Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022
Outer Planet Moons: Environments and Interactions


Outer Planet Moons: Environments and Interactions
Co-organized by MITM
Convener: Shahab Fatemi | Co-conveners: Audrey Vorburger, Lorenz Roth, Elias Roussos, Krishan Khurana
| Fri, 23 Sep, 12:00–13:25 (CEST), 15:30–16:45 (CEST)|Room Andalucia 3
| Attendance Thu, 22 Sep, 18:45–20:15 (CEST) | Display Wed, 21 Sep, 14:00–Fri, 23 Sep, 16:00|Poster area Level 1

Session assets

Discussion on Slack

Orals: Fri, 23 Sep | Room Andalucia 3

Chairpersons: Shahab Fatemi, Audrey Vorburger, Elias Roussos
A current picture of neutral tori at outer planetary systems: unique insight into moon-magnetospheric interactions
howard smith, Jamey Szalay, Ryoichi Koga, Robert Johnson, and Fuminori Tsuchiya
Jamey Szalay, Todd Smith, Eric Zirnstein, David McComas, Luke Begley, Fran Bagenal, Peter Delamere, Robert Wilson, Phil Valek, Andrew Poppe, Quentin Nenon, Frederic Allegrini, Robert Ebert, and Scott Bolton

Water-group gas continuously escapes from Jupiter’s icy moons to form co-orbiting populations of particles, or neutral toroidal clouds. We report the first observations of H2+ pickup ions in Jupiter’s magnetosphere from 13-18 Jovian radii, confirming the presence of a neutral H2 toroidal cloud. Pickup ion densities are consistent with an advecting Europa-genic cloud source. As the observed H2+ ions are originally produced from H2 lost from Europa, the abundance of detected ions allows us to determine that ~1 kg/s of neutral H2 is lost from Europa. Hence, these observations presented here for the first time directly measure ions from a neutral H2 toroidal cloud at Jupiter, prove the cloud provides an additional plasma source in Jupiter’s magnetosphere, and provide the most direct constraints on Europa’s loss of neutral H2 via observations of the neutral toroidal cloud’s primary loss process – pickup ions.

How to cite: Szalay, J., Smith, T., Zirnstein, E., McComas, D., Begley, L., Bagenal, F., Delamere, P., Wilson, R., Valek, P., Poppe, A., Nenon, Q., Allegrini, F., Ebert, R., and Bolton, S.: Water-group pickup ions from Europa-genic neutrals orbiting Jupiter, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-702,, 2022.

Norbert Krupp, Elias Roussos, Peter Kollmann, Chris Paranicas, George Clark, and Krishan Khurana

Pitch angle distribution of energetic particles can be used to understand the global topology of field lines (connected on both ends to the planet, connected on both ends to the moon or connected on one end to the moon and the other end to the planet etc.). The pitch angle distributions on field lines connected on one end to the moon can also be used to gauge the speed at which the field lines are convecting past a moon.

The Galileo spacecraft flew by the Galilean moons multiple times and explored the charged particle distributions in their vicinities. In this paper we will revisit the data of the Energetic Particles Detector EPD onboard Galileo in terms of pitch angle distributions for various energy channels  for different ion species and electrons in the energy range from 15 keV up to several tens of MeV.

We analyzed the Europa flybys E11, E12, E14, E15, E26.; Ganymede flybys G2, G7, G8, G28, G29; Callisto flybys C3, C9, C10.

We will show how different the energy-dependent pitch angle distributions are upstream and downstream of the moons and how different those distributions are between electrons and the various ions.

Electron PADs near Europa are trapped for energies of several 100 keV while for lower energies the PAD shapes are uncertain. Dropout signatures indicate that charged particles are lost in the moons' tenuous exospheres and onto their surface.

PADs near Ganymede showed bi-directional electron distributions for low energies upstream and trapped for higher energies while PADs of protons and heavy ions are more isotropic. Inside Ganymede’s magnetosphere trapped distributions have been observed when the S/C was connected to closed field lines.

The signal-to-noise ratio of energetic electron and ion fluxes near Callisto is a factor of 10 lower than for Europa. PADs near the moon are less clear compared to the other Galilean satellites. Bi-directional ion PADs close to the moon have been observed.

How to cite: Krupp, N., Roussos, E., Kollmann, P., Paranicas, C., Clark, G., and Khurana, K.: Pitch angle distributions (PADs) near the Galilean moons of Jupiter: Galileo flybys revisited, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-290,, 2022.

Juan Sebastian Cervantes Villa and Joachim Saur

Europa, the smallest of the Galilean moons, is embedded within Jupiter’s magnetosphere where a rapidly flowing plasma interacts electromagnetically with the moon’s atmosphere and its surface. The magnetic field in the plasma is also affected by Europa’s induced magnetic field in a subsurface conducting layer. Between 1996 and 2000, the Galileo spacecraft executed eight close flybys of Europa for which magnetic field measurements were obtained. Since then, several numerical magnetohydrodynamic (MHD) models have been developed to examine the interaction between the rapidly flowing Jovian magnetospheric plasma and Europa and its atmosphere (e.g. Kabin et al. [1999], Schilling et al. [2007], Rubin et al. [2015], Harris et al. [2021]).

In this study, we investigate the large scale interaction of Jupiter’s magnetospheric plasma with Europa and its atmosphere with a single fluid MHD model. We apply the 3D multiphysics model ZEUS-MP, based on Duling et al. [2014], and also employed by Blöcker at al. [2016] to describe Europa’s interaction. Our model accounts for ion-neutral collisions, electron impact ionization, dissociative recombination, and electromagnetic induction in a subsurface water ocean. In particular, we prescribe Europa’s molecular oxygen atmosphere with a number of analytical models in which we consider several degrees of asymmetry of the atmosphere and the location of Europa along its orbit around Jupiter, and we constrain its composition with Hubble Space Telescope (HST) spectral images.

The resulting magnetic field is compared with measurements performed by the Galileo magnetometer. We present an analysis of the observations from the Galileo flybys taking into consideration the variable geometry of the trajectories. Our comparative study is used to further constrain properties of the moon’s atmosphere and to quantify the effects of their variability on the plasma interaction.

How to cite: Cervantes Villa, J. S. and Saur, J.: Europa’s interaction with the Jovian magnetosphere: insights from the Galileo flybys, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-212,, 2022.

Peter Addison, Lucas Liuzzo, and Sven Simon

For the entire ion energy range observed at Europa, we calculate spatially resolved maps of the surface sputtering rates of H2O, O2, and H2 from impacts by magnetospheric ions. We use the perturbed electromagnetic fields from a hybrid model of Europa’s plasma interaction, along with a particle-tracing tool, to calculate the trajectories of magnetospheric ions impinging onto the surface and their resultant sputtering yields. We examine how the distribution of the sputtering rates depends on the electromagnetic field perturbations, the angle between the solar radiation and the corotating plasma flow, and the thickness of the oxygen-bearing layer within Europa’s surface. Our major findings are: (a) Magnetic field-line draping partially diverts the impinging ions around Europa, reducing the sputtering rates on the upstream hemisphere, but allowing for substantial sputtering from the downstream hemisphere. In contrast, zero sputtering occurs in much of the downstream hemisphere with uniform electromagnetic fields. (b) If the oxygen-bearing surface layer is thin compared to the penetration depth of magnetospheric ions, thermal ions dominate the O2 sputtering rates, and the region of strongest sputtering is persistently located near the upstream apex. However, if the oxygen-bearing layer is thick compared to the penetration depth, energetic ions sputter the most O2, and the location of maximum sputtering follows the sub-solar point as Europa orbits Jupiter. (c) The global production rate of O2 from Europa’s surface varies by a factor of 3 depending upon the moon’s orbital position, with the maximum particle release occurring when Europa’s Sun-lit and upstream hemispheres coincide.

