arXiv subjects

Leigh N. Fletcher

Publications and source records attributed to Leigh N. Fletcher.

At least 19 recordsLinked to original sources

arXiv2026

The Ultraviolet Spectrograph on ESA's Jupiter Icy Moons Explorer Mission (JUICE-UVS)

The Jupiter Icy Moons Explorer (JUICE) mission, led by ESA, has an Ultraviolet Spectrograph (JUICE-UVS) contributed by NASA and built at Southwest Research Institute. JUICE-UVS is designed to provide a diversity of measurements to further our understanding of the potential habitability of icy ocean worlds at Jupiter and to study Jupiter and the Jovian system as an archetype for gas giants. JUICE-UVS observes photons in the 50-204 nm wavelength range at moderate spectral and spatial resolution along a 7.5 deg slit composed of 7.3 deg x 0.1 deg and 0.2 deg x 0.2 deg contiguous sections. JUICE-UVS performs a comprehensive study of icy satellite atmospheres, plumes, surfaces, and local space environments; Jupiter's atmosphere and aurora; Io and its Io Plasma Torus; and other Jupiter system targets (rings, small moons, etc.) as available. The variety of observational techniques employed include: nadir push-broom imaging, disk scans, limb stares, stellar and solar occultations, Jupiter transit observations, and neutral cloud/plasma torus stares and scans. This paper describes the UVS investigation's science plans, instrument details, concept of operations, and data formats in the context of the JUICE mission's habitability and Jupiter system goals.

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arXiv2026

Early Exploration of the Scientific Discovery Space for the Habitable Worlds Observatory

The Habitable Worlds Observatory (HWO) is a future NASA flagship mission concept identified by the Astro2020 Decadal Survey as the highest priority for large space missions. HWO should conduct "transformative astrophysics" and search for biosignatures in the atmospheres of approximately 25 potentially Earth-like planets. To further the early-stage development of HWO, NASA formed the Science, Technology, Architecture Review Team (START). In turn, START invited the scientific community to join working groups to explore the potential discovery space. In this paper, we present 70 science cases that resulted from this process. The cases address four scientific pillars: growth of galaxies (15 cases), evolution of the elements (13 cases), solar systems in context (32 cases), and living worlds (10 cases). Combined, they would address 27 of the 30 science questions and discovery areas identified by Astro2020. The 140 observing programs needed for the 70 investigations encompass a rich variety of spectroscopic (for 87% of science cases) and photometric (for 30%) observations extending from the UV to the NIR. Additionally, high-contrast and polarimetric capabilities would be needed for 34% and 27% of science cases, respectively. Access to UV wavelengths is critical: 83% of science cases need data at wavelengths <400 nm, and 26% extend to <100 nm. In the NIR, 26% of science cases need observations at wavelengths >=2000 nm. Pursuing the full portfolio of science would also necessitate precise astrometry for planet mass measurement, rapid response capabilities, a large instantaneous field of regard, non-sidereal tracking, saturation mitigation strategies, and high dynamic range.

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arXiv2026

Cloud and ammonia vertical profiles in the equatorial atmosphere of Jupiter determined from visible to near-IR observations made by VLT/MUSE, Cassini/VIMS, IRTF/SpeX and Juno/JIRAM

We present a combined cloud/ammonia model for Jupiter's equatorial atmosphere from 0.1 to 10 bar, consistent with observations made at a range of observation geometries from 0.35 to 5.15 $μ$m by VLT/MUSE, Cassini/VIMS, IRTF/SpeX and Juno/JIRAM. Our cloud model has three components: 1) an optically-thick lower cloud (radius $r$$\sim$$10$ $μ$m) at 1-2 bar; 2) an optically-thin upper cloud ($r$$\sim$$10$ $μ$m) at $\sim$0.55 bar; and 3) a layer of blue-absorbing chromophore particles ($r$$\sim$$0.2$ $μ$m) situated within the main lower cloud. The ammonia profile is intimately linked with the cloud profile with the lower cloud coinciding with an initial drop in ammonia abundance and the upper cloud coinciding with the ammonia condensation level. The large lower cloud particles are highly scattering at visible wavelengths, allowing sunlight to scatter through the clouds and be Rayleigh-scattered from the deep atmosphere. At 5 $μ$m, the lower cloud particles are found to be more absorbing, with the belt/zone differences mostly accounted for by changes in the single-scattering albedo of these particles and secondarily by changes in the cloud opacity. The spectral properties of these lower cloud particles are possibly consistent with a component of water ice. The upper cloud particles need a distinct absorption band near 3 $μ$m, possibly consistent with a component of ammonia ice. We note that we do not need a separate upper-level photochemical haze in our model. Instead, we find that the features seen at methane-absorbing wavelengths are caused by variations in the opacity and vertical extent of the upper cloud layer.

