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.

Jupiter's polar aurora exhibits low brightness temperatures in Juno Microwave Radiometer (MWR) observations when the Juno spacecraft passes over the high-latitude region of the Northern Hemisphere. These cold features are observed predominantly at 0.6 GHz and show both long-term similar to ${\sim} $ hours and short-term changes over time, that is, spans less than the 30-s spacecraft spin period. The MWR "cold spot" observations are associated with polar ultraviolet emission features that are thought to originate from high energy electron precipitation into the Jovian high latitude atmosphere. The energetic electron precipitation produces strong absorptive characteristics at microwave frequencies due to the transient formation of high-density electron regions in the lower stratosphere. In this paper, we describe progress on the analysis of Juno MWR observations of the northern aurora and simulate the effects of heating and electron impact ionization processes due to high energy particle precipitation events in Jupiter's auroral ionosphere. Electron precipitation intensities at energies up to 10 MeV inferred from the Jupiter Energetic-Particle Detector Instrument (JEDI) and Ultraviolet Spectrograph (UVS) instruments are used as a Northern Hemisphere case study to understand the energy deposition and ionization processes in the lower stratosphere, and subsequently used to estimate the microwave and ultraviolet opacity of the auroral region. The northward progression of Juno's perijove during the mission reduces the overflight altitude and allows important insights into effects produced at different length scales with respect to the auroral oval.

Juno’s Microwave Radiometer (MWR) is providing the unprecedented opportunity to explore the dynamical properties and composition of Jupiter’s deep atmosphere, which is arguably one of the most visibly heterogeneous and time variable in the solar system. Since its arrival on 27 August 2016, the MWR has observed variability in microwave emission at wavelengths between 1.3 and 50 cm, sensing from 0.7 bar to over 100 bars of atmospheric pressure at over 57 close approaches to the atmosphere, known as “perijoves”. There has been a concerted effort to collect contextual information from other Juno instruments, as well as ground- and space-based observations to help interpret the MWR results. The space-based observations have included those from Juno’s own visible camera (JunoCam) and its Jupiter Infrared Auroral Mapper (JIRAM), as well as the Hubble Space Telescope (HST). The ground-based observations have included images and spectra from both professional and citizen-science astronomers. We report here observations that are constrained to spatial resolutions of 2 degrees in latitude or better, and have been subject to recent improvements in the calibration drift for all MWR’s channels with an improved relative calibration uncertainty of 0.5% or better over the entire mission. This has allowed us to evaluate zonal-mean temperatures and variability with improved confidence that these are real and not an artifact of receiver drift. The region that by far shows the greatest variability from a zonal mean is the North Equatorial Belt, (NEB: 12oN-16oN planetocentric) with a 2% standard deviation from the mean at all levels sensed by the MWR except for the 50-cm channel that senses variability in temperature and ammonia and water composition at pressures in excess of 100 bars of pressure. Among the strongest variability associated with discrete features in the atmosphere is a major upwelling and subsequent clearing of cloud cover in the North Temperate Belt (NTB: 20oN-26oN) in August-September of 2020. In general, the microwave antenna temperature variability often but not always correlates with visible or near- to mid-infrared variability. In some regions, such as the Equatorial Zone (EZ: 3oS-6oN), substantial variability is detected not only in regions above the level of the water-condensate cloud (~10 bars) but also at great depth (>100 bars). An important part of our next steps will be to examine where variabilities in the zonal-mean microwave brightness are the result of zonally discrete features in the atmosphere, particularly the NEB.

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.

MotivationRecent close-up views of Jupiter’s polar regions by NASA’s Juno spacecraft are providing a wealth of information about the dynamics and composition of Jupiter’s poles. We present thermal imaging observations from a series of repeated observations over fifteen years. These images complement the observations made by the Juno spacecraft by observing in a spectral region not covered by its instrumentation, providing a near-global context for the narrow fields-of-view of Juno’s Microwave Radiometer and JunoCam instruments and providing a long term baseline to study Jovian atmospheric evolution. In this work, we specifically focus on the distinct thermal signatures of Jupiter’s northern and southern polar regions in both the troposphere and stratosphere. Although Cassini CIRS maps of Jupiter in 2000 could see this transition to coll polar vortices (e.g. Simon-Miler et al. 2006, Fletcher et al. 2016), the spatial resolution of the 8-m facility provides access to higher latitudes.DataWe present thermal imaging from the Subaru Telescope using the COoled Mid-Infrared Camera and Spectrometer (COMICS, Kataza et al., 2000), between 7.8 and 25 μm. These data map temperatures in the upper troposphere (100 – 500 mbar) and stratosphere (20 – 0.5 mbar), and they constrain the distribution of tropospheric gases and condensate aerosols. This data set covers 2005 to 2020, allowing for the investigation of long-term trends, as well as comparisons with Juno and Juno-supporting observations at other wavelengths from 2016 onward. Preliminary ResultsFigure 1 illustrates the composite polar maps of brightness temperature for each hemisphere using images measured in January, 2017. The retrieved temperatures in each latitude circle were derived from these data were binned over μ (= cosine of emission angle) and the centre-to-limb variation was inverted using the NEMESIS radiative transfer code (Irwin et al., 2008). The results demonstrated that tropospheric temperatures exhibit a steep decline of at least 2 K poleward of 60°N-63°N (planetocentric), which we believe marks the boundary of a tropospheric polar vortex. A similar drop in temperature takes place more gradually over 54°S-64°S. The precise latitude of the inferred vortex boundary varies slightly between observations in both hemispheres. No seasonal trends in these latitude variations were observed. Stratospheric polar temperatures are affected by auroral-related heating at 140° – 230°W (System III) at high-northern latitudes (>55°N) and 330° – 90°W at high-southern latitudes (