How to cite: Addison, P., Liuzzo, L., and Simon, S.: Effect of the Magnetospheric Plasma Interaction and Solar Illumination on Ion Sputtering of Europa’s Surface Ice, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-2,, 2022.

Audrey Vorburger, Shahab Fatemi, André Galli, Shane Carberry Mogan, Lorenz Roth, and Peter Wurz

Ganymede’s water exosphere has been observed spectroscopically on several occasions since the first detection of atomic hydrogen in Ganymede’s exosphere in 1997 [1]. From these observations a consistent picture of Ganymede’s exosphere has emerged: Ganymede’s day-side exosphere is dominated by sublimated water with inferred column densities of up to several 1e15 cm-2, while elsewhere the exosphere is dominated by sputtered molecular oxygen (inferred column densities of several 1e14 cm-2) at low altitudes and by atomic oxygen (inferred column densities of several 1e13 cm-2) at higher altitudes [2-9]. In addition, atomic hydrogen has been observed with inferred column densities of a few 1e12 cm-2 [1, 4, 10]. Whereas many modeling approaches have been able to reproduce the inferred H2O and O2 densities, they have struggled to re-create the high inferred atomic oxygen and hydrogen column densities [11-13].

In this work, we present new simulations of Ganymede’s water-related exosphere. Our modeling results reproduce the observed H2O emissions well by sublimating water at Ganymede’s day-side surface temperature. The observed OI emission lines, which were interpreted as an O2 atmosphere, on the other hand, agree with a sputter source, with Jupiter’s magnetospheric plasma acting as the sputter agent.

Ganymede has a complex magnetic field, that shields part of the surface (mainly the equatorial regions) from impinging plasma ions and electrons, leaves the polar caps exposed to unhindered plasma precipitation, and accelerates the precipitating plasma in the separatrix, resulting in strong auroral emissions [2-8]. We show that the thermal electrons reaching the polar caps are insufficient to produce the amount of atomic oxygen and hydrogen inferred from the observations, and that an interaction between the water atmosphere and auroral electrons is necessary. In addition, we will discuss how the Particle Environment Package [14] onboard ESA’s JUpiter and ICy moons Explorer [15] will help us learn more about Ganymede’s atmosphere and plasma environment.


[1] Barth, C. A., C. W. Hord, A. I. F. Stewart, W. R. Pryor, K. E. Simmons, W. E. McClintock, J. M. Ajello, K. L. Naviaux, and J. J. Aiello (1997), “Galileo ultraviolet spectrometer observations of atomic hydrogen in the atmosphere of Ganymede”, Geophysical Research Letter, 24(17), 2147–2150.

[2] Hall, D. T., P. D. Feldman, M. A. McGrath, and D. F. Strobel (1998), “The Far-Ultraviolet Oxygen Airglow of Europa and Ganymede”, The Astrophysica Journal, 499(1), 475–481.

[3] Brown, M. E., and A. H. Bouchez (1999), “Observations of Ganymede’s visible aurorae”., in Bulletin of the American Astronomical Society, vol. 31.

[4] Feldman, P. D., M. A. McGrath, D. F. Strobel, H. W. Moos, K. D. Retherford, and B. C. Wolven (2000), “HST/STIS Ultraviolet Imaging of Polar Aurora on Ganymede”, The Astrophysical Journal, 535(2).

[5] McGrath, M. A., X. Jia, K. Retherford, P. D. Feldman, D. F. Strobel, and J. Saur (2013), “Aurora on Ganymede”, Journal of Geophysical Research (Space Physics), 118(5), 2043–2054.

[6] Saur, J., S. Duling, L. Roth, X. Jia, D. F. Strobel, P. D. Feldman, U. R. Christensen, K. D. Retherford, M. A. McGrath, F. Musacchio, A. Wennmacher, F. M. Neubauer, S. Simon, and O. Hartkorn (2015), “The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals”, Journal of Geophysical Research (Space Physics), 120(3).

[7] Musacchio, F., J. Saur, L. Roth, K. D. Retherford, M. A. McGrath, P. D. Feldman, and D. F. Strobel (2017), “Morphology of Ganymede’s FUV auroral ovals”, Journal of Geophysical Research (Space Physics), 122(3).

[8] Molyneux, P. M., J. D. Nichols, N. P. Bannister, E. J. Bunce, J. T. Clarke, S. W. H. Cowley, J. C. Gérard, D. Grodent, S. E. Milan, and C. Paty (2018), “Hubble Space Telescope Observations of Variations in Ganymede’s Oxygen Atmosphere and Aurora”, Journal of Geophysical Research (Space Physics), 123(5).

[9] Roth, L., N. Ivchenko, G. R. Gladstone, J. Saur, D. Grodent, B. Bonfond, P. M. Molyneux, and K. D. Retherford (2021), “Evidence for a sublimated water atmosphere on Ganymede from Hubble Space Telescope observations”, Nature Astronomy, 5.

[10] Alday, J., L. Roth, N. Ivchenko, K. D. Retherford, T. M. Becker, P. Molyneux, and J. Saur (2017), “New constraints on Ganymede’s hydrogen corona: Analysis of Lyman-α emissions observed by HST/STIS between 1998 and 2014”, Planetary and Space Science, 148.

[11] Marconi, M. (2007), A kinetic model of ganymede’s atmosphere, Icarus, 190(1).

[12] Turc, L., L. Leclercq, F. Leblanc, R. Modolo, and J.-Y. Chaufray (2014), Modelling ganymede’s neutral environment: A 3d test-particle simulation, Icarus, 229.

[13] Leblanc, F., A. Oza, L. Leclercq, C. Schmidt, T. Cassidy, R. Modolo, J. Chaufray, and R. Johnson (2017), On the orbital variability of ganymede’s atmosphere, Icarus, 293.

[14] Barabash, S., Wurz, P., Brandt, P., Wieser, M., Holmström, M., Futaana, Y., et al. (2013). “Particle Environment Package (PEP)”, European Planetary Science Congress 2013.

[15] Grasset, O., Dougherty, M. K., Coustenis, A., Bunce, E. J., Erd, C., Titov, D., et al. (2013). “JUpiter ICy moons Explorer (JUICE): An ESA mission to orbit Ganymede and to characterise the Jupiter system”. Planetary and Space Science, 78, 1–21.

How to cite: Vorburger, A., Fatemi, S., Galli, A., Carberry Mogan, S., Roth, L., and Wurz, P.: 3D Monte-Carlo Simulation of Ganymede’s Water-Related Exosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-635,, 2022.

Lucas Liuzzo, Andrew Poppe, Peter Addison, Sven Simon, Quentin Nenon, and Chris Paranicas

Jupiter’s moon Callisto is exposed to a highly dynamic magnetospheric environment. During a full synodic period, properties of the local magnetospheric field and thermal plasma environment change by an order of magnitude, and Callisto’s resulting interaction with the ambient plasma displays a strong variability.

In this study, we combine results from the AIKEF hybrid and GENTOo test-particle models to constrain the variability of energetic particle dynamics and quantify their flux onto the top of Callisto’s atmosphere during a synodic period. For three positions of Callisto with respect to the center of the Jovian current sheet (at maximum distance above, maximum distance below, and embedded within), we model the interaction between Callisto’s atmosphere/ionosphere, its induced field, and ambient magnetospheric plasma environment, and we trace energetic ions (hydrogen, oxygen, and sulfur) and electrons through the perturbed electromagnetic fields. Our findings highlight the important role that Callisto's interaction with the low energy magnetospheric plasma and signatures associated with the moon’s induced field have on shaping the dynamics and flux patterns of the high-energy particles, which may play a role in the asymmetric ionization of, and energy deposition into, Callisto's neutral atmosphere.

