The Io Plasma Torus (IPT) plays a key role in the workings of the Jupiter System at large. It is a complex system driven by Io’s volcanism and surface-atmosphere that interacts with numerous Jupiter System objects. Despite significant and varied modelling efforts, the description of its spatial structure and temporal variability remains challenging, especially because of insufficient data coverage.In this EGU Poster, we analyze the IPT's spectral emissions and spatio-temporal dynamics to establish the optical specifications for a future ground-based observation system. Our main conclusions are as follows:1- Temporal variability: the large diversity of objects in the Jupiter System with which the IPT interacts, and the complex, highly non-linear nature of these interactions, contribute to the strong observed temporal variability of the IPT, which displays a broad range of time scales, from hourly to multi-decadal. Capturing all timescales requires hourly, intercalibrated observations, necessitating dedicated space platforms and/or a longitudinal ground network.2- Spatial scales: the Io system includes interconnected objects of very different spatial extensions, from tens of km with Io’s volcanoes and plumes, to more than 1000 Rj with the nebula(e). Hence, an observation system covering the Io system in a comprehensive way will need to combine observations with very diverse spatial coverages, from sharp AO observations (e.g. 0.02’’ achieved with the LBT) to 5.5°.3- Spectral extension: electromagnetic emissions generated by the Io system cover a very large part of the electromagnetic spectrum, and the different components of the system emit to a large part in different wavelength ranges and in the different spectral lines corresponding to different neutral and ionized species. Hence, a combined set of telescopes covering this system in a comprehensive way will have to optimally combine observations of different spectral lines in different spectral ranges. 4- Complementary observations: beyond the body of UV / EUV observations from space, ground-based observations over the last 50 years have also borne very valuable fruit. Indeed, instrumentation necessary to image the IPT does not necessarily need to be expensive: simple designs using smart "amateur-class" equipment already allow for the observation of the brightest lines. As spaceborne and ground-based observations offer complementary advantages and limitations, a future comprehensive observation system for the IPT will likely have to combine both.Given stringent time resolution constraints, and aiming at an affordable budget envelope, the development of a longitudinal network of telescopes appears as particularly cost-effective and promising. It could build on the successful IPT telescopes that already exist in different longitude sectors and complement them with one or several ones at key locations, including the European and African sectors. In France, such an effort will be coordinated at the national level, allowing one to take full advantage of synergies between radio observations at Nançay and new optical observations. In this poster, we outline design guidelines for a smart, multi-site, multi-spectral system capturing the IPT's spatiotemporal dynamics and coupling processes that will address the choice of telescope as well as of the spatial (coronagraph) and spectral (color filters) filtering systems.

Io and its torus, the “Io System” for short, play a key role in the global dynamics of the Jupiter System. While Io’s interior is heated by tides, its extended gas and plasma tori, driven by Io’s volcanic activity, feed mass, momentum and energy into the magnetosphere and its fast-spinning magnetodisk. The complex interplay between these different elements results in a highly dynamic system, whose variability spans a broad range of timescales, from hours to decades and more, and remains poorly understood. Despite the current limitations in our knowledge of the Io system, progress in understanding its variability will directly translate into a better understanding of the mechanisms driving this variability, and as a direct consequence, into a much better grasp of the drivers and variabilities of the Jupiter System as an integrated whole.

