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Jupiter's Great Red Spot (GRS) was mapped by the James Webb Space Telescope (JWST)/Mid‐Infrared Instrument (4.9–27.9 μ ${\upmu }$m) in July and August 2022. These observations took place alongside a suite of visual and infrared observations from; Hubble, JWST/NIRCam, Very Large Telescope/VISIR and amateur observers which provided both spatial and temporal context across the jovian disc. The stratospheric temperature structure retrieved using the NEMESIS software revealed a series of hot‐spots above the GRS. These could be the consequence of GRS‐induced wave activity. In the troposphere, the temperature structure was used to derive the thermal wind structure of the GRS vortex. These winds were only consistent with the independently determined wind field by JWST/NIRCam at 240 mbar if the altitude of the Hubble‐derived winds were located around 1,200 mbar, considerably deeper than previously assumed. No enhancement in ammonia was found within the GRS but a link between elevated aerosol and phosphine abundances was observed within this region. North‐south asymmetries were observed in the retrieved temperature, ammonia, phosphine and aerosol structure, consistent with the GRS tilting in the north‐south direction. Finally, a small storm was captured north‐west of the GRS that displayed a considerable excess in retrieved phosphine abundance, suggestive of vigorous convection. Despite this, no ammonia ice was detected in this region. The novelty of JWST required us to develop custom‐made software to resolve challenges in calibration of the data. This involved the derivation of the "FLT‐5" wavelength calibration solution that has subsequently been integrated into the standard calibration pipeline. Plain Language Summary: Regularly observed for over 150 years, Jupiter's Great Red Spot (GRS) is one of the best documented storms in the Solar System. Despite the frequency of observations, crucial questions remain unanswered regarding the internal composition, dynamics and driving mechanism for the storm. Mid‐infrared observations acquired by the James Webb Space Telescope allowed us to peer past the colorful clouds to assess the composition and dynamics of the jovian weather layer. Data from the mid‐infrared instrument was modeled in the 7.30–10.75 μ ${\upmu }$m range to "retrieve" the temperature distribution. Further modeling of these temperatures allowed us to derive the wind speeds throughout the vortex, enabling us to assess the dynamics of the GRS and how the vortex interacts with its surroundings. In addition, a series of hot‐spots were observed above the GRS that could be the result of atmospheric wave activity. The distribution of ammonia was also mapped in this spectral range. Comparison of the distribution of ammonia to the cloud distribution implied that this molecule may condense into the thick layers of cloud above the GRS. Finally phosphine, indicative of upwelling air was mapped and allowed us to identify a small convective storm north‐west of the GRS. Key Points: Jupiter's Great Red Spot (GRS) was observed by James Webb Space Telescope/Mid‐Infrared Instrument in 2022 to study the 3D structure of temperature, aerosols and gaseous speciesA series of stratospheric hot‐spots were discovered to be co‐moving with the GRS in the longitude directionElevated phosphine and a complex distribution of ammonia gas were observed inside the GRS [ABSTRACT FROM AUTHOR]

Jupiter's South Polar Region (SPR) was observed by James Webb Space Telescope/Mid‐Infrared Instrument in December 2022. We used the Medium Resolution Spectrometer mode to provide new information about Jupiter's South Polar stratosphere. The southern auroral region was visible and influenced the atmosphere in several ways: (a) In the interior of the southern auroral oval, we retrieved peak temperatures at two distinct pressure levels near 0.01 and 1 mbar, with warmer temperatures with respect to non‐auroral regions of 12 ± 2 K and 37 ± 4 K respectively. A cold polar vortex is centered at 65°S at 10 mbar. (b) We found that the homopause is elevated to 590−118+25 ${590}_{-118}^{+25}$ km above the 1‐bar pressure level inside the auroral oval compared to 460−50+60 ${460}_{-50}^{+60}$ km at neighboring latitudes and with an upper altitude of 350 km in regions not affected by auroral precipitation. (c) The retrieved abundance of C2H2 shows an increase within the auroral oval, and it exhibits high abundances throughout the polar region. The retrieved abundance of C2H6 increases toward the pole, without being localized in the auroral oval, in contrast with previous analysis (Sinclair et al., 2018, https://doi.org/10.1016/j.icarus.2017.09.016). We determined that the warming at 0.01 mbar and the elevated homopause might be caused by the flux