The JUICE mission has been launched by an Ariane 5 launcher on April 14, 2023 and is now on its way to reach Jupiter and its icy moons in 2031. The focus of JUICE is to characterise the conditions that may have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasis on the internally active ocean-bearing worlds, Ganymede and Europa. Following a Jupiter Touring phase of 4 years, JUICE will become the first orbiter of a moon that is not our own, entering Ganymede orbit in 2034.

The spacecraft passed its commissioning review successfully on July 19, 2023, following the Near Earth Commissioning Phase (NECP), and, despite a few hickups, the ESA and multi-national instruments teams are now operating our interplanetary ship successfully. The preparation of the first combined flyby of the Earth and the Moon  in the history of space exploration (August 2024) is on-going. The first planning training exercise was completed by the Science Ground Segment, complementing the preparation of the strategic science planning of the Jupiter Tour.

How to cite: Altobelli, N., Witasse, O., Vallat, C., Tanco, I., Dietz, A., and Erd, C. and the JUICE TEAMS: The JUICE mission - an overview, since launch and beyond , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20679, https://doi.org/10.5194/egusphere-egu24-20679, 2024.

Scheduled to launch in October 2024, NASA’s Europa Clipper will set out on a journey to explore the habitability of Jupiter’s icy ocean world Europa. After a 5.5 yr cruise that includes gravity assists at Mars and Earth, the spacecraft will enter orbit around Jupiter and will perform nearly 50 flybys of Europa over a four-year period. To explore Europa as an integrated system and achieve a complete picture of its habitability, the Europa Clipper mission has three main science objectives to characterize: (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 be acquired by the spacecraft’s radiation monitoring system.

Assembly, test, and launch operations (ATLO) of the Europa Clipper spacecraft are progressing well, and the flight system integration and environmental testing has been completed at the Jet Propulsion Laboratory. Currently, the flight system is undergoing operations testing, and in May 2024, the spacecraft will be shipped to NASA’s Kennedy Space Center at Cape Canaveral, Florida. There, the remaining integration activities will occur for the solar array and REASON antennas followed by final flight system tests. The launch period begins on 10 October 2024. To provide details on the mission’s instruments and planned investigations, the Europa Clipper science team is publishing manuscripts in a special issue of Space Science Reviews, and the team continues to work towards optimizing science return through preparation of the mission’s Strategic Science Planning Guide. As well, collaborative science opportunities with ESA’s JUpiter ICy moons Explorer (JUICE) mission, which will overlap in its tour period at Jupiter and make observations of Europa, are being discussed informally among the science teams. Onward to Europa!

How to cite: Craft, K. L., Pappalardo, R., Buratti, B., Korth, H., Daubar, I., Phillips, C., Klima, R., Howell, S., Leonard, E., Matiella Novak, A., Ray, T., Kampmeier, J., and Paczkowski, B. and the Europa Clipper Science Team: The Europa Clipper Mission and its Final Stretch to Launch, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14097, https://doi.org/10.5194/egusphere-egu24-14097, 2024.

Chemically stratified layers in the deep oceans of icy moons may strongly influence the oceans’ dynamics, thermal and chemical evolution, and therefore their habitability. Such layers can form during the differentiation of the refractory cores as they heat up due to the decay of long-lived radioactive elements. In the case of Ganymede, salts could be transported through the high-pressure ice layer to form a denser salt water layer at the base of the ocean. Such a layer would inhibit ocean convection, limiting chemical and thermal transport. It is therefore crucial to understand how these layers form and what specific signatures they may leave in geophysical observations of future space missions. The present work describes numerical simulations of the formation of stratified layers and the predicted observables that could be detected by instruments on the JUICE spacecraft.

3-D numerical simulations of Ganymede’s rotating ocean are performed with the PARODY code. Rayleigh-Bénard convection is imposed. We investigate the effect of either a constant flux of heavy salts or a fixed composition at the base of the ocean. Two regimes are identified by varying the dimensionless chemical Rayleigh (buoyancy over viscosity) and Schmidt numbers (viscosity over diffusivity). In the first regime, heavy salts are entrained and mixed in the convective region. In the second regime, the entrainment is too weak and a chemically stratified layer develops, eventually filling the entire ocean.

Extrapolation to Ganymede suggests the current existence of a chemically stratified layer at the base of the ocean with a thickness close to 30 km. By considering different stratifications in Ganymede’s ocean in the PlanetProfile and ForcedTides codes, we show that signatures of stratified layers might be detected in the gravity field, induced magnetic field, and tidal deformation responses. The problem of non-uniqueness in the individual observations points to the need to jointly invert these datasets from the JUICE mission to constrain the existence and properties of stratified oceanic layers.