How to cite: Liuzzo, L., Poppe, A., Addison, P., Simon, S., Nenon, Q., and Paranicas, C.: Energetic particle fluxes onto Callisto's atmosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-282,, 2022.

Alexis Bouquet, Grégoire Danger, Laura Tenelanda-osorio, Philippe Boduch, Hermann Rothard, Julien Maillard, Isabelle Schmitz-Afonso, Carlos Afonso, Philippe Schmitt-Kopplin, Fabrice Duvernay, Cintia Pires da Costa, and Lawry Honold

We present the results of the implantation of sulfur ions in ice samples (H2O:C3H8) in conditions relevant to Europa and other jovian satellites. The samples were prepared and irradiated at 80 K, and were thick enough to ensure the projectiles were implanted in the ice, allowing the sulfur projectiles to become part of the ensuing chemistry. The evolution of the samples was followed with Fourier Transform Infra-Red (FT-IR) spectroscopy, and the organic residues were analyzed off-site through Ultra High Resolution Mass Spectrometry (UHRMS). The UHRMS shows formation of a complex, diverse refractory organic matter, however no evidence of organosulfur formation has been found.



Energetic particles from Jupiter’s magnetosphere (electrons, protons, oxygen and sulfur ions) are likely to be a key driver of the chemical evolution of the icy satellite’s surface, especially Europa; they can alter organic matter deposited on the surface from the internal ocean. In the case of impinging ions, in addition to the stopping power and total energy of the projectile [1], their reactivity is a possible factor in the chemistry. Sulfur is abundant in Jupiter’s magnetosphere [3] due to Io’s volcanic activity, and highly reactive. Experiments with sulfur projectiles have been performed and have shown the efficient creation of sulfuric acid in water ice [4, 5]; previous experiments by our group with interstellar analogs showed it can become part of the organic chemistry triggered by irradiation and form organosulfurs [6]. Here, in temperature conditions relevant to Europa (80K), we investigate the composition of the organic residue generated by the irradiation of a water:propane ice by sulfur ions.


We performed the experiments at the ARIBE low-energy line at the Grand Accélérateur National d’Ions Lourds (GANIL) in Caen, France. The projectiles were 105 keV  S6+ and 105 keV Ar7+ (the latter to produce a reference sample with a non-reactive projectile). The samples were prepared at 80K on a ZnSe window from a 2:1 H2O:C3H8 gas mixture and irradiated at a fluence of approximately 1014 ions. To ensure the products would be abundant enough to be detected, cycles of deposition-irradiation were repeated up to 15 times. The finally obtained samples were slowly warmed up to 300K to sublimate the volatiles and leave the refractory organic residue. This residue was analyzed off-site using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). This FT-ICR-MS technique represents the highest mass resolving power (R > 106) and highest mass accuracy (<200 ppb) among all mass spectrometric instruments [7]. This technique allows for detection and identification of species well beyond what is accessible with FT-IR. Two ionization techniques were used: Laser Desorption Ionization and Electro-Spray Ionization.


Infrared spectroscopy shows little difference to previous work on irradiation with electrons of similar ices [8], except for the early production of CO2 and modest abundance of CH4. No qualitative difference was seen between Ar-irradiated and S-irradiated samples in the IR.  

The results from the ESI or LDI FT-ICR-MS analysis show a very diverse, (3000 + annotations) refractory (average Double Bond Equivalent=14) organic matter (Figure 1). The residue features an insoluble phase. Heavy molecules (m/z>200) are common, showing that a fairly low dose is enough to form large molecules. No organosulfur could be identified, in stark contrast with our previous experiments [6]. Analysis of the soluble phase by ESI-FT-ICR shows that the oxygen-bearing products tend to be lighter. We discuss how our results compare to experiments using electrons ([8], and our own work).


Figure 1: Annotations (spot size is a function of intensity) obtained with the LDI-FT-ICR analysis, showing number of carbon atoms vs double bond equivalent (DBE) and number of oxygen atoms. A large amount of the residue is oxygen poor and highly aromatic.


A.B. and G.D. acknowledge the CNRS program "Programme National de Planétologie" (P.N.P, INSU), G.D. acknowledges the “Programme de Physique et Chimie du Milieu Interstellaire” (P.C.M.I, INSU) and the “Centre National d’Etudes Spatiales” (C.N.E.S) (exobiology program). H.R., P.B. and C.P.dC. acknowledge funding from Région Normandie through RIN EMERGENT SCHINOBI.


[1] Teolis et al. JGR: Planets 122.10 (2017): 1996-2012.
[2] von Steiger, R., Schwadron, N., Fisk, L., et al. 2000, JGR: Space Physics, 105, 27217
[3] Paranicas, C., Cooper, J., Garrett, H., Johnson, R., & Sturner, S. 2009, Europa. University of Arizona Press, Tucson, 529
[4] Ding et al. Icarus 226.1 (2013): 860-864.
[5] Strazzulla, et al. Icarus 192.2 (2007): 623-628.
[6] Ruf, et al. ApJL, 885(2), L40 (2019).
[7] Ruf et al.(2017) PNAS 114(11), 2819-2824.
[8] Hand, K. P., & Carlson, R. W. JGR: Planets, 117(E3). (2012)

How to cite: Bouquet, A., Danger, G., Tenelanda-osorio, L., Boduch, P., Rothard, H., Maillard, J., Schmitz-Afonso, I., Afonso, C., Schmitt-Kopplin, P., Duvernay, F., Pires da Costa, C., and Honold, L.: Organic chemistry on the surface of jovian icy satellites: formation of complex refractory organic matter by implantation of sulfur ions into water-alkanes ices, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-812,, 2022.

Lunch break
Chairpersons: Audrey Vorburger, Shahab Fatemi, Elias Roussos
Olivier Witasse and the the JUICE Teams

JUICE - JUpiter ICy moons Explorer - is the first large mission in the ESA Cosmic Vision 2015-2025 programme. The mission was selected in May 2012 and is currently in its final testing phase. Due to launch in April 2023 and to arrive at Jupiter in July 2031, it will spend at least three ½ years making detailed observations of Jupiter and three of its largest moons, Ganymede, Callisto and Europa.  The status of the project and the main milestones until launch are presented.

The focus of JUICE is to characterise the conditions that might have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasis on the three ocean worlds Ganymede, Europa, and Callisto. Ganymede, the largest moon in the Solar System, is identified as a high-priority target because it provides a unique and natural laboratory for analysis of the nature, evolution and potential habitability of icy worlds and waterworlds in general, but also because of the role it plays within the system of Galilean satellites, and its special magnetic and plasma interactions with the surrounding Jovian environment.

JUICE will also perform a multidisciplinary investigation of the Jupiter system as an archetype for gas giants. The Jovian atmosphere will be studied from the cloud top to the thermosphere. Concerning Jupiter’s magnetosphere, investigations of the three dimensional properties of the magnetodisc and of the coupling processes within the magnetosphere, ionosphere and thermosphere will be carried out. JUICE will study the moons’ interactions with the magnetosphere, gravitational coupling and long-term tidal evolution of the Galilean satellites.

