Orals: Mon, 4 May, 08:30–10:15 | Room 0.94/95
Juno has transformed our view of Jupiter through major discoveries about its interior structure, origin, and evolution; atmospheric dynamics and composition; magnetic dynamo; and polar magnetosphere. The natural evolution of Juno’s polar orbit brings new regions within reach with every close passage to Jupiter, as the inbound equator crossing marches ever closer to the giant planet. The 1st extended mission began in August 2021 and provided the first close flybys of Io, Europa and Ganymede since the Galileo mission. The second extended mission (EM2) began in October 2025, providing opportunities for Juno to probe previously unexplored regions, and to follow up on Juno’s discoveries made during its prime and 1st extended missions. During EM2, Juno dvies deep into Jupiter's inner radiation belts, where the rings and inner moons reside, providing an opportunity to investigate these components and their complex interaction, yielding a unique data set to compare with other giant planet ring systems, including the ice giants. Juno’s polar perijoves provide the opportunity to continue the exploration of Jupiter’s circumpolar cyclones over a wide range of altitudes/depths via imagery, occultations and microwave sounding. Radio science occultations will characterize the upper atmosphere to levels as deep as 0.5 bar. Gravity passes over the north polar region will constrain the depth and mass of the polar cyclones and will also be compared to MWR's sounding of the same. An overview of the major results from Juno including new results obtained during EM2 will be presented.
How to cite: Levin, S. and the Juno Science Team: Science from Juno’s Continuing Extended Mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22848, 2026.
Juno’s Extended Mission trajectory enables unprecedented high-resolution (~6-35 km scale) Stellar Reference Unit (SRU) limb imaging and aurora observations on Jupiter’s night side. The SRU is a low-light, broadband visible wavelength (450-1000 nm) star tracker, with a peak sensitivity from ~570-800 nm, that Juno utilizes as a multi-disciplinary science instrument. High altitude views of the atmosphere on Jupiter’s limb have been acquired in equatorial and high northern latitude regions, including within the auroral region. Our presentation will discuss Juno’s findings from this unique data set, including structural features observed from a few hundred to over a thousand km above the 1 bar level and their place within the interconnected inner Jovian system.
How to cite: Becker, H., Brennan, M., Waite, J. H., Greathouse, T., Kammer, J., Freund, D., Atreya, S., Florence, M., Bolton, S., and Alexander, J.: An unprecedented view of Jupiter’s upper atmosphere and aurorae at visible wavelengths, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8287, 2026.
Radio occultation experiments provide one of the most direct probes of the shallow atmosphere of Jupiter, the only region of the gas giant accessible to in-situ measurements and a key interface between the deep interior and the observable cloud layer. By measuring the refraction of radio signals as they pass through the atmosphere, radio occultations yield high-vertical-resolution profiles of temperature, pressure, and composition, offering unique constraints on the thermal and dynamical structure of the stratosphere and upper troposphere. During its extended mission, beginning in July 2023, the Juno spacecraft has conducted the first radio occultations of Jupiter since the Voyager era, significantly expanding both the spatial coverage and scientific scope of these measurements. Using coherent two-way, multi-frequency radio links and detailed ray-tracing techniques, Juno’s occultations provide precise vertical profiles up to pressures of ~0.5 bar across a wide range of latitudes. When combined with contemporary ground-based observations, these profiles place new constraints on the variability and circulation of Jupiter’s shallow atmosphere. In this talk, I will present an overview of results from two years of Juno radio occultations, highlighting what they reveal about Jupiter’s stratospheric and upper-tropospheric structure and how they compare with earlier infrared measurements from Voyager and Cassini, as well as modern ground-based datasets. Particular attention will be given to recent occultations sampling Jupiter’s polar regions, which offer new insights into the thermal structure and dynamics of the polar stratospheric vortex. Together, these observations illustrate the renewed power of radio occultations as a tool for understanding Jupiter’s atmospheric dynamics and its coupling across vertical and latitudinal scales.
How to cite: Kaspi, Y., Smirnova, M., Galanti, E., Caruso, A., Fletcher, L., Buccino, D., Fonsetti, M., Gomez-Casajus, L., Hubbard, W., Orton, G., Parisi, M., Park, R., Zannoni, M., Steffes, P., Levin, S., Tortora, P., and Bolton, S.: An Overview of the Juno Radio Occultations at Jupiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16092, 2026.