How to cite: Pinceloup, M., Bouffard, M., Vance, S., Melwani Daswani, M., and Styczinski, M.: Formation of chemically stratified layer in Ganymede’s ocean: implications for upcoming JUICE mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10976, https://doi.org/10.5194/egusphere-egu24-10976, 2024.

One of the most important realizations that planetary scientists have come to in the last 20 years is that in the search for potential habitability in our solar system, the focus need not only be on planetary bodies close to the Sun, where water on the surface is in liquid state. Based on Galileo and Cassini observations in the Jupiter and Saturn systems, there are many potential places in our solar system where sub-surface liquid water oceans may exist.

JUICE magnetometer (J-MAG) measurements (such as those made by the magnetometers on the Galileo and Cassini spacecraft) enable an understanding to be gained of the interior structure of the icy moons of Jupiter, specifically those of Ganymede, Callisto and Europa. Of particular interest are knowledge of the depth at which the liquid oceans reside beneath their icy surfaces, the strength of any internal magnetic fields such as at Ganymede and the strength of any induced magnetic fields arising within these oceans.

The primary science objectives of JUICE which will be constrained by the magnetic field observations and which drove the performance requirements of the J-MAG instrument include:

• At Ganymede:
• Characterization of the extent of the ocean and its relation to the deeper interior
• Characterization of the ice shell
• Characterization of the local environment and its interactions with the Jovian magnetosphere
• Description of the deep interior and magnetic field generation
• At Europa, further constrain the depth of the liquid ocean and its conductivity
• At Callisto, characterize the outer shells, including the ocean

How to cite: Dougherty, M.: Using magnetic field observations from the Galilean moons to diagnose ocean properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1416, https://doi.org/10.5194/egusphere-egu24-1416, 2024.

On 14 April 2023, the JUpiter ICy moons Explorer (JUICE) of ESA was launched from Europe's Spaceport in French Guiana. It will arrive at Jupiter and its moons in July 2031. Here we describe how JUICE will investigate the interior of the three icy Galilean moons, Ganymede, Callisto and Europa. Best insights into their interior, such as from an induced magnetic field, tides, rotation variations, and radar reflections, will be obtained during close flybys of the moons with altitudes of about 1000 km or less and during the Ganymede orbital phase at an average altitude of about 500 km and less. The 9-month long orbital phase around Ganymede, the first of its kind around another moon than our moon, will allow an unprecedented and detailed insight into the moon’s interior, from the central regions where a magnetic field is generated to the internal ocean and outer ice shell. Multiple flybys of Callisto will constrain the density structure, clarify the differences in evolution compared to Ganymede and will provide key constraints on the origin and early evolution of the Jupiter system. JUICE will visit Europa only during two close flybys and will perform geophysical investigations on selected areas, complementary to those performed by Europa Clipper.

We emphasize the synergistic aspects of the different geophysical investigations, showing how different instruments will work together to probe the hydrosphere, internal differentiation, dynamics, and evolution of these icy moons. In situ measurements and remote sensing observations will support the geophysical instruments to achieve these goals by providing complementary information about tectonics, potential plumes, surface composition, and exchange processes between ocean, ice and surface. Additional insight into the dissipative processes in the Jupiter system will be provided by accurate tracking of the JUICE spacecraft.

How to cite: Van Hoolst, T., Tobie, G., and Vallat, C. and the JUICE WG1 SSR: Investigating the interior of Ganymede, Callisto and Europa with JUICE, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6318, https://doi.org/10.5194/egusphere-egu24-6318, 2024.

Under low pressure and temperature, most rocks have extremely low electrical conductivities (< 10^-9 S/m) which rise dramatically at temperatures encountered in deep interiors of solid bodies. The presence of ferric iron (Fe³⁺), whose abundance is related to the oxygen fugacity of the rock, lowers the activation energy of conduction and enhances rock conductivity further. Most models of the interior of Europa are consistent with the presence of a highly-conducting metallic iron core with a radius between 200 and 700 km (e.g., Kuskov and Kronrod, 2005). Thus, the mantle and the core of Europa are likely highly conducting and are expected to create measurable induction response. Accounting for this deep conductivity would not only improve the modeling of the physical parameters of the ocean but help further constrain the properties of Europa’s deeper interior.

Since the discovery of induction response from Europa’s ocean (Khurana et al., 1998), numerous studies have reexamined the electromagnetic induction signatures obtained by the Galileo spacecraft using increasingly sophisticated techniques to model the induction field and the moon/plasma interaction field (see e.g. Zimmer et al. 2000; Schilling et al. 2007; Vance et al. 2021). However, these studies have ignored the effect of induction from the deeper interior. Also, no studies have been performed for lower conductivities of the ocean and for longer period waves (such as the orbital period of Europa = 85.2 h) which can probe deeper even through a highly conducting ocean.