The JUICE payload consists of 10 state-of-the-art instruments plus one experiment that uses the spacecraft telecommunication system with ground-based instruments. A remote sensing package includes imaging (JANUS) and spectral-imaging capabilities from the ultraviolet to the sub-millimetre wavelengths (MAJIS, UVS, SWI). A geophysical package consists of a laser altimeter (GALA) and a radar sounder (RIME) for exploring the surface and subsurface of the moons, and a radio science experiment (3GM) to probe the atmospheres of Jupiter and its satellites and to perform measurements of the gravity fields. An in situ package comprises a powerful suite to study plasma and neutral gas environments (PEP) with remote sensing capabilities of energetic neutrals, a magnetometer (J-MAG) and a radio and plasma wave instrument (RPWI), including electric fields sensors and a Langmuir probe. An experiment (PRIDE) using ground-based Very Long Baseline Interferometry (VLBI) will support precise determination of the spacecraft state vector with the focus at improving the ephemeris of the Jovian system.

The key milestones until launch are:

  • Spacecraft flight model environmental acceptance test campaign (mechanical, thermal) and deployment tests
  • Spacecraft flight model end-to-end communication tests with the flight control team
  • Readiness review of the ground segment
  • Mission qualification and acceptance review
  • Shipment to Kourou (French Guyana) and launch campaign

How to cite: Witasse, O. and the the JUICE Teams: JUICE (Jupiter Icy Moon Explorer): September 2022 status report, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-645,, 2022.

Stas Barabash, Pontus Brandt, and Peter Wurz and the PEP Team

1. PEP objectives

The PEP suite explores the particle populations in the Jovian system to answer three overarching science questions:

(1) How does the corotating magnetosphere of Jupiter interact with Ganymede, Callisto, Europa, and Io?

(2) How do internal and solar wind drivers cause such energetic, time variable and multi-scale phenomena in the steadily rotating giant magnetosphere of Jupiter?

(3) What are the structure and composition of the icy moons exospheres and how do they response to the external conditions?


2. PEP suite

PEP measures positive and negative ions, electrons, exospheric neutral gas, thermal plasma and energetic neutral atoms present in all domains of the Jupiter system over nine decades of energy from < 0.001 eV to > 1 MeV with full angular coverage. The six PEP sensors are:

  • Jovian plasma Dynamics and Composition analyzer (JDC);
  • Jovian Electrons and Ions analyzer (JEI);
  • Jovian Energetic Electrons (JoEE);
  • Jovian Energetic Neutrals and Ions sensors (JENI);
  • Jovian Neutrals Analyzer (JNA);
  • Neutral gas and Ion Mass spectrometer (NIM).

For the first time at Jupiter PEP combines global imaging via remote sensing using ENAs with in-situ measurements and performs global imaging of Europa/Io tori and magnetosphere combined with energetic ion measurements. Using low energy ENAs originating from the particle – surface interaction PEP investigate space weathering of the icy moons by precipitation particles. PEP will first-ever directly sample the exospheres of Europa, Ganymede, and Callisto with high mass resolution.

Figure 1: PEP suite and PEP sensors

3. PEP ready to go

All flight models of the PEP sensors and electronics as well as central processing unit and common power supply system have been tested, qualified, and calibrated. The complete model was delivered to ESA and ready for launch in April 2023. All sensors performance fulfilles the mission requirements. PEP will provide the most comprehensive simultaneous measurements of the plasma and neutral gas environment in the Jovian system and at the Galilean moon.

How to cite: Barabash, S., Brandt, P., and Wurz, P. and the PEP Team: The Particle Environment Package (PEP) for the JUICE mission: Ready to go!, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-681,, 2022.

Jan Bergman and Jan-Erik Wahlund

The Radio & Plasma Wave Investigation (RPWI) onboard the ESA JUpiter ICy moons Explorer (JUICE) is here described in detail. 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 like, e.g., electromagnetic and plasma waves, electrostatic acceleration structures, induction fields etc. A full wave vector, waveform, polarization, and Poynting flux determination is aimed for. In addition, RPWI will enable characterization of 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. RPWI can also detect micrometeorite impacts, estimate dust charging, monitoring the spacecraft potential as well as the integrated EUV flux. The sensors consist of four 10 cm diameter Langmuir probes each mounted at the tip of 3 m long booms, a triaxial search coil magnetometer and a triaxial radio antenna system both mounted on the 10.5 m long MAG boom, each with radiation resistant pre-amplifiers near the sensors. There are three receiver boards, 2x Digital Processing Units (DPU) and 2x Low Voltage Power Supply (LVPS) boards in a central box in a radiation vault at the centre of the JUICE spacecraft. Together, the RPWI system can carry out a powerful and ambitious planetary science investigation in and around the Galilean icy moons and the Jovian space environment. Some of the more important science objectives & capabilities will be described here. RPWI focuses, apart from cold plasma studies, on the understanding of how, through electro-dynamic and electromagnetic coupling, the momentum and energy transfer occur in the surrounding space environments and 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 will hopefully deliver data from the near surface during the final crash orbit.

How to cite: Bergman, J. and Wahlund, J.-E.: The Radio and Plasma Wave Investigation (RPWI) for the JUpiter ICy moons Explorer (JUICE), Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-838,, 2022.

Investigating Jovian Radiation Environment by the Europa Clipper Mission
Insoo Jun, Chris Paranicas, and Richard Meitzler
Alfred McEwen, Lynn Carter, Daniella DellaGiustina, Laszlo Kestay, Brett Denevi, Amanda Haapala, Joseph Westlake, Ryan Park, Krishan Khurana, Nicolas Thomas, Peter Wurz, and Joern Helbert

Io, the world with the greatest tidal flexing, volcanic and tectonic activity, and mass-loss in our solar system, begs for dedicated exploration.  Missions such as Juno and JUICE, along with Earth-based telescopes such as JWST and ALMA, will acquire important Io observations over the next 15 years, as could Europa Clipper.  However, a mission designed for Io science is necessary to accomplish key science goals that have been consistently prioritized in the National Academy of Sciences Decadal Surveys and the ESA Voyage 2050 (Thomas, 2021, Experimental Astronomy online), including understanding the early evolution of terrestrial planets, tidally heated exoplanets and ocean worlds, and magnetospheric physics across the galaxy.  The NASA Discovery-class Io Volcano Observer (IVO; McEwen et al., 2021, LPSC 1352) completed Phase A in 2021 and was deemed selectable, but was not chosen for programmatic (i.e., non-science/engineering) reasons.  The IVO concept study demonstrated how a total of ten carefully designed, close Io flybys could determine the melt distribution in Io’s interior to confirm or refute the presence of a magma ocean, constrain Io’s global average lithospheric structure, identify where and how Io is losing heat, and determine processes and rates for Io’s volatile loss.  Such encounters would also measure Io’s rate of orbital migration, key to determining the stability of the LaPlace resonance that heats Europa and Ganymede, as well as Io.  The ambitious (for Discovery) science payload included a magnetometer, plasma instrument, narrow-angle camera, thermal mapper, neutral mass spectrometer, plus a telecom system for gravity science and options for a student-collaboration wide-angle camera (WAC), and a technology demonstration UV spectrometer.   