of charged particles depositing their energy in the SPR. The 1‐mbar hotspot may arise from adiabatic heating resulting from auroral‐driven downwelling. The cold region at 10 mbar may be caused by radiative cooling by stratospheric aerosols. The differences in spatial distribution seem to indicate that the hydrocarbons analyzed are affected differently by auroral precipitation. Plain Language Summary: James Webb Space Telescope/Mid‐Infrared instrument observed Jupiter's south polar region in December 2022. The instrument acquired spectroscopic data in the mid‐infrared part of the spectrum, which is sensitive to the temperature of the atmosphere and the chemical abundances. These observations revealed that within the auroral oval there are two regions of high temperatures located at two different altitudes. These are presumably caused by two different phenomena: direct heating from the incoming charged particles in the aurora at a height of 0.01 mbar and adiabatic heating in downdrafts at lower levels. A decrease in temperature was also observed as we approached the South Pole, probably caused by a cold polar vortex associated with stratospheric hazes. We found that the altitude of the homopause (the limit between the well‐mixed part of the atmosphere and the part where molecules are separated according their specific weight) is altered by the auroras, being up to 100 km higher in the auroral region. The atmospheric abundances of acetylene and ethane showed an enrichment of acetylene within the auroral oval, and of ethane at the pole, which may indicate that these molecules are not affected in the same way by the energy input of the aurora. Key Points: The homopause is spatially variable within the polar region and highest within the auroral ovalThe atmosphere inside the Southern Auroral Oval at 1 and 0.01 mbar shows a warming compared with non‐auroral regionsThe C2H2 abundance is enhanced inside the Southern Auroral Oval at 0.1 and 7 mbar, and C2H6 shows an increase polewards [ABSTRACT FROM AUTHOR]

Using images at multiple mid‐infrared wavelengths, acquired in 2018 May using the Very Large Telescope Imager and Spectrometer (VISIR) instrument on ESO's Very Large Telescope (VLT), we study Jupiter's pole‐to‐pole thermal, chemical and aerosol structure in the troposphere and stratosphere. We confirm that the pattern of cool and cloudy anticyclonic zones and warm cloud‐free cyclonic belts persists throughout the mid‐latitudes, up to the polar boundaries, and evidence a strong correlation with the vertical maximum windshear and the locations of Jupiter's zonal jets. At high latitudes, VISIR images reveal a large region of mid‐infrared cooling poleward ∼64°N and ∼67°S extending from the upper troposphere to the stratosphere, co‐located with the reflective aerosols observed by JunoCam, and suggesting that aerosols play a key role in the radiative cooling at the poles. Comparison of zonal‐mean thermal properties and high‐resolution visible imaging from Juno allows us to study the variability of atmospheric properties as a function of altitude and jet boundaries, particularly in the cold southern polar vortex. However, the southern stratospheric polar vortex is partly masked by a warm mid‐infrared signature of the aurora. Co‐located with the southern main auroral oval, this warming results from the auroral precipitation and/or joule heating which heat the atmosphere and thus cause a significant stratospheric emission. This high emission results from a large enhancement of both ethane and acetylene in the polar region, reinforcing the evidence of enhanced ion‐related chemistry in Jupiter's auroral regions. Plain Language Summary: A fundamental inquiry driving NASA's Juno mission was the investigation of the potential changes of Jupiter's famous banded structure below the top most clouds. As NASA's Juno spacecraft lacks instrumentation sensitive to the mid‐infrared, we have used the ground‐based Very Large Telescope Imager and Spectrometer (VISIR) on ESO's Very Large Telescope (VLT) to support the mission since 2016. The 2018 May data set provides a comprehensive view of Jupiter's pole‐to‐pole thermal, chemical, and aerosol structure; including the Great Red Spot; and the auroral‐related heating in the southern polar stratosphere. We show that the alternating pattern of cool cloudy zones and warm cloud‐free belts correlate to the zonal winds locations, extends from the equator to the boundary of the polar vortices (∼64°N and ∼67°S). Comparing this ground‐based data set with Juno observations, we show that the polar regions experience radiative cooling from the upper troposphere to the stratosphere, probably induced by the reflective polar aerosols, and confined at the poles by the polar vortices. However, the southern stratospheric polar vortex is