We present Earth-based observations of Jupiter from 1994 and 2009, which respectively capture the effects on Jupiter’s atmosphere by the impacts of Comet D/Shoemaker-Levy 9 (SL9) and the impact by an unknown object whose visible impression on Jupiter’s appearance was discovered by Anthony Wesley. Previous studies have suggested the 2009 impactor was by an asteroid on the basis of differences in Jupiter’s atmospheric response compared to the 1994 impact by SL9. These differences include detections of 9.1-μm silicate features in the 2009 impact site (Orton et al., 2010, Icarus 211, 587-602) and the fact the 2009 debris field shrank faster (Hammel et al., 2010, ApJL 715, L150-L154), both of which suggest the 2009 impactor was more rocky/refractory in composition. However, Schenk et al. 2004 (Jupiter: The Planet, Satellites and Magnetosphere, Bagenal, Dowling, McKinnon, 427-456) state that comets are orders of magnitude more likely to impact Jupiter than asteroids since Jupiter should have cleared its orbit a long time ago. Thus, either (1) the 2009 impact was caused by an asteroid and therefore a statistical fluke, (2) Jupiter-Family Comets (JFCs) are a highly heterogeneous population, with some containing rocky/refractory interiors hidden from remote-sensing, or (3) there is a population of asteroids among bodies classified as JFCs. In order to explore these hypotheses, we performed a comparative spectral re-analysis of broadband imaging and low-resolution spectra measured during/after the 1994 and 2009 impacts. The comparison used consistent procedures for reduction and calibration of the data, atmospheric models, radiative-transfer software and spectroscopic line data in order to facilitate direct comparisons between 1994 and 2009 events.

Images of Jupiter taken during the year 2000 Cassini flyby revealed the early stages and evolution of a high northern-latitude UV Great Dark Spot over a three-month period. They also provided a window on the circulation of Jupiter's polar stratosphere. Jupiter's rarely-detected UV Great Dark Spot (UVGDS) is unusual in several respects. It is an ephemeral feature, twice appearing as an oval with size and shape similar to Jupiter's Great Red Spot (GRS). Like the GRS, it is an anticyclonic feature. It is unlike the GRS in that: (1) A gas, and/or very small particles (radius < < 1 micro meter, of unknown composition but likely hydrocarbon) is responsible for its contrast with its surroundings; (2) It appears to be a shallow feature, confined to the stratosphere; (3) It evolves (moves in System III longitude, elongates and tilts) over a period of months; and (4) It may be produced by an auroral event as inferred by its proximity to the southern extent of Jupiter's main auroral oval. However, we did not identify a specific auroral trigger event. We measure the rotation rate for the UVGDS to have been similar to 20 degrees per Earth day. To investigate the dynamical regime of this feature, we applied an automated cloud feature tracking algorithm to Cassini Imaging Science Subsystem images of Jupiter's northern hemisphere (30 degrees N - 80 degrees N) in the near-IR continuum, methane band, and ultraviolet filters. From these images we were able to derive zonal wind profiles from the middle troposphere cloud tops to the lower stratosphere and track the evolution of the UV Great Dark Spot. Differences in mean zonal wind speed between the continuum and methane band filters indicate a weakening of jets with altitude as far north as 75 degrees N latitude at the altitudes sampled by these filters. We also observe notable differences between the ultraviolet and the other two filters: (1) Winds are significantly weaker and mostly westward in the ultraviolet relative to lower altitudes at all latitudes equatorward of 60 degrees N latitude; (2) Poleward of 60 degrees N latitude, winds observed in the ultraviolet may be faster than those observed in the continuum and methane bands, though we are less confident in this result as Jupiter's haze morphology and the lack of small, discrete, unambiguous trackable features present unique challenges to obtaining reliable mean zonal winds in the ultraviolet at high latitudes.

