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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]

Uranus and Neptune are the last unexplored planets of the Solar System. I show that they hold crucial keys to understand the atmospheric dynamics and structure of planets with hydrogen atmospheres. Their atmospheres are active and storms are believed to be fueled by methane condensation which is both extremely abundant and occurs at low optical depth. This means that mapping temperature and methane abundance as a function of position and depth will inform us on how convection organizes in an atmosphere with no surface and condensates that are heavier than the surrounding air, a general feature of gas giants. Using this information will be essential to constrain the interior structure of Uranus and Neptune themselves, but also of Jupiter, Saturn, and numerous exoplanets with hydrogen atmospheres. Owing to the spatial and temporal variability of these atmospheres, an orbiter is required. A probe would provide a reference profile to lift ambiguities inherent to remote observations. It would also measure abundances of noble gases which can be used to reconstruct the history of planet formation in the Solar System. Finally, mapping the planets' gravity and magnetic fields will be essential to constrain their global composition, structure and evolution. [ABSTRACT FROM AUTHOR]

We develop new angular momentum evolution models for stars with masses of 0.5 to 1.6 M☉ and from the pre-main-sequence (PMS) through the end of their main-sequence (MS) lifetime. The parametric models include magnetic braking based on numerical simulations of magnetized stellar winds, mass-loss-rate prescription, core-envelope decoupling as well as disc locking phenomena. We have also accounted for recent developments in modelling dramatically weakened magnetic braking in stars more evolved than the Sun.We fit the free parameters in our model by comparing model predictions to rotational distributions of a number of stellar clusters as well as individual field stars. Our model reasonably successfully reproduces the rotational behaviour of stars during the PMS phase to the zero-age main-sequence (ZAMS) spin-up, sudden ZAMS spin-down and convergence of the rotation rates afterwards. We find that including core-envelope decoupling improves our models, especially for low-mass stars at younger ages. In addition, by accounting for the almost complete suppression of magnetic braking at slow-spin periods, we provide better fits to observations of stellar rotations compared to previous models. [ABSTRACT FROM AUTHOR]

Seismology represents a unique method to probe the interiors of giant planets. Recently, Saturn’s f-modes have been indirectly observed in its rings, and there is strong evidence for the detection of Jupiter global modes by means of ground-based, spatially-resolved, velocimetry measurements. We propose to exploit Juno’s extremely accurate radio science data by looking at the gravity perturbations that Jupiter’s acoustic modes would produce. We evaluate the perturbation to Jupiter’s gravitational field using the oscillation spectrum of a polytrope with index 1 and the corresponding radial eigenfunctions. We show that Juno will be most sensitive to the fundamental mode ( n = 0 ), unless its amplitude is smaller than 0.5 cm/s, i.e. 100 times weaker than the n ∼ 4 − 11 modes detected by spatially-resolved velocimetry. The oscillations yield contributions to Juno’s measured gravitational coefficients similar to or larger than those expected from shallow zonal winds (extending to depths less than 300 km). In the case of a strong f-mode (radial velocity ∼ 30 cm/s), these contributions would become of the same order as those expected from deep zonal winds (extending to 3000 km), especially on the low degree zonal harmonics, therefore requiring a new approach to the analysis of Juno data. [ABSTRACT FROM AUTHOR]

Context. The recent discovery and characterization of the diversity of the atmospheres of exoplanets and brown dwarfs calls for the development of fast and accurate analytical models. Aims. We wish to assess the goodness of the different approximations used to solve the radiative transfer problem in irradiated atmospheres analytically, and we aim to provide a useful tool for a fast computation of analytical temperature profiles that remains correct over a wide range of atmospheric characteristics. Methods. We quantify the accuracy of the analytical solution derived in paper I for an irradiated, non-grey atmosphere by comparing it to a state-of-the-art radiative transfer model. Then, using a grid of numerical models, we calibrate the different coeffcients of our analytical model for irradiated solar-composition atmospheres of giant exoplanets and brown dwarfs. Results. We show that the so-called Eddington approximation used to solve the angular dependency of the radiation field leads to relative errors of up to ~5% on the temperature profile. For grey or semi-grey atmospheres (i.e., when the visible and thermal opacities, respectively, can be considered independent of wavelength), we show that the presence of a convective zone has a limited effect on the radiative atmosphere above it and leads to modifications of the radiative temperature profile of approximately ~2%. However, for realistic non-grey planetary atmospheres, the presence of a convective zone that extends to optical depths smaller than unity can lead to changes in the radiative temperature profile on the order of 20% or more. When the convective zone is located at deeper levels (such as for strongly irradiated hot Jupiters), its effect on the radiative atmosphere is again on the same order (~2%) as in the semi-grey case. We show that the temperature inversion induced by a strong absorber in the optical, such as TiO or VO is mainly due to non-grey thermal effects reducing the ability of the upper atmosphere to cool down rather than an enhanced absorption of the stellar light as previously thought. Finally, we provide a functional form for the coeffcients of our analytical model for solar-composition giant exoplanets and brown dwarfs. This leads to fully analytical pressure-temperature profiles for irradiated atmospheres with a relative accuracy better than 10% for gravities between 2.5ms-2 and 250ms-2 and effective temperatures between 100K and 3000 K. This is a great improvement over the commonly used Eddington boundary condition. [ABSTRACT FROM AUTHOR]