Radio occultation experiments represent one of the main tools available to sound the atmospheres of celestial bodies, providing vertically resolved information on refractivity and thermal properties with high altitude resolution. In these experiments, a spacecraft’s radio signal is tracked as it propagates through the atmospheric limb, and the resulting changes in its frequency are used to retrieve refractivity profiles and infer temperature and density as a function of altitude.
Over the last two years, Juno has performed numerous radio occultation experiments, significantly expanding the latitudinal and longitudinal coverage of Jupiter’s atmosphere with respect to the Pioneer and Voyager era, and enabling the first close‐up investigations of the planet’s polar regions. These measurements provide a unique opportunity to explore the vertical structure of Jupiter’s atmosphere across a wide range of dynamical regimes. In a subset of the available data, the retrieved temperature–pressure profiles exhibit oscillatory features superimposed on the background stratification, which may be consistent with the presence of wave‐like structures in Jupiter’s atmosphere.
We explore the working hypothesis that such oscillations could arise from gravity‐wave‐induced perturbations of refractivity along the occultation path, which may be preserved in the retrieved vertical profiles. Identifying gravity‐wave signatures in radio occultation data is inherently challenging, as it relies on high‐precision background characterisation and because the expected signals can be comparable in amplitude to background variability and retrieval noise.
To investigate this possibility, we apply a dedicated analysis to the occultation‐derived vertical profiles, aimed at separating large‐scale background structures from smaller‐scale perturbations and testing whether the residuals exhibit coherent, wave‐like properties. The analysis combines diagnostics in both spectral and physical space, allowing candidate signals to be evaluated in terms of their characteristic vertical scales, phase behaviour, and amplitude structure. A conservative approach is adopted throughout, with the objective of minimising false detections in the presence of strong background variability and measurement noise. We will present representative case studies from Juno radio occultations and discuss their implications for the detection and interpretation of potential gravity‐wave signatures in Jupiter’s atmosphere.
How to cite: Fonsetti, M., Caruso, A., Zannoni, M., Tortora, P., Steffes, P., and Bolton, S.: Potential Gravity-Wave Signatures in Jupiter’s Atmosphere from Juno Radio Occultations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20744, 2026.
The equatorial jets observed on the Jovian planets—Jupiter, Saturn, Uranus, and Neptune—exhibit extreme zonal flow patterns, manifesting as either strongly prograde (in the gas giants) or strongly retrograde (in the ice giants). Existing theories have often treated gas giants and ice giants separately, primarily focusing on the differences between deep and shallow dynamics. However, gravity measurements from the Juno spacecraft have revealed that Jupiter's convective envelope may share similarities with those of the ice giants, challenging traditional distinctions between these planetary types and highlighting the potential for a unified explanation.
We present results from a convection-driven anelastic General Circulation Model that introduces a unifying mechanism to explain the equatorial jets on all four Jovian planets. In these simulations, the convective dynamics and planetary rotation drive the formation of tilted convection columns that extend cylindrically from the deep interior to the outer atmospheric layers. These columns play a crucial role in shaping zonal wind patterns, with the tilting of the convection columns introducing asymmetries in momentum transport that lead to the bifurcation of the flow into either superrotation (prograde jets) or subrotation (retrograde jets) in the equatorial region.
Through a detailed analysis of the convection-driven columnar structures, we demonstrate that the equatorial wave properties and the leading-order momentum balance share remarkable similarities across different planetary types. Our findings comprehensively explain the potential for both equatorial superrotation and subrotation under constant physical conditions, thereby elucidating the diverse zonal wind patterns observed on the Jovian planets and providing deeper insight into the mechanisms driving equatorial jet formation. Furthermore, the Juno Microwave Radiometer (MWR) may provide evidence for such tilted convection structures, underscoring the necessity of a thorough understanding of their dynamical contributions.
How to cite: Duer-Milner, K., Gavriel, N., Galanti, E., Tziperman, E., and Kaspi, Y.: From Gas to Ice Giants: A Unified Mechanism for Equatorial Jets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19371, 2026.
