NASA’s Europa Clipper spacecraft successfully launched on 14 October 2024, on its interplanetary journey to Jupiter, where it will repeatedly encounter Europa during low-altitude (generally 25–100 km) flybys designed to enable exploration of the satellite and investigate its habitability. Europa Clipper’s 5.5 yr cruise includes gravity assists at Mars (1 March 2025) and Earth (1 December 2026). The spacecraft will enter orbit around Jupiter (11 April 2030) and will perform 49 science flybys of Europa over a 4.3-yr Jovian tour.
To explore Europa as an integrated system and achieve a complete picture of its habitability, the Europa Clipper mission has three main science objectives: Characterization of: (1) the ice shell and ocean including their heterogeneity, properties, and surface–ice–ocean exchange; (2) Europa’s composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) Europa’s geology including surface features and localities of high science interest. Additionally, several cross-cutting science topics will be investigated through searching for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. These science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS) consisting of a wide and a narrow angle camera (WAC, NAC), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments are the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be obtained using the spacecraft’s telecommunication system, and valuable scientific data will also be acquired by the spacecraft’s radiation monitoring system.
As of this writing, the spacecraft is performing extremely well on its way toward the Mars gravity assist. Deployments of the ECM boom and REASON antennas has been successful. All initial subsystem and instrument functional checkouts are complete and also have been a success. The Europa Clipper team is nearing completion of publication of a set of manuscripts in a topical collection of Space Science Reviews, and the science team continues to work towards optimizing science return through preparation of the mission’s Strategic Science Planning Guide. Joint discussions continue on potential opportunities for unique collaborative science with ESA’s JUpiter ICy moons Explorer (JUICE) mission, which will overlap in its tour period at Jupiter.
This work is supported by NASA through the Europa Clipper Project.
How to cite: Pappalardo, R., Korth, H., and Buratti, B. and the Europa Clipper Science Team: Europa Clipper Post-Launch Update , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7629, https://doi.org/10.5194/egusphere-egu25-7629, 2025.
Following its launch on April 14, 2023, aboard an Ariane 5 rocket, the European Space Agency’s JUpiter ICy moons Explorer (JUICE) mission is on its way to rendezvous with the Jupiter system in 2031. JUICE will investigate the conditions that may have led to habitable environments on Jupiter's icy moons—Europa, Callisto, and Ganymede. Equipped with a comprehensive suite of 10 state-of-the-art scientific instruments and one experiment, the spacecraft will study the Jupiter system, including the planet's atmosphere and magnetosphere together with the structure and local environments of the Galilean moons, to better understand the complex interactions at play.
Ganymede, the largest moon in the Solar System, will be the primary target of the mission due to its potential as a natural laboratory for studying icy worlds and water worlds. Its unique magnetic interactions with Jupiter, coupled with its role within the Galilean satellite system, make it an invaluable target for exploration.
JUICE’s 8-year journey includes four gravity assists, and the first one, a first of its kind Lunar-Earth flyby, took place in August 2024. At that time, JUICE passed 750 km above the Moon and 6,800 km above Earth, operating all instruments successfully and confirming their excellent scientific performances.
Upon arrival at Jupiter, JUICE will perform 62 orbits spread over more than three years, performing numerous flybys of Europa (2), Callisto (23), and Ganymede (11), before entering into orbit around Ganymede for an additional 10 months; this final orbit will be initially elliptical and circular at high altitude, followed by a 5-month period in circular orbit at altitudes of 500 km and then 200 km.
This presentation will provide an overview of JUICE’s mission objectives, its past activities and current status, as well as the next steps in the mission cruise phase.
How to cite: Vallat, C., Altobelli, N., Witasse, O., Belgacem, I., Cappuccio, P., Costa, M., and Kotsiaros, S.: The ESA's Juice mission status, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21485, https://doi.org/10.5194/egusphere-egu25-21485, 2025.
Launched in April, 2023, ESA’s JUpiter ICy moons Explorer (JUICE) is now two years into its journey to the Jupiter system. Upon arrival in 2031, the spacecraft will orbit Jupiter for 3.5 years, making 35 total encounters with Ganymede, Europa, and Callisto, before going into orbit about Ganymede for 1 year. NASA’s Europa Clipper successfully launched in October 2024, and arrives in the Jupiter system in 2030, more than a year before JUICE. Orbiting Jupiter, the Clipper spacecraft will spend a year in the system before focusing on ~52 flybys of Europa during a nominal three-year primary mission phase, while also making multiple serendipitous flybys of Ganymede and Callisto.
A preliminary analysis of potential joint science opportunities has been conducted by a small team of scientists from the JUICE and Clipper mission teams. Ideas have been collated from JCSC members as well as from three joint Clipper-JUICE workshops (2018, 2019, 2022), and the Science Traceability Matrix from a prior joint ESA-NASA study, the Europa Jupiter System Mission (EJSM). We have produced two reports on science that can be accomplished during the two spacecrafts’ cruise and Jupiter approach phases, and potential opportunities once JUICE and Clipper are both in orbit around Jupiter. For the former, we note that cruise represents a rare occasion for joint measurements of interplanetary space between the orbits of Mars and Jupiter, and an unprecedented opportunity for an upstream solar wind monitor (JUICE) during approach to the Jupiter system once Clipper is already orbiting Jupiter. For the latter, we find that the presence of two flagship-class, well-instrumented spacecraft in the Jovian system during the same 4.3 year period affords extraordinary opportunities to increase the science return beyond that possible from each mission alone. Joint observations are possible of all four Galilean satellites, the Jovian rings and small satellites, Jupiter’s atmosphere, and the magnetosphere. 100 potential joint science objectives have been identified, of which 50 are considered high priority. These include many synergistic measurements; some which would take place contemporaneously, and some measurements that are coordinated but asynchronous; and many complementary objectives such as cross-calibration of instruments and also serendipitous opportunities. The data return would be further enhanced by coordination with ground- or space-based assets during some of the measurements.
