OPS5
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Discussion on Slack
Orals: Fri, 23 Sep | Room Andalucia 3
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.
Introduction:
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.
Experiments
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.
Results
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.
Acknowledgements
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.
References
[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, https://doi.org/10.5194/epsc2022-812, 2022.
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, https://doi.org/10.5194/epsc2022-681, 2022.
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, https://doi.org/10.5194/epsc2022-37, 2022.
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).