Results from the Juno investigation of Jupiter have challenged our understanding of Jupiter origin and evolution. As the archetype of giant planets, the study of Jupiter provides knowledge needed to understand the origin of our own solar system and the planetary systems being discovered around other stars. Jupiter uniquely informs us about the origin of our own planetary system. The mass of Jupiter’s heavy element core and the abundance of heavy elements in the atmosphere discriminate among models for giant planet formation. Measurements by Juno of Jupiter’s gravity field suggest Jupiter’s core is diffuse, extended and contains compositional gradients. These new results require new models of Jupiter’s formation and evolution. The gravity science results on the measurement of J4 coupled to current estimates on the hydrogen and helium equation of state suggests Jupiter’s interior composition has low metallicity, potentially solar or even sub-solar. This is inconsistent with measurements of the atmosphere by both Juno and the Galileo probe which indicate the atmospheric composition is of higher metallicity (2-4x solar).
The combined results from Juno provide new constraints on theories of Jupiter’s formation and evolution and giant planets in general. A summary of Juno’s results relevant to Jupiter’s formation and evolution will be presented along with a discussion of theoretical implications on Jupiter, and giant planets both within our solar system and beyond.
How to cite: Bolton, S., Stevenson, D., Atreya, S., Guillot, T., Galanti, E., Helled, R., Howard, S., Idini, B., Iess, L., Ingersoll, A., Kaspi, Y., Levin, S., Li, C., Lunine, J., Miguel, Y., Militzer, B., Park, R., and Ziv, M.: Juno Results: Implications on the Origin and Evolution of Jupiter and Exoplanets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8735, 2026.
How to cite: Ziv, M., Galanti, E., and Kaspi, Y.: Characteristic Interior Structures of Jupiter and Saturn Revealed with Machine Learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11026, 2026.
Planetary magnetic fields are traditionally modelled as the result of convective dynamo action within a single, well-defined electrically conducting region (e.g., the liquid iron core inside a terrestrial planet or the metallic hydrogen layer inside a gas giant). However, recent theoretical and observational developments suggest that many planetary bodies may host nested dynamo regions, where multiple layers of convection in electrically conducting fluids can support dynamo action. In particular, Juno revealed that in Jupiter there is likely a deep dynamo region in its dilute core as well as a secondary dynamo region, sitting atop a compositionally stable, stratified layer. In this study, we present a suite of three-dimensional magnetohydrodynamic (MHD) numerical models exploring the behaviour and evolution of such nested dynamos.
Our MHD dynamo simulations explore the fundamental differences between nested and single-layer dynamos in a systematic way. These nested dynamos represent the next frontier of planetary dynamo investigations. They are crucial for understanding the dynamics and evolution of these multi-layered bodies and their space environments, which are characterised by their internal magnetic fields.
How to cite: Wulff, P., Cao, H., and Aurnou, J.: A Systematic Exploration of Nested Dynamos, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14518, 2026.
Observations with Juno’s Microwave Radiometer (MWR), taken in late 2022 and covering a longitude range from 70oW to 50oE and a latitude range from ~20oS to ~50oN at frequencies of 0.6, 1.2, 2.5, 5.2, 10, and 22 GHz, allow us to constrain the depth and subsurface structure of Europa’s ice shell. The observed temperature gradient constrains the thickness of the thermally conductive part of the ice shell, and pores or cracks beneath the surface scatter microwaves, enabling us to characterize the size and distribution of the scatterers. Assuming pure water ice, our best-fit model has conductive ice shell thickness 29±10 km, negligible surface reflectivity, volume fraction of scatterers 0.045, scale height of scatterers 219 m, and scatterer size distribution power law index -3.96. The size, depth, and volume fraction of the scatterers suggest that they alone are likely not capable of carrying nutrients between the ocean and the surface. Ice salinity of 15 mg/kg would reduce our estimate of the thickness by about 5 km. A thermally convective layer would increase the total ice shell thickness but only slightly decrease our estimate of the conductive layer. We will discuss these and other complications, as well as next steps.
How to cite: Levin, S., Zhang, Z., Bolton, S., Brown, S., Ermakov, A., Feng, J., Hand, K., Misra, S., Siegler, M., Stevenson, D., McKinnon, W., and Akiba, R.: Europa’s Sub-Surface Ice Observed With The Juno Microwave Radiometer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8470, 2026.