There are currently no firm commitments from NASA or ESA to accomplish science beyond that of each mission’s primary science objectives. However, discussions continue and we are hopeful that our recommendations for the opportunities afforded by the two missions’ alignment will enable resource support to be found.
How to cite: Bunce, E., Prockter, L., and Choukroun, M. and the JUICE Clipper Steering Committee: Exploring the Jupiter System through unique joint JUICE and Europa Clipper observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18227, https://doi.org/10.5194/egusphere-egu25-18227, 2025.
The internal differentiation of the Galilean moons remains an open question. Gravity data from the Galileo mission indicate that Callisto's interior is only partially differentiated, while magnetic field observations suggest the presence of a subsurface ocean. Similarly, recent reanalysis of Galileo data challenges the longstanding assumption of a metallic core in Europa.
Estimates of the temperature distribution within the growing satellites, combined with the dynamics of liquid water and the sedimentation of rock particles, could provide insights into the development of the internal structures of the present-day Jovian moons. We compute the thermal evolution of the interiors including radiogenic heating, accretional heating from multiple impacts, tidal heating, and heating from the surrounding circumplanetary disk environment.
We investigate the most plausible internal structures of the Galilean moons by combining observational data with multiple formation scenarios. Specifically, we address the paradox of Callisto's subsurface ocean coexisting with its cold interior and explore the conditions that could facilitate iron melting and the formation of a metallic core in Europa and Ganymede. Furthermore, we examine the debated hypothesis of the existence of a primordial ocean on Io.
How to cite: Bennacer, Y., Mousis, O., Monnereau, M., and Hue, V.: Insights from Formation Scenarios into the Internal Differentiation of the Galilean Moons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10236, https://doi.org/10.5194/egusphere-egu25-10236, 2025.
Europa’s radial structure consists of a thin ice Ih shell overlying a subsurface ocean and a large solid core. The thickness of the outer ice shell is strongly related to Europa’s thermal and geological histories. Estimates of this thickness range from a few kilometers to several tens of kilometers, with values deduced from the analysis of surface geological features being on the lower end (a few kilometers and less), and values predicted by modelling thermal evolution being on the upper end (up to a few tens of kilometers). Here, we model the thermal evolution of Europa's ice shell using a parameterized convection approach that explicitly accounts for the release of heat (assumed to have a tidal origin) within this shell. We explore changes in the thickness of this ice shell depending on several parameters, including the bulk ice viscosity, amount of tidal heating, and ocean composition. We further consider possible cyclical variations in the amount of tidal heating in response to changes in the eccentricity of Europa’s orbit. Our calculations show that ice shell thickness is mostly influenced by both the ice bulk viscosity and tidal heating. While significant in absence of tidal heating, the ocean composition has no or few influence when tidal heating is accounted for. Interestingly, for dissipated tidal heat and viscosity around 1 TW and 1014 Pa·s, respectively, which are within the expected range of values for these parameters, our calculations predict an ice shell thickness in the range 15-45 km and, at the top of this shell, and a stagnant lid around 10 km in thickness, in agreement with recent estimates from impact basin morphology. Our calculations further indicate that a 10% change in orbital eccentricity may trigger variations in the ice shell thickness of approximately 15 km, which further helps to reconcile estimates based on geological features and modelled thermal history.
How to cite: Chen, J.-C., Deschamps, F., and Hsieh, W.-P.: Europa’s ice shell thickness : estimates from thermal evolution models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5409, https://doi.org/10.5194/egusphere-egu25-5409, 2025.
Theoretical calculations going back to the pioneering work of E.M. Shoemaker predict a strong apex-antapex gradient in crater formation rate on Ganymede (and other satellites), but while both Ganymede’s bright and dark terrain (younger and older, respectively) exhibit such asymmetries, they are not nearly as pronounced as predicted, by more than an order of magnitude. Several explanations have been offered: 1) crater saturation (plausible for dark terrain–and Callisto–but not bright terrain); 2) planetocentric impactors (these would have to come from beyond Callisto, as sesquinaries are ruled out given Gilgamesh ejecta fragments are too small); 3) mega-impact temporary unlocking of synchronous rotation (though the necessary young basins are unknown); 4) nonsynchronous rotation (a perennial possibility); and 5) true polar wander (TPW) due to insolation-driven shell thickness variations. We have previously addressed the latter possibility (McKinnon et al., Fall AGU 2023), calculating the shell thickness as a function latitude and deriving the degree-2 gravitational response as function of compensation state. For highly compensated shells overlying an internal ocean, excess polar surface topography drives inertial-interchange TPW in which the poles rotate about the tidal a-axis to align with the leading-trailing direction of motion. Earlier in Ganymede’s history, when its global heat flow was high, repeated 90° episodes of polar wander, or continual drift of the icy shell about its tidal axis, could have markedly reduced the satellite’s ultimate (or cumulative) apex-antapex cratering asymmetry. Only at later times, when Ganymede’s ice shell was sufficiently thick for solid state convection, would the latitudinal shell thickness variation be muted if not eliminated and the potential for TPW curtailed.
The attitudinal instability of the ice shell depends on the mechanism of shell compensation. For static models of isostasy (material boundaries), the classic model of pressure balance is the least stable, whereas equal masses above and below (neutral buoyancy) is the most stable. The former prescription leads to unbalanced body forces, however, whereas equal masses leads to unbalanced pressures at depth. We adopt the principle of total force balance: body forces (buoyancy) + basal traction (pressure difference) = 0, which is an intermediate case.
Finally, there is the issue of Ganymede’s enigmatic subjovian dome. As fully revealed by Juno stereo, it is ~700 × 450 km across and ~3 km high. There is no obvious surface construction (cryovolcanic or otherwise) and a 3-km thick water laccolith also seems implausible. Could the dome be a remnant of a thickened polar shell, frozen into a now thickened ice lithosphere and strength supported (and ultimately rotated to a-axis)? Implied stresses are ~1.5 MPa (supportable), but its ~3-km height would imply a >~30-km former isostatic root, difficult to accept given basal ice flow and oceanic heat transport. Future JUICE observations of both Ganymede’s sub- and antijovian region (where a similar dome should exist if this hypothesis is correct) should be telling.