To address this problem, we have used the recursive method of Srivastava (1966) for a multiple layer model of Europa’s deep interior. The results from this preliminary exploration show that for a range of core radii and mantle conductivities, the deeper interior modifies the signal from the ocean by several nT at the two primary frequencies. The 85.2 h period penetrates through the ocean and elicits increasing response from the deep mantle as its conductivity is increased (from generation of stronger eddy currents). The 11.1 h period on the other hand produces a weaker response  with increasing mantle conductivity because the eddy currents are already at their highest level (100% induction from the ocean) but begin to follow a deeper path through the mantle and thus their magnetic response at the surface appears weaker.

Khurana, K.K., M.G. Kivelson, D. J. Stevenson, and others (1998) Induced magnetic fields as evidence for subsurface oceans in Europa and Callisto, Nature, 395, 777-780.

Kuskov O.L. and V.A. Kronrod (2005) Internal structure of Europa and Callisto, Icarus, 177, 550-569.

Srivastava, S.P. (1966) Theory of the magnetotelluric method for a spherical conductor, Geophys. J. Roy. Astro. Soc. 11, 373-387.

Vance, S. D., Styczinski, M. J., Bills, B. G., Cochrane, C. J., Soderlund, K. M., Gomez-Perez, N., & Paty, C. (2021). Magnetic induction responses of Jupiter's ocean moons including effects from adiabatic convection. J. Geophys. Res. : Planets, 126, e2020JE006418.

Zimmer, C., K.K. Khurana, and M.G. Kivelson (2000) Subsurface oceans on Europa and Callisto:  Constraints from Galileo magnetometer observations, Icarus, 147, 329.

How to cite: Khurana, K., Cao, H., and Stixrude, L.: The Impact of Europa’s Deep Interior on the Electromagnetic Induction Signal from Europa’s Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4522, https://doi.org/10.5194/egusphere-egu24-4522, 2024.

Solid-state convection has been proposed to occur within Europa’s ice shell based both on the interpretation of observed geological activity during Galileo spacecraft exploration and theoretical investigations. Laboratory experiments have investigated the effect of grain size insensitive creep and grain size sensitive creep on the ductile behaviour of polycrystalline ice. The ice grain size and the ice impurities content and, consequently, the viscosity of the ice within Europa’s ice shell are poorly constrained, limiting the possibility to understand if solid-state convection can occur under Europa’s ice shell conditions. To investigate how diurnal tidal flexing and the internal dynamics of Europa’s ice shell influence the ice grain crystals’ evolution, we adopted a thermal-mechanical numerical model that uses finite differences and marker-in-cell techniques, implementing the dynamic recrystallization of the ice and the ice grain evolution in a self-consistent way with the numerical model. We found that solid-state convection within Europa’s ice shell can occur if it is diurnally tidally deformed, as the tidal stresses within the ice shell operate to reduce the ice grain sizes and the ice viscosity. We discuss future radio science experiments, in combination with radar sounder investigations, that will be capable of characterizing the possible presence of solid-state convection within Europa’s ice shell.

Acknowledgements: G.M. acknowledges support from the Italian Space Agency (2023-6- HH.0).

How to cite: Mitri, G.: Dynamic recrystallization within Europa’s ice shell: Implications for solid-state convection , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8353, https://doi.org/10.5194/egusphere-egu24-8353, 2024.

The rocky Jovian moon, Io, exhibits global volcanism that is driven by heat dissipated by tidal deformation. The large rate of heat exported by this volcanism, in conjunction with evidence in the form of magnetic induction, suggests that the mantle may contain a significant fraction of partial melt. This melt may be present in regions where both solid and liquid coexist at the macroscale. Nevertheless, existing models to investigate the location and magnitude of tidal heating consider an internal structure consisting of layers of pure solid or liquid. Such models are not appropriate for tidal deformation of partially molten materials. Building upon recent advancements in the theory of gravitational poroviscoelastic dynamics, we model tidal heating within Io, taking into account the effect of a two-phase, partially molten asthenosphere. 

The solid regions are modelled as a Maxwell viscoelastic material, and the top and bottom of the asthenosphere are treated as impermeable boundaries. We find that tidal dissipation within the fluid-filled pores depends on the ratio of the asthenosphere’s permeability to the melt’s viscosity. Thus, a low-viscosity melt and highly permeable pore-network favour enhanced tidal dissipation within the fluid. When this ratio, representing the Darcy drag, is large enough, fluid dissipation can exceed that within the solid grains when solid viscosity is high (> 10¹⁷ Pa s) or ultra-low (< 10¹¹ Pa s). Tidal dissipation by the pore-hosted melt exhibits its own distinct tidal heating pattern, which always produces enhanced heating towards low latitudes.