partly masked by a large auroral emission, a signature of an interaction between the magnetosphere and stratosphere of Jupiter, which causes a ∼20 K warming as deep as the middle stratosphere. Excess hydrocarbons within the polar domain reinforces the evidence of enhanced ion‐related chemistry in Jupiter's auroral regions, resulting from charged particles precipitating from the top of the atmosphere to lower altitudes. Key Points: Jupiter's belt/zone thermal structure extends from the equator to the edge of the polar vortices and correlates with the zonal jetsThe cold polar vortices coincides with reflective aerosols, suggesting dynamical entrainment by the northernmost and southernmost jetsTemporal evolution of the southern auroral hotspot shows a stratospheric cooling after a solar wind compression event [ABSTRACT FROM AUTHOR]

We use a long‐term record of ground‐based mid‐infrared (7.9–24.5 μm) observations, captured between 1984 and late 2019 from 3‐m and 8‐m class observatories (mainly NASA's Infrared Telescope Facility, ESO's Very Large Telescope, and the Subaru Telescope), to characterize the long‐term, multi‐decade variability of the thermal and aerosol structure in Jupiter's atmosphere. In this study, spectral cubes assembled from images in multiple filters are inverted to provide estimations of stratospheric and tropospheric temperatures and tropospheric aerosol opacity. We find evidence of non‐seasonal and quasi‐seasonal variations of the stratospheric temperatures at 10 mbar, with a permanent hemispherical asymmetry at mid‐latitudes, where the northern mid‐latitudes are overall warmer than southern mid‐latitudes. A correlation analysis between stratospheric and tropospheric temperature variations reveals a moderate anticorrelation between the 10‐mbar and 330‐mbar temperatures at the equator, revealing that upper‐tropospheric equatorial temperatures are coupled to Jupiter's Equatorial Stratospheric Oscillation. The North and South Equatorial Belts show temporal variability in their aerosol opacity and tropospheric temperatures that are in approximate antiphase with one another, with moderate negative correlations in the North Equatorial Belt and South Equatorial Belt changes between conjugate latitudes at 10°–16°. This long‐term anticorrelation between belts separated by ∼15° is still not understood. Finally we characterize the lag between thermal and aerosol opacity changes at a number of latitudes, finding that aerosol variations tend to lag after thermal variations by around 6 months at multiple latitudes. Plain Language Summary: Jupiter's atmosphere displays a wide variety of perturbations in its temperatures, clouds and aerosols. In this study, we use a large set of ground‐based observations captured in the mid‐infrared between 1984 and 2019 to characterize long‐term changes in the temperatures and aerosols. This long‐term analysis show a number of cyclic disturbances, and allows us to distinguish between seasonal and non‐seasonal changes in Jupiter's atmosphere. In particular, we observe that the northern mid‐latitudes above 30° are continuously warmer than their counterpart latitudes in the south at 10 mbar pressure level (the stratosphere), potentially due to differences in the polar haze in Jupiter, which extends to lower latitudes in the north compared to the south. Additionally, our study reveals for the first time that the thermal oscillation present in Jupiter's equatorial stratosphere at the 10‐mbar pressure level (known as Jupiter's Equatorial Stratospheric Oscillation) is also observed to descend to higher pressures (330 mbar), meaning that it is not confined to the stratosphere. Finally, we also discuss the lag between temperature and aerosol changes at diverse latitudes to try to identify the mechanisms responsible for the different atmospheric disturbances observed on Jupiter. Key Points: Ground‐based multi‐wavelength images are used to compute stratospheric and tropospheric temperature and tropospheric aerosol opacity mapsResults reveal that upper‐tropospheric equatorial temperatures are coupled to Jupiter's Equatorial Stratospheric OscillationStratospheric temperatures at 10 mbar show a permanent hemispherical asymmetry at mid‐latitudes, with northern mid‐latitudes overall warmer than their counterparts [ABSTRACT FROM AUTHOR]