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 degrees 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, ). 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. 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. The homopause is spatially variable within the polar region and highest within the auroral oval The atmosphere inside the Southern Auroral Oval at 1 and 0.01 mbar shows a warming compared with non-auroral regions The C2H2 abundance is enhanced inside the Southern Auroral Oval at 0.1 and 7 mbar, and C2H6 shows an increase polewards

Observations of the Jovian upper atmosphere at high latitudes in the UV, IR and mm/sub-mm all indicate that the chemical distributions and thermal structure are broadly influenced by auroral particle precipitations. Mid-IR and UV observations have shown that several light hydrocarbons (up to 6 carbon atoms) have altered abundances near Jupiter's main auroral ovals. Ion-neutral reactions influence the hydrocarbon chemistry, with light hydrocarbons produced in the upper stratosphere, and heavier hydrocarbons as well as aerosols produced in the lower stratosphere. One consequence of the magnetosphere-ionosphere coupling is the existence of ionospheric jets that propagate into the neutral middle stratosphere, likely acting as a dynamical barrier to the aurora-produced species. As the ionospheric jets and the background atmosphere do not co-rotate at the same rate, this creates a complex system where chemistry and dynamics are intertwined. The ion-neutral reactions produce species with a spatial distribution following the SIII longitude system in the upper stratosphere. As these species sediment down to the lower stratosphere, and because of the progressive dynamical decoupling between the ionospheric flows and the background atmosphere, the spatial distribution of the auroral-related species progressively follows a zonal distribution with increasing pressures that ultimately produces a system of polar and subpolar hazes that extends down to the bottom of the stratosphere. This paper reviews the most recent work addressing different aspects of this environment.

Introduction: NASA’s Spitzer Infrared Spectrometer (IRS) acquired mid-infrared (5 - 37 micron) disc-averaged spectra of Neptune in May 2004, November 2004, November 2005, and May 2006. Meadows et al., (2008, doi: 10.1016/j.icarus.2008.05.023) discovered Neptune's complex hydrocarbons methylacetylene and diacetylene and derived their abundances using the May 2004 data. The rest of the Neptune data has yet to be published. The data have all been reduced using the same methodology as Rowe-Gurney et al., (2021, doi: 10.1016/j.icarus.2021.114506) used for Uranus, so that each year can be reliably compared.We detect the same hydrocarbons seen in Meadows et al., (2008). This includes the strongest bands of methane (CH4), acetylene (C2H2) and ethane (C2H6) as-well-as weaker but still clearly recognisable features of ethylene (C2H4), carbon dioxide, methyl (CH3), methylacetylene (C3H4) and diacetylene (C4H2).At Uranus, there was a considerable longitudinal variation in stratospheric emission detected in the Spitzer data for multiple epochs (Rowe-Gurney et al., 2021). A variation is not present at Neptune in 2005 or late 2004, when all the separate longitudes displayed the same brightness temperature. In May 2004 a stratospheric variation is present, although it is tentative due to the deviation only appearing at a single longitude and because there are larger uncertainties on this early dataset. If the variation is real then it could be caused by stratospheric methane injection associated with convective clouds or perturbations to the location of the south polar warm vortex (Orton et al., 2012, doi: 10.1016/j.pss.2011.06.013).Optimal Estimation Retrievals: The data from 2005 have optimised exposure times, multiple observed longitudes, and therefore the lowest noise. It is this data we are using to derive the vertical structure of the temperature and composition in the stratosphere and upper troposphere (between around 1 nanobar and 2 bars of pressure). We present full optimal estimation inversions (using the NEMESIS retrieval algorithm, Irwin et al., 2008, doi: 10.1016/j.jqsrt.2007.11.006) of the globally averaged November 2005 data with the aim of constraining the temperature profile and the abundances of the stratospheric hydrocarbons. We fit both the low-resolution (R~120) and high-resolution (R~600) module data, testing multiple temperature priors derived from chemical models (Moses et al., 2018, doi: 10.1016/j.icarus.2018.02.004) and observations from AKARI (Fletcher et al., 2010, doi: 10.1051/0004-6361/200913358). Initial findings show that we are sensitive to stratospheric D/H ratio (derived from the relative abundances of CH4 and CH3D) and therefore we will attempt to constrain this value by finding the best fit for our model.Conclusion: Full spectrum mid-infrared data from Neptune in 2005 taken by the Spitzer Infrared Spectrometer is to be analysed using optimal estimation retrievals for the first time. The globally-averaged stratospheric temperature structure and the abundances of stratospheric hydrocarbons will be determined along with the ratio of D/H. The disc-averaged thermal and chemical structure from Spitzer will likely be our best characterisation of Neptune’s thermal structure until JWST/MIRI acquired spatially-resolved mid-infrared spectroscopy in 2022.