Every modern scientist faces the challenge of building a community to promote their project and turn it into a reality. But how do we move from a fragmented group of individuals to a proactive, recognizable, and collaborative network? In this presentation, I will share candid lessons from two long-term case studies from my career: the birth and growth of EUROPLANET, and the transatlantic build-up of the Jupiter exploration community.Case Study 1: EUROPLANET – From National Silos to a European IdentityWorking on the Cassini-Huygens mission in the 2000s, a small group of European scientists made a frustrating discovery: Europe had a large, talented planetary science community, but it was insufficiently visible. We worked in national silos (French, German, Italian, UK, etc.), competing quietly rather than collaborating openly. With encouragement from ESA, we decided to target the EU Framework Programme—not with a pure science proposal, but with a network proposal. The goal was community-building itself. One of the key difficulties was to get acquainted with the funding schemes and selection procedures of the Framework Programme, and to understand how to do lobbying towards the Commission. We won in 2004. EUROPLANET was born in 2005, on the year of the landing of Huygens on Titan, and has been growing continuously over two decades.What worked?Lobbying & Stakeholders: We identified key players outside science—EU officers and ESA management. They became our community’s sponsors, giving us legitimacy.Building Identity: We created a strong brand (name, logo, motto) deliberately. "EUROPLANET" signaled "European, not national." This gave a fragmented group a single, recognizable face at conferences and in media.The Catalyst Effect: Winning the first EU grant encouraged people to collaborate. That mandatory collaboration built trust that outlasted the funding.What didn't work? Assuming that shared scientific interest alone would unite us. Of course it helped – we had a common language and shared interest. But we needed a political and financial framework on top of it.Case Study 2: The Jupiter Exploration Community – Transatlantic SynchronizationSimultaneously, in the wake of the successful Cassini-Huygens transatlantic collaboration experience, interest in Jupiter (and Europa) grew on both sides of the Atlantic: as Jupiter and its fascinating Galilean moons appeared as the next logical step after Saturn and Titan. But Europe and the US were working independently—risking duplication or, worse, no mission at all. Using the nascent EUROPLANET network and personal contacts at NASA, we deliberately built a transatlantic community of scientists, engineers, and agency representatives before any mission was selected. Even Japan and Russia joined at the time, in what was named the EJSM-Laplace collaborative study.What worked?Diversity & Inter-cultural Tensions: European and US funding cycles, meeting cultures, and decision-making styles differ dramatically. We succeeded by acknowledging these tensions openly—alternating meeting locations, co-authoring white papers, and explicitly discussing cultural differences rather than pretending they didn't exist.Exchange Tools (pre-social media): Before modern platforms, discipline mattered more than tool. Regular telecons, shared document repositories, and dedicated email lists created a rhythm of communication.Involving the Public: The Jupiter community early-on engaged amateur astronomers for observing campaigns (e.g., impacts on Jupiter). This turned citizen science into a community-building tool that produced publishable data and public visibility.What didn't work? Waiting for agencies to solve the coordination problem. They were busy. We had to build the community first—then the agencies followed. In the end, while the two agencies developed their two missions independently, JUICE and Europa Clipper will execute together a cosmic ballet around Jupiter in the 2030’s!Key Takeaways for Any ScientistFrom these two experiences, I learned that community-building is not a "soft skill." It is a strategic activity requiring the same planning, risk-taking, and persistence as a space mission. Keys to success include (but are not limited to):Agency endorsement (ESA/NASA) is a powerful catalyst. Use it to bring skeptical scientists to the table.A strong brand (logo, motto, name) is not superficial. It creates mental shortcuts for a fragmented community to self-identify.Build the community before the project. For Jupiter, the community existed before the mission was approved—which made the mission inevitable.Explicitly manage cross-cultural tensions. Do not ignore them. Name them. Structure your meetings to address them.Citizen science is a low-stakes, high-reward entry point for public engagement that also strengthens internal community bonds.Building a community around a project remains “learning by doing” experience: everyone who believes in a beautiful and strong project should go that path. But the greatest lesson I learnt from these two experiences is this: beyond the success of the project itself, it is being part of the community that carries it out that is the most valuable and rewarding experience, for us humans.