Recent observations by NASA’s Juno mission have revealed
that many of Io’s volcanic hot spots are in fact lava lakes,
characterized by a colder central crust surrounded by a hotter
peripheral ring. In this study, we investigate the thermal properties
of about twenty such lava lakes, providing new constraints on their
structure and energy budget. Our analysis shows that these features
contribute a much larger fraction of Io’s total thermal emission than
previously estimated. We also explore the relationship between the
average temperature of the crust and the evolutionary state of each
lake, offering insights into the frequency of resurfacing processes.
Finally, we propose an improved assessment of Io’s global thermal
output, but we emphasize that only observations that cover the full
surface with sufficient spatial resolution can yield realistic values
for the planet’s volcanic total heat flux.
How to cite: Mura, A., Lopes, R., Radebaugh, J., Mouginis-Mark, P., Tosi, F., Zambon, F., and Bolton, S.: Lava Lakes on Io: crust age and implications for thermal output, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12732, 2026.
Posters on site: Thu, 7 May, 10:45–12:30 | Hall X4
The high-resolution images of Jupiter obtained by the Junocam instrument on the Juno mission show a wide range of small-scale compact clouds suggestive of active convection. These features have horizontal sizes of 10-50 km and have been named in the recent literature as pop-up clouds because of their morphological characteristics [1]. The pop-up clouds appear as elevated towers projecting shadows over different meteorological systems [2, 3], and their appearance seems linked to the type of atmospheric region where they develop (in zones such as the South Tropical Zone, in anticyclones including the Great Red Spot, or in cyclones, and Folded Filamentary Regions and polar regions) [4]. Their shadows indicate cloud tops 5-20 km above their environments, although some observations have found more extreme altitudes for some specific pop-up clouds [2, 3]. Although the vertical structure and overall morphology of pop-up clouds suggest they are analogous to Altocumulus Castellanus [1], the lack of evidences of strong divergence at their cloud tops has also led to comparisons with Cumulus Humilis [4].
Compared with strong Jovian convective disturbances [5, 6], pop-up clouds seem to represent less energetic convective storms compatible with ammonia powered moist convection [1, 3-4]. To investigate these clouds we run simulations of moist convective storms using a three-dimensional cloud resolving model at a spatial resolution of 0.5 km. We run several experiments to investigate cloud top altitudes for ammonia moist convection under a variety of ammonia abundances and environmental conditions and we also explore the energetics of these storms. We show that ascending ammonia cumulus clouds over a surrounding homogenous cloud cannot develop large vertical structures compatible with the lengths of the shadows observed. We explore under which conditions ammonia convective storms can ascend to higher levels when forced from below. We also explore the atmospheric conditions in which ammonia pop-up clouds develop isolated over a deeper homogenous NH4SH cloud [3].
References
[1] Hansen et al. (2019). JunoCam Images of Castellanus Clouds on Jupiter. AGU Fall Meeting Abstracts, 2019, P44A-05. https://ui.adsabs.harvard.edu/abs/2019AGUFM.P44A..05H
[2] Orton et al. (2022). Investigating Relative Cloud Heights in Jupiter Using Juno's JunoCam Imager. AAS/Division for Planetary Sciences Meeting Abstracts #54, 54, 306.06. https://ui.adsabs.harvard.edu/abs/2022DPS....5430606O
[3] Guillot et al. (2024). How high are Jupiter's clouds? From high-resolution JunoCam images to a multi-wavelength analysis. EGU24. doi:10.5194/egusphere-egu24-17351
[4] Palotai et al. (2023). Moist Convection in the Giant Planet Atmospheres. Remote Sens. 2023, 15, 219. doi:10.3390/rs15010219
[5] Sánchez-Lavega et al. (2008). Depth of a strong jovian jet from a planetary-scale disturbance driven by storms. Nature, 451(7177), 437–440. doi:10.1038/nature06533
[6] Sánchez-Lavega et al. (2017). A planetary-scale disturbance in the most intense Jovian atmospheric jet from JunoCam and ground-based observations, Geophysical Research Letters, 44, 4679–4686. doi:10.1002/2017GL073421.