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arXiv2026

Detection of propadiene (CH$_2$CCH$_2$), propene (C$_3$H$_6$) and non-detection of propane (C$_3$H$_8$) in Jupiter's northern polar stratosphere

We report the first detection of stratospheric propadiene (CH$_2$CCH$_2$) and propene (C$_3$H$_6$) at Jupiter's mid-to-high northern latitudes using IRTF-TEXES measurements recorded on March 5-6, 2025. Using radiative transfer software to quantitatively test for the presence of propadiene and propene, we report a $>$12-$σ$ detection of propadiene and a $>$17-$σ$ detection of propene inside Jupiter's northern auroral region (henceforth 'NAR'), where the species are most concentrated. For example, at 62$^\circ$N inside Jupiter's NAR, we derive a 1-mbar propadiene abundance of 2.0 $\pm$ 0.2 ppbv, which is 40 $\pm$ 3 higher than abundances predicted by the Moses & Poppe (2017) photochemical model (henceforth 'MP17'), and significantly higher than the 1.2-ppbv upper limit abundance derived at 42$^\circ$N (the lowest latitude sampled by the observations). Similarly, we derive a 1-mbar propene abundance of 8.1 $\pm$ 0.5 ppbv at 62$^\circ$N inside Jupiter's NAR, which is 28 $\pm$ 2 higher than the MP17 predicted abundance and higher than the 6-ppbv 1-mbar upper limit abundance derived at 42$^\circ$N. The fact that propadiene and propene are most enriched inside Jupiter's NAR strongly suggests that perturbations to the chemistry by auroral-related heating and exogenous ions/electrons are responsible for their significant enrichment. Spectral features of propane (C$_3$H$_8$) were not detected at any of the locations sampled by the data: 3-$σ$ upper limits of 10 ppbv were derived at the 10-mbar level at 62$^\circ$N inside Jupiter's NAR. The non-detection of propane could, in part, be explained by the vertical sensitivity of its spectral features to deeper pressures, where there is negligible auroral-related heating. The results of this work advocate for development of ion-neutral chemistry models of Jupiter's polar stratosphere.

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arXiv2026

Juno Microwave Radiometer Observations Reveal A Warmer Polar Atmosphere on Jupiter

The intriguing circumpolar cyclone pattern at Jupiter's poles raises fundamental questions about how these systems are organized vertically and, further, how the planet's internal heat shapes and sustains them in the absence of solar insolation. We report recent close-in observations of Jupiter's north pole acquired by NASA's Juno Microwave Radiometer (MWR), which achieved comprehensive microwave mapping of the region at an unprecedentedly high resolution. Using six-channel measurements from eleven perijove passes (PJ51-PJ61) poleward of 75N, we derive polar-mean nadir brightness temperatures and limb-darkening spectra that together point to two equally plausible atmospheric scenarios: (1) a dry-adiabatic profile with slightly depleted ammonia gas at a few bars, or (2) a moist-adiabatic profile with uniform ammonia. Markov chain Monte Carlo retrievals yield a deep ammonia abundance of 354.8+12.0/-11.0 ppmv (3+/-0.1 x solar) and a water abundance of 1.8+1.5/-1.1 x 1000 ppmv (2.1+1.8/-1.3 x solar), resembling previous estimates at lower latitudes. Remarkably, the north pole is found to be 6-7 K warmer than the equator at the 1-bar level, although the inferred difference is close to the 1-sigma uncertainty level. If confirmed, this result would suggest an enhanced internal heat flux toward the poles, which is consistent with the more intense lightning activity observed at high latitudes.

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arXiv2025

Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Key Targets of Opportunity on Gas and Ice Giants and their satellites

The Extremely Large Telescope (ELT) will transform our knowledge of the outer planets and their satellite systems; however the visibility of unique targets of opportunity with high scientific value will be reduced for northern objects. Uranus' declination favors observations from the Northern Hemisphere until 2055, and Neptune will be favored from the Northern Hemisphere from 2027 for the next 90 years. Jupiter and Saturn experience cycles of better observability from either hemisphere on cycles of 10 and 30 years. These planets and their satellite systems often offer unique opportunities for discovery through time-critical observations. We argue that a 30-m class size telescope in the Northern Hemisphere with complementary scientific instrumentation to that on the ELT will secure the possibility of observing high-impact unpredictable phenomena in these systems.

