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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]

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.

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]

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]

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 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]

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]

The global energy budget is pivotal to understanding planetary evolution and climate behaviors. Assessing the energy budget of giant planets, particularly those with large seasonal cycles, however, remains a challenge without long-term observations. Evolution models of Saturn cannot explain its estimated Bond albedo and internal heat flux, mainly because previous estimates were based on limited observations. Here, we analyze the long-term observations recorded by the Cassini spacecraft and find notably higher Bond albedo (0.41 ± 0.02) and internal heat flux (2.84 ± 0.20 Wm -2 ) values than previous estimates. Furthermore, Saturn's global energy budget is not in a steady state and exhibits significant dynamical imbalances. The global radiant energy deficit at the top of the atmosphere, indicative of the planetary cooling of Saturn, reveals remarkable seasonal fluctuations with a magnitude of 16.0 ± 4.2%. Further analysis of the energy budget of the upper atmosphere including the internal heat suggests seasonal energy imbalances at both global and hemispheric scales, contributing to the development of giant convective storms on Saturn. Similar seasonal variabilities of planetary cooling and energy imbalance exist in other giant planets within and beyond the Solar System, a prospect currently overlooked in existing evolutional and atmospheric models., (© 2024. The Author(s).)

The Juno spacecraft has been collecting data to shed light on the planet's origin and characterize its interior structure. The onboard gravity science experiment based on X-band and Ka-band dual-frequency Doppler tracking precisely measured Jupiter's zonal gravitational field. Here, we analyze 22 Juno's gravity passes to investigate the gravity field. Our analysis provides evidence of new gravity field features, which perturb its otherwise axially symmetric structure with a time-variable component. We show that normal modes of the planet could explain the anomalous signatures present in the Doppler data better than other alternative explanations, such as localized density anomalies and non-axisymmetric components of the static gravity field. We explain Juno data by p-modes having an amplitude spectrum with a peak radial velocity of 10-50 cm/s at 900-1200 μHz (compatible with ground-based observations) and provide upper bounds on lower frequency f-modes (radial velocity smaller than 1 cm/s). The new Juno results could open the possibility of exploring the interior structure of the gas giants through measurements of the time-variable gravity or with onboard instrumentation devoted to the observation of normal modes, which could drive spacecraft operations of future missions., (© 2022. The Author(s).)

Lightning flashes have been observed by a number of missions that visited or flew by Jupiter over the past several decades. Imagery led to a flash rate estimate of about 4 × 10 -3 flashes per square kilometre per year (refs. 1,2 ). The spatial extent of Voyager flashes was estimated to be about 30 kilometres (half-width at half-maximum intensity, HWHM), but the camera was unlikely to have detected the dim outer edges of the flashes, given its weak response to the brightest spectral line of Jovian lightning emission, the 656.3-nanometre Hα line of atomic hydrogen 1,3-6 . The spatial resolution of some cameras allowed investigators to confirm 22 flashes with HWHM greater than 42 kilometres, and to estimate one with an HWHM of 37 to 45 kilometres (refs. 1,7-9 ). These flashes, with optical energies comparable to terrestrial 'superbolts'-of (0.02-1.6) × 10 10  joules-have been interpreted as tracers of moist convection originating near the 5-bar level of Jupiter's atmosphere (assuming photon scattering from points beneath the clouds) 1-3,7,8,10-12 . Previous observations of lightning have been limited by camera sensitivity, distance from Jupiter and long exposures (about 680 milliseconds to 85 seconds), meaning that some measurements were probably superimposed flashes reported as one 1,2,7,9,10,13 . Here we report optical observations of lightning flashes by the Juno spacecraft with energies of approximately 10 5 -10 8  joules, flash durations as short as 5.4 milliseconds and inter-flash separations of tens of milliseconds, with typical terrestrial energies. The flash rate is about 6.1 × 10 -2 flashes per square kilometre per year, more than an order of magnitude greater than hitherto seen. Several flashes are of such small spatial extent that they must originate above the 2-bar level, where there is no liquid water 14,15 . This implies that multiple mechanisms for generating lightning on Jupiter need to be considered for a full understanding of the planet's atmospheric convection and composition.