How to cite: Avalle-Gràcia, P., Ullibarri-Lombraña, J., Hueso, R., Iñurrigarro, P., Barrado-Izagirre, N., and Sánchez-Lavega, A.: Cloud resolving models of Jupiter ammonia storms applied to Junocam observations of small-scale convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-491, https://doi.org/10.5194/egusphere-egu26-491, 2026.
Juno’s Microwave Radiometer (MWR) has provided an unprecedented opportunity to explore the dynamical properties and composition of Jupiter’s deep atmosphere. Its visible atmosphere is arguably the most heterogeneous and time-variable in the solar system. Since Juno’s arrival on 2016 August 27, the MWR has observed microwave emission at wavelengths between 1.3 and 50 cm, sensing from 0.7 bar to over 100 bars of pressure, at over 75 close approaches to the atmosphere. A concerted effort has collected MWR-supporting contextual information from other Juno instruments, as well as ground- and space-based observations, sensing the upper atmosphere at complementary wavelengths.
We report here observations of long-term variability in Jupiter over 2016-2025, limited to data with spatial resolutions no worse than 2° in latitude, which have been subject to careful corrections to the calibration drift for all MWR’s channels with an improved relative calibration uncertainty of 0.5% or better over the zonal mean for the entire mission to date. This has allowed us to evaluate long-term variability with confidence that observed variability is not an artifact of receiver drift. The North Equatorial Belt, (NEB: 12°N-16°N) shows the greatest variability with a standard deviation of 2% of the time-averaged 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: 20°N-26°N) in August-September of 2020. In general, the microwave brightness temperature variability often but not always correlates with visible or near- to mid-infrared variability. In some regions, such as the Equatorial Zone (EZ: 3°S-6°N), 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). Because the radiances emitted by Jupiter in the 5-µm spectral region are largely modulated by cloud cover in the 0.7- to 5-bar region, we use such observations as a reference to the variability of cloud-top weather. These observations were made by Juno’s JIRAM instrument and ground-based observations. In general, 5-µm brightness temperatures are anticorrelated with MWR brightness temperatures, explained by an upward motion in a stably stratified atmosphere decreasing NH3 vapor as a function of altitude. The NEB/NTrZ and NTB disturbances are most likely to be caused by baroclinic instabilities that grow fast, return to their initial unperturbed state more slowly and require a lateral density contrast. They do not affect the atmosphere significantly below the 9-bar H2O condensation level. In contrast, the EZ disturbances extend deeper in the atmosphere and are likely to be caused by convective instability, which is more symmetric between its growth and decaying phases and requires a vertical entropy contrast. Current work includes convolving the MWR fields of view over maps of 5-µm radiances to assess whether the measured microwave variability is associated with spatial rather than temporal variability.
How to cite: Orton, G., Zhang, Z., Li, C., Fletcher, L., Levin, S., Oyafuso, F., Brueshaber, S., Wong, M. H., Momary, T., Bolton, S., Baines, K., Dahl, E., and Sinclair, J.: Juno Microwave Radiometer Measurements of the Depths of Spatial and Temporal Variability in Jupiter , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8820, 2026.
Since 2016, the Juno Microwave Radiometer (MWR), has been observing Jupiter’s atmosphere at frequencies of 0.6, 1.2, 2.6, 5.2, 10.0, and 22 GHz. The resulting data set has dramatically altered our understanding of giant planet atmospheres. MWR measurements of Jupiter’s atmosphere have yielded surprising conclusions about Jupiter’s temperature and composition vs depth and latitude, characterized multiple storms in 3 dimensions, and shed light on the global circulation. We will summarize some of the most important findings from MWR, with an emphasis on the most recent results, and describe work in progress as well as future plans. We will also briefly describe how to make use of this valuable data set.
How to cite: Li, C., Steven, L., Bolton, S., and Ingersoll, A. and the Juno MWR Team: Jupiter’s Atmosphere Observed by the Juno Microwave Radiometer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13475, 2026.
