The spectral signature of hydrogen sulphide (H2S) above the cloud tops in Uranus’ atmosphere was detected in 2018 [1]. The H2S humidity can be used as a tracer of Uranus’ overturning circulation [2] - peaks and troughs in the latitudinal humidity distribution may correspond to regions of local upwelling and downwelling near the H2S condensation level. We analysed observations from Gemini-NIFS and VLT-SINFONI, taken between 2009 and 2014, to study the H2S humidity distribution of Uranus. In our previous analysis of H2S on Neptune [3], we found a significant degeneracy between the methane (CH4) and H2S distributions, so we prescribe a latitudinally varying deep methane abundance previously derived from HST-STIS spectra [4]. We deconvolve the observations and extract spectra using the Minnaert limb-darkening approximation, which has been applied in several analyses of Ice Giant observations [3,4,5]. We fit a parameterised aerosol model and the H2S humidity to our extracted spectra with nested sampling using our open-source radiative transfer code, archNEMESIS [6]. Our atmospheric model has a large number of parameters, and to make nested sampling computationally feasible we utilise a trained neural network for early exploration of the parameter space during our retrievals. Since our observations span several years, we search for temporal changes. We find changes in the aerosol structure and aerosol spectral properties corresponding to the development of Uranus' north polar hood, in agreement with previous work [4,8]. If we assume that the CH4 distribution is stable over time, then our results show no significant changes in the H2S distribution. Our results show a general equator-to-pole decrease in the H2S humidity, similar to what has been found in microwave analyses that are sensitive to the deep H2S distribution [7]. Superimposed on this are local increases, which are fairly evenly spaced in latitude. We found a somewhat similar pattern in our analysis of H2S on Neptune [3], and an analysis of Neptune with VLT/MUSE also found peaks in reflectivity with a similar spacing [5]. These results are suggestive of a complex circulation pattern near the deep H2S aerosol layer. [1] Irwin, P. G. J., et al. (2018). Detection of hydrogen sulfide above the clouds in Uranus's atmosphere. Nature Astronomy, 2(5), 420-427. [2] Fletcher, L.N., et al. (2020). Ice Giant Circulation Patterns: Implications for Atmospheric Probes. Space Sci Rev 216, 21[3] Penn, J., et al. (2026). Reconciling Near-Infrared and Microwave Analyses of Neptune’s Hydrogen Sulphide Distribution. Monthly Notices of the Royal Astronomical Society, 548, 2, [4] James, A., et al. (2023). The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations. Journal of Geophysical Research: Planets, 128(10), e2023JE007904.[5] Irwin, P. G. J., et al. (2023). Latitudinal Variations in Methane Abundance, Aerosol Opacity and Aerosol Scattering Efficiency in Neptune's atmosphere determined from VLT/MUSE. Journal of Geophysical Research: Planets, 128(11), e2023JE007980.[6] Alday, J., et al. (2025). archNEMESIS: An Open-Source Python Package for Analysis of Planetary Atmospheric Spectra. Journal of Open Research Software, doi:10.5334/jors.554.[7] Molter, E. M., et al. (2021). Tropospheric Composition and Circulation of Uranus with ALMA and the VLA. The Planetary Science Journal, 2(1), 3.[8] Sromovsky, L. A., et al. (2024). The puzzling north polar region of Uranus: Continued zero-shear winds and increasing brightness from 2015 through 2022 according to 7 years of Keck AO imaging. Icarus, 420, 116186.