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arXiv2025

Exploring Giant Planet Atmospheres with Habitable Worlds Observatory

Visible and ultraviolet imaging and spectroscopy of Solar System giant planets can set the paradigm for the atmospheric, ionospheric, and magnetospheric processes shaping the diversity of giant exoplanets, brown dwarfs, and their interactions with stellar hosts. Spectra of their molecular absorptions, aerosol scattering, airglow, and auroral emissions can reveal these dynamic atmospheres in three dimensions. Given that giant planets are extended, bright, moving, and rotating objects, with extreme dynamic range and highly variable appearances, they impose specific mission and instrumentation requirements on future large space-based optical/UV observatories like the proposed Habitable Worlds Observatory (HWO). We advocate that HWO must have the capability to track non-sidereal targets like the giant planets and their satellites; should be able to view auroras and atmospheres without saturation (e.g., through the use of filters or fast read-out modes); and with a high dynamic range to explore faint objects near bright discs. HWO should enable spatially-resolved spectroscopy from $\sim80$ nm to $\sim900$ nm, capturing H$_2$ Lyman and Werner band series and H Lyman-$α$ in the far-UV; molecular absorptions and scattering in the mid-UV/visible; and deep hydrogen/methane absorptions in the 800-900 nm for cloud characterisation and CH$_4$ mapping. Imaging should enable time-resolved observations, from seconds to create auroral movies, to hours for cloud tracking and winds, to months and years for atmosphere/ionosphere variability. We advocate that an imager should have sufficient field of view to capture Jupiter ($>50$\arcsec), and that UV/visible integral field spectrographs be considered with both narrow ($3$\arcsec) and wide ($>10$\arcsec) field capabilities to provide efficient mapping of atmospheres and auroras. [Abbr]

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arXiv2025

On the Detection of Exorings in Reflected Light with JWST NIRCam

When directly imaging a cold giant exoplanet hosting a ring system, the reflected light from the rings can outshine the planet's thermal emission and reflected-light in the near-infrared. Consequently, an exoring may be detectable at a significantly lower contrasts than is required to image the exoplanet itself. Here we investigate the detectability of exorings in near-infrared reflected light using NIRCam coronagraphy PanCAKE simulations of two nearby mature stars, Proxima Centauri and Tau Ceti. Under the most favorable assumptions, we find JWST 2$μ$m NIRCam coronagraphy (F200W + MASK335R) is capable of detecting an exoring system with a radius of 2.8 times that of Saturn's A-ring for planets on an orbit with a = 1.3-1.9 AU. Broader simulations indicate that NIRCam can probe large planetary ring systems around mature exoplanets comparable in size to circumplanetary disks, which can reach up to 1000 times the radius of Saturn's A-ring. These results suggest that NIRCam F200W coronagraphy could serendipitously detect large exorings in reflected light under the right conditions. A combined analysis of F200W coronagraphic observations of confirmed exoplanets could provide the first empirical constraints on the occurrence rate of large exorings. Confirming the existence and frequency of exorings spanning the scale between circumplanetary disks and the rings of the Solar System giant planet could offer new insight into the formation, evolution, and architecture of planetary systems.

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arXiv2025

Improved H2-He and H2-H2 Collision-Induced Absorption Models and Application to Outer-Planet Atmospheres