Context. Circumstellar diffsks are known to contain a significant mass in dust ranging from micron to centimeter size. Meteorites are evidence that indiffvidual grains of those sizes were collected and assembled into planetesimals in the young solar system. Aims. We assess the efficiency of dust collection of a swarm of non-drifting planetesimals with radiffiranging from 1 to 103 km and beyond. Methods. We calculate the collision probability of dust drifting in the diffsk due to gas drag by planetesimal accounting for several regimes dependiffng on the size of the planetesimal, dust, and orbital diffstance: the geometric, Safronov, settling, and three-body regimes. We also include a hydrodynamical regime to account for the fact that small grains tend to be carried by the gas flow around planetesimals. Results. We provide expressions for the collision probability of dust by planetesimals and for the filtering efficiency by a swarm of planetesimals. For standard turbulence condifftions (i.e., a turbulence parameter α = 10-2), filtering is found to be inefficient, meaning that when crossing a minimum-mass solar nebula (MMSN) belt of planetesimals extendiffng between 0.1AU and 35AU most dust particles are eventually accreted by the central star rather than collidiffng with planetesimals. However, if the diffsk is weakly turbulent (α = 10-4) filtering becomes efficient in two regimes: (i) when planetesimals are all smaller than about 10 km in size, in which case collisions mostly take place in the geometric regime; and (ii) when planetary embryos larger than about 1000 km in size dominate the diffstribution, have a scale height smaller than one tenth of the gas scale height, and dust is of millimeter size or larger in which case most collisions take place in the settling regime. These two regimes have very diff erent properties: we find that the local filtering efficiency xfilter;MMSN scales with r-7/4 (where r is the orbital diffstance) in the geometric regime, but with r-1/4 to r1/4 in the settling regime. This implies that the filtering of dust by small planetesimals should occur close to the central star and with a short spread in orbital diffstances. On the other hand, the filtering by embryos in the settling regime is expected to be more gradual and determined by the extent of the diffsk of embryos. Dust particles much smaller than millimeter size tend only to be captured by the smallest planetesimals because they otherwise move on gas streamlines and their collisions take place in the hydrodynamical regime. Conclusions. Our results hint at an inside-out formation of planetesimals in the infant solar system because small planetesimals in the geometrical limit can filter dust much more efficiently close to the central star. However, even a fully-formed belt of planetesimals such as the MMSN only marginally captures inward-drifting dust and this seems to imply that dust in the protosolar diffsk has been filtered by planetesimals even smaller than 1 km (not included in this study) or that it has been assembled into planetesimals by other mechanisms (e.g., orderly growth, capture into vortexes). Further refinement of our work concerns, among other things: a quantitative description of the transition region between the hydro and settling regimes; an assessment of the role of diffsk turbulence for collisions, in particular in the hydro regime; and the coupling of our model to a planetesimal formation model. [ABSTRACT FROM AUTHOR]

Context. Semi-grey atmospheric models (with one opacity for the visible and one opacity for the infrared) are useful for understanding the global structure of irradiated atmospheres, their dynamics, and the interior structure and evolution of planets, brown dwarfs, and stars. When compared to direct numerical radiative transfer calculations for irradiated exoplanets, however, these models systematically overestimate the temperatures at low optical depths, independently of the opacity parameters. Aims. We investigate why semi-grey models fail at low optical depths and provide a more accurate approximation to the atmospheric structure by accounting for the variable opacity in the infrared. Methods. Using the Eddington approximation, we derive an analytical model to account for lines and/or bands in the infrared. Four parameters (instead of two for the semi-grey models) are used: a visible opacity (κv), two infrared opacities, (κ1 and κ2), and β (the fraction of the energy in the beam with opacities κ1). We consider that the atmosphere receives an incident irradiation in the visible with an effective temperature Tirr and at an angle μ, and that it is heated from below with an effective temperature Tint. Results. Our non-grey, irradiated line model is found to provide a range of temperatures that is consistent with that obtained by numerical calculations. We find that if the stellar flux is absorbed at optical depth larger than τlim = (κR=κ1κ2)(κRκP/3)1/2, it is mainly transported by the channel of lowest opacity whereas if it is absorbed at τ ≳ τlim it is mainly transported by the channel of highest opacity, independently of the spectral width of those channels. For low values of β (expected when lines are dominant), we find that the non-grey effects significantly cool the upper atmosphere. However, for β ͱ 1/2 (appropriate in the presence of bands with a wavelength-dependence smaller than or comparable to the width of the Planck function), we find that the temperature structure is affected down to infrared optical depths unity and deeper as a result of the so-called blanketing effect. Conclusions. The expressions that we derive can be used to provide a proper functional form for algorithms that invert the atmospheric properties from spectral information. Because a full atmospheric structure can be calculated directly, these expressions should be useful for simulations of the dynamics of these atmospheres and of the thermal evolution of the planets. Finally, they should be used to test full radiative transfer models and to improve their convergence. [ABSTRACT FROM AUTHOR]

The accurate determination of Saturn's gravitational coefficients by Cassini could provide tighter constraints on Saturn's internal structure. Also, occultation measurements provide important information on the planetary shape which is often not considered in structure models. In this paper we explore how wind velocities and internal rotation affect the planetary shape and the constraints on Saturn's interior. We show that within the geodetic approach the derived physical shape is insensitive to the assumed deep rotation. Saturn's re-derived equatorial and polar radii at 100 mbar are found to be 54,445 ± 10 km and 60,365 ± 10 km, respectively. To determine Saturn's interior, we use one-dimensional three-layer hydrostatic structure models and present two approaches to include the constraints on the shape. These approaches, however, result in only small differences in Saturn's derived composition. The uncertainty in Saturn's rotation period is more significant: with Voyager's 10h39m period, the derived mass of heavy elements in the envelope is 0-7M⊕. With a rotation period of 10h32m, this value becomes <4M⊕, below the minimum mass inferred from spectroscopic measurements. Saturn's core mass is found to depend strongly on the pressure at which helium phase separation occurs, and is estimated to be 5-20M⊕. Lower core masses are possible if the separation occurs deeper than 4 Mbar. We suggest that the analysis of Cassini's radio occultation measurements is crucial to test shape models and could lead to constraints on Saturn's rotation profile and departures from hydrostatic equilibrium. [ABSTRACT FROM AUTHOR]