Titan's middle atmosphere has a well-observed north-south haze asymmetry (NSA), with a mysteriously sharp boundary that migrates seasonally across the equator. Several stratospheric trace species display similarly steep latitudinal gradients near the equator, yet the origin of these abrupt transitions is not well understood. Here we map the distributions of multiple trace species between 40°S and 40°N using observations from Cassini's Composite Infrared Spectrometer spanning almost half a Titan year, providing the highest-latitudinal-resolution view of Titan’s equatorial stratosphere to date. The measurements provide unique insight into the dynamics of Titan's equatorial region, which cannot be constrained using conventional thermal wind balance techniques. We show that composition boundaries near the equator follow a strikingly similar migration to Titan's haze NSA boundary, suggesting the NSA boundary is driven primarily by dynamics rather than chemistry or haze microphysics. Comparison with the Titan Atmospheric Model (TAM) general circulation model shows that the steep equatorial gradients are established primarily by vertical transport associated with the meridional overturning circulation. The observed offset of the boundary from the equator is explained by horizontal transport of enriched air, driven predominantly by horizontal eddies rather than mean-flow advection. These results reveal the dynamical origin of Titan’s enigmatic equatorial boundary and constrain the seasonal evolution of its global circulation.

Modified CLEAN is a deconvolution technique derived from the classic CLEAN algorithm, adapted for application to extended planetary targets. We have previously demonstrated its effectiveness in enhancing the spatial resolution of recent (2018) ground-based observations of Neptune, revealing additional atmospheric structure beyond that accessible with standard processing techniques.We are now extending this work to legacy near-infrared integral-field spectroscopy data obtained in 2009 and 2011 with the Near-infrared Integral Field Spectrograph (NIFS). The older datasets are more challenging to work with as they have stronger artefacts from the optical system and calibration procedures in both the science and standard star measurements.As with all deconvolution methods, modified CLEAN performs optimally in low-noise conditions, where calibration data are smooth and have a high signal-to-noise ratio. This required a series of preprocessing steps. Principal component analysis was applied to both science and calibration observations to suppress noise and remove instrumental systematics. Telescope pointing information, not explicitly recorded for the original NIFS science observations, was reconstructed from ancillary data. Disk fitting and de-rotation were used to align and combine all observations within individual observing blocks. Finally, residual atmospheric refraction present in the standard NIFS pipeline products was identified and corrected.These processing steps improve the performance of the modified CLEAN algorithm on the legacy NIFS datasets, giving improved spatial resolution and more reliable interpretation of Neptune’s atmospheric structure. This work demonstrates the continued scientific value of archival ground-based observations when combined with modern data analysis and deconvolution techniques.

Among the giant planets of the Solar System, Uranus's exceptionally low temperatures yield the weakest thermal radiance, hampering measurements of its infrared spectrum. Consequently, its thermal and compositional structures have remained poorly characterised, limiting our understanding of how atmospheric temperatures, circulation, and photochemistry respond to the planet's anomalously weak internal heat flux and the seasonal variations in insolation driven by its high axial tilt. Leveraging the exceptional sensitivity of JWST's MIRI and NIRSpec instruments, we present the first spatially resolved measurements of Uranus's spectrum spanning the near- and mid-infrared (1.66--28.70~$\mu$m), revealing how temperatures, composition, and clouds vary across the planet's northern hemisphere. Together, these observations provide the most comprehensive view of Uranus's middle atmosphere to date and offer new insights into its unique structure.

The aerosol scheme for Jupiter's upper hazes and clouds is still debated to this day, for the Cr & egrave;me Br & ucirc;l & eacute;e aerosol scheme has trouble in fitting some specific Jovian atmospheric features (Braude et al., 2020; Dahl et al., 2021). We analyse observations of Jupiter acquired with CARMENES in 2019, from visible to near infrared (0.52-1.71 mu m), to test three competing aerosols schemes. These observations are unique due to their spectral coverage with both high spatial and spectral resolutions, paving the way for future observations of Solar System objects. We used a model with two blue wavelength attenuating hazes (chromophores) by Anguiano-Arteaga et al., (2021); Anguiano-Arteaga et al., (2023), a model that has a single blue attenuating haze by Braude et al., (2020) and a model where the blue attenuating haze is physically constrained in a thin layer ("Cr & egrave;me Br & ucirc;l & eacute;e model") with amore up to date parameter values from P & eacute;rez-Hoyos et al., (2020). We grouped the observations into 5 regions of the atmosphere of Jupiter and performed a Minnaert limb-darkening approximation, producing synthetic spectra at 0 degrees and 61.45 degrees zenith angles for each. We found that the properties of the highest aerosol layer dominate the fit to the observations, with particle size (Models A and B) and cloud base abundance (Models A and C) being the most influential parameters. We found that the extended chromophore model from Braude et al., (2020) fits the observations better than the other two models. However, none of the tested schemes fully reproduce the data, as all yield x2/Nfree values greater than unity, indicating limitations in the current aerosol parametrisations. These results suggest that a consistent characterisation of Jovian aerosols requires models constrained by a broader spectral range, including ultraviolet observations sensitive to chromophore absorption and thermal infrared data probing deeper cloud layers.