How to cite: Hay, H., Katz, R., and Hewitt, I.: Tidal Dissipation in a Partially Molten Asthenosphere on Io, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9753, https://doi.org/10.5194/egusphere-egu24-9753, 2024.

Spiked, icy features, akin to the ‘penitentes’ on Earth [1], have been found on other airless bodies in the solar system as well, such as the 'bladed terrains' of Pluto [2] and the 'spires' of Callisto [3]. These features, thought to be formed due to sublimation erosion, are present in young, crater-less regions and hence represent an active response of the surfaces of these bodies to changing seasonal and climatic conditions. Interestingly, penitente formation has also been hypothesized on Europa [4], albeit the feasibility of that process on Europa has been questioned [5]. A fundamental limitation of testing this hypothesis for Europa is the lack of images at the resolution of the proposed penitente features (~ 15 m), unlike the images of the bladed terrains of Pluto from New Horizons and spires of Callisto from Galileo which clearly show these features. 

Photometric roughness models peer below the resolution limit of the camera to offer a glimpse of any surface roughness that is in the geometric optics limit.  Our roughness model [6], which has been successfully fit to a range of planetary bodies [7,8], will enable us to probe the surface roughness of Europa and test the penitente-hypothesis. We are locating Galileo images from the equatorial regions of Europa (within an equatorial zone restricted to ±24° where they are hypothesized to exist) and extracting scans of specific intensity (I/F) with backplanes of geometric coordinates. We will fit these I/F curves with our photometric model to derive roughness values, which will be compared to the proposed roughness of ~ 60° [4]. This predicted roughness is very high, so its effect on the light reflected from the surface should be easily detectable. To get a useful point of comparison for the roughness values we obtain for Europa, we will also perform a roughness analysis of the spires of Callisto, which are in a similar size regime of ~ 100 m. 

[1] Claudin, P. et al. (2015), Phys. Rev. E, 92(3), 033015; [2] Moore, J., et al. 2018, Icarus 300, 129-144, [3] Howard, A. D., & Moore, J. M. (2008). GRL, 35(3), L03203 [4] Hobley, D.E.J. et al. (2018). Nat. Geosci., 11(12), 901-904. [5] Hand, K.P. et al. ( 2020). Nat. Geosci., 13(1), 17-19. [6] Buratti, B. J., & J. Veverka (1985), Icarus 64, 320-328; [7] Buratti, B. J. et al. (2006). Planet. & Space Sci. 54, 1498-1509 [8] Lee, J. et al.  (2010), Icarus 206, 623-630.

How to cite: Mishra, I. and Buratti, B.: Testing the penitente hypothesis on Europa via photometric roughness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11367, https://doi.org/10.5194/egusphere-egu24-11367, 2024.

Volcanic activity at Europa’s seafloor is one of the key questions regarding the habitability of its subsurface ocean. The suitable conditions for hydrothermalism on Europa’s seafloor are conditioned by the heat released from the underlying silicate mantle, supplied by both radiogenic and tidal heating. The orbital resonance between Io, Europa, and Ganymede forces their orbit and maintains non-zero eccentricities. Tidal heating due to eccentricity tides on Io is so extreme that it  produces intense volcanism.  Even though tidal heating  in Europa’s silicate mantle is expected to be much weaker than on Io due to its greater distance to Jupiter,   Běhounková et al. [1] showed that it may still be sufficient to maintain Europa’s mantle in a partially molten state  for several tens to hundred millions of years, particularly during periods of increased eccentricity. Due to inefficient melt transport through the thick lithosphere of Europa [2], melt produced during periods of enhanced eccentricity may accumulate and in turn affect the tidal heating, as it is the case for Io, implying a possible runaway melt process in the silicate interior of Europa.

In this context, the goal of this study is to evaluate the effect of melt accumulation on the tidal heat production of Europa’s silicate mantle. For that purpose, we follow the approach developed to model the solid tides in Io’s partially molten interior [3], taking into account the effect of melt on the viscoelastic properties of the mantle. We adapt it to the context of Europa, corresponding to a deeper and thinner asthenosphere than on Io. We show that, whatever the partially molten layer thickness, melt accumulation increases tidal heat production and tidal dissipation even exceeds radiogenic heating. For equivalent volume of accumulated melt, the thinner the layer, the more pronounced this effect is. Our results show that the accumulation of melt, over timescales consistent with the 3D model prediction of Běhounková et al. [1], may significantly affect the tidal dissipation amplitude and its pattern. The potential presence of such melt accumulations may be tested by future measurements by Europa Clipper and JUICE from the combined analysis of gravimetric, altimetric and magnetic data, which might reveal long-wavelength anomalies which could be confronted to our model prediction.