The next Discovery mission proposal opportunity is expected in 2025 or later, but an opportunity to propose an Io mission in NASA’s New Frontiers (NF) program is anticipated in 2023.  How might that differ from a Discovery-class mission?  An Io orbiter to provide better geophysical measurements has been suggested in the past, but would be very challenging deep inside Jupiter’s gravity well and high radiation zone. An orbiter might be feasible if new, more capable launch vehicles become available. On the other hand, the IVO Discovery concept would accomplish all of the science objectives of NF, and could be augmented in several key ways using the additional resources available in NF. A radiation design to support more than 10 encounters is a relatively straightforward enhancement. Ka-band would improve the data downlink capability and gravity science.  With twice as many Io encounters, it would be possible to more completely map Io’s surface at multiple wavelengths; encounter Io over additional values of orbital true anomaly for improved gravity science, magnetic induction, and measuring Io’s libration; and sample more longitudes and times of day to understand Io’s atmosphere, plumes, magnetospheric interactions, and mass loss. The WAC, which is especially important for mapping Io’s topography, could be a required Baseline experiment. There are many science instruments that would be valuable additions, including altimetry, ultraviolet and near-IR spectroscopy, a dust mass spectrometer, passive radar sounding (using Jupiter radiation), active radar sounding, and additional fields and particle instruments.  Greater emphasis may be placed on tracing the mass and energy flows in the Io-Jupiter system, especially because the new US Planetary Science and Astrobiology Decadal Survey places much emphasis on understanding planetary systems relevant to exoplanets. Interferometric synthetic aperture radar (InSAR) would be challenging but could transform our understanding of active processes on Io.  An even more daring idea is to deliver a penetrator that could measure Io’s seismicity and conducted heat flow, perhaps also with a laser retroreflector or radio transponder to measure Io’s rotational and tidal deformation.  However, getting substantial data back to the main spacecraft for transmittal to Earth is challenging in the very fast flybys that are preferred to keep the total ionizing radiation dose low.  In terms of international collaboration, we expect a thermal mapper from DLR and a neutral mass spectrometer from UBE, plus science co-investigators; additional contributions are possible.  In summary, a highly capable mission to one of the most exciting objects in the Solar System is overdue. 

Figure: Io is a spectacular target to observe both in daytime and at night (simulated hot spots).

How to cite: McEwen, A., Carter, L., DellaGiustina, D., Kestay, L., Denevi, B., Haapala, A., Westlake, J., Park, R., Khurana, K., Thomas, N., Wurz, P., and Helbert, J.: A NASA New Frontiers Mission Concept to Io, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-37,, 2022.

William B. McKinnon and Kevin J. Zahnle

Abstract. Bierson and Nimmo [1] have proposed that, under certain circumstances, as Galilean-scale satellites accrete they may lose substantial (if not all) of their accreted water ice. This is not, however, a get out of jail free card for satellite accretion models or scenarios. Each satellite accretion model (of which there are many) must be evaluated against the parameters chosen in [1], and the modest ice content of Europa and the apparent anhydrous nature of Io accounted for. Here we evaluate published models in this light, and focus especially on the roles of background protojovian subnebula temperatures and pressures.

Introduction. The formation of Jupiter in the core accretion–gas capture model inevitably ends with a circumplanetary accretion and/or decretion disk (CPD) around the planet. Numerous satellite formation models have been proposed [2-11], with different parameters for disk structure (surface density, temperature, opacity, viscosity). All rely on inferences and assumptions of mass and angular momentum inflow to Jupiter. Numerical gap opening calculations [e.g., 12] provided the basis for the gas-starved model [2-4]. Later 3D radiative-hydrodynamic inflow calculations prompted consideration of heliocentric planetesimal capture as the dominant source of satellite-building solids [13]. Hypotheses for dust and small pebble deposition range from distant infall [e.g., 14] to close-in infall and formation of an outflowing, decretion disk [15]. Multiple generations of satellites may form and be lost [3], Or maybe not, if a magnetospheric cavity opens up close to Jupiter and the innermost satellite, destined to become Io, stalls there [e.g., 16,17].

The thermal environment of Io and Europa’s formation could have been hot enough to largely devolatilize any small, accreting satellitesimals, including the ablated fragments of heliocentric planetesimals that encounter the CPD [8]. Some models call for accretion of Io and Europa in the cold outer disk followed by inward type I migration [e.g., 15,18]. Ultimate removal of major amounts of ice is a non-trivial requirement in such scenarios.

Hydrodynamic Wind. We consider a water vapor atmosphere at the saturation vapor pressure (SVP) of a water ocean formed during accretion [1]. If the outflow wind speed u, which increases away from the surface, becomes transonic at the critical radius rc = GM/2c2 (where G is the gravitational constant, M the satellite mass, and c the isothermal sound speed), then the outflow can continue unimpeded [19,20]. For example, If Europa accreted with a 300 K water surface, the SVP would be 3.35 kPa, with a c = 372 m/s. The isothermal atmosphere is a favorable case for hydrodynamic escape, and because it admits simple analytic solutions for u(r), it is well-suited to this discussion. The critical distance rc = 7.4Re, where Re is Europa’s present radius. At the surface rs [20]:

For the 300 K Europa case above, us ≈ 0.04 m/s, and for steady-state (mass flux conserved) outflow, both the thermodynamic and ram pressure at rc are ≈6 mPa. Such pressures are low compared with the CPD pressures in even gas-starved models [1,2], even far from Jupiter, which suggests that CPD details as well as accretional mass, radius and surface T, determine if blowoff is possible (e.g., Fig. 1).

Figure 1. Escape of isothermal water vapor atmospheres from Io is suppressed by the back pressure of the CPD if the back pressure exceeds the wind's critical point pressure. E.g., for a nebular pressure of 1 Pa, an escaping wind begins to blow only for T>400 K. If the back pressure exceeds the critical pressure, the flow reverses sign and Io accretes nebular gas.

Discussion. Ram and thermodynamic pressures at the critical, transonic radius are strong functions of satellite radius and accretional surface temperature. Larger values imply free flow to the background CPD, whereas smaller values (if below ambient) imply the wind is inhibited (the pressure boundary condition at rc cannot be met). Because saturation is assumed at the surface, the actual atmospheric pressure should follow the saturation vapor curve, implying even lower transonic pressures and more stringent limits [19,20]. For cold CPD conditions consistent with the condensation of water ice (<200 K) or its survival in small satellitesimals, any H2O loss will depend critically on accretion timescale and surface temperatures reached [1]. For accretion of icy satellitesimals in warm to hot CPD conditions, such as resulting from inward drift or direct capture from heliocentric orbit, the satellitesimals themselves should actively sublimate prior to accretion. Such comet-style loss would not in itself contribute to isotopic shifts [cf. 1]. Most importantly, however, the hydrodynamic loss model discussed here is an idealization, and implicitly assumes a static background gas subnebula (or lack thereof). The reality of satellite accretion involves a nebular headwind, which will act to sweep any water vapor atmosphere away from the growing satellite. This process is daunting to model, but will both act to accelerate water vapor loss (the ultimate limit being free sublimation) but at the same time increase sublimation cooling.

Acknowledgement. WBM thanks NASA’s Europa Clipper project.


[1] Bierson, C. J. and F. Nimmo. 2020. ApJ, 897, L43.

[2] Canup. R.M. and W.R. Ward. 2002. AJ, 124, 3404-3423.

[3] Canup, R.M. and W.R. Ward. 2006. Nature, 441, 834-839.

[4] Canup, R. M. and W. R. Ward. 2009.  In Europa, 59-83.

[5] Mosqueira, I., and P.R. Estrada. 2003. Icarus, 163, 198-231.

[6] Mosqueira, I. and P.R. Estrada. 2003. Icarus, 163, 232-255.

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[13] Schulik, M., et al. 2020. A&A, 642, A187.

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How to cite: McKinnon, W. B. and Zahnle, K. J.: On the Potential Hydrodynamic Loss of Water Vapor During Accretion of the Galilean Satellites, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1015,, 2022.