It has been proposed that the enrichment in noble gases found by Galileo in the atmosphere of Jupiter can be explained by their delivery inside cold planetesimals. We propose instead that this is a sign that the planet formed in a chemically evolved disc and that noble gases were acquired mostly in gaseous form during the envelope capture phase of the planet. We show that the combined settling of grains to the disc mid-plane in the cold outer layers, the condensation of noble gases on to these grains at temperatures below 20–30 K, and the evaporation from high disc altitudes effectively lead to a progressive, moderate enrichment of the disc. The fact that noble gases are vaporized from the grains in the hot inner disc regions (e.g. Jupiter formation region) is not a concern because a negative temperature gradient prevents convection from carrying the species into the evaporating region. We show that the ∼2 times solar enrichment of Ar, Kr and Xe in Jupiter is hence naturally explained by a continuous growth of the planet governed by viscous diffusion in the protosolar disc in conjunction with an evaporation of the disc and its progressive enrichment on a million-year time-scale. [ABSTRACT FROM AUTHOR]

We know that giant planets played a crucial role in the making of our Solar System. The discovery of giant planets orbiting other stars is a formidable opportunity to learn more about these objects, what their composition is, how various processes influence their structure and evolution, and most importantly how they form. Jupiter, Saturn, Uranus, and Neptune can be studied in detail, mostly from close spacecraft flybys. We can infer that they are all enriched in heavy elements compared to the Sun, with the relative global enrichments increasing with distance to the Sun. We can also infer that they possess dense cores of varied masses. The intercomparison of presently characterized extrasolar giant planets shows that they are also mainly made of hydrogen and helium, but that they either have significantly different amounts of heavy elements, have had different orbital evolutions, or both. Hence, many questions remain and need to be answered to make significant progress on the origins of planets. [ABSTRACT FROM AUTHOR]

Discusses the formation of giant extrasolar planets. Atmospheric components of Jupiter and Saturn; Interior structure of the two giant planets; Factors which contribute to the difficulty in examining the formation of giant extrasolar planets.

Provides information on the interiors of giant planets inside and outside the solar system. Why the structure and composition of giant planets is evolving; Division of interiors of Jupiter and Saturn; Structure of Uranus and Neptune; Radii of extrasolar giant planets.

We report on the discovery and characterization of three planets orbiting the F8 star HD 28109, which sits comfortably in |${TESS}$| 's continuous viewing zone. The two outer planets have periods of |$\rm 56.0067 \pm 0.0003~d$| and |$\rm 84.2597_{-0.0008}^{+0.0010}~d$|⁠ , which implies a period ratio very close to that of the first-order 3:2 mean motion resonance, exciting transit timing variations (TTVs) of up to |$\rm 60\, min$|⁠. These two planets were first identified by |${TESS}$|⁠ , and we identified a third planet in the |${TESS}$| photometry with a period of |$\rm 22.8911 \pm 0.0004~d$|⁠. We confirm the planetary nature of all three planetary candidates using ground-based photometry from Hazelwood , |${ASTEP}$|⁠ , and LCO , including a full detection of the |$\rm \sim 9\, h$| transit of HD 28109 c from Antarctica. The radii of the three planets are |${\it R}_b=2.199_{-0.10}^{+0.098} ~{\rm R}_{\oplus }$|⁠ , |${\it R}_c=4.23\pm 0.11~ {\rm R}_{\oplus }$|⁠ , and |${\it R}_d=3.25\pm 0.11 ~{\rm R}_{\oplus }$|⁠ ; we characterize their masses using TTVs and precise radial velocities from ESPRESSO and HARPS, and find them to be |${\it M}_b=18.5_{-7.6}^{+9.1}~M_{\oplus }$|⁠ , |${\it M}_c=7.9_{-3.0}^{+4.2}~{\rm M}_{\oplus }$|⁠ , and |${\it M}_d=5.7_{-2.1}^{+2.7}~{\rm M}_{\oplus }$|⁠ , making planet b a dense, massive planet while c and d are both underdense. We also demonstrate that the two outer planets are ripe for atmospheric characterization using transmission spectroscopy, especially given their position in the CVZ of James Webb Space Telescope. The data obtained to date are consistent with resonant (librating) and non-resonant (circulating) solutions; additional observations will show whether the pair is actually locked in resonance or just near-resonant. [ABSTRACT FROM AUTHOR]

Context. The formation and evolution of protoplanetary disks remains elusive. We have numerous astronomical observations of young stellar objects of different ages with their envelopes and/or disks. Moreover, in the last decade, there has been tremendous progress in numerical simulations of star and disk formation. New simulations use realistic equations of state for the gas and treat the interaction of matter and the magnetic field with the full set of nonideal magnetohydrodynamic (MHD) equations. However, it is still not fully clear how a disk forms and whether it happens from inside-out or outside-in. Open questions remain regarding where material is accreted onto the disk and comes from, how dust evolves in disks, and the timescales of appearance of disk's structures. These unknowns limit our understanding of how planetesimals and planets form and evolve. Aims. We attempted to reconstruct the evolutionary history of the protosolar disk, guided by the large amount of cosmochemical constraints derived from the study of meteorites, while using astronomical observations and numerical simulations as a guide to pinpointing plausible scenarios. Methods. Our approach is highly interdisciplinary and we do not present new observations or simulations in this work. Instead, we combine, in an original manner, a large number of published results concerning young stellar objects observations, and numerical simulations, along with the chemical, isotopic and petrological nature of meteorites. Results. We have achieved a plausible and coherent view of the evolution of the protosolar disk that is consistent with cosmochemical constraints and compatible with observations of other protoplanetary disks and sophisticated numerical simulations. The evidence that high-temperature condensates, namely, calcium-aluminum inclusions (CAIs) and amoeboid olivine aggregates (AOAs), formed near the protosun before being transported to the outer disk can be explained in two ways: there could have either been an early phase of vigorous radial spreading of the disk that occurred or fast transport of these condensates from the vicinity of the protosun toward large disk radii via the protostellar outflow. The assumption that the material accreted toward the end of the infall phase was isotopically distinct allows us to explain the observed dichotomy in nucleosynthetic isotopic anomalies of meteorites. It leads us toward intriguing predictions on the possible isotopic composition of refractory elements in comets. At a later time, when the infall of material waned, the disk started to evolve as an accretion disk. Initially, dust drifted inward, shrinking the radius of the dust component to ∼45 au, probably about to about half of the width of the gas component. Next, structures must have emerged, producing a series of pressure maxima in the disk, which trapped the dust on Myr timescales. This allowed planetesimals to form at radically distinct times without significantly changing any of the isotopic properties. We also conclude that there was no late accretion of material onto the disk via streamers. The disk disappeared at about 5 My, as indicated by paleomagnetic data in meteorites. Conclusions. The evolution of the protosolar disk seems to have been quite typical in terms of size, lifetime, and dust behavior. This suggests that the peculiarities of the Solar System with respect to extrasolar planetary systems probably originate from the chaotic nature of planet formation and not from the properties of the parental disk itself. [ABSTRACT FROM AUTHOR]