How to cite: McKinnon, W. B. and Schenk, P. M.: The Enduring Enigma of Ganymede’s Muted Apex-Antapex Cratering Asymmetry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15104, https://doi.org/10.5194/egusphere-egu25-15104, 2025.
Hexahydrite is a hydrated magnesium sulfate (MgSO4∙6H2O), whose existence has been suggested on icy satellites like Europa and Ganymede [1]. Spectral characterization of minerals of this kind at the typical conditions found on the surface of the icy moons of Jupiter is essential to better constrain their existence and the implication of their detection, also in view of the future observations coming from the MAJIS (Moons and Jupiter Imaging Spectrometer) instrument [2,3] on board the ESA JUICE mission. We evaluate the variation of spectral features depending on environmental conditions by measuring the reflectance spectra of hydrated salts, in the infrared spectral range, at the representative low surface temperatures and pressures of the icy moons, with a spectral resolution comparable to the one of MAJIS. We used the experimental setup CAPSULA [4], which is a cylindric chamber that allows a controlled environment with pressure down to 10-8 mbar, and temperature down to 40 K, coupled to a FTIR spectrometer equipped with an MCT detector, allowing the acquisition of spectral reflectance of samples. In the first set of measurements, the sample was brought to a pressure of 10-6 mbar, acquiring spectra. Then, it was chilled to 40 K, and additional spectra were acquired during the warming up to room temperature. The sample shows a spectral variation due to dehydration and amorphization, as confirmed later by Raman spectra. During the warming up, the spectra show no variation with temperature, which is coherent with an almost anhydrous sulfate inert to temperature variation. The second set of measurements was performed using a slower vacuum pump to better characterize the pressure dependence. The spectra [Figure 1] show that at about 140 mbar the sample starts to change its structure. However, once exposed back to air, the sample returns to its initial structure, a crystalline hexahydrite, forming a crustal structure on its surface which swells, as shown in Figure 2.
The results shown in this abstract are a starting point to better constrain the correlation between the spectral features of planetary analogs for the icy satellites and their physical properties. From these preliminary measurements, the change in the structure of this sample tends to suggest that it is improbable to find its crystalline and hydrated form (hexahydrite) at the extremely low pressure on the surface of the icy moons (10-8-10-12 mbar), at least not occasionally or transient. If it was present, it could come from a subsurface liquid reservoir or even the underground ocean and should be continuously replenished. With this regard, a deeper laboratory investigation is required.
Acknowledgments: This work has been developed under the ASI-INAF agreement n. 2023-6-HH.0. CAPSULA setup is funded in the frame of INAF Fundamental Research Grant 2022.
References: [1] McCord et al. (2010) Icarus, 209, 639-650. [2] Piccioni et al. (2019) IEEE 5th IWMA, 318-323. [3] Poulet et al. (2024) SSR 220, 27. [4] DeAngelis et al. (IN PRESS) Mem. S.A.It., 75, 282.
How to cite: Furnari, F., Piccioni, G., DeAngelis, S., Stefani, S., Tosi, F., Carli, C., Ferrari, M., and LaFrancesca, E.: Infrared reflectance spectra of Hexahydrite at typical Jupiter’s icy moons environmental conditions., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11300, https://doi.org/10.5194/egusphere-egu25-11300, 2025.
We study the formation of atmospheres from icy surfaces due to electron precipitation, relevant for the icy moons of the solar system. Using a setup similar as described in reference [1], we conduct laboratory experiments irradiating macroscopic ice samples [2] with electrons, to simulate the processing of the icy moons’ surfaces. The experiments are conducted in high vacuum and at a temperature of 95 K to 105 K, reflecting the conditions at the icy moons. Using a time-of-flight mass spectrometer, we measure the sputter yields of water and radiolytic products, such as the species H, H2, O, OH, H2O, O2, H2O2, and O3. We also measure the timescales of release of the species, and particularly the oxygen retention in ice.
The ice sputter yields of less produced species are critical to model the atmosphere of the icy moons [3] and necessary to infer the surface composition of the icy moons using data from the upcoming Jupiter Icy Moons Explorer and Europa Clipper missions.
[1] Tinner, Chantal, et al. "Electron‐induced radiolysis of water ice and the buildup of oxygen." Journal of Geophysical Research: Planets 129.12 (2024): e2024JE008393.
[2] Pommerol, Antoine, et al. "Experimenting with mixtures of water ice and dust as analogues for icy planetary material: recipes from the ice laboratory at the University of Bern." Space science reviews 215 (2019): 1-68.
[3] Vorburger, Audrey, and Peter Wurz. "Europa’s ice-related atmosphere: the sputter contribution." Icarus 311 (2018): 135-145.
How to cite: Obersnel, L., Galli, A., Fausch, R., Pommerol, A., Ottersberg, R., Vorburger, A., Tinner, C., and Wurz, P.: Formation of atmospheres from icy surfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4237, https://doi.org/10.5194/egusphere-egu25-4237, 2025.
The Galileo mission discovered a distorted magnetic field around Jupiter’s moon Europa that is best explained by induction in a subsurface ocean. NASA’s Europa Clipper mission will revisit the moon and measure the field with much higher precision. The data should yield field models with an error of about one nano Tesla (nT). We explore whether this is precise enough for detecting any induction due to zonal flows or the effects of conductivity variations caused by salinity gradients. Our tools comprise analytical solutions, the Matlab code SVzon, and the MHD code MagIC. Unfortunately, we find that both zonal winds and salinity gradients likely have signals well below the expected error level. For example, assuming an electrical conductivity of 10 S/m, flows with peak velocities of about 10 m/s are required to reach the one nT level, which seems excessively fast. We also explore the flows driven by the induction process itself via Lorentz forces. These flows are dominated by geostrophic zonal winds that are reminiscent of the Reynolds-stress driven winds observed in Jupiter’s or Saturn’s cloud decks. Balancing the Lorentz force with viscous drag indicates that these induction-driven flows in Europa’s ocean would remain very slow with velocities below 10-5 m/sec. This is orders of magnitude slower than any convective driven flows.