Paul Schenk, Bonnie Buratti, Roger Clark, Paul Byrne, William McKinnon, Isamu Matsuyama, Francis Nimmo, and Francesca Scipioni
  • 1. Introduction

Tethys is unusual among icy moons for its low bulk mean density of 0.985 g/cm3, suggesting a low rock mass fraction and/or high porosity.  Like other mid-sized icy satellites Tethys has an intense fracture history [1], including Ithaca Chasma as well as several hundred arcuate andlinear troughs, grooves, and cracks.   Unique to Tethys, however, are dark reddish linear features visible to Cassini under high solar illumination conditions (a lower albedo and flatter spectral signature in the green–IR range; Figs. 1, 2).   Our CDAP-funded research is focused on mapping these features and testing hypotheses for their formation and implications for Tethys’ evolution

Figure 1: Color view of Tethys showing IR lineations (reddish arcs).  Cassini IR3, green, UV3 image composite.

Figure 2: Preliminary spectral plot showing IR lineaments (red) and adjacent cratered plains (green) from ISS images.

Figure 3: Global map of fractures, ridges, and lineations on Tethys.  IR lineations are shown in red. Odysseus is large circle at upper center.

1.1 IR-Lineations

There are at least three prominent sets in the northern anti-Saturn hemisphere, centered on the anti-Saturn meridian (Fig. 3).  Each setconsists of ~5–10 parallel lineations a few kilometers across and 50–250 km long. The lineations are remarkably curvilinear (i.e., non-sinuous), do not follow great circles, and are not deflected by major impact structures: they cross the floor of the 400-km-diameter, 9-km-deep Odysseus impact basin as if it were not there.

Although more poorly observed, sub-Saturn hemispheric color imaging at low-phase angle clearly shows a similar set of arcuate, reddishlineations on that hemisphere, despite deposition of E-ring dust particles from Enceladus [2] indicating that these features are being renewed on some time-scale.

The red lineaments centered near ~25° N, 175°E were imaged at high resolution. Mapping at ~90–125 m/pixel (Fig. 4) (together with stereo andlower resolution color imaging) shows no discrete scarp, ridge, or other tectonic manifestation along the ~100 km portion of the feature soimaged.  Only a faint discoloration of the surface has been identified (Fig. 5). Further, >20 dark spots 200–800 m in diameter lie along this setof lineaments.  These spots are characterized by very low albedos, sharp boundaries, and no evidence of raised rims consistent with an impactorigin. Of these, >60% are situated at the bottom of impact craters.

Figure 4: High-resolution, 90 m/pixel mosaic of IR lineaments, merged with IR3–Gr–UV3 color mosaic.

Figure 5: Enlargement of high-resolution view in Figure 4 showing reddish lineament (red arrows) and small dark spots (blue arrows).

Red streaks centered at 45° N, 333°E were targeted for high resolution ISS and VIMS observations in late 2015 (although the VIMS cubes were partially corrupted).    As at the above site no discrete faults, scarps or grooves was resolved here despite pixel scales as good as ~60 m.

  • 2. Origin of IR-Lineaments

The spatial pattern of IR lineaments on Tethys shows a strong symmetry (Fig. 3), centered on the current tidal axis with Saturn. A lack ofcorrelation with local geology might suggest an exogenic origin. Conversely, there are no rayed craters at the radial centers of these features.Further, the locations of the patterns on both the sub- and anti-Saturn hemispheres, and the lineaments’ parallel orientations, argue against adisrupted comet origin (à la SL9).  The lineaments have no systematic orientation relative to Odysseus, indicating that stresses arising fromthe relaxation of that basin [3] are not responsible for these features.

Global stresses might have produced the pattern we observe. The IR lineaments may match patterns of strain predicted to result from a non-synchronous rotation stress state, although this is unlikely for a cold, triaxial body like Tethys. The best-fit patterns correspond to a combination of global expansion with true polar wander or tidal axis reorientation (Fig. 6a, b). The misfit for global expansion combined recession is significantly larger (Fig. 6c). The dramatic lack of such features in the southern hemisphere (Fig. 3), where only a few short isolated red streaks are evident, is not explained by any currently considered stress regime. 

Figure 6: (a-c) Observed (red) and predicted (green) tectonic patterns due to combination of global expansion with (a) true polar wander, (b) tidal axis reorientation, (c) orbit recession. Solid and open circles indicate location of initial rotation and tidal axes. (d) Relative frequency distribution of misfit between observed and predicted fault segment azimuths for processes in panels a-c. Labels show mean misfit for each model.

The lack of obvious tectonic deformation despite the strong color signature is unusual (although features may exist below the currentresolution limit). The lineaments could be reactivated ancient fractures, producing a temporal discoloration. At present there is no topographic or morphologic signature to support this. If tectonic, the lineaments might be still forming, with deformation only on a scale below that which we can resolve.

The dark and reddish coloration could be due to a particulate contaminant in the ice grains that is more spectrally visible if the grain sizes are larger along the streaks.  Alternatively, a dark reddish contaminant has been deposited on the surface along the streaks.  Such a contaminant could be due to precipitation of a distinct material along unresolved surface or near-surface fractures, with subsequent mixing of contaminant into the local regolith.  VIMS spectral cubes are being reprocessed to verify whether organic rich materials may be involved.  Low-volume but persistentoutgassing and emplacement of volatiles from the interior (possibly due to clathrate decomposition associated with fracture formation) thecolors of which are distinct from the evolved surface and/or result from alteration due to exposure to the space environment, may be responsible.

The coloration of Tethys unique red streaks, and collocated dark spots, are consistent with active alteration of the surface, given that E-ringaccumulation is expected to remove intrinsic color signatures in a geologically short time period.  Differences in particle sizes of the outgassed material may add to this spectral distinctiveness.

How to cite: Schenk, P., Buratti, B., Clark, R., Byrne, P., McKinnon, W., Matsuyama, I., Nimmo, F., and Scipioni, F.: Red Streaks on Tethys: Evidence for Recent Activity, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-732,, 2022.

Display time: Wed, 21 Sep 14:00–Fri, 23 Sep 16:00

Posters: Thu, 22 Sep, 18:45–20:15 | Poster area Level 1

Chairpersons: Shahab Fatemi, Audrey Vorburger, Elias Roussos
Lea Klaiber, Nicolas Thomas, Raphael Marschall, and Moses Milazzo

Io is the innermost galilean satellite of Jupiter and object to extreme tidal forces. As a result of these forces Io is the most volcanically active body in our solar system. Its large volcanic plumes can rise up to several hundred kilometres above the surface and are one known source of Io's SO2 atmosphere. Additionally, the surface of the moon is covered with surface frost which sublimates in sunlight and condenses during the night or when Io enters eclipse behind Jupiter. Therefore, Io’s atmosphere is a result of the combination of volcanism and sublimation, but it is unknown exactly how these processes work together to create the observed atmosphere. That is why we want to present an approach on modelling Io’s atmosphere and provide a better understanding of the ongoing dynamic processes.

Both, the gas flow of the plume and the sublimation atmosphere, are modelled using the Direct Simulation Monte Carlo (DSMC) method first utilised by G. A. Bird [1]. The DSMC method is the most suitable for this case because the gas dynamics can be modelled over a great range of gas densities which is especially important for rarefied gas flows at high altitudes and on the night side of Io. It is a particle-based method which returns a 3D gas flow field as a result. While we currently focus on single species simulations, our DSMC code is designed to support multiple species enabling us to study the gas emission of other volcanic features as for example lava lakes in the future. This allows us to investigate the influence and contributions of different processes to the atmosphere. The idea of our work is based on simulations done by McDoniel et al. [2].