Constraining the formation processes of small solar system bodies is crucial for gaining insights into planetesimal formation. Their bulk densities, determined by their compressive strengths, offer valuable information about their formation history. In this paper, we utilize a formulation of the compressive strength of dust aggregates obtained from dust N -body simulations to establish the relation between the bulk density and diameter. We find that this relation can be effectively approximated by a polytrope with an index of 0.5, coupled with a formulation of the compressive strength of dust aggregates. The lowest-density trans-Neptunian objects (TNOs) and main-belt asteroids (MBAs) are well reproduced by dust aggregates composed of 0.1 μ m sized grains. However, most TNOs, MBAs, comets, and near-Earth asteroids (NEAs) exhibit higher densities, suggesting the influence of compaction mechanisms such as collision, dust grain disruption, sintering, or melting, leading to further growth. We speculate that there are two potential formation paths for small solar system bodies. One involves the direct coagulation of primordial dust grains, resulting in the formation of first-generation planetesimals, including the lowest-density TNOs, MBAs, and the parent bodies of comets and NEAs. In this case, comets and NEAs are fragments or rubble piles of first-generation planetesimals, and the objects themselves or the rubble are composed of 0.1 μ m sized grains. The other path involves the further potential fragmentation of first-generation planetesimals into the compact dust aggregates observed in protoplanetary disks, resulting in the formation of second-generation planetesimals composed of compact dust aggregates, which may contribute to explaining another formation process of comets and NEAs. [ABSTRACT FROM AUTHOR]

Examines the effect of the condensation of chemical species of high molecular mass in inhibiting the convection in the hydrogen-helium atmospheres of the giant planets. Condensation of methane, ammonia and water; Temperature gradient; Temperature profiles inferred from radio-occulation measurements.

The key to understand our origins is in the interiors of the giant planets. Because Jupiter was one of the first planets to form, its primordial envelope, accreted from the primitive solar nebula, contains crucial information to understand the physics and the chemistry of the protosolar disk that gave birth to the solar system. Heavy elements, even though they are a smaller constituent, are an important input in formation models and therefore crucial to understand the formation history of Jupiter.In orbit since July 2016, Juno mission has lead to a radical change of our knowledge of Jupiter. Its highly accurate gravity data, allows us to calculate new models to understand Jupiter's interior structure and atmospheric dynamics. These models are used to determine the amount of heavy elements and its potential distribution in the interior of Jupiter. In this talk we present our optimized calculations that also explore the effect of different model parameters, towards a better determination of the mass of heavy elements and its distribution in Jupiter's interior. [ABSTRACT FROM AUTHOR]

Ground-based radio-wave observations and the Juno spacecraft have shown that, contrary to expectations, the concentration of ammonia is still variable down to pressures of tens of bars in Jupiter. While mid-latitudes show a strong depletion of ammonia, the equatorial zone of Jupiter has an abundance of NH3 that is nearly uniform. In parallel, Juno determined that the equatorial zone is peculiar for its absence of lightning, which is otherwise prevalent everywhere else in the planet. We show that a model accounting for the presence of small-scale convection, ammonia dissolution in water ice, water storms and large plumes originating in Jupiter's deep atmosphere accounts for the observations. This new vision of the mechanisms at play which are both deep and latitude-dependent have consequences for our understanding of Jupiter's deep interior and of giant planets atmospheres in general. [ABSTRACT FROM AUTHOR]

There are still many open questions regarding the nature of Uranus and Neptune, the outermost planets in the Solar System. In this review we summarize the current-knowledge about Uranus and Neptune with a focus on their composition and internal structure, formation including potential subsequent giant impacts, and thermal evolution. We present key open questions and discuss the uncertainty in the internal structures of the planets due to the possibility of non-adiabatic and inhomogeneous interiors. We also provide the reasoning for improved observational constraints on their fundamental physical parameters such as their gravitational and magnetic fields, rotation rates, and deep atmospheric composition and temperature. Only this way will we be able to improve our understating of these planetary objects, and the many similar-sized objects orbiting other stars. [ABSTRACT FROM AUTHOR]