Jupiter’s atmosphere displays some of the most dramatic weather of any planet in our Solar System, with cycles of activity changing the upper tropospheric and stratospheric temperatures, aerosols, and cloud structures through physical processes that are not yet well understood. In the troposphere, Jupiter’s banded structure undergoes dramatic planetary-scale disturbances that can evolve over short timescales changing its appearance completely at a range of altitudes, from the cloud tops (~500 mbar) to the deeper levels (1-4 bar). Some of these tropospheric variations seem to occur randomly, like the impressive fading and revival of the South Equatorial Belt at 7°-17° S (planetocentric latitude), while others follow a periodic pattern, like the North Equatorial Belt expansions at 7°-17° N (with a ~4.5-year periodicity), the Equatorial Zone disturbances (~7-year period) within ±7° of the equator (Antuñano et al. 2018 doi: https://doi.org/10.1029/2018GL080382) and the convective outbreaks at 21° N in the North Temperate Belt (~5-year period) (Antuñano et al., 2019 doi: https://doi.org/10.3847/1538-3881/ab2cd6). In the stratosphere, Jupiter’s equatorial and off-equatorial temperature and winds at 10-20 mbar exhibit a remarkable 4-5-year periodic oscillation with height forced by waves produced from tropospheric meteorological activity at the equatorial latitudes.Here we use almost 40 years (more than 3 jovian years) of ground-based infrared observations captured at NASA’s Infrared Telescope Facility (IRTF), the Very Large Telescope (VLT) and Subaru between 1980 and 2019 in a number of filters spanning from 7.9 to 24.5 µm. These filters sample upper tropospheric and stratospheric temperatures and aerosols via collision-induced hydrogen and helium absorption, and emission from stratospheric hydrocarbons. This long-term time series is used to (i) understand the impact of the previously mentioned tropospheric activity on the periodicity of the stratospheric temperature oscillations, (ii) characterize the long-term variability of Jupiter’s atmosphere at different altitudes in the upper troposphere and stratosphere, and (iii) investigate the long-term thermal, chemical and aerosol changes in Jupiter’s troposphere. In particular, we generate Lomb-Scargle periodograms and apply a Wavelet Transform analysis to our dataset to look for potential periodicities on the brightness temperature variability in different filters and compare them to previously reported cyclic activity at visible wavelengths (sensing the ammonia cloud top at ~500 mbar) and 5 µm (sensing the 1-4 bar pressure level). Finally, a Principal Component Analyses (PCA) is also performed to analyse the correlation of the brightness temperature variations at different belts and zones.

We present results from a comprehensive analysis of mid-infrared imaging of Neptune's atmosphere. Using all currently available ground-based images, we show how Neptune's mid-infrared emission has changed over the past decades in images sensitive to stratospheric ethane, methane, and temperatures. Neptune's stratospheric thermal emission appears to vary significantly on sub-seasonal timescales of years or less with significant latitudinal asymmetry not predicted by seasonal radiative and photochemical models. In particular, Neptune's stratospheric temperatures have declined globally since 2003, although northern and southern latitudes varied separately. In just the past few years, Neptune's south polar region has dramatically brightened while the remainder of the stratosphere has grown colder. These collective observations provide the strongest evidence to date that processes produce significant variability in Neptune's stratosphere on sub-seasonal timescales. Background: Despite being the most distant giant planet from the Sun, the ice giant Neptune possesses an extremely dynamic atmosphere, with meteorological phenomena evolving over a surprising range of timescales. Theory predicts Neptune's 165-year orbital period should modulate Neptune's stratospheric temperatures and chemistry [1] and, potentially, upper tropospheric temperatures [2] very slowly across seasons lasting several decades. But a growing body of mid-IR observations over the past decades are starting to reveal that Neptune's stratosphere is likely even more dynamic and variable than previously known [3].Analysis: Ground-based imaging of Neptune at mid-infrared wavelengths (~7.7--24.5 µm) dating back to 2003 are collected, calibrated, and analysed to reveal trends in time. Results: Significant changes in radiance are detected over the past two decades, with some occurring over periods of just a few years. For example, images sensing stratospheric ethane show a significant drop in radiance between 2006 and 2009, particularly at southern mid-latitudes (see Figure 1). By 2018, similar images show emission further reduced. However, between 2018 and 2020, the southern pole grew dramatically brighter. Our analysis indicates these observed changes are primarily due to changes in the stratospheric temperatures and, likely, the ethane mixing ratios. These results further suggest the importance of modulating solar UV flux and/or sub-seasonal dynamical processes in Neptune's stratosphere.Figure 1. Images of Neptune acquired in different years in filters sensitive to emission from stratospheric ethane. (Left) Images acquired with the VLT-VISIR 12.2 µm filter show a that the observed radiances drop over time, beginning at southern mid-latitudes (Right) Images from Subaru-COMICS 12.4 µm filter show a dramatic increase in the south polar radiance between late 2008 and mid-2020. Together, these data suggest a rapid brightening of the Neptune's south polar vortex between mid-2018 and mid-2020.References:[1] Moses et al., 2018, Icarus 307: 124-145[2] Li et al., 2018, JQSRT, 217, 1105 353[3] Hammel et al., 2006, ApJ, 664, 1326-1333

Using images at multiple mid-infrared wavelengths, acquired in May 2018 using the 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 $\sim$64$^{\circ}$N and $\sim$67$^{\circ}$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.

