESA code, we construct rotating and non-rotating interior models for Jupiter and Saturn and sought to align these models to the observed radii. Rotation exerts a significant influence on their structures, distorting planetary, and stellar structures in distinct ways. Regarding gas planets' structure, two pivotal uncertain parameters depend on a possible separation between hydrogen and helium in the protosolar disc gas due to unequal evaporation between these two gases. In an extreme scenario where only hydrogen is lost and no heavy elements or helium are lost, Jupiter and Saturn would have a core mass of zero. However, this approach fails to yield a solution for Uranus and Neptune. Instead, our models indicate that hydrogen and helium were likely lost together during the protosolar disc phase, resulting in core masses of approximately 40, 25, 14, and 12 M⊕ for Jupiter, Saturn, Neptune, and Uranus, respectively. These findings are highly compatible with the observed mass–radius relationship of exoplanets, as well as the seismic and Juno data for Jupiter's near-surface temperature. [ABSTRACT FROM AUTHOR]

In this work, we develop a rocky planet interior model and use it to investigate the evolution of catastrophically evaporating rocky exoplanets. These planets, detected through the dust tails produced by evaporative outflows from their molten surfaces, can be entirely destroyed in a fraction of their host star's lifetime. To allow for the major decrease in mass, our interior model can simultaneously calculate the evolution of the pressure and density structure of a planet alongside its thermal evolution, which includes the effects of conduction, convection and partial melting. We first use this model to show that the underlying planets are likely to be almost entirely solid. This means that the dusty tails are made up of material sampled only from a thin dayside lava pool. If one wishes to infer the bulk compositions of rocky exoplanets from their dust tails, it is important to take the localized origin of this material into account. Secondly, by considering how frequently one should be able to detect mass loss from these systems, we investigate the occurrence of sub-Earth mass exoplanets, which is difficult with conventional planet detection surveys. We predict that, depending on model assumptions, the number of progenitors of the catastrophically evaporating planets is either in line with, or higher than, the observed population of close-in (substellar temperatures around 2200 K) terrestrial exoplanets. [ABSTRACT FROM AUTHOR]

In this paper, we propose a fully coupled two-phase poroelastic deformation theory for a spherically layered and self-gravitating Earth. The earth model consists of a solid inner core, a fluid outer core and poroelastic mantle and crust. The boundary-value problems are posed in the Laplace-transformed domain using the spherical system of vector functions, and analytical solutions are obtained in each layer using the dual-variable and position matrix method. As an application, the surface loading problem is considered. The undrained and drained limits are discussed with the corresponding governing equations, which are different from the conventional ones where body force is ignored. Numerical examples show that the poroelastic effect can be significant since the difference between the results for undrained and drained limits are large with obvious time-dependent deformation. This newly derived theory for the coupled boundary-value problem will have broad applications, such as displacement and gravity change due to groundwater depletion, poroelastic rebound after an earthquake and risk evaluation of earthquakes induced by water injection. [ABSTRACT FROM AUTHOR]

Tidal interactions between moons and planets can have major effects on the orbits, spins, and thermal evolution of the moons. In the Saturn system, tidal dissipation in the planet transfers angular momentum from Saturn to the moons, causing them to migrate outwards. The rate of migration is determined by the mechanism of dissipation within the planet, which is closely tied to the planet's uncertain structure. We review current knowledge of giant planet internal structure and evolution, which has improved thanks to data from the Juno and Cassini missions. We discuss general principles of tidal dissipation, describing both equilibrium and dynamical tides, and how dissipation can occur in a solid core or a fluid envelope. Finally, we discuss the possibility of resonance locking, whereby a moon can lock into resonance with a planetary oscillation mode, producing enhanced tidal migration relative to classical theories, and possibly explaining recent measurements of moon migration rates. [ABSTRACT FROM AUTHOR]

The contrasting internal luminosity of Uranus and Neptune present a challenge to our understanding of the origin and evolution of these bodies, as well as extra-solar ice giants. The thermal evolution of Neptune is known to be nearly consistent with an entirely fluid interior, but this is not a unique solution, and does not account for the tidal dissipation required by the migration of its moons. We examine a model that has been previously shown to explain the thermal and tidal evolution of Uranus: one that features a growing, frozen core. The core traps heat in the interior, affecting the cooling time scale, and provides a source of tidal dissipation. We review the growing, frozen core model, and the computation of thermal and tidal evolution. We then apply this model to Neptune. We find that the growing frozen core model can account for the observed internal luminosity of Neptune and the migration of its moons, in the form of resonances that were either encountered or avoided in the past. We discuss prospects for observational tests of the growing frozen core model and possible implications for understanding the gas giants. [ABSTRACT FROM AUTHOR]

How turbulent convective fluctuations organize to form larger-scale structures in planetary atmospheres remains a question that eludes quantitative answers. The assumption that this process is the result of an inverse cascade was suggested half a century ago in two-dimensional fluids, but its applicability to atmospheric and oceanic flows remains heavily debated, hampering our understanding of the energy balance in planetary systems. We show using direct numerical simulations with spatial resolutions of 122882 × 384 points that rotating and stratified flows can support a bidirectional cascade of energy, in three dimensions, with a ratio of Rossby to Froude numbers comparable to that of Earth's atmosphere. Our results establish that, in dry atmospheres, spontaneous order can arise through an inverse cascade to the largest spatial scales. [ABSTRACT FROM AUTHOR]