Ganymede, the only satellite in the Solar System possessing an intrinsic magnetic field, is continuously immersed in Jupiter’s magnetosphere. The relative motion of this conducting body through the jovian magnetic field, together with the presence of closed magnetic field regions around Ganymede, leads to the precipitation of energetic electrons along these closed field lines, producing ultraviolet auroral emissions.In sunlit auroral regions, these emissions are superimposed on the solar radiation reflected by the surface, making an accurate knowledge of the surface spectral reflectance essential for a proper interpretation of the observed UV spectra.We used Juno/UVS observations obtained during the 34th perijove to derive the spectral reflectance of Ganymede’s surface in the 140-205 nm range. The analysis was performed with a non-local thermodynamic equilibrium radiative transfer model initially developed for auroral emission studies, which self-consistently includes the reflection of the incident solar flux by the surface. By fitting the UVS spectra in illuminated auroral regions, we retrieved spatially resolved reflectance values.The inferred reflectance exhibits strong spatial and spectral variability, ranging from about 0.1% to 8% over the [140-205] nm interval, revealing a highly heterogeneous surface. This variability is likely the signature of long-term irradiation by energetic particles, which modifies the physical structure, crystallinity, and chemical composition of surface ice. The resulting UV reflectance maps show no clear correlation with visible-wavelength surface morphology, indicating that irradiation-driven processes dominate over geological features in controlling the UV albedo.These new reflectance constraints constitute a key input for future modeling of Ganymede’s ultraviolet aurora and will be particularly valuable for the interpretation of upcoming observations by the JUICE/UVS instrument.

Context . Ganymede is the only moon in the Solar System with an intrinsic magnetic field that actively interacts with the Jupiter magnetosphere. This precipitates energetic electrons that generate ultraviolet (UV) auroral emission. Aims . In sunlit auroral regions, the observed emission partly overlaps with the solar continuum reflected by the surface. An accurate modeling of the observed UV spectra therefore requires precise knowledge of the surface spectral reflectance. Methods . We analyzed Juno/UVS data acquired during the 34th perijove (PJ) flyby to constrain the Ganymede surface reflectance in the 140−205 nm range. We used the non-local thermal equilibrium radiative transfer model originally developed to simulate the auroral emission of Ganymede, which also accounts for the reflection of solar flux by the satellite surface, to fit the observed spectra in sunlit auroral regions. Results . Our results revealed that the reflectance varies strongly spatially and spectrally from 0.1% to 8% in the [140 nm; 205 nm] wavelength range. This indicates a significant surface heterogeneity. This variability likely reflects long-term interactions between the icy surface of Ganymede and precipitating energetic particles, which alter the ice structure and crystallinity and its chemical composition. In addition, the derived reflectance maps show no clear correlation with the visible surface features of Ganymede, suggesting that the UV reflectance is primarily shaped by irradiation-driven processes and not by the geological morphology. Conclusions . The resulting reflectance maps provide a critical input for future UV auroral emission modeling, particularly in preparation for observations by the Juice/UVS mission.

We review the key observations and theories relevant to the origin and evolution of the Galilean satellites. Key observations include: the potentially undifferentiated nature of Callisto; the increasing ice fraction with semi-major axis; the present-day existence of the Laplace resonance; the potential resurfacing of Ganymede mid-way through its evolution; and the metal-enriched nature of Jupiter’s envelope. The most widely accepted theory for the formation of the satellites is the so-called “starved disk” model, although newer alternatives including decretion disks and pebble accretion have also been proposed. Models that allow slow satellite formation in a cold disk are preferred, based on the density progression and Callisto’s apparent differentiation state. Major model uncertainties include the angular momentum distribution of the material infalling to the circumplanetary disk, the source of the solids, and the thermal and viscosity structure of the disk. We identify six outstanding questions, some of which will be answered by JUICE, Europa Clipper and Tianwen-4. A major difficulty in answering some questions is overprinting of primordial characteristics by later events.

The Lower Thermosphere–Ionosphere (LTI) is the interface region between the Earth’s atmosphere and space. It is modulated by the energy and momentum deposition from the magnetosphere above and by the impacting waves from the lower atmosphere. The LTI region is defined by the co-existence and interaction of neutral and ionized species within the region’s electric and magnetic fields. This interplay results in unique and complex interactions between neutrals and plasmas, that are not fully understood and quantified to this date. In this paper we present an overview of some of the most important open questions related to ion/neutral coupling and the resulting collisional electrodynamics, collisional energetics and collisional dynamics processes. We outline the key reasons for addressing these questions, and highlight methodologies that can lead to their closure in the upcoming years.