In a first case, we are investigating the flow of SO2 gas from the source of a plume, into the umbrella-shaped canopy and eventually back onto the surface locally. Additionally, we also study the interaction of the plume with an ambient sublimation atmosphere. In a second case, data obtained by the Galileo SSI experiment is used to create a surface albedo map of Io which enables us to calculate a more precise global thermal model for the sublimation atmosphere. We can then place plumes on the surface and study the interaction of volcanic and sublimation effects globally. Finally, we are also able to implement dust particles in the plume and analyse the effect for different dust sizes. From these results we can calculate images of the column density and the reflectance which in a next step could be used to compare to observational data.

Overall, our goal is to gain a better understanding of the plume structure, the interaction with the ambient atmosphere and the overall contribution of different processes to Io's atmosphere in preparation for future missions such as JUICE, Europa Clipper and a possible future Io Volcano Observer.


[1] Bird, G. A. (1994). Molecular Gas Dynamics and the Direct Simulation of Gas Flows.

[2] McDoniel, W. et al. (2019). Simulation of Io’s plumes and Jupiter’s plasma torus. Phys. Fluids 31, 077103. DOI: 10.1063/1.5097961.

How to cite: Klaiber, L., Thomas, N., Marschall, R., and Milazzo, M.: DSMC Simulations of Io’s atmosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-931,, 2022.

Peter Addison, Lucas Liuzzo, Hannes Arnold, and Sven Simon

We combine the electromagnetic fields from a hybrid model with a particle-tracing code to calculate the time-varying spatial distribution of magnetospheric ion flux onto the surface of Jupiter’s moon Europa. The electromagnetic fields at Europa are perturbed by the sub-alfvénic interaction of the moon’s ionosphere and induced dipole with the magnetospheric plasma. These perturbations substantially modify magnetospheric ion trajectories at all energies. We calculate spatially resolved surface flux maps of thermal and energetic ions for various distances between Europa and the center of Jupiter’s magnetospheric plasma sheet. The upstream ion distributions are constrained through in-situ particle data from the Galileo and Juno spacecraft. These maps are then combined to obtain the average distribution of magnetospheric ion surface flux over a full synodic rotation. Our results show that the draping and pileup of the magnetic field reduce ion flux onto Europa’s trailing hemisphere by several orders of magnitude, while a significant number of the incident ions are deflected onto the leading hemisphere. Taking into account the deflection of energetic ions in the draped electromagnetic fields shifts the region of minimum energetic ion surface flux from Europa’s wakeside equator to its ramside equator. This generates an “inverted bullseye” pattern of energetic ion flux centered at the trailing apex. Despite drastic changes to the morphology of the ion surface flux when the alfvénic plasma interaction is included, we still find a strong correlation between variations of sulfuric acid concentration observed across Europa’s surface by Galileo and our modeled sulfur influx pattern.

How to cite: Addison, P., Liuzzo, L., Arnold, H., and Simon, S.: Influence of Europa’s Time-Varying Electromagnetic Environment on Magnetospheric Ion Precipitation and Surface Weathering, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1,, 2022.

Shahab Fatemi, Andrew R. Poppe, Audrey Vorburger, Jesper Lindkvist, and Maria Hamrin

We use a three-dimensional hybrid model of plasma (kinetic ions and charge neutralizing electron fluid) to study the dynamics of the thermal O+ and H+ ions at Ganymede's magnetopause when Ganymede is inside and outside of the jovian plasma sheet. Our kinetic simulations show that ion velocity distributions at the vicinity of the upstream magnetopause of Ganymede are highly non-Maxwellian where the dominant component of the velocity distribution is parallel to the background magnetic field (i.e., Tll>T⊥). At the magnetopause, however, ions are substantially heated and the dominant component of the velocity distribution is perpendicular to the background magnetic field (i.e., Tll<T⊥). We also investigate the energization of the ions interacting with the magnetopause and we find that the energy of those particles on average increases by a factor of 8 and 30 for the O+ and H+ ions, respectively. The energy of these ions is mostly within 1-100 keV for both species after interaction with the magnetopause, but a few percentage reach to 0.1-1 MeV. Our simulations show that a small fraction (<25%) of the co-rotating Jovian plasma reach the magnetopause, but among those more than 50% cross the high power density regions at the magnetopause and gain energy. Finally, we compare our simulation results with Galileo observations of Ganymede's magnetopause crossings (i.e., G8 and G28 flybys). There is an excellent agreement between our simulations and observations, particularly our simulations fully capture the size of the magnetosphere and reproduce the sharp magnetic transients at the magnetopause crossings.

How to cite: Fatemi, S., Poppe, A. R., Vorburger, A., Lindkvist, J., and Hamrin, M.: Hybrid simulations of jovian plasma interaction with Ganymede's magnetopause, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-27,, 2022.

Elke Kersten, Anatoly E. Zubarev, Irina E. Nadezhdina, Thomas Roatsch, Klaus-Dieter Matz, and Claudia Camila Szczech

1. Introduction

In preparation of the JUICE mission with the primary target Ganymede [1] we generated a new controlled version of the global Ganymede image mosaic from Voyager 1 and 2 and Galileo images [2] based on a new 3D control point network from Zubarev et al., 2016 [3]. In 2021, the Juno mission acquired new Ganymede images with its onboard wide-angle camera JunoCam [4]. We used the best available images from Perijove 34 to integrate them into the global Ganymede mosaic.

2. Image data

On June 7th, 2021, near the end of Juno’s prime mission, the spacecraft flew by Ganymede to obtain four close-ups of the leading side of the moon from an altitude of about 1046 km. The derived image data has been integrated into the control point network of Ganymede to find a global solution for all three datasets. The new control point network consists of 4968 points.

3. Mosaicking

After aligning the Juno images photogrammetrically to fit onto the global Ganymede mosaic from Voyager and Galileo images brightness and contrast corrections have been applied to the Juno images manually to create a consistent look within the global mosaic. The small crater Anat is defining the longitude system at 232° East and the radius is set to 2631.2 km. The updated version of the global Ganymede mosaic will become available at and will be archived at PSA’s GSF.

4. Outlook

With this work we hope to support the JUICE team during pre-arrival investigations and the observation planning of Ganymede.


[1] Grasset et al., 2013, Planetary and Space Science, 78, 1-21, DOI: 10.1016/S0032063312003777. [2] Kersten et al., 2021, Planetary and Space Science 206, DOI: 10.1016/j.pss.2021.105310. [3] Zubarev et al., 2016, Solar System Research, 50, 5, 352-360, DOI: 10.1134/S0038094616050087. [4] Hansen et al., 2017, Space Science Reviews, 213, pages 475-506.

How to cite: Kersten, E., Zubarev, A. E., Nadezhdina, I. E., Roatsch, T., Matz, K.-D., and Szczech, C. C.: Updated Ganymede Mosaic from Juno Perijove 34 Images, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-450,, 2022.