[1] Běhounková et al., GRL, 48(3), e2020GL090077 (2021),  [2] Bland and Elder, GRL, 49(5), e2021GL096939 (2022). [3] Kervazo et al., A&A, 650, A72 (2021)

How to cite: Kervazo, M., Tobie, G., Behounkova, M., Dumoulin, C., and Choblet, G.: Impact of melt accumulation on tidal heat production in Europa’s mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6113, https://doi.org/10.5194/egusphere-egu24-6113, 2024.

The Surface Dust Analyser (SUDA) is a dust impact mass spectrometer onboard of the Europa Clipper mission for investigating the surface composition of the Galilean moon Europa. The instrument is a Time--Of--Flight (TOF) impact mass spectrometer derived from previously flown dust compositional analyzers on Giotto, Stardust, and Cassini. SUDA uses the technology of the successful Cosmic Dust Analyzer (CDA) operating on Cassini and employs advanced reflectron-type ion optics for increased mass resolution. The instrument will measure the mass, speed, charge, elemental and isotopic composition of impacting grains.

Atmosphereless planetary moons such as the Galilean satellites are wrapped into a ballistic dust exosphere populated by tiny samples from the moon's surface produced by impacts of fast micrometeoroids. SUDA will measure the composition of such surface ejecta during close flybys at Europa to obtain key chemical constraints for revealing the satellite's composition, history, and geological evolution. Because of their ballistic orbits, detected ejecta can be traced back to the surface with a spatial resolution roughly equal to the instantaneous altitude of the spacecraft.

SUDA will detect a wide variety of compounds from Europa's surface over a concentration range of percent to ppm and connect them to their origin on the surface. This allows simultaneous compositional mapping of many organic and inorganic components, including both major and trace compounds, with a single instrument. Any recent tectonic activity, cryovolcanism, or resurfacing event is detectable by variations in the surface composition. This can be linked to corresponding geological features, including the analysis of compositional variations across large craters on Europa. SUDA will further the understanding of Europa's surface couples to its interior source regions.

In this presentation, we will discuss SUDA's unique capabilities to collect compositional ground truth from orbit and how SUDA contributes to the Europa Clipper science goals.

How to cite: Kempf, S. and the SUDA Science Team: SUDA: A SUrface Dust Analyser for compositional mapping of the Galilean moon Europa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17570, https://doi.org/10.5194/egusphere-egu24-17570, 2024.

Recent JWST observations reveal a higher abundance of endogenic CO₂ at Tara Regio, a prominent leading hemisphere chaos (Villanueva et al., 2023; Trumbo and Brown, 2023). Prior findings from Keck also show an excess of H₂O₂ in the same region (Trumbo et al., 2019). Could the emplacement of the ocean-derived CO₂ onto Europa’s surface influence radiolytic chemistry to boost peroxide yields in these enigmatic chaos regions? Increased H₂O₂ at fractured chaos terrains where ocean-surface exchange is more likely is exciting from a habitability stance, as it may facilitate oxidant delivery to the subsurface ocean.

We present laboratory results that show H₂O₂ synthesis increases by 2-3 folds in the presence of trace amounts of CO₂ (< 3 %) when compared to radiolysis of pure water ice. We also discuss correlations between CO₂ and H₂O₂ abundances in the JWST datasets to determine whether Europa’s endogenous CO₂ indeed conspires to inflate H₂O₂ at Tara Regio and possibly other chaos terrains. These JWST observations combined with emerging laboratory measurements set the stage for detailed mapping of CO₂ (via its 2.7 and ~4.23-4.29 µm absorptions) and H₂O₂ (via its 3.5 µm absorption) with MISE (Europa Clipper) and MAJIS (JUICE) at unprecedented spatial resolution.

References:

• Villanueva, G. L. et al., (2023) Science, 381, 1305–1308 
• Trumbo, S. K and Brown, M. E. (2023) Science, 381, 1308–1311
• Trumbo, S. K. et al. (2019) Astronomical Journal, 158, 127

How to cite: Raut, U., Protopapa, S., Mamo, B. D., Villanueva, G., Cartwright, R. J., Teolis, B. D., Retherford, K. D., and Blaney, D. L.: Can endogenic CO2 inflate radiolytic H2O2 in Europa’s Chaos?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6579, https://doi.org/10.5194/egusphere-egu24-6579, 2024.