In the version of the article originally published, all column density values were a factor of 10 too low.Consequently, "two orders" has been changed to "one order" in the abstract and the text, and the values have been corrected on the y axes of Fig. 3 and the color scales in Fig. 4. In addition, in the section "The spatial distribution of CO and HCN", the CO and HCN masses reported in the text were a factor of 10 too low and the loss factors for CO and HCN were a factor of 10 too high; they have been corrected accordingly.Specifically, CO is now shown to have a meridionally uniform column density of 1.86 ± 0.52 × 10 16 cm -2 and the total mass of SL9-derived CO is 5.47 ± 0.26 × 10 14 g.This corresponds to a loss factor of 0.9 ± 0.3 since 1995-1998.HCN has a uniform column density of 22.6 ± 5.7 × 10 13 cm -2 , which is one order of magnitude lower than that measured 6.5 years after the SL9 impacts.The total mass of HCN is 5.0 ± 0.1 × 10 12 g.This corresponds to a loss factor of 5.0 ± 3.0 when compared with the 1995-1998 period, or 12.0 ± 3.5 when compared with the value derived in 2000 from the Cassini flyby data.The conclusions of the paper remain unchanged.

. OverviewJupiter's banded structure undergoes remarkable global-scale disturbances that can completely change its appearance from the deep troposphere below the cloud deck (2-7 bar) to the stratosphere (~1 mbar). These events can alter Jupiter's cloud structure, aerosols, and temperature field through mechanisms that are not well understood, and provide relevant insights into Jupiter’s time-variable atmospheric dynamics. Characterizing Jupiter's atmospheric changes in the long-term is crucial to better understand the origin and nature of the planetary scale disturbances, distinguishing between seasonal or mechanical forcing, and enables further investigation of the coupling of Jupiter's belts and zones that could explain the presence of 'Global Upheavals' (Rogers, 1995). In this study, we will describe how Jupiter's temperatures and aerosols vary over long spans of time, from the top NH3 clouds to the stable mid-stratosphere, and we will show that although Jupiter's troposphere and stratosphere exhibit a large number dynamical phenomena, there exists quasi-periodic patterns that may aid in future predictions of planetary-scale changes to the banded structure.2. Ground-Based ObservationsContinued monitoring of Jupiter from ground-based observatories from the past 40 years has provided an unprecedented resource for understanding the cyclic/non-cyclic environmental changes in temperature, aerosols, and composition governing Jupiter’s dynamic atmosphere. More recently, ground-based observations have provided essential temporal, spectral and spatial resolution to support observations from the Juno spacecraft. Our study uses ground-based mid-infrared observations captured between 1983 and 2019 at wavelengths between 7.9 µm and 24.5 µm by 7 different instruments: the BOLO-1 (1983-1993), AT-1 (1983-1993), MIRAC (1993-1999), MIRLIN (1996-2003) and MIRSI (2003-2011) instruments mounted at the 3-m NASA Infrared Telescope Facility (IRTF) in Hawai'i; the VISIR (2006-2011, 2016-2018) instrument mounted at the 8-m Very Large Telescope (VLT) in Chile; and the COMICS (2005-2019) instrument on the 8-m Subaru Telescope in Hawai'i. Examples of Jupiter images at different wavelengths are given in Figure 1.Figure 1. Examples of images of Jupiter captured by the MIRSI instrument at 7 different wavelengths.3. Multi-Year Cycles of VariabilityAs mentioned above, Jupiter’s belts and zones endure dramatic global-scale changes over short-timescales, where belts expand, contract and even entirely disappear in a complex and turbulent way (e.g., Fletcher et al., 2017, doi:10.1002/2017GL073806). The most remarkable examples of this are the South Equatorial Belt (SEB, at 7°-17° S) fading