Using state-of-the-art ab initio interaction-induced dipole and potential-energy surfaces for hydrogen-helium (H2-He) pairs, we compute the rototranslational collision-induced absorption coefficient at 40-400 K for frequencies covering 0-4000 cm-1. The quantum mechanical scattering calculations account for the full anisotropic interaction potential, replacing the isotropic approximation. The absorption data are expected to be accurate with an uncertainty of 2% or better up to 2500 cm-1. The uncertainty is slightly higher at the highest frequencies where the rototranslational absorption is largely obscured by the rovibrational band. Our improved agreement with measurements at 200-800 cm-1 results from the improvement of the potential energy surface. The previously available rototranslational data set for H2-H2 pairs (Fletcher et al., Astrophys. J. Supp. 235, 24 (2018)) is also extended up to 4000 cm-1. In the rovibrational band previous isotropic potential calculations for H2-He (Gustafsson et al. J. Chem. Physics. 113, 3641 (2000)) and H2-H2 (Borysow, Icarus 92, 273 (1992)) have been extended to complement the rototranslational data set. The absorption coefficients are tabulated for ortho-to-para ratios from normal-H2 to pure para-H2, as well as equilibrium-H2, over 40-400 K. The effect of these updates are simulated for the cold atmosphere of Uranus and warmer atmosphere of Jupiter. They are equivalent to a brightness temperature difference of a fraction of a degree in the rototranslational region but up to 4 degrees in the rovibrational region. Our state-of-the-art modifications correct an otherwise +2% error in determining the He/H2 ratio in Uranus from its spectrum alone.

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arXiv2025

The Atmosphere of Titan in Late Northern Summer from JWST and Keck Observations

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.

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arXiv2024

The James Webb Space Telescope Absolute Flux Calibration. III. Mid-Infrared Instrument Medium Resolution IFU Spectrometer

We describe the spectrophotometric calibration of the Mid-Infrared Instrument's (MIRI) Medium Resolution Spectrometer (MRS) aboard the James Webb Space Telescope (JWST). This calibration is complicated by a time-dependent evolution in the effective throughput of the MRS; this evolution is strongest at long wavelengths, approximately a factor of 2 at 25um over the first two years of the mission. We model and correct for this evolution through regular observations of internal calibration lamps. Pixel flatfields are constructed from observations of the infrared-bright planetary nebula NGC 7027, and photometric aperture corrections from a combination of theoretical models and observations of bright standard stars. We tie the 5--18um flux calibration to high signal/noise (S/N; ~ 600-1000) observations of the O9 V star 10 Lacertae, scaled to the average calibration factor of nine other spectrophotometric standards. We calibrate the 18--28um spectral range using a combination of observations of main belt asteroid 515 Athalia and the circumstellar disk around young stellar object SAO 206462. The photometric repeatability is stable to better than 1% in the wavelength range 5--18um, and the S/N ratio of the delivered spectra is consistent between bootstrapped measurements, pipeline estimates, and theoretical predictions. The MRS point-source calibration agrees with that of the MIRI imager to within 1% from 7 to 21um and is approximately 1% fainter than prior Spitzer observations, while the extended source calibration agrees well with prior Cassini/CIRS and Voyager/IRIS observations.

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arXiv2024

The Thermal Structure and Composition of Jupiter's Great Red Spot From JWST/MIRI

Jupiter's Great Red Spot (GRS) was mapped by the James Webb Space Telescope (JWST)/Mid-Infrared Instrument (4.9-27.9 micron) 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.

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arXiv2024

A patchy CO$_2$ exosphere on Ganymede revealed by the James Webb Space Telescope

Jupiter's icy moon Ganymede has a tenuous exosphere produced by sputtering and possibly sublimation of water ice. To date, only atomic hydrogen and oxygen have been directly detected in this exosphere. Here, we present observations of Ganymede's CO$_2$ exosphere obtained with the James Webb Space Telescope. CO$_2$ gas is observed over different terrain types, mainly over those exposed to intense Jovian plasma irradiation, as well as over some bright or dark terrains. Despite warm surface temperatures, the CO$_2$ abundance over equatorial subsolar regions is low. CO$_2$ vapor has the highest abundance over the north polar cap of the leading hemisphere, reaching a surface pressure of 1 pbar. From modeling we show that the local enhancement observed near 12 h local time in this region can be explained by the presence of cold traps enabling CO$_2$ adsorption. However, whether the release mechanism in this high-latitude region is sputtering or sublimation remains unclear. The north polar cap of the leading hemisphere also has unique surface-ice properties, probably linked to the presence of the large atmospheric CO2 excess over this region. These CO2 molecules might have been initially released in the atmosphere after the radiolysis of CO$_2$ precursors, or from the sputtering of CO$_2$ embedded in the H$_2$O ice bedrock. Dark terrains (regiones), more widespread on the north versus south polar regions, possibly harbor CO$_2$ precursors. CO$_2$ molecules would then be redistributed via cold trapping on ice-rich terrains of the polar cap and be diurnally released and redeposited on these terrains. Ganymede's CO$_2$ exosphere highlights the complexity of surface-atmosphere interactions on Jupiter's icy Galilean moons.