We present the discovery and characterization of two warm mini-Neptunes transiting the K3V star TOI-815 in a K–M binary system. Analysis of its spectra and rotation period reveal the star to be young, with an age of 200−200+400 Myr. TOI-8l5b has a 11.2-day period and a radius of 2.94 ± 0.05 R⊕ with transits observed by TESS, CHEOPS, ASTEP, and LCOGT. The outer planet, TOI-8l5c, has a radius of 2.62 ± 0.10 R⊕, based on observations of three nonconsecutive transits with TESS; targeted CHEOPS photometry and radial velocity follow-up with ESPRESSO were required to confirm the 35-day period. ESPRESSO confirmed the planetary nature of both planets and measured masses of 7.6 ± 1.5 M⊕ (ρP = 1.64−0.31+0.33 g cm−3) and 23.5 ± 2.4 M⊕ (ρP = 7.2−1.0+1.1 g cm−3), respectively. Thus, the planets have very different masses, which is unusual for compact multi-planet systems. Moreover, our statistical analysis of mini-Neptunes orbiting FGK stars suggests that weakly irradiated planets tend to have higher bulk densities compared to those undergoing strong irradiation. This could be ascribed to their cooler atmospheres, which are more compressed and denser. Internal structure modeling of TOI-815b suggests it likely has a H-He atmosphere that constitutes a few percent of the total planet mass, or higher if the planet is assumed to have no water. In contrast, the measured mass and radius of TOI-815c can be explained without invoking any atmosphere, challenging planetary formation theories. Finally, we infer from our measurements that the star is viewed close to pole-on, which implies a spin-orbit misalignment at the 3σ level. This emphasizes the peculiarity of the system's orbital architecture, and probably hints at an eventful dynamical history. [ABSTRACT FROM AUTHOR]

The atmospheres of the four giant planets of our Solar System share a common and well-observed characteristic: they each display patterns of planetary banding, with regions of different temperatures, composition, aerosol properties and dynamics separated by strong meridional and vertical gradients in the zonal (i.e., east-west) winds. Remote sensing observations, from both visiting spacecraft and Earth-based astronomical facilities, have revealed the significant variation in environmental conditions from one band to the next. On Jupiter, the reflective white bands of low temperatures, elevated aerosol opacities, and enhancements of quasi-conserved chemical tracers are referred to as 'zones.' Conversely, the darker bands of warmer temperatures, depleted aerosols, and reductions of chemical tracers are known as 'belts.' On Saturn, we define cyclonic belts and anticyclonic zones via their temperature and wind characteristics, although their relation to Saturn's albedo is not as clear as on Jupiter. On distant Uranus and Neptune, the exact relationships between the banded albedo contrasts and the environmental properties is a topic of active study. This review is an attempt to reconcile the observed properties of belts and zones with (i) the meridional overturning inferred from the convergence of eddy angular momentum into the eastward zonal jets at the cloud level on Jupiter and Saturn and the prevalence of moist convective activity in belts; and (ii) the opposing meridional motions inferred from the upper tropospheric temperature structure, which implies decay and dissipation of the zonal jets with altitude above the clouds. These two scenarios suggest meridional circulations in opposing directions, the former suggesting upwelling in belts, the latter suggesting upwelling in zones. Numerical simulations successfully reproduce the former, whereas there is a wealth of observational evidence in support of the latter. This presents an unresolved paradox for our current understanding of the banded structure of giant planet atmospheres, that could be addressed via a multi-tiered vertical structure of "stacked circulation cells," with a natural transition from zonal jet pumping to dissipation as we move from the convectively-unstable mid-troposphere into the stably-stratified upper troposphere. [ABSTRACT FROM AUTHOR]

The science enabled by the deep and high‐cadence survey that will be performed by the Vera Rubin Observatory has led to an increase of survey and follow‐up capabilities around the world. The infrared, has however, not match this growth due to the challenges caused by the atmospheric and the cost of large detector arrays. In this paper, we present solutions to resolve these challenges and a path toward an Antarctic observatory capable matching the volumetric speed of the Vera Rubin Observatory survey in the infrared k‐band. We will detail the current state of infrared survey telescopes, demonstrate the benefits of Antarctic high‐plateau for such observations, and show some of the development made in detector technologies to make large detector arrays a reality for such application. [ABSTRACT FROM AUTHOR]

Recent formation and structure models of Jupiter suggest that the planet can have composition gradients and not be fully convective (adiabatic). This possibility directly affects our understanding of Jupiter’s bulk composition and origin. In this Letter we present Jupiter’s evolution with a primordial structure consisting of a relatively steep heavy-element gradient of 40 M⊕. We show that for a primordial structure with composition gradients, most of the mixing occurs in the outer part of the gradient during the early evolution (several 107 yr), leading to an adiabatic outer envelope (60% of Jupiter’s mass). We find that the composition gradient in the deep interior persists, suggesting that ∼40% of Jupiter’s mass can be non-adiabatic with a higher temperature than the one derived from Jupiter’s atmospheric properties. The region that can potentially develop layered convection in Jupiter today is estimated to be limited to ∼10% of the mass. [ABSTRACT FROM AUTHOR]

Context. Planets less massive than Saturn tend to rapidly migrate inward in protoplanetary disks. This is the so-called type I migration. Simulations attempting to reproduce the observed properties of exoplanets show that type I migration needs to be significantly reduced over a wide region of the disk for a long time. However, the mechanism capable of suppressing type I migration over a wide region has remained elusive. The recently found turbulence-driven disk winds offer new possibilities. Aims. We investigate the effects of disk winds on the disk profile and type I migration for a range of parameters that describe the strength of disk winds. We also examine the in situ formation of close-in super-Earths in disks that evolve through disk winds. Methods. The disk profile, which is regulated by viscous diffusion and disk winds, was derived by solving the diffusion equation. We carried out a number of simulations and plot here migration maps that indicate the type I migration rate. We also performed N-body simulations of the formation of close-in super-Earths from a population of planetesimals and planetary embryos. Results. We define a key parameter, Kw, which determines the ratio of strengths between the viscous diffusion and disk winds. For a wide range of Kw, the type I migration rate is presented in migration maps. These maps show that type I migration is suppressed over the whole close-in region when the effects of disk winds are relatively strong (Kw ≲ 100). From the results of N-body simulations, we see that type I migration is significantly slowed down assuming Kw = 40. We also show that the results of N-body simulations match statistical orbital distributions of close-in super-Earths. [ABSTRACT FROM AUTHOR]