Hubble Space Telescope Wide‐Field Camera 3 (HST/WFC3) observations spanning 2015 to 2021 confirm a brightening of Uranus' north polar hood feature with time. The vertical aerosol model of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0) (IRW23), consisting of a deep haze layer based at ∼5 bar, a 1–2 bar haze layer, and an extended haze rising up from the 1–2 bar layer, was applied to retrievals on HST Space Telescope Imaging Spectrograph (STIS) (HST/STIS) observations (Sromovsky et al., 2014, 2019, https://doi.org/10.1016/j.icarus.2014.05.016, https://doi.org/10.1016/j.icarus.2018.06.026) revealing a reduction in cloud‐top CH4 volume mixing ratio (VMR) (i.e., above the deep ∼5 bar haze) by an average of 0.0019 ± 0.0003 between 40–80◦N (∼10% average reduction) from 2012 to 2015. A combination of latitudinal retrievals on the HST/WFC3 and HST/STIS data sets, again employing the IRW23 model, reveal a temporal thickening of the 1–2 bar haze layer to be the main cause of the polar hood brightening, finding an average increase in integrated opacity of 1.09 ± 0.08 (∼33% increase) at 0.8 µm north of ∼45°N, concurrent with a decrease in the imaginary refractive index spectrum of the 1–2 bar haze layer north of ∼40°N and longwards of ∼0.7 µm. Small contributions to the brightening were found from a thickening of the deep aerosol layer, with an average increase in integrated opacity of 0.6 ± 0.1 (58% increase) north of 45°N between 2012 and 2015, and from the aforementioned decrease in CH4 VMR. Our results are consistent with the slowing of a stratospheric meridional circulation, exhibiting subsidence at the poles. Plain Language Summary: Uranus' north polar hood—a bright cap‐like feature encircling the northern polar region within its atmosphere—is observed to be brightening over time. Using several observations of Uranus captured between 2012 and 2021 by the Hubble Space Telescope, this study aims to pinpoint, for the first time, the specific changes occurring within the atmosphere leading to this evolution. Analysis of the observations confirmed the predominant cause of the hood's brightening to be changes in the scattering properties of the atmosphere's aerosol layers. A vertical aerosol model consisting of 3 distinct haze layers was employed to investigate these changes. We find that the hood's brightening mainly stems from changes in the middle haze layer in the model (centered at 1–2 bar), finding a thickening of this layer concurrent with an increase in the reflectivity of its aerosols over time at latitudes coincident with the north polar hood (∼45–90°N). Small contributions to the temporal brightening were also found from a ∼10% reduction in cloud‐top methane and a thickening of the deepest haze layer in the model (centered at ∼5 bar) at north polar hood latitudes. Key Points: We confirm that the brightening of Uranus' north polar hood is predominantly due to changes in aerosol scatteringA temporal thickening and increase in aerosol reflectivity of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0)'s 1–2 bar haze is the main cause of the brighteningWe find a further reduction in polar cloud‐top methane over time from retrievals carried out on Hubble Space Telescope's/Space Telescope Imaging Spectrograph observations [ABSTRACT FROM AUTHOR]

Saturn's northern summertime hemisphere was mapped by JWST/Mid‐Infrared Instrument (4.9–27.9 µm) in November 2022, tracing the seasonal evolution of temperatures, aerosols, and chemical species in the 5 years since the end of the Cassini mission. The spectral region between reflected sunlight and thermal emission (5.1–6.8 µm) is mapped for the first time, enabling retrievals of phosphine, ammonia, and water, alongside a system of two aerosol layers (an upper tropospheric haze p < 0.3 bars, and a deeper cloud layer at 1–2 bars). Ammonia displays substantial equatorial enrichment, suggesting similar dynamical processes to those found in Jupiter's equatorial zone. Saturn's North Polar Stratospheric Vortex has warmed since 2017, entrained by westward winds at p < 10 mbar, and exhibits localized enhancements in several hydrocarbons. The strongest latitudinal temperature gradients are co‐located with the peaks of the zonal winds, implying wind decay with altitude. Reflectivity contrasts at 5–6 µm compare favorably with albedo contrasts observed by Hubble, and several discrete vortices are observed. A warm equatorial stratospheric band in 2022 is not consistent with a 15‐year repeatability for the equatorial oscillation. A stacked system of windshear zones dominates Saturn's equatorial stratosphere, and implies a westward equatorial jet near 1–5 mbar at this epoch. Lower stratospheric temperatures, and local minima in the distributions of several hydrocarbons, imply low‐latitude upwelling and a reversal of Saturn's interhemispheric circulation since equinox. Latitudinal distributions of stratospheric ethylene, benzene, methyl, and carbon dioxide are presented for the first time, and we report the first detection of propane bands in the 8–11 µm region. Plain Language Summary: The Saturn system, with its seasonally varying atmosphere, delicate rings, and myriad satellites, presented an ideal early target for JWST. Saturn's extended disc, rapid rotation, and infrared brightness