Introduction. Europa, the most visibly active icy moon of Jupiter, is a prime target for the search for life in the outer solar system. Two spacecraft missions, Europa Clipper from the National Aeronautics and Space Administration (NASA) and the Jupiter Icy Moon Explorer (JUICE) from the European Space Agency (ESA), will conduct extensive observations of its surface, gravity field and environment starting 2030. It has been proposed that liquid briny water reservoirs could be injected and stored in Europa’s ice shell, causing the formation of various geological features. In particular, these reservoirs could occasionally trigger eruptions [1], resulting in flows on the surface and vapor plumes in the atmosphere.

If shallow liquid brine reservoirs are indeed present in Europa's ice shell, they would leave surface evidence that future missions could detect, including local thermal anomalies, ice shell thickness change, and erupted briny solutions with time varying salinity. We present a novel simulation that models thermal, physical, and compositional ice shell and reservoir evolution and eruption, and that predicts the various signatures detectable by future robotic exploration.

Cryomagma chemistry. We conserve enthalpy to solve the coupled chemical evolution and pressurization of freezing brines stored in Europa’s ice shell using current best estimates of the oceanic composition [2] to predict the composition of erupted cryolava. This composition varies with time, as salts concentrate during freezing [3], which could lead to erupted brines of varying composition depending on the reservoir frozen fraction when the eruption is triggered. The equilibrium freezing of oceanic brines is modeled using the software PHREEQC to obtain the liquid and solid fraction of each component of the aqueous solution as a function of the temperature. 

Ice shell and reservoir modelling. We simultaneously model the ice shell and reservoir thermal, physical, and compositional evolution self-consistently building upon the framework of [4]. We solve for the conservation of enthalpy using conservative finite differences in a one-dimensional (1D) spherical shell, propagated explicitly forward in time. The thermophysical properties of the multiphase model are temperature-, pressure-, and composition dependant, thus the composition and physical state are consistently updated at every time step. Finally, modeled eruption frequency and eruptive characteristics are dependent on the properties and their gradients in ice surrounding the reservoir.

Results. Outputs of the model include the temporal evolution of the temperature in the ice shell, reservoir, and at the surface, and the time of eruptions and erupted cryomagma composition (Fig. 1).

Figure 1: Temporal evolution of signatures of a 1 km thick cryomagma reservoir located 1 km bellow the surface.

Acknowledgements. Portions of this research were carried out at the Jet  Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). This work was supported by NASA’s Solar System Workings program (grants #80NM0018F0612 and #80NSSC20K0139)

References. [1] Lesage et al. (2022) PSJ 3(7), 170, [2] Melwani Daswani et al. (2021) GRL 48(18), [3] Naseem et al. (2023) PSJ 4(9), 181, [4] Howell, S. M. (2021) PSJ 2(4), 129.

How to cite: Lesage, E., Howell, S. M., Miller, J. W., Naseem, M., Villette, J., Neveu, M., Melwani Daswani, M., and Vance, S. D.: Cryovolcanism inside out: Signatures of past and present cryovolcanism on Europa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13816, https://doi.org/10.5194/egusphere-egu24-13816, 2024.

Ion precipitation onto Ganymede, shaped by interaction between the Jovian plasma and Ganymede’s magnetosphere, has been connected to brightness patterns and radiolysis products on its surface [1,2]. JUICE will measure ion fluxes in-situ at around 500 km altitude, leaving uncertainties for the precipitation patterns on the surface [3]. At Earth’s Moon, backscattered Energetic Neutral Atoms (ENAs) have been shown to be suitable for studying the ion-surface interaction from an orbiting spacecraft [4]. We now present the first modeling of ENAs created by backscattered H, O and S ions at Ganymede, which will enable JUICE to remotely observe the ion impacts. Using the SDTrimSP code [5], which has been verified for backscattered ENAs at the Moon [6, 7], we account for inputs of magnetospheric plasma precipitation from hybrid simulations [8] and Ganymede’s surface composition from telescopic observations [9].

Our simulation results support that backscattering is an important formation process mainly for atomic H and O populations, whose properties are directly related to the precipitation conditions. Especially backscattered H ENAs dominate over any sputtered ENAs [10] above at least around 1 keV, making them ideal candidates for observing the plasma-surface interaction at Ganymede. Compared to lunar ENAs, backscattering probabilities are lower, but extended high-energy tails occur due to energetic ion populations in the Jovian plasma. The backscattering process thus creates neutral atom contributions that are candidates for observation with both JUICE’s JNA and JENI instruments.

[1]          S. Fatemi, et al., Geophys. Res. Lett. 43 (2016), 4745.

[2]          S.K. Trumbo, et al., Sci. Adv. 9 (2023), eadg3724.

[3]          C. Plainaki , et al., Astrophys. J. 940 (2022), 186.

[4]          Y. Futaana, et al., Gephys. Res. Lett. 40 (2013), 262.