The extreme conditions in Venus’s lower atmosphere make robust calibration of in situ observations challenging. Consequently, measurements from past entry probes provided mixed evidence regarding the existence of a near-surface particulate layer (NSPL). Although the Venera 11 (1978) and Venera 13 and 14 (1982) landers performed in situ spectrophotometric observations during descent, the original datasets were later lost. However, a subset has been reconstructed by digitising graphical outputs produced during the missions’ initial data-processing phase [1]. Following careful analysis to identify and mitigate errors and other artefacts, the reconstructed dataset retains the reliable downward-looking spectra acquired by the three landers from ~62 km altitude to the surface.Previous retrievals from the reconstructed Venera 13 indicated an NSPL centred at ~3.5–5 km, with particulate optical properties consistent with a basaltic composition [2]. Following the methodology of [2], we use NEMESIS, a radiative transfer and retrieval code [3], to perform near-surface retrievals from the reconstructed Venera 11 and Venera 14 datasets. The results from Venera 11, 13, and 14 retrievals are compared with reported detections and non-detections from other instruments on earlier in situ missions, to explore potential formation pathways for the NSPL in light of the combined observational record.References:[1] Ignatiev, N. I., Moroz, V. I., Moshkin, B. E., Ekonomov, A. P., Gnedykh, V. I., Grigor’ev, A. V., and Khatuntsev, I. V. Cosmic Research 35(1), 1–14 (1997).[2] Kulkarni, S. V., Irwin, P. G. J., Wilson, C. F., & Ignatiev, N. I. Journal of Geophysical Research: Planets, 130, e2024JE008728, (2025).[3] Irwin, P. G., Teanby, N. A., de Kok, R., Fletcher, L. N., Howett, C. J., Tsang, C. C., Wilson, C. F., Calcutt, S. B., Nixon, C. A., and Parrish, P. D. Journal of Quantitative Spectroscopy and Radiative Transfer 109(6), 1136–1150 (2008).

The Lunar-Earth Gravitational Assist (LEGA) of 19-20 August 2024 marked the first in-flight opportunity beyond functional checks to perform MAJIS (Moons and Jupiter Imaging Spectrometer) observations on-board the ESA's Jupiter Icy Moons Explorer (JUICE) spacecraft. This unique double flyby involved sequential close approaches to the Moon and Earth, offering an unprecedented configuration to evaluate MAJIS under high radiance, rapidly changing geometric, and operationally constrained conditions. A total of 24 hyperspectral image cubes were acquired (5 targeting the Moon and 19 the Earth) providing a dataset of approximately 7.5 Gbit. This work presents the primary goal of this observation campaign, which was to verify key aspects of MAJIS performance, including radiometric and spectral calibration, straylight behavior, geometric alignment, the use of onboard browse products, and interference tests with other JUICE instruments. This event also enabled assessment of thermal behavior and susceptibility to electromagnetic interference, and provided a first operational benchmark for MAJIS and a basis for refining future observation strategies and data analyses during JUICE's cruise and science phases. In addition, despite limited spatial and temporal coverage of the observations, the analyses presented here and in a series of companion papers of the special issue "The first-ever lunar-Earth flyby: a unique test environment for JUICE" demonstrated the instrument's ability to characterize mineralogical features on the Moon and atmospheric constituents on Earth. Observations include detection of mafic minerals (some associated to fresh excavated materials), thermal emission, and emissivity variations on the Moon at spatial scale of 100-200 m. Characterization of atmospheric absorption features, thermal brightness, icy cloud properties are captured for the Earth at km-scale and briefly discussed in the framework of the atmospheric biosignatures relevant to exoplanet habitability studies. Near-coincident acquisitions with other JUICE instruments and Earth-orbiting spectrometers provided valuable inter-calibration and cross-validation opportunities.