Context. A large fraction of stars host one or multiple close-in super-Earth planets. There is an active debate about whether these planets formed in situ or at greater distances from the central star and migrated to their current position. It has been shown that part of their observed properties (e.g., eccentricity distribution) can be reproduced by N-body simulations of in situ formation starting with a population of protoplanets of high masses and neglecting the effects of the disk gas. Aims. We plan to reassess the in situ formation of close-in super-Earths through more complete simulations. Methods. We performed N-body simulations of a population of small planetary embryos and planetesimals that include the effects of disk-planet interactions (e.g., eccentricity damping, Type I migration). In addition, we also consider the accretion of a primitive atmosphere from a protoplanetary disk. Results. We find that planetary embryos grow very quickly well before the gas dispersal, and thus undergo rapid inward migration, which means that one cannot neglect the effects of a gas disk when considering the in-situ formation of close-in super-Earths. Owing to their rapid inward migration, super-Earths reach a compact configuration near the disk's inner edge whose distribution of orbital parameters matches the observed close-in super-Earths population poorly. On the other hand, simulations including eccentricity damping, but no Type I migration, reproduce the observed distributions better. Including the accretion of an atmosphere does not help reproduce the bulk architecture of observations. Interestingly, we find that the massive embryos can migrate inside the disk edge while capturing only a moderately massive hydrogen/helium atmosphere. By this process they avoid becoming giant planets. Conclusions. The bulk of close-in super-Earths cannot form in situ, unless Type I migration is suppressed in the entire disk inside 1 AU. [ABSTRACT FROM AUTHOR]

Highlights: [•] Overall review of the exoplanet program of CoRoT. [•] Statistical output of the planet search. [•] Specific analyses of CoRoT exoplanets. [Copyright &y& Elsevier]

The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activities of the interior working group of the Ariel mission, and list the desirable theoretical developments as well as the challenges in linking planetary atmospheres, bulk composition and interior structure. [ABSTRACT FROM AUTHOR]

High-resolution spectroscopic searches for the starlight reflected from close-in extrasolar giant planets have the capability of determining the optical albedo spectra and scattering properties of these objects. When combined with radial velocity measurements they also yield the true mass of the planet. To date, only two such planets have been targeted for reflected-light signals, yielding upper limits on the optical albedos of the planets. Here we examine the prospects for future searches of this kind. We present Monte Carlo estimates of prior probability distributions for the orbital velocity amplitudes and planet/star flux ratios of six bright stars known to harbour giant planets in orbits with periods of less than 5 d. Using these estimates, we assess the viability of these targets for future reflected-light searches using 4- and 8-m class telescopes. [ABSTRACT FROM AUTHOR]

Jupiter's atmosphere is dominated by multiple jet streams which are strongly tied to its 3D atmospheric circulation. Lacking a rigid bottom boundary, several models exist for how the meridional circulation extends into the planetary interior. Here, we show, collecting evidence from multiple instruments of the Juno mission, the existence of midlatitudinal meridional circulation cells which are driven by turbulence, similar to the Ferrel cells on Earth. Different than Earth, which contains only one such cell in each hemisphere, the larger, faster rotating Jupiter can incorporate multiple cells. The cells form regions of upwelling and downwelling, which we show are clearly evident in Juno's microwave data between latitudes 60°S $60{}^{\circ}\mathrm{S}$ and 60°N $60{}^{\circ}\mathrm{N}$. The existence of these cells is confirmed by reproducing the ammonia observations using a simplistic model. This study solves a long‐standing puzzle regarding the nature of Jupiter's subcloud dynamics and provides evidence for eight cells in each Jovian hemisphere. Plain Language Summary: The cloud layer of Jupiter is divided into dark and bright bands that are shaped by strong east‐west winds. Such winds in planetary atmospheres are thought to be tied with a meridional circulation. The Juno mission collected measurements of Jupiter's atmosphere at various wavelengths, which penetrate the cloud cover. Here, we provide evidence, using the Juno data, of eight deep Jovian circulation cells in each hemisphere encompassing the east‐west winds, gaining energy from atmospheric waves, and extending at least to a depth of hundreds of kilometers. Different than Earth, which has only one analogous cell in each hemisphere, known as a Ferrel cell, Jupiter can contain more cells due to its larger size and faster spin. To support the presented evidence, we modeled how ammonia gas would spread under the influence of such cells and compared it to the Juno measurements. The presented results shed light on the unseen flow structure beneath Jupiter's clouds. Key Points: Measurements from multiple instruments of the Juno mission are interpreted to reveal the meridional circulation beneath Jupiter's clouds16 Jet‐paired deep cells, extending from the cloud deck down to at least 240 bar, are revealed between latitudes 60°S $60{}^{\circ}\mathrm{S}$ and 60°N $60{}^{\circ}\mathrm{N}$, driven by turbulence similar to Earth's Ferrel cellsThe findings are supported by modeling the advection of tracers due to the cells, showing agreement with NH3 ${\mathrm{N}\mathrm{H}}_{3}$ data [ABSTRACT FROM AUTHOR]

Jupiter’s Great Red Spot (GRS) is the largest atmospheric vortex in the Solar System and has been observed for at least two centuries. It has been unclear how deep the vortex extends beneath its visible cloud tops. We examined the gravity signature of the GRS using data from 12 encounters of the Juno spacecraft with the planet, including two direct overflights of the vortex. Localized density anomalies due to the presence of the GRS caused a shift in the spacecraft line-of-sight velocity. Using two different approaches to infer the GRS depth, which yielded consistent results, we conclude that the GRS is contained within the upper 500 kilometers of Jupiter’s atmosphere. [ABSTRACT FROM AUTHOR]