How to cite: de Langen, I. and Wicht, J.: Magnetic Induction in Europa’s Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6013, https://doi.org/10.5194/egusphere-egu25-6013, 2025.
Near Ganymede, the magnetic field is a superposition of Jupiter’s magnetospheric magnetic field, the field arising from sources within the moon, the field generated by plasma currents driven by the interaction of flowing magnetospheric plasma with the conducting moon, and the field arising from ionospheric currents. Previous fits to Ganymede’s internal field have not identified the contributions of plasma and ionospheric currents, although their contributions can obscure the signature of sources internal to the moon. Fortunately, using magnetohydrodynamic (MHD) simulations whose output agrees well with the measurements acquired on close passes by Galileo and Juno, we can estimate the moon-scale contributions of plasma sources. By subtracting the magnetic signatures of plasma and ionospheric currents from the measured field, we approximate measurements made in a current-free region. We fit the corrected data from different sets of flybys either as a sum of low order spherical harmonics or as a permanent dipole moment plus an induced dipole with approximately the same rms errors. For the induced dipole model, data from multiple flybys occurring at different phases of Jupiter’s rotation are used to represent the time-variation of the external field at Ganymede. Compared with earlier estimates, the magnitude of the permanent dipole moment does not change significantly in either analysis. However, for the permanent plus induced dipole model, the induction efficiency decreases from 0.84 to ~ 0.72. The reduced efficiency places new constraints on the thickness of the ice shell above the ocean and the ocean’s depth and conductivity.
How to cite: Jia, X., Kivelson, M., Khurana, K., and Walker, R.: Improved Models of Ganymede's Permanent and Induced Magnetic Fields Based on Galileo and Juno Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5230, https://doi.org/10.5194/egusphere-egu25-5230, 2025.
The JUpiter ICy moons Explorer (JUICE) is an ESA L-class mission dedicated to studying Jupiter and its Galilean moons. Launched on April 14, 2023, the spacecraft will reach the Jovian system in mid-2031 after a series of Earth and Venus gravity assists. On August 20, 2024, JUICE successfully completed the first-ever Lunar-Earth Gravity Assist (LEGA), involving a Moon flyby at 777 km altitude the day before.
The spacecraft’s scientific payload is composed by 10 instruments. Among them there is the 3GM (Gravity and Geophysics of Jupiter and the Galilean Moon) radio science package, which includes a Ka band Transponder (KaT) for gravity measurements, an Ultra Stable Oscillator (USO) for dual-frequency downlink experiments, and a High Accuracy Accelerometer (HAA). The HAA calibrates non-gravitational accelerations in the frequency band [10⁻⁴–10⁻¹ Hz], primarily due to propellant sloshing. The LEGA event provided a valuable opportunity to calibrate most of the JUICE instruments by collecting data near celestial objects. The Moon closest approach (CA) occurred on August 19, 2024, at 21:14:56 UTC, was preceded by an Earth occultation, started around 20:36 UTC and ended at 21:09 UTC, during which the spacecraft experienced solar radiation pressure (SRP) drops and abrupt temperature changes.
The HAA collected data at a 10 Hz sampling rate in the -2h/+1h time interval around Moon CA, although it was switched on 48 hours before to ensure thermal stability. Active thermal control was disabled during LEGA, since previous inflight tests had evidenced the need for an optimization of thermal control setting parameters. Analysis of HAA data along the spacecraft’s +Z axis revealed gravity gradient accelerations closely matching theoretical predictions. Additional dynamic signals were also detected during the umbra phase. These included oscillations at 0.45 Hz caused by vibrations of the magnetometer boom, excited by a 72° rotation of the SWI antenna. During eclipse egress, a rapid transition from umbra to full illumination caused SRP “kicks” and temperature spikes, exciting the 0.13 Hz solar array vibration mode. These thermal snap effects are consistent with expectations from mathematical modelling, and similar trends with opposite signs have been observed during the eclipse ingress, albeit with smaller oscillation amplitudes due to a smoother illumination-umbra transition.
HAA data from other axes, while noisier and more susceptible to temperature effects, also matched the expected gravity gradient signal and revealed to be perfectly co-aligned with signals caused by vibrations induced by SWI antenna operations. Despite the absence of active thermal control during LEGA, the HAA proved effective in capturing dynamic perturbations, demonstrating its capability to support JUICE’s scientific objectives.
How to cite: De Filippis, U., Di Benedetto, M., Durante, D., and Iess, L.: Analysis of 3GM High Accuracy Accelerometer data collected during JUICE LEGA , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9476, https://doi.org/10.5194/egusphere-egu25-9476, 2025.