and revival cycles (e.g., Sánchez-Lavega & Gomez, 1996, doi:10.1006/icar.1996.0067; Fletcher et al., 2017, doi:10.1016/j.icarus.2017.01.001), where the typically warm and dark belt at visible wavelengths transforms into a cold, cloud-covered whitish zone in timescales of months, remaining disturbed for years before energetic storms trigger the revival of the belt. A similar ‘revival’ process occurs semi-periodically at the North Temperate Belt (NTB, at 21°-28° N), where energetic convective storms rising from the water layer in the deep troposphere at this belt interact with the background flow producing a new low-albedo band over the southern half of the NTB (e.g., Sánchez-Lavega et al., 2017, doi: 10.1002/2017GL073421). At lower latitudes, the North Equatorial Belt (NEB, at 7°-17° N) is observed to expand northward in time intervals of 3 to 5 years, causing a gradual decrease in reflectivity (darkening) at the neighbouring North Tropical Zone (NTrZ, at 18°-21° N), typically originated from wave-like bulges of materials impinging on the NTrZ (e.g. Rogers, 1995; Fletcher et al., 2017, 10.1002/2017GL073383). Finally, Jupiter’s Equatorial Zone (EZ, within ±7° of the equator) experiences a rare 7-year cyclic disturbance, where the typically white (NH3 cloud-covered) and cold EZ displays a new 5-μm-bright (NH3 cloud-free) band encircling the planet south of the equator, accompanied by a reddish coloration at visible wavelengths (e.g., Antuñano et al., 2018, doi: 10.1029/2018GL080382; Rogers, 1995). In this presentation, we will show zonal-mean brightness temperature maps spanning the period between 1983 and 2019 at 5 different wavelengths (7.9 µm, 8.6 µm, 10.7 µm, 18.7 µm and 20.5 µm) and between 1996 and 2019 at 8 wavelengths (same list plus 13.0 µm, 17.6 µm and 24.5 µm). We will describe the temporal and latitudinal variability of the brightness temperature at each of these wavelengths, looking for potential correlation/anticorrelation between changes at different belts that could help to reveal the processes underpinning the jovian global upheavals. We will also compare changes at different wavelengths to better understand the vertical extent of the global-scale disturbances in Jupiter’s banded structure.4. Temperature and Aerosol Opacity: VariabilityZonal-mean radiance profiles at different wavelengths can be stacked together to form 5-point (7.9 µm, 8.6 µm, 10.7 µm, 18.7 µm and 20.5 µm) spectral image cubes between 1983 and 2019 and 8-point (the same plus 13.0 µm, 17.6 µm, and 24.5 µm) spectral image cubes between 1996 and 2019. These spectral image cubes can then be inverted independently using the radiative-transfer and retrieval code NEMESIS (Irwin et al., 2008, doi:10.1016/j.jqsrt.2007.11.006), to obtain crude estimations of stratospheric temperatures at 10-20 mbar (constrained by the 7.9 µm wavelength), upper-tropospheric (100-300 mbar) and mid-tropospheric (~500 mbar) temperatures (constrained by the 17.6 µm-24.5 µm and 10.7 µm, respectively), and tropospheric aerosol opacity at 400-600 mbar (constrained by the 8.6 µm wavelength). Here, we will show stratospheric and tropospheric temperature and aerosol opacity maps between 1983 and 2019. We will describe the timescales of the variability observed in these maps by presenting a Lomb-Scargle analysis, and we will compare their periodicity to previously reported cyclic activity in Jupiter’s atmosphere, describing how temperature and aerosols vary during the planetary-scale disturbances. We will also compare the periodicity found at different belts, showing an NEB-SEB anticorrelation in the aerosol opacity and mid-tropospheric temperatures, and differences in the temperature field and aerosol opacity between hemispheres will be discussed. Finally, we will reveal a tropospheric-stratospheric coupling associated with Jupiter's Equatorial Stratospheric Oscillation.