[5]          A. Mutzke, et al., IPP Report 2019-02 (2019).

[6]          P.S. Szabo, et al., Geophys. Res. Lett. 49 (2022), e2022GL101232.

[7]          P.S. Szabo, et al., J. Geophys. Res.: Planets 128 (2023), e2023JE007911.

[8]          A.R. Poppe, et al., J. Geophys. Space Phys. 123 (2018), 4614.

[9]          N. Ligier, et al., Icarus 333 (2019), 496.

[10]       A. Pontoni, et al., J. Geophys. Space Phys. 127 (2022), e2021JA029439.

How to cite: Szabo, P. S., Poppe, A. R., Mutzke, A., Liuzzo, L., and Carberry Mogan, S. R.: Constraining Ion Precipitation onto Ganymede’s Surface with Backscattered Energetic Neutral Atoms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13075, https://doi.org/10.5194/egusphere-egu24-13075, 2024.

The MAss Spectrometer for Planetary EXploration (MASPEX) is a multi-bounce time-of-flight neutral gas mass spectrometer with unprecedented spaceborne mass resolution and sensitivity. It is capable of measuring and identifying minor and trace gases requiring mass resolution of m/Δm ~ 25,000 at abundances of parts-per-million in Europa’s exosphere. Exospheric sources of gases include exsolved, sublimed, sputtered, and radiolytically produced volatiles from Europa’s surface and interior. These gases can be used to characterize surface composition and identify volatiles outgassed from Europa’s interior. Of particular relevance in characterizing Europa’s habitability are the ratios of organic compounds such as alkanes, alkenes, alkynes, alcohols, ethers, aldehydes, amides, amines, and nitriles that undergo chemical transformations, which can be used to determine oxidation states, pH, temperature, and free energy availability of an interior ocean, perched lake, or a gas source region in the ice shell (e.g., a diapir).

This paper presents: 1) the principles and ground-calibrated performance of the MASPEX instrument that is now integrated onto the Europa Clipper spacecraft and planned to be launched in October of 2024, 2) the planned scientific investigation and its critical role in the study of Europa’s habitability, 3) the operational plans, and 4) the anticipated data products from the MASPEX investigation. The paper will also discuss the complexity of the investigation and its requisite need for the acquisition of supporting geochemical, impact fragmentation, and sputtering/radiolytic data sets that help to characterize the geochemical reaction framework and the anticipated modification of chemical species due to impacts with the instrument’s thermalizing chamber, and from radiolysis and sputtering. In the latter context we present the science team’s efforts to generate the necessary data sets, and we encourage interested scientists to contribute to this important endeavor, which is essential for the maximum success of the MASPEX investigation.

How to cite: Waite, J. H., Burch, J. L., Brockwell, T., Young, D. T., Miller, K., Glein, C. R., Wyrick, D. Y., Teolis, B. D., Bolton, S. J., Choukroun, M., McGrath, M. A., McKinnon, W. B., Mousis, O., Sephton, M. A., Shock, E., Zolotov, M. Y., Persyn, S. C., Stone, J. M., Perryman, R., and Ray, C. and the MASPEX Science and Instrument Teams: The Europa Clipper MASPEX Investigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6809, https://doi.org/10.5194/egusphere-egu24-6809, 2024.

In this study, we use the Direct Simulation Monte Carlo (DSMC) method [1] to investigate the collisional fraction of the atmospheres of Europa, Ganymede, and Callisto. The extent of the collisional atmosphere of the icy moons is still subject to ongoing debate. While Europa’s atmosphere is tenuous and effectively collisionless, the exobase for Ganymede and Callisto is expected to be located above a thin collision-dominated atmospheric layer [2].

In the 2030s, both ESA's Jupiter Icy Moons Explorer (JUICE) and NASA's Europa Clipper mission are set to explore Jupiter's icy moons from up close, using high-resolution mass spectrometers to sample their atmospheres. The Neutral gas and Ion Mass spectrometer (NIM) of the Particle Environment Package (PEP) onboard JUICE [3] and the MAss Spectrometer for Planetary EXploration (MASPEX) onboard Europa Clipper [4] will determine the atmospheric composition of the moons and potentially sample plume material on Europa. The collisional fraction of their atmospheres affects the abundances of the various species that will be measured, and hence also the deduction of the underlying surface composition. Therefore, obtaining a comprehensive understanding of atmospheric structures, including the collisional fraction, is imperative for both missions. This knowledge is essential to ensure the correct interpretation of the measured data once it becomes available.