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arXiv2024

Temperature and composition disturbances in the southern auroral region of Jupiter revealed by JWST/MIRI

Jupiters south polar region was observed by JWST Mid Infrared Instrument in December 2022. We used the Medium Resolution Spectrometer mode to provide new information about Jupiters South Polar stratosphere. The southern auroral region was visible and influenced the atmosphere in several ways. 1: 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 pm 2 K and 37 pm 4 K respectively. A cold polar vortex is centered at 65S at 10 mbar. 2: We found that the homopause is elevated to 590+25-118 km above the 1-bar pressure level inside the auroral oval compared to 460+60-50 km at neighboring latitudes and with an upper altitude of 350 km in regions not affected by auroral precipitation. 3: 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 towards the pole, without being localized in the auroral oval, in contrast with previous analysis. 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 South Polar Region. 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.

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arXiv2024

Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Planetary and Cometary Atmospheres

The study of planets and small bodies within our Solar System is fundamental for understanding the formation and evolution the Earth and other planets. Compositional and meteorological studies of the giant planets provide a foundation for understanding the nature of the most commonly observed exoplanets, while spectroscopic observations of the atmospheres of terrestrial planets, moons, and comets provide insights into the past and present-day habitability of planetary environments, and the availability of the chemical ingredients for life. While prior and existing (sub)millimeter observations have led to major advances in these areas, progress is hindered by limitations in the dynamic range, spatial and temporal coverage, as well as sensitivity of existing telescopes and interferometers. Here, we summarize some of the key planetary science use cases that factor into the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST), a proposed 50-m class single dish facility: (1) to more fully characterize planetary wind fields and atmospheric thermal structures, (2) to measure the compositions of icy moon atmospheres and plumes, (3) to obtain detections of new, astrobiologically relevant gases and perform isotopic surveys of comets, and (4) to perform synergistic, temporally-resolved measurements in support of dedicated interplanetary space missions. The improved spatial coverage (several arcminutes), resolution ($\sim1.2''-12''$), bandwidth (several tens of GHz), dynamic range ($\sim10^5$) and sensitivity ($\sim1$ mK km s$^{-1}$) required by these science cases would enable new insights into the chemistry and physics of planetary environments, the origins of prebiotic molecules and the habitability of planetary systems in general.

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arXiv2024

Super-adiabatic Temperature Gradient at Jupiter's Equatorial Zone and Implications for the Water Abundance

The temperature structure of a giant planet was traditionally thought to be an adiabat assuming convective mixing homogenizes entropy. The only in-situ measurement made by the Galileo Probe detected a near-adiabatic temperature structure within one of Jupiter's 5$μ$m hot spots with small but definite local departures from adiabaticity. We analyze Juno's microwave observations near Jupiter's equator (0 ~ 5$^o$N) and find that the equatorial temperature structure is best characterized by a stable super-adiabatic temperature profile rather than an adiabatic one. Water is the only substance with sufficient abundance to alter the atmosphere's mean molecular weight and prevent dynamic instability if a super-adiabatic temperature gradient exists. Thus, from the super-adiabaticity, our results indicate a water concentration (or the oxygen to hydrogen ratio) of about 4.9 times solar with a possible range of 1.5 ~ 8.3 times solar in Jupiter's equatorial region.

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arXiv2024

Infrared Characterisation of Jupiter's Equatorial Disturbance Cycle

We use an infrared dataset captured between 1984 and 2017 using several instruments and observatories to report five rare equatorial disturbances that completely altered the appearance of Jupiter's Equatorial Zone (EZ): the clearance of tropospheric clouds revealed a new 5-$μ$m-bright band encircling the planet at the equator, accompanied by large 5-$μ$m-bright filaments. Three events were observed in ground-based images in 1973, 1979 and 1992. We report and characterize for the first time the entire evolution of two new episodes of this unusual EZ state that presented their maximum 5-$μ$m-brightness in December 1999 and February 2007, coinciding with a brown coloration south of the equator and with large bluish filaments and white plumes in the northern EZ at visible wavelengths. We characterize their typical infrared-bright lifetimes of 12-18 months, with possible periodicities of 6-8 or 13-14 years. We predict that a full-scale equatorial disturbance could occur in 2019-21.

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arXiv2024

Investigating Thermal Contrasts Between Jupiter's Belts, Zones, and Polar Vortices with VLT/VISIR

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.

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