Above the dynamic clouds in Neptune’s atmosphere, the temperatures and photochemical composition within Neptune’s stratosphere are expected to respond to slowly modulating insolation over decades [1]. With Neptune’s seasons stretching over more than forty years, the entire history of reliable infrared observations resolving the planet’s disk comprises a mere fraction of a season. Yet, as we shall show, within this relatively brief window, observations appear to show changes in emission that would imply that sub-seasonal processes are significantly modifying the chemical and/or thermal structure in Neptune's stratosphere.We present an analysis of the mid-infrared images and spectra of Neptune acquired using the VISIR instrument at the Very Large Telescope (VLT) between 2006 and 2018. Images in Q-band (17.65, 18.72, 19.50 µm) are used to infer upper-tropospheric temperatures (~200 mbar), while Neptune’s stratosphere (~1 mbar) is analyzed using a combination of imaging and spectra sensitive to emission from ethane (12.2 µm), methane (7.9 µm), and the S(1) hydrogen quadrupole (17.03 µm).While we find that temperatures in the upper troposphere show no significant changes in time (remaining consistent with temperatures inferred from 1989 Voyager-IRIS measurements [2, 3]), the stratospheric emission appears to have changed unexpectedly over the past decade. Absolute radiances are uncertain, but relative trends in the spatially resolved emission are robust and show an asymmetric change in brightness temperature of up to ~3 K between and 2006 and 2008. The 2008 trend in emission continued throughout 2009 observations before returning to a relatively more symmetric pattern in 2018 (see Figure 1). Combined with the 2006 H2 S(1) quadrupole data, the observations indicate that the distribution of stratospheric emission observed in 2006 can likely be explained by the stratospheric temperature structure. However, no contemporaneous VLT-VISIR observations of the quadrupole emission were made in subsequent years, and so the nature of the observed changes between 2006 and 2008-2009 are ambiguous–they can potentially be explained by changes in the stratospheric temperatures, changes in the ethane abundances, or changes in both temperature and chemistry. The timing of these changes coincides with an extended maximum in Neptune’s photometric brightness following the 2005 southern summer solstice [4] and a decline in the discrete cloud coverage apparent in HST imaging [5]. Altogether, these observations suggest that Neptune’s stratosphere experiences intra-seasonal changes that may be coupled to dynamical forcing or variable mixing from the troposphere on timescales of years or less. Figure 1. Relative variation in the longitudinally averaged brightness temperatures inferred from 12.2 µm emission (ethane at ~1 mbar) as a function of latitude for observations from 2006 (light green), 2008 (blue), 2009 (dark green) and 2018 (orange). Example images corresponding to these years are shown in the inset. Absolute calibrations are uncertain and show some spread, so relative trends have been normalized to roughly coincide (arbitrarily) at southern latitudes and the planet limbs, with zero here chosen by the mean. These trends show that the stratospheric emission in 2008 and 2009 differed in shape from those observed in 2006 and 2018, possibly indicating a change in stratospheric temperatures or ethane. The red curve shows the trend in stratospheric hydrogen quadrupole emission for 2006 and suggests that the observed trend in 12.2 µm emission in 2006 was likely primarily determined by the temperature structure. [1] Moses, J. I., Fletcher, L. N., Greathouse, T. K., Orton, G. S., & Hue, V. 2018, Icar, 307, 124.[2] Conrath, B.J., Flasar, F.M., Gierasch, P.J., 1991. Thermal structure and dynamics of Neptune’s atmosphere from Voyager measurements. J. Geophys. Res. 96, 18931–18939.[3] Fletcher, Leigh N., et al. "Neptune at summer solstice: zonal mean temperatures from ground-based observations, 2003–2007." Icarus 231 (2014): 146-167.[4] Lockwood, G. W. "Final compilation of photometry of Uranus and Neptune, 1972–2016." Icarus 324 (2019): 77-85.[5] Karkoschka, Erich. "Neptune’s cloud and haze variations 1994–2008 from 500 HST–WFPC2 images." Icarus 215.2 (2011): 759-773.

Reflected sunlight observations from the Ultraviolet Spectrograph (UVS) on the Juno spacecraft were used to study the distribution of acetylene (C$_2$H$_2$) at Jupiter's south pole. We find that the shape of the C$_2$H$_2$ absorption feature varies significantly across the polar region, and this can be used to infer spatial variability in the C$_2$H$_2$ abundance. There is a localized region of enhanced C$_2$H$_2$ absorption which coincides with the location of Jupiter's southern polar aurora; the C$_2$H$_2$ abundance poleward of the auroral oval is a factor of 3 higher than adjacent quiescent, non-auroral longitudes. This builds on previous infrared studies which found enhanced C$_2$H$_2$ abundances within the northern auroral oval. This suggests that Jupiter's upper-atmosphere chemistry is being strongly influenced by the influx of charged auroral particles and demonstrates the necessity of developing ion-neutral photochemical models of Jupiter's polar regions.

A multi-decade record of ground-based mid-infrared (7–25μm) images of Saturn is used to explore seasonal and non-seasonal variability in thermal emission over more than a Saturnian year (1984–2022). Thermal emission measured by 3-m and 8-m-class observatories (notably NASA's Infrared Telescope Facility, Subaru, and ESO's Very Large Telescope) compares favourably with synthetic images based on both Cassini-derived temperature records and the predictions of radiative climate models. We find that 8-m class facilities are capable of resolving thermal contrasts on the scale of Saturn's belts, zones, polar hexagon, and polar cyclones, superimposed onto large-scale seasonal asymmetries. Seasonal changes in brightness temperatures of ∼30 K in the stratosphere and ∼10 K in the upper troposphere are observed, as the northern and southern polar stratospheric vortices (NPSV and SPSV) form in spring and dissipate in autumn. The timings of the first appearance of the warm polar vortices is successfully reproduced by radiative climate models, confirming them to be radiative phenomena, albeit entrained within sharp boundaries influenced by dynamics. Axisymmetric thermal bands (4–5 per hemisphere) display temperature gradients that are strongly correlated with Saturn's zonal winds, indicating winds that decay in strength with altitude from the cloud-tops to the ∼1-mbar level, and implying meridional circulation cells in Saturn's upper troposphere and stratosphere forming the system of cool zones and warm belts. Saturn's thermal structure is largely repeatable from year to year (via comparison of infrared images in 1989 and 2018), with the exception of low-latitudes. Here we find evidence of inter-annual variations because the equatorial banding at 7.9μm is inconsistent with a ∼15-year period for Saturn's equatorial stratospheric oscillation, i.e., it is not strictly semi-annual. Either the oscillation has a longer period closer to ∼20 years, or its progression is naturally variable and interrupted by tropospheric meteorology (e.g., storms). Finally, observations between 2017–2022 extend the legacy of the Cassini mission, revealing the continued warming of the NPSV during northern summer in line with predictions of radiative climate models.