We report on new results analyzing Io’s upwelling thermal emission over the range of 0.6 to 22 GHz acquired with the Juno Microwave Radiometer (MWR) in December 2023 and February 2024. The microwave emission spectrum from the surface of Io is retrieved from the MWR calibrated brightness temperatures and represents the vertical temperature gradient in the upper 10s of meters of Io. A large spectral slope (>20K) is observed at all latitudes in the lowest frequency MWR channels suggesting significant endogenic near-surface heating. The spectral slope increases toward the north pole. We compare two end-member model fits to the MWR spectra; a conductive model and a model comprising cooling lava flows. The conductive model implies heat flows ranging from 1-3 W/m2. The alternative model of relatively fresh lava flows or heat vents covered by a cold, highly insulating crusts fits the MWR spectra with flows covering about 10% of the surface with a 3-8m thick crust. We show the regional distribution of sub-surface temperature anomalies with depth, comparing to previously catalogued hot spots, flow units and volcanic centers. We will discuss how model assumptions, such as the microwave loss tangent of the crust material and magma temperature, impact the results.
How to cite: Brown, S., Adumitroaie, V., Bolton, S., Ermakov, A., Feng, J., Levin, S., Siegler, M., and Zhang, Z.: Distribution of Sub-surface Heating on Io, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14124, 2026.
Radio occultation experiments constitute a powerful tool for probing the vertical structure of planetary atmospheres and ionospheres. Recently, the Juno mission has enabled a new generation of radio science investigations of Jupiter, allowing the characterization of its ionospheric electron density with a spatial resolution and latitudinal coverage not previously achievable. In this contribution, we present recent results from Juno radio occultation experiments conducted during the spacecraft’s extended mission, with a focus on their implications for the morphology and variability of Jupiter’s ionosphere.
As Juno passes behind Jupiter’s limb relative to Earth-based antennas, its radio signal propagates through the planet’s neutral atmosphere and ionized layers, undergoing refraction. This effect is observed as a deviation in the signal frequency received by NASA Deep Space Network antennas, compared to propagation through free space. The ionospheric contribution is inherently frequency-dependent and can be separated from non-dispersive effects associated with neutral refractivity and spacecraft motion by exploiting Juno’s dual-frequency radio links. In particular, this analysis is based on simultaneous X-band and Ka-band observations. Vertical electron density profiles are subsequently retrieved through an inversion procedure based on the ray-tracing technique, which accounts for Jupiter’s oblateness and assumes local axial symmetry of the ionosphere. A rigorous uncertainty assessment is performed using Monte Carlo simulations, allowing the propagation of measurement noise into confidence intervals for the retrieved profiles.
The data set considered here includes multiple occultation events acquired since mid-2023, at an approximate monthly cadence near perijove. Some of these events sample high-latitude regions in the northern hemisphere, providing new constraints on the ionospheric structure in proximity to the main auroral oval. The new results add to the occultations previously conducted by Pioneer, Voyager, and Galileo, providing us with a large data set. All these measurements reveal significant variability in peak electron density and vertical layering with latitude, longitude, and solar illumination conditions, and also point to a potential influence of magnetic field variations on ionospheric dynamics.
These observations provide new insights into Jupiter’s ionosphere and place important constraints on physical and empirical models. This work demonstrates the continued scientific return of Juno radio occultations and their relevance for the interpretation of future measurements from upcoming missions such as JUICE and Europa Clipper.
How to cite: Caruso, A., Fonsetti, M., Coffin, D., Buccino, D., Smirnova, M., Gomez Casajus, L., Zannoni, M., Galanti, E., Withers, P., Tortora, P., Park, R. S., Kaspi, Y., Parisi, M., Hubbard, W., Orton, G., Steffes, P., and Bolton, S.: New Constraints on Jupiter’s Ionosphere from Juno Radio Occultations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14571, 2026.
The Juno Extended Mission (EM) included close fly-bys of Jupiter’s moons Ganymede, Europa and Io between 2021 – 2024. Juno carries a 6-channel microwave radiometer (MWR) operating between 0.6-22 GHz. The broad frequency range of the MWR probes successively deeper into the sub-surface of these bodies with the 0.6GHz channel probing the deepest. For Ganymede and Europa, the MWR is sensitive to the temperature from the surface to 10s of km into the ice shell over the six frequencies. For Io, the penetration is much shallower, on the order of 10s of meters maximum depth. The sub-surface temperature, dielectric and surface roughness properties are encoded in the spectra obtained by the MWR. We will provide an overview of the latest analysis of data from each moon, focusing on the new information gained from this unique planetary instrument. This includes ice shell thickness, surface/sub-surface composition and heat flow for the icy moons. For Io, the MWR data provide the latitudinal dependence of the temperature below the diurnal layer and the spectra indicate significant endogenic heating in the upper 10-20 meters that increases with latitude. The MWR was designed for observing the deep atmosphere of Jupiter but has now demonstrated unique capability for observing the sub-surface of terrestrial planets and planetary moons. From lessons learned analyzing Juno MWR data, we will discuss how future instruments could be configured specifically for targeting icy or rocky solar system bodies.