The observed zonal winds at Jupiter's cloud tops have been shown to be closely linked to the asymmetric part of the planet's measured gravity field. Here, we examine to what extent, and at which latitudes, must the flows at depth resemble those at the cloud level to match the gravity signal. We show, using both the symmetric and asymmetric parts of the measured gravity field, that the observed cloud‐level wind profile between 25°S and 25°N must extend unaltered to depths of thousands of kilometers. Poleward, the midlatitude deep jets also contribute to the gravity signal, but might differ somewhat from the cloud‐level winds. We analyze the likelihood of this difference and give bounds to its strength. We also find that to match the gravity measurements, the winds must project inward in the direction parallel to Jupiter's spin axis, and decay inward in the radial direction. Plain Language Summary: Observations of Jupiter's cloud‐tops reveal very strong atmospheric winds reaching 500 km/hr. Using very accurate measurements of the planet's gravity field, provided by NASA's Juno spacecraft, the cloud‐level winds were found to extend thousands of kilometers into the interior of Jupiter, with a wind profile similar to that observed at the clouds level. However, analysis of various measurements suggested that at some latitudinal regions the flow below the clouds might be different to some extent. Here we explore the constraints posed by the Juno gravity measurements on the latitudinal profile of the zonal flow in Jupiter below the cloud level. We find that to explain the detailed latitudinal structure of the wind‐attributed gravity field, the cloud‐level winds in the 60°S–60°N range have to extend deep into the planet, approximately keeping their observed latitudinal profile. With that, we find that most of the wind‐induced gravity signal comes from the 25°S to 25°N region, where the strongest jets reside, suggesting that in the midlatitudes the observed jets at the cloud level might be somewhat different at depth. Key Points: Jupiter's cloud‐level wind profile extended to depth, matches in sign and amplitude both the measured odd and residual‐even gravity harmonicsThe majority of the signal comes from the wind profile between 25°S and 25°N, which must extend unaltered thousands of kilometers deepThe gravity signal also implies that from the cloud‐tops downward the flow must be organized in a columnar structure and also decay radially [ABSTRACT FROM AUTHOR]

The Juno spacecraft provides unique close‐up views of Jupiter underneath the synchrotron radiation belts while circling Jupiter in its 53‐day orbits. The microwave radiometer (MWR) onboard measures Jupiter thermal radiation at wavelengths between 1.37 and 50 cm, penetrating the atmosphere to a pressure of a few hundred bars and greater. The mission provides the first measurements of Jupiter's deep atmosphere, down to ~250 bars in pressure, constraining the vertical distributions of its kinetic temperature and constituents. As a result, vertical structure models of Jupiter's atmosphere may now be tested by comparison with MWR data. Taking into account the MWR beam patterns and observation geometries, we test several published Jupiter atmospheric models against MWR data. Our residual analysis confirms Li et al.'s (2017, https://doi.org/10.1002/2017GL073159) result that ammonia depletion persists down to 50–60 bars where ground‐based Very Large Array was not able to observe. We also present an extension of the study that iteratively improves the input model and generates Jupiter brightness temperature maps which best match the MWR data. A feature of Juno's north‐to‐south scanning approach is that latitudinal structure is more easily obtained than longitudinal, and the creation of optimum two‐dimensional maps is addressed in this approach. Key Points: Residual analysis provides a direct method to compare any Jupiter atmosphere model with the MWR observationsThe iterative residual analysis process generates 2‐D Jupiter maps revealing the deep structures of upper atmosphere features [ABSTRACT FROM AUTHOR]

The nature and structure of the observed east-west flows on Jupiter and Saturn have been a long-standing mystery in planetary science. This mystery has been recently unraveled by the accurate gravity measurements provided by the Juno mission to Jupiter and the Grand Finale of the Cassini mission to Saturn. These two experiments, which coincidentally happened around the same time, allowed the determination of the overall vertical and meridional profiles of the zonal flows on both planets. This paper reviews the topic of zonal jets on the gas giants in light of the new data from these two experiments. The gravity measurements not only allow the depth of the jets to be constrained, yielding the inference that the jets extend to roughly 3000 and 9000 km below the observed clouds on Jupiter and Saturn, respectively, but also provide insights into the mechanisms controlling these zonal flows. Specifically, for both planets this depth corresponds to the depth where electrical conductivity is within an order of magnitude of 1 S m−1, implying that the magnetic field likely plays a key role in damping the zonal flows. An intrinsic characteristic of any gravity inversion, as discussed here, is that the solutions might not be unique. We analyze the robustness of the solutions and present several independent lines of evidence supporting the results presented here. [ABSTRACT FROM AUTHOR]

The temperature structure of a giant planet was traditionally thought to be an adiabat assuming convective mixing homogenizes entropy. The only in-situ measurement made by the Galileo Probe detected a near-adiabatic temperature structure within one of Jupiter's 5 μm hot spots with small but definite local departures from adiabaticity. We analyze Juno's microwave observations near Jupiter's equator (0– 5 oN) and find that the equatorial temperature structure is best characterized by a stable super-adiabatic temperature profile rather than an adiabatic one. Water is the only substance with sufficient abundance to alter the atmosphere's mean molecular weight and prevent dynamic instability if a super-adiabatic temperature gradient exists. Thus, from the super-adiabaticity, our results indicate a water concentration (or the oxygen to hydrogen ratio) of about 4.9 times solar with a possible range of 1.5– 8.3 times solar in Jupiter's equatorial region. • The Juno/MWR finds a super-adiabatic temperature gradient across the water condensation layer at Jupiter's equatorial zone. • The deep atmosphere has a higher potential temperature than the shallow atmosphere at the equatorial zone. • The deep O/H ratio on Jupiter is between 1.4 - 8.3 times solar with the optimal estimate at about 4.9 solar. [ABSTRACT FROM AUTHOR]