provided a challenge for the small fields‐of‐view of the Mid‐Infrared Instrument (MIRI), requiring a mosaic to map Saturn's northern summertime hemisphere. This exquisite data set reveals Saturn's banded structure, discrete vortices, the warm polar vortices, and the continued evolution of an oscillatory pattern of warm and cool anomalies over Saturn's equator. We show evidence that a stratospheric circulation pattern detected by Cassini during northern winter has now fully reversed in northern summer, with the low‐latitude stratosphere being cool and depleted in aerosols due to summertime upwelling. MIRI provides access to spectral regions that were not possible with the Cassini spacecraft, particularly in the 5–7 μm region where reflected sunlight and thermal emission blend together. Ammonia and phosphine are enriched at Saturn's equator, suggesting strong mixing from the deeper troposphere. MIRI's high sensitivity enables the first identification of previously unseen emission propane bands, along with the first measurements of the distribution of several gaseous species: tropospheric water, and stratospheric ethylene, benzene, methyl, and carbon dioxide. Key Points: Saturn's northern summertime hemisphere was mapped by JWST/Mid‐Infrared Instrument (MIRI) to study seasonal evolution of temperatures, aerosols, and compositionThe data show evidence for changing temperatures and winds in the equatorial oscillation, polar vortices, and interhemispheric stratospheric circulationMIRI spectral coverage and sensitivity enables mapping of several gases for the first time, particularly in ranges inaccessible to Cassini [ABSTRACT FROM AUTHOR]

We use ground‐based mid‐infrared (8–20 μm) data acquired by three different instruments between 2005 and 2008 to characterize the variability of tropospheric temperature and aerosol opacity during the 2006–2007 Equatorial Zone disturbance. This disturbance is part of a repeating pattern of cloud‐clearing events at Jupiter's equator, observed as a significant brightening at 5 μm (sensing the 2‐ to 7‐bar region) and darkening at visible wavelengths (sensing the ∼0.7‐bar pressure level). The data reveal a brightness temperature increase of ∼3.1 K between 2005 and February 2007 at 8.6‐μm sensing tropospheric aerosol opacity and temperature near 0.6–0.8 bar. At wavelengths sensing tropospheric ammonia and temperatures between 150 and 600 mbar, the brightness temperature remains largely invariant between 2005 and 2008. The tropospheric vertical temperature profile and the tropospheric aerosol opacity were derived from images captured in different filters on four different dates, one for each year. The retrieved aerosol opacity at ∼0.6–0.8 bar shows a decrease at 2–5°S of ∼45% in 2006 and ∼65% in 2007, with respect to 2008. This is consistent with cloud clearing/thinning during the coloration of the Equatorial Zone at visible wavelengths. This brightening at 8.6 μm started in 2005 and preceded the brightening at 5 μm, which started in April 2006. The results also suggest that cloud clearing during the Equatorial Zone disturbances is not simply the result of tropospheric warming, at least at p < 0.7 bar. We propose that cloud clearing occurs due to a decrease in the ammonia gas upwelling at the equator. Plain Language Summary: Jupiter's equatorial latitudes between ∼7°, known as the Equatorial Zone (EZ), undergo dramatic planetary‐scale disturbances that completely alter its appearance at different altitudes of the troposphere between 0.7 and 4 bar. Here we characterize the last EZ disturbance, observed in 2006–2007, to investigate what atmospheric conditions vary during these disturbances. Retrieved aerosol opacity at ∼0.6 bar shows a decrease at 2–5°S of ∼45% in 2006 and ∼65% in 2007, with respect to 2008, consistent with cloud clearing/thinning during these events. This removal of aerosol opacity is observed to start in 2005, a year before the deeper clouds are cleared. These results indicate that the EZ disturbance involves the clearing of both the ammonia ice cloud near 0.7 bar and the deeper NH4SH clouds with each cloud deck responding at different times. Results also suggest that cloud clearing during the EZ disturbances is not simply the result of tropospheric warming in the middle‐to‐high troposphere. We propose that cloud clearing occurs due to a decrease in the ammonia gas upwelling from deeper levels. Key Points: We characterize the 2006–2007 Equatorial Zone disturbance that completely altered the appearance of Jupiter's equatorial latitudesRetrieved aerosol opacity at ∼0.6 bar decreases by 45–65% at 2–5°S during the EZ disturbances, consistent with cloud clearing/thinningCloud clearing during the EZ disturbances is not simply the result of tropospheric warming, at least at p < 0.7 bar [ABSTRACT FROM AUTHOR]