In Titan's atmosphere, the chemistry of small hydrocarbons and nitriles represent an important link from molecular species to the ubiquitous organic haze that gives Titan its characteristic yellow color. Here we present a new search for two previously undetected molecules, triacetylene (C_6H_2) and the gas phase dicyanoacetylene (C_4N_2), using the Echelon-Cross-Echelle Spectrograph (EXES) instrument aboard the SOFIA (Stratospheric Observatory For Infrared Astronomy) aircraft. We do not detect these two molecules but determine upper limits for their mixing ratios and column abundances. We find the 3σ upper limits on the uniform volume mixing ratio (VMR) above 100 km for C_6H_2 to be 4.3×10^-11 which is lower than the photochemical model predictions. This new upper limit suggests that the growth of linear molecules is inhibited. We also put a strict upper limit on the uniform VMR for gas phase C_4N_2 above 125 km to be 1.0×10^-10. This upper limit is well below the saturation mixing ratio at this altitude for C_4N_2 and greatly limits the feasibility of C_4N_2 forming ice from condensation.

Saturn's moon Titan undergoes a long annual cycle of 29.45 Earth years. Titan's northern winter and spring were investigated in detail by the Cassini-Huygens spacecraft (2004-2017), but the northern summer season remains sparsely studied. Here we present new observations from the James Webb Space Telescope (JWST) and Keck II telescope made in 2022 and 2023 during Titan's late northern summer. Using JWST's mid-infrared instrument, we spectroscopically detected the methyl radical, the primary product of methane break-up and key to the formation of ethane and heavier molecules. Using the near-infrared spectrograph onboard JWST, we detected several non-local thermodynamic equilibrium CO and CO2 emission bands, which allowed us to measure these species over a wide altitude range. Lastly, using the near-infrared camera onboard JWST and Keck II, we imaged northern hemisphere tropospheric clouds evolving in altitude, which provided new insights and constraints on seasonal convection patterns. These observations pave the way for new observations and modelling of Titan's climate and meteorology as it progresses through the northern fall equinox, when its atmosphere is expected to show notable seasonal changes.

Using a newly developed 'holistic atmospheric model of the aerosol structure in Uranus's atmosphere, based upon observations made by Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS), Gemini/Near-Infrared Integral Field Spectrometer(NIFS), and NASA Infrared Telescope Facility(IRTF)/SpeX from 2000 to 2009, we make a new estimate of the bolometric Bond albedo of Uranus during this time of A* = 0.338 +/- 0.011, with a phase integral of q* = 1.36 +/- 0.03. Then, using a simple seasonal model, developed to be consistent with the disc-integrated blue and green magnitude data from the Lowell Observatory from 1950 to 2016, we model how Uranus's reflectivity and heat budget vary during its orbit and determine new orbital-mean average values for the bolometric Bond albedo of A=0.349 +/- 0.016 and for the absorbed solar flux of P-in = 0.604 +/- 0.027 W m(2). Assuming the outgoing thermal flux to be Poul0.693 +/- 0.013 W m(2), as previously determined from Voyager 2 observations, we arrive at a new estimate of Uranus's average heat flux budget of P-out/P-in 1.15 +/- 0.06, finding considerable variation with time due to Uranus's significant orbital eccentricity of 0.046. This leads the flux budget to vary from P-out/P-in 1.03 near perihelion, to 1.24 near aphelion. We conclude that although P-out/P-in is considerably smaller than for the other giant planets, Uranus is not in thermal equilibrium with the Sun