How to cite: Brown, S., Bolton, S., Levin, S., and Zhang, Z.: Peering into the Sub-surface of Jovian Moons with Microwave Radiometry: Latest Findings from the Juno Extended Mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15803, 2026.
Saturn's magnetosphere, shaped by solar wind interaction with its dipole field, differs from Earth's due to faster rotation and Enceladus's internal plasma sources. An ongoing focus of investigation is how the internal plasma sources and rapid rotation result in a different global magnetospheric picture. The magnetospheric cusp, a crucial interaction region between solar wind and planetary magnetic field, serves as an indicator of global magnetic configuration. Here we utilize Cassini observations from 2004 to 2010 to study dawn-dusk asymmetry in Saturn's cusp distribution with peak occurrence in the post-noon sector and signatures extending to post-dusk, resembling recent observations of Jupiter's post-dusk cusp. We further examine magnetic topology using high-resolution magnetohydrodynamic simulations to visualize the cusp asymmetry, providing a global view of Saturn’s magnetic topology near the magnetopause. This asymmetry of cusp distribution demonstrates how rapid rotation and internal plasma sources fundamentally alter magnetospheric configuration, offering insights for understanding other rotating planetary systems within and beyond the solar system.
How to cite: Xu, Y., Yao, Z., Arridge, C., Zhang, B., Chen, J., Badman, S., Ray, L., Coates, A., Ye, S., Qin, T., Zheng, Z., Dunn, W., and Wei, Y.: Global Distribution of Saturn’s Cusp, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15808, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 4
EGU26-5870 | ECS | Posters virtual | VPS27
Juno Constraints on Io’s Interior: Tidal Response and Melt StabilityMon, 04 May, 16:15–18:00 (CEST) vPoster Discussions
Jupiter’s moon Io is the most volcanically active body in the Solar System, powered by intense internal heating due to tidal dissipation. Although tidal friction is widely accepted as the main energy source, how this heat is distributed within Io and how it shapes the moon’s internal structure remain open questions. In this study, we use Io’s tidal response, quantified through the degree-2 Love number (k2), to constrain its interior, using recent estimates derived from Juno observations (Park et al., 2025).
We model Io with a three-layer structure consisting of a fluid core, a viscoelastic mantle, and a crust, using an adapted version of the California Planetary Geophysics Code (CPGC). Tidal dissipation is self-consistently coupled to mantle rheology through an Andrade model, with viscosity and shear modulus updated as functions of the local melt fraction. We explore two end-member scenarios that differ in the treatment of the Andrade parameter β: in the first, β is held constant, representing a uniform dissipation regime dominated by deep-mantle heating; in the second, β varies with depth, allowing dissipation to be preferentially localized in the upper mantle. In both scenarios, viscosity and shear modulus evolve with melt fraction.
Our results identify several partially molten mantle configurations whose real part of k2 is consistent with Juno constraints. In all acceptable models, melt fractions remain below the threshold required to form a global magma layer. To test the physical viability of these states, we compare thermodynamic melt production with the capacity for melt migration. We find that melt transport is efficient enough to prevent long-term melt accumulation, favoring a stable, partially molten “magma sponge” rather than a global magma ocean. These results provide new constraints on Io’s thermal state and are consistent with independent estimates of its global volcanic output.
How to cite: Paris, M., Mura, A., Zambon, F., Genova, A., Tosi, F., Piccioni, G., Consorzi, A., Mitri, G., Sordini, R., Noschese, R., Cicchetti, A., Plainaki, C., Bolton, S., and Sindoni, G.: Juno Constraints on Io’s Interior: Tidal Response and Melt Stability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5870, 2026.