The Jovian Energetic Neutrals and Ions (JENI) Camera and the Jovian Energetic Electrons (JoEE) belong to the six-sensor suite Particle Environment Package (PEP) on board the JUICE mission. JENI is a combined ion and ENA camera with 90°x120° Field-of-View and an energy range from a few keV to 110 keV for ENAs and from a few keV to 5 MeV for ions. Only one mission, Cassini, has captured ENA images of the Jovian system before during its distant flyby. Those images revealed emissions coming from the Europa neutral gas torus, but were too distant to resolve details on its spatial distribution and variability. The Juno mission has detected ENA emissions originating from both the Europa and also the Io torus, that indicate azimuthally asymmetric distributions. In ENA mode, JENI will image the Europa and Io tori, to investigate their spatial distribution and long-term variability providing global constraints to physical models of their sources. Although a predominant fraction of the ENAs from the tori originate from charge exchange between magnetospheric energetic ions and the neutral gas, a significant fraction may originate from charge exchange between the energetic ions and the ambient plasma in the tori. This opens up the intriguing possibility to also diagnose the plasma dynamics and distribution of the tori. JENI also targets the explosive recurrences of vast regions of heated plasma in the Jovian magnetotail (“injections”) that may be the engine behind the periodic radio emissions from rotating, magnetized planets, such as Saturn, Jupiter and perhaps even brown dwarfs. In ion mode, JENI will provide the detailed in-situ measurements of the energetic ion environment necessary to understand the physical heating and transport processes underlying the global context provided by the ENA images. JoEE is an electron spectrometer that near-simultaneously provides the energetic electron spectrum in multiple look directions over the energy range from 28 keV up to 2 MeV. JoEE’s prime objectives are to investigate the acceleration mechanisms of Jovian radiation belt electrons and their interaction with the Jovian moons. The Juno mission has recently made important electron measurements that provides useful guidance for deepening the JoEE objectives.
In this presentation an overview is given of JENI and JoEE, with emphasis on the ENA observations and their expected science return. This includes imaging of the Europa and Io tori distribution and variability, quasi-periodic magnetospheric injections, and their relation to rotationally periodic radio emissions from planets and brown dwarfs.
How to cite: Brandt, P., Clark, G., Kollmann, P., Mitchell, D., Gkioulidou, M., Haggerty, D., Barabash, S., Wurz, P., Krupp, N., Roussos, E., Paty, C., Jia, X., Khuarana, K., Allegrini, F., Pontoni, A., and Smith, T.: Energetic Neutral Atom (ENA) Imaging and In-Situ Energetic Particle Exploration of the Jovian Magnetosphere and Moon Environment from JUICE/PEP, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5083, https://doi.org/10.5194/egusphere-egu25-5083, 2025.
The Radio & Plasma Wave Investigation (RPWI) onboard the ESA JUpiter ICy moons Explorer (JUICE) is described. The RPWI provides an elaborate set of state-of-the-art electromagnetic fields and cold plasma instrumentation, including active sounding with the mutual impedance and Langmuir probe sweep techniques, where several different types of sensors will sample the thermal plasma properties, including electron and ion densities, electron temperature, plasma drift speed, the near DC electric fields, and electric and magnetic signals from various types of phenomena, e.g., radio and plasma waves, electrostatic acceleration structures, induction fields etc. A full wave vector, waveform, polarization, and Poynting flux determination will be achieved. RPWI will enable characterization of the Jovian radio emissions (including goniopolarimetry) up to 45 MHz, has the capability to carry out passive radio sounding of the ionospheric densities of icy moons and employ passive sub-surface radar measurements of the icy crust of these moons. RPWI can also detect micrometeorite impacts, estimate dust charging, monitor the spacecraft potential as well as the integrated EUV flux. Together, the integrated RPWI system can carry out an ambitious planetary science investigation in and around the Galilean icy moons and the Jovian space environment. Some of the most important science objectives and instrument capabilities will be described. RPWI focuses, apart from cold plasma studies, on the understanding of how, through electrodynamic and electromagnetic coupling, the momentum and energy transfer occur with the icy Galilean moons, their surfaces and salty conductive sub-surface oceans. The RPWI instrument is planned to be operational during most of the JUICE mission, during the cruise phase, in the Jovian magnetosphere, during the icy moon flybys, and in particular Ganymede orbit, and may deliver data from the near surface during the final crash orbit. We will also show some data from the last Lunar-Earth flyby.
How to cite: Wahlund, J.-E. and the The RPWI consortium: The Radio & Plasma Wave Investigation (RPWI) for the JUpiter ICy moons Explorer (JUICE), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17398, https://doi.org/10.5194/egusphere-egu25-17398, 2025.
On 14 October 2024, NASA’s Europa Clipper spacecraft was successfully launched from Kennedy Space Center with the goal to explore Jupiter’s moon Europa to investigate its habitability. A key investigation to achieve this goal is the characterization of the moon’s ice shell and global subsurface ocean using induced magnetic fields observed by the Europa Clipper Magnetometer. The Europa Clipper Magnetometer (ECM) consists of three three-axis fluxgate magnetometers mounted in gradiometer configuration on an 8.5 m-long, coilable boom. With the instrument checked out and all three sensors sampling the magnetic field at 16 vector samples per second, the magnetometer boom was deployed on 5 November 2024. The acquired data demonstrate that the boom deployed successfully to its full length. In addition, the observations obtained during the boom extension provide the first insight into the spacecraft magnetic field post launch and represent the only measurements of a quasi-radial profile of these contamination fields. As such, they are critical for the validation of a detailed, multi-pole magnetic model of the spacecraft, which was established pre-launch during the hardware integration and test phase of the mission. Initial results show that the observations compare favorably with the magnetic model consisting of 240 individual offset dipoles and that the magnetic cleanliness requirement to limit the spacecraft magnetic field at the outboard sensor to less than one nanotesla is met. Finally, corrected for the spacecraft field, the ECM observations provide the spacecraft’s first observations of the interplanetary magnetic field enroute to Mars, where Europa Clipper will execute a gravity assist maneuver. In this presentation, we report the first magnetic field measurements by the Europa Clipper Magnetometer, assessment of the spacecraft magnetic field, comparison with the spacecraft magnetic model, and ultimately the first observations of the magnetic field in the solar wind by Europa Clipper.
How to cite: Korth, H., Cochrane, C., Joy, S., Bouchard, M., Contreras, J., Biersteker, J., Blacksberg, J., Dang, K., Dawson, O., Jia, X., Khurana, K., Kivelson, M., Narvaez, P., Perley, M., Pierce, D., Raymond, C., Richter, I., Sherman, S., Strangeway, R., and Weiss, B.: First Observations by the Europa Clipper Magnetometer and Assessment of the Spacecraft Magnetic Field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4366, https://doi.org/10.5194/egusphere-egu25-4366, 2025.