The Cassini spacecraft observed Titan from 2004 to 2017, capturing key atmospheric features, including the tilt of the middle atmosphere and the formation and breakup of winter polar vortices. We analyze low spectral resolution infrared observations from Cassini’s Composite Infrared Spectrometer (CIRS), which provide excellent spatial and temporal coverage and the best horizontal spatial resolution of any of the CIRS observations. With approximately 4 times higher meridional resolution than previous studies, we map the stratospheric temperature for almost half a Titan year. We determine the evolution of Titan’s stratospheric tilt, finding that it is most constant in the inertial frame, directed 120° ± 6° west of the Titan–Sun vector at the northern spring equinox, with seasonal oscillations in the tilt magnitude between around 2 . ° 5 and 8°. Using the high meridional resolution temperature field, we reveal finer details in the zonal wind and potential vorticity. In addition to the strong winter zonal jet, a weaker zonal jet in Titan’s summer hemisphere is observed, and there is a suggestion that the main winter hemisphere jet briefly splits into two. We also present the strongest evidence yet that Titan’s polar vortex is annular for part of its life cycle.

Seasonal Variability of Stratospheric H₂O on TitanTitan is Saturn’s largest moon and one of the most complex Earth-like bodies in our Solar system. It hosts a thick, complex atmosphere with weather systems [1], rich C-N-H photochemistry [2], and unique surface features such as lakes of methane [3]. The presence of organic hazes and oxygen-bearing molecules in the atmosphere make Titan astrobiologically important and provides an analogous natural laboratory to study pre-biotic Earth [4] and exoplanets with similar climates. Understanding Titan’s atmosphere is also pertinent to inform NASA's Dragonfly mission set to arrive in 2034 [5].Water vapour is an important, yet poorly understood presence in Titan’s atmosphere. It plays a vital role in distributing oxygen molecules, which are otherwise scarce, throughout the planet to form species such as CO, CO2 and H2CO [2]. Water vapour was first detected in Titan’s atmosphere in 1998 by the Infrared space Observatory [6]. Since then, only a handful of studies from Herschel [7], CIRS [8] and the INMS [9] instruments have provided observations. Due to modelling difficulty and its low abundances, there is limited information on seasonal, global and vertical abundances of Titan’s H2O with research focusing on averages and single measurements.146 far-IR observations acquired by CIRS on-board the Cassini spacecraft were analysed to form the first-reported global picture of H2O abundances in Titan’s stratosphere across its 13-year mission, improving on previous studies. Using the most recent photochemical model [2] as an a priori in the NEMESIS radiative transfer modelling tool [10] and a new method of applying parameterised gaussian cross-sections [11] to fit the poorly understood hazes, we present results showing the seasonal variability of water vapour at pressures of ~ 0.1-10 mbar. We discuss our results and its implications, and compare our findings to previous work. References: [1] N.A. Teanby et al. (2017) Nat. Commun. 8, 1586. [2] V. Vuitton et al. (2019) Icarus 324, 120-190. [3] M. Mastrogiuseppe et al. (2019) Nat. Astron. 3, 535-542. [4] D.W. Clarke and J.P. Ferris (1997) Orig. Life Evol. Biosph. 27, 225-248. [5] J.W. Barnes et al. (2021) Planet. Sci. J. 2, 130. [6] A. Coustenis et al. (1998) A&A 336, 85-89. [7] R. Moreno et al. (2021) Icarus 221, 753-767. [8] V. Cottini et al. (2012) Icarus 220(2), 855-862. [9] J. Cui et al. (2009) Icarus 200, 581-615. [10] P.G.J. Irwin (2008) J. Quant. Spec. Radiat. Transf. 109, 1136–1150. [11] N.A. Teanby (2007) Math Geol, 39, 419–434. [12] S. Bauduin et al. (2018) Icarus, 311, 288-305.