Highlights • We describe the first attempt to measure Jupiter's zonal winds with Doppler imaging spectroscopy in the visible domain • Observations were performed with a new concept of imaging spectrograph dedicated to measuring atmospheric dynamics • Zonal wind profiles of Jupiter, obtained in 2015 and 2016, are compared with wind profiles from cloud-tacking observations • Both profiles are compatible with the cloud-tracking, except in a small band at the north of the equatorial belt • We show that Doppler velocities can be measured with sufficient precision to put in evidence the zonal winds on Jupiter Abstract We present the first measurements of Jupiter's wind profile ever obtained with Doppler velocity measurements in the visible. Hitherto, knowledge about atmospheric dynamics has been obtained with cloud-tracking techniques, which consist of tracking visible features from images taken at different dates. However, cloud tracking indicates the motion of large cloud structures, which is an indication of the speed of iso-pressure regions, rather than the speed of the actual atmospheric particles. Doppler imaging is as challenging – motions are usually less than 100 m s − 1 – as appealing because it measures the speed of cloud particles instead of large cloud structures. Significant difference could appear in the case of atmospheric waves interfering with cloud structures. Here we present the first scientific results of a Doppler imaging spectrometer that is dedicated to giant-planet seismology and atmospheric dynamics by providing instantaneous line-of-sight-velocity maps of the planets of the solar system. The instrument has been developed in the framework of the projects JOVIAL (Jovian Oscillations through Velocity Images At several Longitudes) and JIVE in NM (Jovian Interiors from Velocimetry Experiment in New Mexico). It is a Fourier transform spectrometer with a fixed optical path difference working in the mid-visible domain, which monitors the position of solar Fraunhofer lines that are reflected in the planets' upper atmospheres. After describing the instrument principle and the different steps of data reduction, we report measurement of the average zonal wind speed of Jupiter, as a function of latitude, from datasets obtained in 2015 and 2016 with two different telescopes, when the planet was close to its opposition. Our results are consistent between the two years. We compare the results with wind profiles obtained by cloud tracking on HST (Hubble Space Telescope) images taken at the same epoch, and identify a significant discrepancy in the North Equatorial Belt and northern part of the Equatorial Zone. [ABSTRACT FROM AUTHOR]

Using astrometric observations spanning more than a century and including a large set of Cassini data, we determine Saturn's tidal parameters through their current effects on the orbits of the eight main and four coorbital Moons. We have used the latter to make the first determination of Saturn's Love number from observations, k 2 =0.390 ± 0.024, a value larger than the commonly used theoretical value of 0.341 (Gavrilov & Zharkov, 1977), but compatible with more recent models (Helled & Guillot, 2013) for which the static k 2 ranges from 0.355 to 0.382. Depending on the assumed spin for Saturn's interior, the new constraint can lead to a significant reduction in the number of potential models, offering great opportunities to probe the planet's interior. In addition, significant tidal dissipation within Saturn is confirmed (Lainey et al., 2012) corresponding to a high present-day tidal ratio k 2 / Q =(1.59 ± 0.74) × 10 −4 and implying fast orbital expansions of the Moons. This high dissipation, with no obvious variations for tidal frequencies corresponding to those of Enceladus and Dione, may be explained by viscous friction in a solid core, implying a core viscosity typically ranging between 10 14 and 10 16 Pa.s (Remus et al., 2012). However, a dissipation increase by one order of magnitude at Rhea's frequency could suggest the existence of an additional, frequency-dependent, dissipation process, possibly from turbulent friction acting on tidal waves in the fluid envelope of Saturn (Ogilvie & Lin, 2004; Fuller et al. 2016). [ABSTRACT FROM AUTHOR]

The Juno mission has revolutionized and challenged our understanding of Jupiter. As Juno transitioned into its extended mission, we review the major findings of Jupiter's internal structure relevant to understanding Jupiter's formation and evolution. Results from Juno's investigation of Jupiter's interior structure imply that the planet has compositional gradients and is accordingly non-adiabatic, with a complex internal structure. These new results imply that current models of Jupiter's formation and evolution require a revision. In this paper, we discuss potential formation and evolution paths that can lead to an internal structure model consistent with Juno data, and the constraints they provide. We note that standard core accretion formation models, including the heavy-element enrichment during planetary growth is consistent with an interior that is inhomogeneous with composition gradients in its deep interior. However, such formation models typically predict that this region, which could be interpreted as a primordial dilute core, is confined to ∼10% of Jupiter's total mass. In contrast, structure models that fit Juno data imply that this region contains 30% of the mass or more. One way to explain the origin of this extended region is by invoking a relatively long (~2 Myrs) formation phase where the growing planet accretes gas and planetesimals delaying the runaway gas accretion. This is not the same as the delay that appears in standard giant planet formation models because it involves additional accretion of solids in that period. However, both the possible new picture and the old picture are compatible with the formation scenario recently proposed to explain the separation of two meteoritic populations in the solar system. Alternatively, Jupiter's fuzzy core could be a result of a giant impact or convection post-formation. These novel scenarios require somewhat special and specific conditions. Clarity on the plausibility of such conditions could come from future high-resolution observations of planet-forming regions around other stars, from the observed and modeled architectures of extrasolar systems with giant planets, and future Juno data obtained during its extended mission. • Jupiter has a complex internal structure: it's not fully mixed and has a fuzzy core. • The fuzzy core could be a signature of the formation process and/or core erosion. • The equation of state of hydrogen is important for modeling Jupiter's interior. • The origin of Jupiter's enriched atmosphere is still unknown. • Combining the aspects of Jupiter's formation, evolution and structure is critical. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including European Space Agency (ESA), cosmic microwave background (CMB) and space observatory Planck Collaboration.