Europa Clipper launched on October 14, 2024 and is now en route to Europa to study this icy moon with a subsurface ocean. Characterizing Europa’s subsurface ocean is critical to assess its habitability – the primary goal of the Europa Clipper mission. The Plasma Instrument for Magnetic Sounding, or PIMS, consists of 4 Faraday cups (Ram, Zenith, Anti-ram, Nadir) on 2 sensors (PIMS Upper and PIMS Lower) located on opposite sides of Europa Clipper. PIMS measures the current induced by plasma particles with sufficient E/q to make it through a modulated grid placed at AC high voltage (HV). The HV waveform applied to the modulator grid consists of a DC level and a sine wave with a pre-set amplitude; thus, the particles that can pass through the grid produce an AC current. PIMS will characterize the plasma in Europa’s magnetic environments, which will allow for the subtraction of the plasma contribution from the magnetic induction signal measured by the Europa Clipper Magnetometer (ECM). Subtracting the plasma contributions from the induced field measurements will provide a more accurate derivation of the ocean depth and conductivity, and ice shell thickness.
PIMS was powered on for the first time since Europa Clipper’s launch in December 2024. While the goal of this checkout was to assess PIMS’s post-launch health, a welcome surprise was the detection of a coronal mass ejection (CME) by the Zenith cup on PIMS Upper. This fortuitous detection was made during only a ~1-hour period that PIMS was running in science mode. Several other observatories also observed this CME, including MMS and the L1 constellation at Earth, and STEREO-A elsewhere at 1 AU. These observations along with PIMS on Europa Clipper allow for some rare multipoint analysis of the size, shape, and propagation of this CME.
The solar cycle is currently at maximum with an increased number of solar events driving space weather effects in geospace around Earth and beyond. These “first light” measurements clearly demonstrate the importance of PIMS, and Europa Clipper, as a working asset for understanding space weather in the Earth-Mars region – a region of space otherwise lacking instrumentation for these measurements. CMEs are the biggest space weather hazards for astronauts, which makes turning PIMS and ECM on and having them collecting data during Europa Clipper’s interplanetary cruise phase all the more important.
How to cite: Luspay-Kuti, A., Turner, D., McNutt, R., Crew, A., Smith, H. T., Nordheim, T., Waller, D., Cochrane, C., Stevens, M., Kivelson, M., Jia, X., Paty, C., Khurana, K., Rymer, A., Slavin, J., Korth, H., and Mandt, K.: The Plasma Instrument for Magnetic Sounding (PIMS) on Europa Clipper: some explosive “first light” observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13104, https://doi.org/10.5194/egusphere-egu25-13104, 2025.
The Europa Imaging System (EIS), on the Europa Clipper spacecraft, consists of a narrow-angle camera (NAC) and a wide-angle camera (WAC) that are designed to work together to address high-priority science objectives regarding Europa's geology, recent activity, composition, and the nature of its ice shell. Observations will range from plume-search imaging at 10-km pixel scale, to global mapping at ≤100-m pixel scale, to extremely high-resolution imaging at ≤1-m pixel scale. As part of the Europa Clipper payload, EIS will investigate the geologic processes at work in the ice shell, search for current activity and plumes, and constrain the potential for exchange of material with the subsurface ocean.
EIS accommodates variable geometries and illumination conditions during high-relative-velocity, low-altitude flybys with both framing and pushbroom imaging capability using rapid-readout 8-Megapixel (4k x 2k) CMOS detectors. Color observations are acquired in pushbroom mode using up to six broadband filters. The data processing units (DPUs) perform digital time delay integration (TDI) to enhance signal-to-noise ratios and allow utilization of readout strategies to measure and correct spacecraft jitter.
The NAC has a 2.3° x 1.2° field of view (FOV) with a 10-μrad instantaneous FOV (IFOV) to achieve 0.5-m pixel scale over a swath 2 km wide and several km long from a range of 50 km. It is mounted on a 2-axis gimbal with ±30° cross- and along-track pointing that enables independent targeting and near-global (≥90%) mapping at ≤100-m pixel scale (to date, only ~14% of Europa has been imaged at ≤500 m/pixel), as well as stereo imaging from as close as 50-km altitude for digital topographic models (DTMs) with ≤4-m ground sample distance (GSD) and ≤1-m vertical precision. The NAC will also perform distant observations to search for potential erupting plumes.
The WAC has a 48° x 24° FOV with a 218-μrad IFOV, achieving 11-m pixel scale from a range of 50 km at the center of a 44-km-wide swath and generating DTMs with 32-m GSD and ≤5-m vertical precision. It is designed to acquire 3-line pushbroom stereo and color swaths along flyby ground-tracks.
EIS science goals include: constraining the formation processes of landforms by characterizing geologic structures, units, and global cross-cutting relationships; identifying relationships between surface and sub-surface structures and potential near-surface water detected by ice-penetrating radar; investigating compositional variability; searching for evidence of recent or current activity, including potential erupting plumes; constraining ice-shell thickness from global shape measurements via limb fits; characterizing surface clutter to aid interpretation of deep and shallow radar sounding; and characterizing the surface at meter scales to identify scientifically compelling sites and landing hazards. We will present anticipated EIS observations during the planned tour at Jupiter, opportunities for collaborative science with other Europa Clipper instruments and with JUICE, and how the cameras will address key aspects of Europa to improve our understanding of the habitability of this ocean world.
How to cite: Turtle, E., Patterson, W., and McEwen, A. and the EIS Team: Europa Imaging System (EIS) on the NASA Europa Clipper Mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20919, https://doi.org/10.5194/egusphere-egu25-20919, 2025.
The NASA Europa Clipper mission will explore Jupiter’s icy moon Europa via multiple flybys in the early 2030s (Pappalardo et al., 2024). The ocean world Europa is one of the most promising locations to search for life elsewhere in the Solar System and thus, Europa Clipper’s main goal is to characterize Europa’s habitability (Vance et al., 2024).