Context. Voyager-2 radio occultation measurements have revealed changes in the atmospheric refractivity within a 2-4 km layer near the 1.2-bar level in Uranus and the 1.6-bar level in Neptune. These changes were attributed to the presence of a methane cloud, consistent with the observation that methane concentration decreases with altitude above these levels, closely following the saturation vapor pressure. However, no clear spectral signatures of such a cloud have been detected thus far in the spectra acquired from both planets. Aims. We examine methane cloud properties in the atmospheres of the ice giants, including vertical ice distribution, droplet radius, precipitation rates, timescales, and total opacity, employing microphysical simulations under different scenarios. Methods. We used a one-dimensional (1D) cloud microphysical model to simulate the formation of methane clouds in the ice giants. The simulations include the processes of nucleation, condensation, coagulation, evaporation, and precipitation, with vertical mixing simulated using an eddy-diffusion profile (Keddy). Results. Our simulations show cloud bases close to 1.24 bars in Uranus and 1.64 bars in Neptune, with droplets up to 100 mu m causing high settling velocities and precipitation rates (similar to 370 mm per Earth year). The high settling velocities limit the total cloud opacity, yielding values at 0.8 mu m of similar to 0.19 for Uranus and similar to 0.35 for Neptune, using Keddy = 0.5 m2 s-1 and a deep methane mole fraction (muCH4) of 0.04. In addition, lower Keddy or muCH4 values result in smaller opacities. Methane supersaturation is promptly removed by condensation, controlling the decline in muCH4 with altitude in the troposphere. However, the high settling velocities prevent the formation of a permanent thick cloud. Stratospheric hazes made of ethane or acetylene ice are expected to evaporate completely before reaching the methane condensation level. Since hazes are required for methane heterogeneous nucleation, this suggests either a change in the solid phase properties of the haze particles, inhibiting evaporation, or the presence of photochemical hazes.

We present radiative transfer analyses of IRTF-TEXES and SOFIA-EXES mid-infrared spectra of Jupiter's mid- to high latitudes recorded between 2019 April 16 and 2023 July 20. The spectra were inverted across a photochemical model grid of varying eddy diffusion coefficient profiles, and the quality of fi t of the synthetic spectra to the observed was used to constrain the CH4 homopause level. For a subset of latitudes/dates, we find that the CH4 homopause level is elevated in the region enclosed inside of, or magnetospherically poleward of, the northern ultraviolet main auroral emissions ( MAEs ) in comparison to the region outside or equatorward of the MAE. For example, using SOFIA-EXES results on 2021 June 10, we derived a CH4 homopause level of log(p(H)(nbar)) = 1.54(-0.69 )(+0.51)or z(H) = 453 (+128)(-76 )km above 1 bar poleward of the northern MAE at 68oN compared to a lower limit of 128- log(p(H)) > 2.43 and upper limit of z(H) < 322 km derived equatorward of the northern MAE. We therefore conclude that the region poleward of the northern MAE is, at times, subject to enhanced vertical transport resulting from auroral energy deposition. The exact mechanisms responsible for the enhanced vertical transport in Jupiter's auroral regions are uncertain: time-dependent circulation modeling of Jupiter's polar atmosphere is required to better understand this phenomenon. Poleward of the southern MAE, derived homopause levels agreed within uncertainty with those at equatorward locations. However, we consider this result a spatial sampling artifact rather than concluding that the southern auroral region is not subject to enhanced vertical transport.

ArchNEMESIS is an open-source Python package developed for the analysis of remote sensing spectroscopic observations of planetary atmospheres. It is based on the widely used NEMESIS radiative transfer and retrieval tool, which has been extensively used for the investigation of a wide variety of planetary environments. The main goal of archNEMESIS is to provide the capabilities of its Fortran-based predecessor, keeping or exceeding the efficiency in the calculations, and benefitting from the advantages Python tools provide in terms of usability and portability. The code, stored in a public GitHub repository under a GPL-v3.0 license, is accompanied by detailed documentation available at https://archnemesis.readthedocs.io/.