The new phase of exploration offers multiple perspectives, for the space community and for many other sectors of activity. But it also brings some threats to the preservation of scientific research and environmental stewardship of Mars. A proactive integration of environmental awareness into the new wave of exploration will be the best way to mobilize public and private stakeholders, federate their resources and their creativity, and preserve for future generations the natural environment of Mars. The new wave of robotic and sample return from Mars will hopefully take place in an era of increased environmental awareness for our own planet, in which close monitoring of environmental impacts of human activities will drive innovative solutions to mitigate themIn this presentation we describe land-use and management policies by various countries and U.S. Agencies in an effort to balance environmental preservation, resource utilization and economic interests. In particular we compare the U.S federal land management system and ecotourism policies with preservation of natural landscapes and resource use. We describe the Mars Sample return re-re-design concepts from the eight selected teams with regard to sustainable exploration of Mars.

The moon Io, the most volcanically active body in the Solar System, functions as the “energy converter” of the Jovian environment: tidal heating by Jupiter and its Galilean satellites powers intense outgassing that sustains both the neutral and plasma tori and feeds the Jovian magnetodisk via centrifugal processes. Spacecraft traversals and remote observations, from ground‐based telescopes to JAXA’s Hisaki, have revealed the Io Plasma Torus’s (IPT) intricate spatial architecture and variability across timescales from hours to decades. Yet, fully characterizing the drivers of IPT structure and magnetospheric dynamics remains an open challenge. In this respect, NASA’s Juno mission, in its highly inclined, low‑perijove trajectory, provides in situ measurements of magnetic perturbations, plasma composition and abundance, through both plasma wave and radio occultation experiments, while refining tidal‐dissipation models through gravity science. Complementarily, a future network of longitudinally distributed Earth‑based observatories will deliver continuous, global monitoring of auroral emissions and torus brightness, capturing rapid fluctuations that single‐station views cannot. The synergy of Juno’s detailed local sampling and round‑the‑clock remote surveillance promises a holistic view of source–sink interactions driving Jupiter’s magnetosphere and the Io torus.

An accurate knowledge of the orientation, the tidal deformability, and the gravity field of a celestial body is fundamental to provide constraints on its internal structure. These quantities may be retrieved by processing radiometric tracking and altimetry data from a probe in orbit around such body. This paper presents a method to combine altimetry crossovers with two-way Doppler tracking observations at normal equation level, using the Bernese GNSS Software and the pyXover software library. This method was applied to a proposed 200km altitude orbiter around Callisto, a privileged destination for the upcoming phase of Solar System exploration. Enhancing “standard” Doppler tracking with altimetry generally benefited both orbit determination and a joint estimation of the orientation of the north pole and of planetary librations. The retrieval of low-degree gravity field parameters was also improved by the addition of altimetry data. However, the improvements on the estimated parameters were highly dependent on the characteristics of the simulation, e.g., the underlying topography roughness. Overall, combining radioscience with altimetry data accounted for a visible reduction of correlations among estimated parameters, while also allowing for a consistent estimation of the “vertical” Love number h2 along with gravity.

The interchange instability drives the concurrent cold iogenic plasma convection and energetic particle injection in the Jovian inner magnetosphere. We use an improved Rice Convection model-Jupiter to simulate plasma transport under a more realistic magnetic field configuration, which is determined by magnetodisc currents. A series of runs were conducted to parametrically investigate the effect of the magnetic field configuration on the convection system. Simulation results show that the azimuthal magnetodisc current significantly influences plasma convection. The asymmetry in the longitudinal distribution of the azimuthal current strongly enhances the longitudinal asymmetry in the initial stage of magnetospheric evolution. The instability and associated plasma radial velocity tend to increase with increasing current intensity. By the quasi-steady stage, the longitude-averaged mass flux remains similar and is largely unaffected by variations in current intensity. The longitudinal asymmetry also becomes less pronounced during this phase. The radial current has little effect on the convection system, while the magnetic tilt angle can slightly reduce the instability.