In the future, a follow-on landed mission may possibly explore Europa from its surface (Phillips et al., in revision). Based on current technology, terrain relative navigation (TRN) would be used to safely navigate to a landing site. Here we show that 12 of the 49 currently designed Europa Clipper flybys contain at least one portion where the fundamental requirements for TRN are fulfilled:
- daytime illumination with incidence angle ~30° to 60°;
- and 0.5 to 1 meter pixel scales, which for acquisition by the EIS instrument means that the altitude is 50–100 km.
We use the term ‘reconable’ to refer to these 12 flybys. Using data from the Galileo mission, we study what is currently known about these reconable areas, and rank them based on scientific criteria. Three of the reconable flybys have exceptional scientific interest, and therefore receive the highest rank 1*, where * denotes a reconable flyby. Rank 1* flybys are E5, E19 and E22. The remaining nine reconable flybys are a lower rank of 2*, where * also denotes a reconable flyby.
We also identify and rank supporting flybys, which are not reconable in themselves but provide supporting data that can be used to further characterize the reconable areas. Rank 2 supporting flybys provide particularly insightful and/or necessary contextual data. Rank 3 are default supporting flybys. The current rankings reflect our present-day knowledge, and are highly likely to change with Europa Clipper’s in-depth study of the moon’s geological, geochemical and geophysical characteristics.
Our work demonstrates the process that can be used by the Europa Clipper team to assess reconable areas. We conclude that there are areas on Europa with particular scientific interest that Europa Clipper will be able to fully characterize for potential future in-situ exploration.
How to cite: Belgacem, I., Scully, J. E. C., Parekh, R. A., Phillips, C. B., Grima, C., Collins, G. C., Craft, K., Detelich, C., Leonard, E., Mishra, I., Patterson, W., Prockter, L. M., Sutton, S. S., Stickle, A. M., and Wyrick, D. Y.: Reconnaissance of potential landing sites by Europa Clipper, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18691, https://doi.org/10.5194/egusphere-egu25-18691, 2025.
Understanding the formation of subsurface oceans and their survival is of fundamental importance to identify potentially habitable worlds. An important control on ocean evolution is the composition of the ice shell, specifically the presence and abundance of clathrate hydrates – crystalline inclusion compounds that form when water solidifies in the presence of gases under appropriate low temperature and high-pressure conditions. Because all common clathrate structures consist of at least 85% water, many clathrate physical properties are similar to those of water ice Ih. However, the differences in mechanical strength, thermal conductivity and density may have a significant effect on geologic processes of planetary environments. The stability, composition and distribution of clathrate hydrates in ocean worlds remain poorly understood.
This study examines the composition of mixed CH4-CO2 clathrate hydrates that could form in ocean worlds and assesses their potential to sink or float, contributing to the formation of a clathrate layer at the top or bottom of the internal ocean, and potentially facilitating their incorporation in the outer ice shell. Our calculations are mainly based on pure water systems, with some preliminary analyses incorporating inhibitors such as ammonia and salts. Using a thermodynamic model based on the statistical thermodynamic approach of Van der Waals and Platteeuw, we evaluate the density and composition of CH4-CO2 clathrate hydrates under conditions relevant to Europa, Titan, and Enceladus. Simulations are conducted around 273 K and at pressures ranging up to several hundred MPa.
By refining constraints on the presence and composition of clathrate hydrates in ice shells, this research contributes to understanding the conditions necessary for maintaining potentially habitable subsurface liquid water reservoirs. This work provides valuable insights for interior modeling of icy bodies and supports ongoing and future missions, including JUICE, Europa Clipper, and Dragonfly.
How to cite: Gloesener, E., Choukroun, M., Vu, T. H., Davies, A. G., Sotin, C., Pirim, C., and Chazallon, B.: Composition and Density of Clathrate Hydrates in Ocean Worlds: Implications for Insulating Ice Shells, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17285, https://doi.org/10.5194/egusphere-egu25-17285, 2025.
Introduction. Hydrated salts such as magnesium sulfates are expected to be found at the surface of Europa [1], possibly originating from hydrothermal activity in the moon’s subsurface ocean. To support the identification of these compounds from remote-sensing instruments data of the icy moons, such as from MAJIS [2,3] onboard the ESA JUICE mission [4], it is of paramount importance to investigate the spectral response of these compounds across different experimental conditions [5]. Here, we focus on the spectral changes of hexahydrite (MgSO4 · 6H2O) upon dehydration via vacuum processing and subsequent re-hydration, investigated at various optical configurations to optimize re-hydrated magnesium salt detection via remote sensing.
Materials and Methods. We produced a 13-mm diameter pellet of approximately 1-mm thickness by pressing 300 mg of hexahydrite powder with grain size between 75 and 100 µm for 1 minute under a pressure of 10 tons (fig.1). We acquired spectral reflectance infrared data from 0.8 to 15 microns of the pellet’s surface at various geometric configurations using a Bruker FTIR-spectrometer coupled to a goniometer. A set of 15 different geometric configurations have been acquired with illumination angle i = 0°, 30°, 40°, 60, and a variety of emission angles. The pellet was put in a vacuum chamber, and the pressure was decreased progressively for 2 hours, down to P ~ 2.3 mBar. Ambient air was then progressively reintroduced in the chamber until the pressure in the vacuum cell reached 1 Bar. The pellet was then exposed to the air for several days. The spectral evolution of the pellet’s surface during the pressure decrease and its re-exposure to ambient air was followed via a Bruker Hyperion FTIR microscope. After this period of exposure, the pellet underwent the same spectroscopic geometric characterization described before to assess if and how the spectroscopic features of hexahydrite behave differently at various geometric configurations before and after the vacuum processing.
Figure 1. hexahydrite pellet before vacuum processing.