In the last twenty years, spectroscopic imaging observations of Uranus and Neptune, the solar system’s ‘Ice Giants’, have revolutionised our understanding of the atmospheres of these cold, distant worlds. In spectroscopic imaging observations, each pixel in the resolved image of the planet contains a continuous spectrum, which can be used to probe gaseous abundances as well as the precise vertical distribution of scattering particles, which is something that filter imaging alone cannot achieve. For example, observations made near 800 nm with the STIS instrument on Hubble Space Telescope have determined that the abundance of methane varies strongly with latitude in these atmospheres, with roughly a factor of two depletion at polar latitudes compared to the equator. At longer wavelengths (~1.5 μm), observations made with the NIFS instrument at Gemini-North have revealed not only the presence of hydrogen sulphide, but also hints of its latitudinal variation.In this presentation we will highlight recent advances made with spectral imaging observations, using HST/STIS and also the MUSE instrument at the ESO Very large Telescope. On both planets the weight of evidence supports an atmospheric aerosol structure comprised of: 1) a deep layer of aerosol/H2S ice near the H2S condensation level at p > 5 bar; 2) a middle layer of aerosol/CH4-ice near the CH4 condensation level at p = 1 – 2 bar; and 3) an upper layer of photochemical haze. Variation in opacity and scattering properties of the middle aerosol layer near 1 – 2 bar are found to be responsible for the bulk difference in colour between Uranus and Neptune, and also for the seasonal cycle of Uranus’s colour. Meanwhile, variations in the reflectivity of the particles in the deep layer are found to be responsible for the dark spots seen in Neptune’s (and occasionally Uranus’s) atmosphere and in Neptune’s dark South Polar Wave near 60°S. In addition, a new class of deep bright cloud has been identified in Neptune’s atmosphere using VLT/MUSE, which hints at deep, vigorous convection.While it is important that HST/STIS and VLT/MUSE monitoring observations will continue, the James Webb Space Telescope has recently observed both Uranus and Neptune using the NIRSpec instrument in Integral Field Unit (IFU) mode (i.e., spectroscopic imaging) at even longer wavelengths from 1.6 to 5.2 μm. These observations will advance even further our understanding of these distant worlds, although we note that extending such observations to NIRSpec’s shorter wavelengths would allow JWST to also recover the latitudinal variation of hydrogen sulphide, a key tracer of deep convection.

The visible spectrum of Jupiter contains absorption bands of methane (619 nm) and ammonia (647 nm) that can be used to probe the cloud-top pressures and ammonia abundance in Jupiter's atmosphere. Recently, it has been shown that filter-averaged observations of Jupiter made with telescopes and filters accessible to backyard astronomers can be reduced to yield ammonia maps that bear a remarkable similarity with distributions derived using more complex radiative transfer methods. Here, we determine the reliability of this method by applying it to observations made with the MUSE instrument at ESO's Very Large Telescope, and find excellent correspondence with the retrieved products from multiple-scattering retrieval model analyses. We find that the main level of reflection in Jupiter's atmosphere is at 2-3 bar, which is far beneath the anticipated ammonia ice condensation level at similar to ${\sim} $ 0.7 bar, and conclude that pure ammonia ice cannot be the main cloud constituent. We show that the spatial variations of ammonia determined at 2-3 bar are strongly correlated with those determined from thermal-infrared observations, and microwave observations by the Very Large Array and the Juno spacecraft. Finally, we show that the same technique can be applied to observations of Saturn, again yielding maps of ammonia abundance at 2-3 bar that are well-correlated with thermal-IR observations made near 5 mu $\mu $m by Cassini/VIMS and JWST/MIRI. Similarly, the main level of reflectivity is found to be lie far beneath the expected condensation level of ammonia in Saturn's atmosphere at similar to ${\sim} $ 1.8 bar.