Jupiter’s Polar Regions host a very strong auroral activity. The Jovian auroras leave their imprint in the ultraviolet spectral region, but also in the Mid-Infrared, which suggests that they can influence the thermal structure by heating up not only the thermosphere, but also the stratosphere by particle precipitation. Some studies suggest that auroral activity also influences the atmospheric chemistry by enhancing or depleting some stratospheric hydrocarbons produced by photochemistry, as well as other components such as HCN. Some hypotheses link these variations with the presence of polar hazes at high latitudes on Jupiter.JWST performed several observations of the Jovian System in 2022, most of them as part of the Early Release Science program 1373 (ERS-1373). One of these observations targeted the South Polar Region. On the 24th of December 2022, two spectrometers on board JWST, NIRSPec and MIRI carried out this observation, covering the spectral range from 1 to 28 μm (with the wavelengths beyond 15 microns completely saturated). Along with this observation, another earlier one was performed on July 2022 (OBS-1022), as part of the commissioning program. This complementary observation only covered the ranges 4.9-5.8, 7.4-8.8 and 11.5-13.5 μm, since it aimed only at testing the pointing of the instrument.Both of these observations allowed us to obtain sufficient spectral and spatial information to map stratospheric temperature and hydrocarbons abundances.We will show a complete analysis of the 1022 dataset. Despite the limited spectral range, we were able to measure stratospheric temperatures at pressures between 10 and 0.1 mbar and map the homopause height. To do so, we first needed to retrieve the homopause height (which determines the methane vertical profile of Jupiter) by a simultaneous analysis of fourteen different models of the atmosphere. We found that the auroral oval leaves an imprint in the stratosphere, creating a warmer region where the auroral oval can be spotted in the UV and IR. The analysis also shows an upwards displacement of the homopause level in the auroral oval, in agreement with previous studies but with a much better spatial resolution. We were also able to retrieve 3D maps of acetylene VMR.Along with this analysis, we will present preliminary results on MIRI 1373 observation. This observation covers the full spectral region from 5 to 28 μm and, hence, it has sufficient information to determine the abundances and distributions of other molecules, such as ammonia, phosphine, ethylene and ethane among others. We will also present processed NIRCam images from the polar region as a support for the spectral analysis.

We present a study of the long term variability of Jupiter’s mid-infrared CH4 auroral emissions. 7.7–7.9 μm images of Jupiter recorded by NASA’s Infrared Telescope Facility, Subaru and Gemini-South over the last three decades were collated in order to quantify the magnitude and timescales over which the northern auroral hotspot’s CH4 emission varies. These emissions predominantly sound the 10- to 1-mbar pressure range and therefore highlight the temporal variability of lower-stratospheric auroral-related heating. We find that the ratio of the radiance of the poleward northern auroral emissions to a lower-latitude zonal-mean, henceforth ‘Relative Poleward Radiance’ or RPR, exhibits variability over a 37% range and over a range of apparent timescales. We searched for patterns of variability in order to test whether seasonally varying solar insolation, the 11-year solar cycle, or short-term solar wind variability at Jupiter’s magnetopause could explain the observed evolution. The variability of the RPR exhibits a weak (r < 0.2) correlation with both the instantaneous and phase-lagged solar insolation received at Jupiter’s high-northern latitudes. This rules out the hypothesis suggested in previous work (e.g. Sinclair et al. 2017a, 2018) that shortwave solar heating of aurorally produced haze particles is the dominant auroral-related heating mechanism in the lower stratosphere. We also find the variability exhibits negligible (r < 0.18) correlation with both the instantaneous and phase-lagged monthly-mean sunspot number, which therefore rules out a long-term variability associated with the solar cycle. On shorter timescales, we find moderate correlations of the RPR with solar wind conditions at Jupiter in the preceding days before images were recorded. For example, we find correlations of r = 0.45 and r = 0.51 of the RPR with the mean and standard deviation solar wind dynamical pressure in the preceding 7 days. The moderate correlation suggests that either: (1) only a subset of solar wind compressions lead to brighter, poleward CH4 emissions and/or (2) a subset of CH4 emission brightening events are driven by internal magnetospheric processes (e.g. Io activity) and independent of solar wind enhancements.