Preliminary results and discussion. Results indicate that the hexahydrite pellet does not fully rehydrate after exposure to the ambient air for multiple days. Moreover, the changes in the Reststrahlen bands upon vacuum-driven dehydration suggest that the dehydration was coupled with crystal lattice amorphization (fig.2). The optimal geometric configuration to detect this amorphization, as well as other spectroscopic changes related to the vacuum processing, is still to be determined and data analysis is still ongoing.
Figure 2. The S-O stretching and S-O bending features decrease in intensity and widen after vacuum processing, which is compatible with lattice amorphization.
Acknowledgments. This work has been developed under the ASI-INAF agreement n.2023-6-HH.0.
Bibliography. [1] Dalton J. B. et al. 2005. Icarus 177 (2): 472–90. [2] Poulet F. et al. 2024. Space Sci Rev 220. [3] Piccioni G. et al. 2019. IEEE. pp. 318–323. [4] Grasset O. et al. 2013. Planet Space Sci. 78: 1–21. [5] De Angelis S. et al. 2017. Icarus 281 (January):444–58.
How to cite: Rubino, S., Furnari, F., Stefani, S., Piccioni, G., Ferrari, M., Carli, C., De Angelis, S., and Tosi, F.: Geometry-induced variations and effects on the remote-sensing identification of re-hydrated magnesium sulfates on the Galilean Icy-Moons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11962, https://doi.org/10.5194/egusphere-egu25-11962, 2025.
ESA’s Jupiter Icy moons Explorer (Juice), equipped with a highly capable suite of geophysical instruments will accurately measure Ganymede’s tidal Love numbers k2 and h2 with the radio science experiment 3GM and the laser altimeter GALA during the low altitude orbital phase (GCO-500) (Van Hoolst et al. 2024).
As part of a prospective study for this upcoming exploration of Ganymede, we compute the moon’s tidal response across a wide range of interior structure models. Anelasticity is modeled with the Andrade rheology and several combinations of values of its parameters following the approach of Amorim and Gudkova (2025). Ganymede's hydrosphere is modeled using the equations of state of pure water and NaCl solutions with different concentrations following the SeaFreeze representation (Journaux et al. 2020). The ice shell is assumed to be either fully conductive or convective, depending on its thickness and viscosity assumptions. We systematically vary the thicknesses of the outer ice shell and hydrosphere, as well as the reference viscosity values of the ice shell and the high-pressure ice layer above the silicate mantle.
For each fixed hydrosphere configuration, we explore all possible structures of the silicate mantle and liquid core so that our models’ moment of inertia is within the acceptable range of values (Gomez Casajus et al. 2022). The influence of each parameter on the tidal Love numbers, as well as on the phase lags of k2 and h2, is analyzed. This approach aims to determine how measurements of these quantities by Juice can provide constraints on Ganymede's interior structure and thermal state.
How to cite: Tobie, G., Oliveira Amorim, D., Bove, L., and Choblet, G.: Inferring the structure and thermal state of Ganymede’s interior with tidal Love numbers and moment of inertia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12033, https://doi.org/10.5194/egusphere-egu25-12033, 2025.
The rotational motion of a celestial body is influenced by its internal structure, shape, and the gravitational torques exerted by external massive bodies. The European Space Agency's JUpiter ICy moon Explorer (JUICE) mission aims to explore the Jupiter system, focusing primarily on Ganymede. After performing a series of flybys of Ganymede, Europa, and Callisto, JUICE will enter its main scientific phase, during which it will orbit Ganymede for several months. Throughout this phase, the spacecraft will gather extensive data, including gravity and altimetry measurements, surface images, and magnetic field observations. By combining these data sets, researchers will gain valuable insights into Ganymede's orientation.
This analysis is based on a coupled numerical integration of both the orbital dynamics of the Jupiter system and Ganymede's rotational dynamics. The integration tracks a set of Euler angles for each layer of Ganymede, capturing how they evolve over time. The model of Ganymede’s orientation incorporates not only the gravitational torques from external bodies but also the internal coupling torques between the moon's different layers, including viscoelastic, gravitational, and inertial torques.
Viscoelastic torque arises from the differential angular velocities between adjacent layers, leading to shear forces at their boundaries due to viscosity. Gravitational torque is caused by the misalignment of the principal axes of inertia between the layers, which works to realign them [1]. Inertial coupling torque results from interactions between the solid and fluid layers, where the solid boundaries constrain the motion of the fluid layer. In this dynamic system, the physical properties, shape, and dimensions of each layer are crucial to Ganymede's librations.
This study examines how variations in Ganymede's internal structure affect its orientation. The current model assumes a three-layer structure [2]: a solid inner core (with an overlying high-pressure ice layer), an icy outer shell, and a subsurface ocean layer. By varying the physical properties, shape, and dimensions of these layers, we assess their impact on Ganymede's libration. The analysis highlights the sensitivity of Ganymede’s orientation to changes in its internal structure model.
The upcoming JUICE mission will provide real data on the amplitude of Ganymede’s libration. Any libration effects smaller than the mission's detection threshold will be undetectable by the spacecraft. Therefore, the sensitivity analysis presented here is essential for forecasting the mission's data analysis capabilities and understanding which features of Ganymede’s libration may be measurable.
[1] Van Hoolst, T., Rambaux, N., Karatekin, Ö., Dehant, V., & Rivoldini, A. (2008). The librations, shape, and icy shell of Europa. Icarus, 195(1), 386-399. https://doi.org/10.1016/j.icarus.2007.12.011
[2] Gomez Casajus, L., Ermakov, A. I., Zannoni, M., Keane, J. T., Stevenson, D., Buccino, D. R., et al. (2022). Gravity field of Ganymede after the Juno Extended Mission. Geophysical Research Letters, 49, https://doi.org/10.1029/2022GL099475
How to cite: Tartaglia, P., De Marchi, F., Di Benedetto, M., Iess, L., and Fienga, A.: THE IMPACT OF VARIUS INTERNAL STRUCTURE MODELS ON GANYMEDE’s ROTATIONAL STATE, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20058, https://doi.org/10.5194/egusphere-egu25-20058, 2025.