Recent observations from the Juno spacecraft during its transit over flux tubes of the Galilean moons have identified sharp enhancements of particle fluxes at discrete energies. These banded structures have been suspected to originate from a bounce resonance between particles and standing Alfven waves generated by the moon-magnetospheric interaction. Here, we show that predictions from the above hypothesis are inconsistent with the observations, and propose an alternative interpretation that the banded structures are remote signals of particle absorption at the moons. In this scenario, whether a particle would encounter the moon before reaching Juno depends on the number of bounce cycles it experiences within a fixed section of drift motion determined by moon-spacecraft longitudinal separation. Therefore, the absorption bands are expected to appear at discrete, equally-spaced velocities consistent with the observations. This finding improves our understanding of moon-plasma interactions and provides a potential way to evaluate the Jovian magnetospheric models.

This article explores the different formation scenarios of the Kronian moons system in the context of a highly dissipative Saturn, with the objective of identifying the most likely of these scenarios. First, we review the diversity of objects – moons and rings – orbiting solar system giant planets, and the diversity of their architectures, which formation scenarios must reproduce. We then identify in this broader context the specific features of the Saturn system, such as the particularly large spectrum of its moon masses, the uniqueness of Titan and the presence of both dense and tenuous rings, before discussing the applicability of the different giant planet moon formation scenarios to the Saturn case. We discuss each of the most relevant scenarios and their respective merits. Finally, we tentatively propose a “favorite” scenario and we identify the key observations to be made by future space missions and/or Earth-based telescopic observations to validate this scenario or possibly alternative ones.

The magnetospheres of gas giants are characterised by their strong magnetic fields, the fast rotation of the planet and the presence of embedded active moons (Io at Jupiter, Enceladus at Saturn), releasing neutral gas and, from there, plasma in the innermost regions of the systems. Their dynamics is believed to be controlled by a balance between the centrifugal force acting on cororating plasmas trapped in the planetary magnetic field, plasma pressure gradients and magnetic forces. This balance determines the rate of outward transport of mass, angular momentum and energy and has a strong influence on the global configuration and dynamics of the magnetospheres. It results in the formation of a magnetodisk of plasma at the planetary equator, and a global outward transport of plasma from the innermost source regions to the outer magnetosphere where it is lost through magnetospheric boundaries or downtail. Until now, description of this transport has followed two different approaches in the literature. “Corotation enforcement” models focus on the description of angular momentum transport in a disk exchanging momentum with the planetary thermosphere/ionosphere via electric current systems transferring magnetic torques. They assume mass and conservation but do not explicitly describe the transport processes through the magnetodisk. On the contrary, radial diffusion models do not explicitly take into account angular momentum transport nor exchanges between the planet and the magnetospheric plasma, but they describe radial transport of mass and energy assuming a certain state of turbulence in the magnetodisk. We present a unifying approach of the radial transport of mass, angular momentum and energy, using turbulent diffusion and including sources and sinks of plasma of arbitrary radial distribution throughout the disk. Our set of coupled equations independently describes momentum exchange with the two conjugate ionospheres, thus allowing for the study of interhemispheric asymmetries, such as the ones revealed by Juno, in this coupling. We will present solutions of our coupled set of transport equations that explore the different possible causes and effects of interhemispheric asymmetries in magnetodisk/planet coupling, with emphasis on the cases of latitudinally thin and thick disks corresponding respectively to the cases of Jupiter and Saturn. We will compare the outputs of our models with recent observational constraints brought by the Juno and Cassini missions.

Abstract Injection flux tubes, characterized by localized equatorial magnetic field enhancements and concomitant hot plasma populations, contribute to Saturn's magnetospheric convection cycle by transporting magnetic flux radially inward. The sharp magnetic gradients at the flux‐tube edges have been demonstrated to enable the trapping of equatorially mirroring particles, leading to their energy‐dispersionless signatures in spacecraft observations. Here, we present a statistical distinction between flux tubes with and without particle‐trapping features in the electron cyclotron harmonic (ECH) wave properties. The particle‐trapping flux tubes carry stronger ECH waves in the high‐harmonic bands, whereas the other category is usually accompanied only by fundamental‐mode waves. This distinction is largely attributed to the higher content of energetic electrons within the particle‐trapping flux tubes. These results improve our understanding of the association between injection flux tubes and the high‐band ECH waves therein, suggesting a unique role of particle‐trapping flux tubes in Saturnian magnetospheric dynamics.