A range of concepts for long duration aerial missions, using high altitude balloons operating in the clouds of Venus, have been studied by NASA and JPL for the Planetary Science and Astrobiology Decadal Survey and for NASA's competitive New Frontiers and Discovery programs. These concepts offer a rich set of scientific opportunities in atmospheric chemistry, astrobiology, atmospheric dynamics, seismology and sub-cloud surface imaging. The Venus aerobot would be sustained in flight by a variable-altitude balloon and carry a payload of instruments at altitudes between 52 and 62 km. The aerobot would fly in the cloud layer containing sulfuric acid aerosols and be subject to large temperature extremes as it traverses a range of altitudes and latitudes at different times of day. To achieve the desired lifetime on the order of one Venus day we have defined a solar power system that would supply power over the full altitude range while the aerobot is circumnavigating the planet. We have initiated development of the requisite technology, including rechargeable batteries, solar arrays, and a peak power tracker for this challenging mission. Specifically, we have fabricated triple-junction inverted metamorphic (IMM) solar cells optimized for power generation in the unique spectrum of light expected at 51.5 km altitude and measured 34.0 mW/cm(2) power output at room temperature in initial testing. We developed a coating to protect aerobot solar panels from corrosion in sulfuric acid and demonstrated survival without performance degradation after 96 hours in 96% aqueous sulfuric acid at room temperature. Initial performance data were obtained on a peak power tracker showing 96% power conversion efficiency. In addition, we have developed specialized lithium-ion cells intended to operate between -30 and 100 degrees C and demonstrated 80% capacity retention after 90 cycles at 100% depth of discharge at 100 deg C. These cells were incorporated into a 4s1p battery module and successfully tested under expected flight-like random vibration and thermal vacuum conditions. These results represent key steps in the process of developing the power system technology needed to bring the Venus aerobot mission to fruition.

ABSTRACT Spectroscopic phase curves of hot Jupiters measure their emission spectra at multiple orbital phases, thus enabling detailed characterization of their atmospheres. Precise constraints on the atmospheric composition of these exoplanets offer insights into their formation and evolution. We analyse four phase-resolved emission spectra of the hot Jupiter WASP-43b, generated from a phase curve observed with the Mid-Infrared Instrument/Low Resolution Spectrometer onboard the JWST, to retrieve its atmospheric properties. Using a parametric 2D temperature model and assuming a chemically homogeneous atmosphere within the observed pressure region, we simultaneously fit the four spectra to constrain the abundances of atmospheric constituents, thereby yielding more precise constraints than previous work that analysed each spectrum independently. Our analysis reveals statistically significant evidence of NH$_3$ (4$\sigma$) in a hot Jupiter’s emission spectra for the first time, along with evidence of H$_2$O (6.5$\sigma$), CO (3.1$\sigma$), and a non-detection of CH$_4$. With our abundance constraints, we tentatively estimate the metallicity of WASP-43b at 0.6$-6.5\times$ solar and its C/O ratio at 0.6$-$0.9. Our findings offer vital insights into the atmospheric conditions and formation history of WASP-43b by simultaneously constraining the abundances of carbon, oxygen, and nitrogen-bearing species.

In this paper, the improved design of an Ice Giants Net Flux Radiometer (IG-NFR), for inclusion as a payload on a future Uranus probe mission, is given. IG-NFR will measure the net radiation flux, in seven spectral bands, each with a 10° Field-Of-View (FOV) and in five viewing angles as a function of altitude. Net flux measurements within spectral filter bands, ranging from solar to far-infrared, will help derive radiative heating and cooling profiles, and will significantly contribute to our understanding of the planet’s atmospheric heat balance and structure, tropospheric 3-D flow, and compositions and opacities of the cloud layers. The IG-NFR uses an array of non-imaging Winston cones integrated to a matched thermopile detector Focal Plane Assembly (FPA), with individual bandpass filters and windows, housed in a vacuum micro-vessel. The FPA thermopile detector signals are read out in parallel mode, amplified and processed by a multi-channel digitizer application specific integrated circuit (MCD ASIC) under field programmable gate array (FPGA) control. The vacuum micro-vessel rotates providing chopping between FOV’s of upward and downward radiation fluxes. This unique design allows for small net flux measurements in the presence of large ambient fluxes and rapidly changing temperatures during the probe descent to ≥10 bar pressure.