The DSMC method is a computation technique, where rarefied gas flows are simulated by tracking the motion of individual particles, including their collisions and interactions, to provide insight into the macroscopic gas dynamics. Therefore, this method is ideal for studying thin atmospheres that transition from being collisional near the surface to ballistic at higher altitudes, such as the atmospheres of the icy Galilean moons. The model [5, 6] used herein includes different physical and chemical processes that create the atmospheres of the icy moons, such as sputtering due to interactions with Jupiter's magnetosphere, the sublimation of surface ice, and photochemical reactions.

[1] Bird, G. A. (1994). Molecular gas dynamics and the direct simulation of gas flows.
[2] Schlarmann, L., et al. (2024), in preparation.
[3] Grasset, O., et al. (2013). Planetary and Space Science, 78, 1-21.
[4] Phillips, C. B., and Pappalardo, R. T. (2014). Eos, Transactions AGU, 95(20), 165-167.
[5] Carberry Mogan, S. R., et al. (2021). Icarus, 368, 114597.
[6] Carberry Mogan, S. R., et al. (2022). Journal of Geophysical Research: Planets, 127(11).

How to cite: Schlarmann, L., Vorburger, A., Carberry Mogan, S. R., and Wurz, P.: Exploring the Collisionality of the Icy Galilean Moon Atmospheres., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-352, https://doi.org/10.5194/egusphere-egu24-352, 2024.

The Galileo spacecraft performed close flybys of the moon Ganymede between 1996 and 2001. We reanalysed data of the energetic particles detector EPD onboard Galileo and derived the particle fluxes, energy spectra, and pitch angle distributions in the energy range of several keV to MeV during Ganymede flybys G2, G7, G8, G28, and G29. We find sharp dropouts in ion and electron fluxes as signatures of the loss cones inside the Ganymede magnetosphere as well as trapped electron distribution. Additionally, bi-directional field-aligned and butterfly distributions were found as well. We discuss these findings compared with simulation results in charactering Ganymede’s magnetosphere and in the context of future measurements with the Particle Environment Package PEP onboard the Juice mission which will be in orbit around Ganymede in 2032.

How to cite: Krupp, N., Roussos, E., Fränz, M., Kollmann, P., Clark, G., Paranicas, C., Khurana, K., Barabash, S., and Galli, A.: Energetic particle measurements near Ganymede: Galileo EPD data revisited and perspectives for Juice PEP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7724, https://doi.org/10.5194/egusphere-egu24-7724, 2024.

How to cite: Beth, A., Galand, M., Modolo, R., Leblanc, F., Jia, X., Huybrighs, H., and Carnielli, G.: Ionospheric environment of Ganymede during the Galileo flybys, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11772, https://doi.org/10.5194/egusphere-egu24-11772, 2024.

At the very end of its growth, Jupiter became surrounded by a disk composed of gas and dust, where the Galilean moon presumably formed. It is supposed that satellitesimals formed by streaming instability and grew by pebble accretion. Once the satellitesimals reacedh a significant size, they undergone an inward type I migration by gravitational interaction with the disk. In the early stages of the circumplanetary disk, the migration of satellitesimals occurred over so short timescales that most bodies fell onto Jupiter, suggesting that the Galilean moons formed later during the disk’s evolution.  Other studies suggest that the moons sequentially formed and migrated inward. This suggests that the moons were trapped in mean motion resonances, halting their migration.  In the coming years, the ESA mission JUICE and NASA mission Europa-Clipper will study the Galilean moons composition and provide hints on their formation conditions.

In this context, we aim to model the evolution of a 2-dimensional circumplanetary disk around Jupiter. To do this, we have constructed a quasi-stationary circumplanetary disk model that considers viscous heating, accretion heating, and heating of the upper layers of the circumplanetary disk by Jupiter. The thermal structure is determined by a grey atmosphere radiative transfer model. We show that the heating by Jupiter of the upper layers of the disk induces flaring and disk self-shadowing effects, which locally increase and decrease the disk temperature, respectively. The resulting temperature variations can be up to 50 K relative to the surrounding disk temperature. Consequently, the circumplanetary disk can produce transient hotter and colder regions that can last up to 10 kyr. The alternance of hot and cold regions in the Jovian circumplanetary disk has then profound implications for the formation conditions of the Galilean moons.

How to cite: Schneeberger, A., Mousis, O., and Lunine, J.: Impact of Jupiter's heating and self-shadowing on the structure of its circumplanetary disk , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8573, https://doi.org/10.5194/egusphere-egu24-8573, 2024.

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 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 provide 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. G., Gkioulidou, M., Haggerty, D., Barabash, S., Wurz, P., Krupp, N., Roussos, E., Paty, C., Jia, X., Khurana, K., Allegrini, F., Pontoni, A., and Smith, H. 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 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12178, https://doi.org/10.5194/egusphere-egu24-12178, 2024.