Low-energy Energetic Neutrals Atom imaging of Jovian icy moons by PEP/JNA on JUICE
Manabu Shimoyama, Angèle Pontoni, Stefan Karlson, Kazushi Asamura, Peter Wurz, Martin Wieser, and Stas Barabash
Patrick Bambach, Norbert Krupp, Markus Fränz, Elias Roussos, Philipp Heumüller, Henning Fischer, Frank Meyer, and Istvan Szemerey


Electrostatic analyzers are key instruments for understanding magnetospheric plasma. Their measurements
also contribute to the determination of the surface and interior composition of moons and planets. They
measure properties in particle charge, energy and 3D velocity vectors of electrons and ions. Calibration of
these instruments is challenging. Ground facilities can not reproduce the electromagnetic and radiation
background of Jupiter. Also the particle flows and, their full energy- and 3D flow spectrum over the
complete field of view of a spherical analyzers can not be produced by our facilities. Instead beams
larger than the field of view of at least one detector channel reproduce step-vise parts of the parameter
spaces of the expected spectrum. By combining simulations, ground based calibration and in-flight
calibration, the reliability of the calibration can be increased. The calibration of the flight model of
the The Jupiter Electron and Ion Spectrometer (JEI) showed good agreement with the simulations, except
for a significant discrepancy in azimuth resolution and the geometric factor at high pole inclinations.
After a final upgrade of the test bench, we will allow for better comparison of results between
The Jupiter Icy Moons Explorer (JUICE) and the BepiColombo missions by cross-calibrating JEI and
the The Planetary Ion Camera (PICAM).

Plain Language Summary
Charged particles interact with magnetic field, planets and moons. Measuring the properties of these par-
ticles helps to understand the interaction and allows to analyze the surfaces and interiors of planets and
moons as a result of their interaction with their surrounding magnetic field. Unfortunately, calibration of
these instruments is complicated because accelerators only produce a small spectrum of the target particle
streams at once. In order to improve the results, calibration measurements on the ground are combined
with simulations and later with calibrations during the mission using known plasma, like the solar wind. The
calibration for JEI agreed with the simulations, except for high polar angles(Fig. 1.)
This is due to the different beams used for calibration and simulation. 
1 Introduction

JUICE will explore the Jovian magnetosphere and three of the four Galilean moons. After several fly-
bys of Europa and Callisto it will eventually enter orbit around Ganymede. JEI is part of The Particle Environ-
ment Package (PEP) on JUICE. JEI will measure electron and ion distributions in the range from a few eV to a few
MeV with almost full hemispheric coverage.
PICAM on BepiColombo has overlaps with JEI in its energy range from 1 eV to 3 keV. While mea-
suring ions only, PICAM has additionally a time-of-flight unit, which allows to resolve incoming particles
at a m/δm ratio of 100. There are links between Mercury and Ganymede. Besides being similar
size, they are the only known solid objects in the solar system other than Earth that have intrinsic mag-
netic fields. While the magnetic moments are similar in strength, Mercury is exposed to a supersonic plasma
of the solar wind while Ganymede is only surrounded by the subsonic plasma of Jupiter’s magnetosphere. 

2. Results

For all JEI models, including the qualification model, the polar-, energy- and azimuth resolution could be
measured in agreement with the accompanying simulations and within the specifications of the original
proposal. The resolutions and deflector response are plotted in Fig. 2. Only the azimuth resolution deviates
at higher polar inclinations from the simulations. The deviation directly affects the geometric factor, which
differs over the polar inclinations in the same range.
The deviation is suspected to be reasoned by the different exposure of the sensor in the particle flow be-
tween the simulations and the beam in the test facility. Simulations and measurements with an off-center
beam are currently conducted to confirm the cause. 
A slight coaxial misalignment between the inner and outer spheres could be measured due to the deviations
of the individual energy peaks of the channels.
Currently the positing system is under replacement to allow joint measurements of JEI and PICAM.
This works is supported by DLR grants 50QW1702
and 50QJ1503.

How to cite: Bambach, P., Krupp, N., Fränz, M., Roussos, E., Heumüller, P., Fischer, H., Meyer, F., and Szemerey, I.: The Calibration results of the Flight model of the Jovian Electron and Ion spectrometer for the Jupiter Icy Moons Explorer and their link to Mercury, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1093,, 2022.

Alice Le Gall, Robin Sultana, Léa Bonnefoy, Cédric Leyrat, and Michael A. Janssen

The Cassini mission explored Saturn’s system from 2004 to 2017. On its board, a RADAR operating at a wavelength of 2.2 cm (13.78 GHz), had been initially designed for the exploration of the surface of Titan but also regularly turned its antenna towards the main airless icy satellites of Saturn (Elachi et al., 2004). In addition to its active mode, the Cassini RADAR included a passive (or radiometry) mode designed to record the thermal emission from the targeted surfaces at 2.2-cm. The scientific objectives of Cassini RADAR icy satellite observations were to provide constraints on the thermal, physical and compositional properties of the first few meters below the surface of the investigated objects. Doing so, it brings insights into the degree of purity and maturity of their water-ice regolith which are both indicative of their geological activity and interaction with their environment.

The RADAR dataset acquired on icy moons has already proved to be very fruitful bringing light to notable differences among Saturn’s mid-sized satellites (Ostro et al., 2006; 2010; Le Gall et al., 2019).  However, it has not been fully analyzed yet. Following the final analysis of Cassini RADAR active observations of Saturn’s icy moons described in Le Gall et al. (2019) and expanding and improving upon the work of Ostro et al. (2006; 2010), we here present the analysis of all Cassini distant passive RADAR observations of these objects. This represents a total of 63 observations collected during 4 flybys of Mimas, 10 of Enceladus, 3 of Tethys, 6 of Dione, 9 of Rhea, 3 of Iapetus, 1 of Phoebe.

Most of Cassini RADAR icy satellite observations were distant i.e., occurred at ranges where the antenna beamwidth is comparable to or greater than the apparent angular extent of the target’s disk and were thus primarily designed to provide disk-integrated quantities: hemispheric-averaged radar albedos in the RADAR active mode and disk-integrated brightness temperatures in the passive mode. We here present the reduction of all available Cassini passive radiometry data with the goal of providing a range of possible values for the disk-averaged 2.2-cm emissivity of Saturn’s main airless satellites (separating their leading and trailing sides if relevant). These latter are obtained as a function of their possible thermal and electrical properties using a combined thermal and radiative transfer model (Le Gall et al., 2012; Bonnefoy et al., 2020). As an example, Fig. 1 displays the emissivity values obtained for Mimas from 4 distant radiometry observations. These values are shown as a function the assumed thermal inertia and ratio of electrical and thermal skin depths of Mimas’s near-surface. For all sets of parameters they are very low, as low as 0.5. For comparison, the disk 2.2-cm emissivity of Iapetus (Le Gall et al., 2014), Phoebe and Titan (see Sultana et al., this conference) is close to 0.9. Mimas low emissivity is indicative of subsurface mostly made of pure water ice and where volume scattering is very efficient maybe due to a highly fractured structure. We find that Enceladus and Tethys also exhibit low emissive surfaces and that, as a general rule, moon-to-moon and hemispheric emissivity variations seems to reflect variations in the moon interaction with Saturn’s dust rings, namely the E-ring for Enceladus and its neighbours and Phoebe’s ring further away from Saturn (Iapetus and Phoebe). 

The derived emissivities will be analysed in light of the (active) radar albedos measured on the same hemispheres. Both active and passive microwave observations will be compared to several combined emissivity-backscatter models thus providing further clues on the physical properties of the icy moons. Their implications in terms of surface geology and evolution will be discussed.


Fig. 1: 2.2-cm emissivity of Mimas’s surface derived from Cassini distant radiometry observations and a combined thermal and radiative transfer model as a function of Mimas subsurface thermal and electrical properties (namely its thermal inertia and the ratio of its electrical and thermal skin depths). The sub-spacecraft point of each distant observation is indicated on an ISS map of the satellite.

How to cite: Le Gall, A., Sultana, R., Bonnefoy, L., Leyrat, C., and Janssen, M. A.: Microwaving Saturn's airless icy moons Mimas, Enceladus, Tethys, Dione, Rhea, Iapetus and Phoebe, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-607,, 2022.