Jupiter's moon Callisto orbits in a highly variable magnetospheric environment depending on its position relative to the Jovian current sheet. The Juno and Galileo missions have visited the Jovian magnetosphere and crossed Callisto's orbit several times in a variety of configurations, providing an opportunity to better characterize Callisto's orbital environment. The aim of this work is to characterize the variability of Jupiter's magnetospheric environment properties at Callisto's orbit. After identifying the time intervals during which both missions crossed the moon's orbit, Juno's charged particle data from the Jupiter Energetic Particle Detector Instrument and the Jovian Auroral Distributions Experiment are combined to build composite spectra of the electron differential fluxes and derive the electron density and pressure. Based on these observations, we provide empirical models of the energy spectrum of the electron flux for different positions. The electron densities and pressures estimated from our composite energy spectra vary from 0.2 cm −3 and 0.1 nPa, respectively, at the center of the current sheet to 0.009 cm −3 and 0.004 nPa, respectively, outside. We compare these observations with those obtained by the Energetic Particles Detector onboard Galileo, which reveal an additional variation of electron fluxes with local time, possibly due to a variation of the current sheet thickness. A similar comparison of magnetic field observations with the latest magnetic field models shows a good agreement. These results can be used for studying the moon‐magnetosphere interactions in preparation for the arrival of the Jupiter Icy Moons Explorer, which will perform multiple flybys of Callisto.

The dynamics of giant planet magnetospheres is controlled by a complex interplay between their fast rotation, their interaction with the solar wind, and their diverse internal plasma and momentum sources. In the ionosphere, the Hall and Pedersen conductances are two key parameters that regulate the intensity of currents coupling the magnetosphere and the ionosphere, and the rate of angular momentum transfer and power carried by these currents. We perform a comparative study of Hall and Pedersen conductivities and conductances in the four giant planets of our Solar System - Jupiter, Saturn, Uranus and Neptune. We use a generic ionospheric model (restraining the studied ions to H3+ ${\mathrm{H}}_{3}<^>{+}$, CH5+ ${\text{CH}}_{5}<^>{+}$, and meteoric ions) to study the dependence of conductances on the structure and composition of these planets' upper atmospheres and on the main ionization sources (photoionization, ionization by precipitating electrons, and meteoroid ablation). After checking that our model reproduces the conclusions of Nakamura et al. (2022), at Jupiter, that is, the contribution of meteoric ions to the height-integrated conductances is non-negligible, we show that this contribution could also be non-negligible at Saturn, Uranus and Neptune, compared with ionization processes caused by precipitating electrons of energies lower than a few keV (typical energies on these planets). However, because of their weaker magnetic field, the conductive layer of these planets is higher than the layer where meteoric ions are mainly produced, limiting their role in magnetosphere-ionosphere coupling.

The interchange process is an important mechanism for radial transport of plasma in the magnetospheres of the gas giants, namely Jupiter and Saturn. During this process, dense and cold flux tubes that move outwards are replaced by returning flux tubes with warm and tenuous plasma. In this study, we conduct a statistical analysis of the magnetic variation and plasma properties inside the returning flux tubes, based on the observations from magnetometer (MAG) and JADE onboard the Juno spacecraft during its first 45 perijove traverses. We detect the returning flux tubes by recognizing the low-energy electron flux sudden drop, within the range of M < 20 R _J (Jupiter radii). The results have illustrated that the flux tubes with increased magnetic field account for the majority of the events. There is no significant relationship between the events with increased or decreased magnetic field and magnetic latitude, and both types of events are observed mostly near the equatorial plane, while events with depressed magnetic field are more frequently observed at larger distances from Jupiter with longer time duration (or larger flux tube volume). Furthermore, the crossover energy separating decreased low-energy electron flux and increased high-energy electron flux of the returning flux tubes is around several keV, depending on the type of magnetic field variation. These results provide great insight into the mass and magnetic flux transport in the inner Jovian magnetosphere.