SB13
To fully exploit space mission data and prepare for upcoming missions, laboratory experiments are an essential part of calibrating instruments on board future spacecraft, verifying data returned by missions and informing numerical models of the diverse environments present on these bodies.
Analyzing returned samples from asteroids and comets substantially furthers our understanding of these small bodies in the Solar System. Both carbonaceous asteroids and comets are potentially analogous to the rocky interiors and primordial icy crusts of icy moons.
We seek contributions discussing laboratory experiments or studies with a laboratory component, including the analysis of returned samples, and their applications to icy ocean worlds, comets or asteroids.
BioSigN (BioSignatues and habitable Niches) is a space experiment supported by ESA and foreseen to be performed in Low Earth Orbit on the exposure lab Exobio on Bartholoméo to be fixed outside the Columbus Module on the International Space Station (ISS). The main objective of BioSigN is to support and prepare future planetary exploration missions to Mars, Enceladus, Europa and/or Titan by conducting exposure experiments on the ISS. To maximize the scientific output, the outcome of BioSigN will be connected to the results obtained on ground from recent and up-coming planetary analogue field site studies and planetary simulation facilities. The BioSigN project is conceived to achieve three central objectives:
- To analyse to what extent selected organisms and (micro-)fossils acquired from Icy Moon/Marsanalogue field sites (terrestrial and ocean/deep sea location) can survive/outlast the conditions of space exposure;
- To evaluate by the obtained results the habitability of present/past Mars and of the icy ocean worlds in the solar system.
- To test the (in)stability of a particular set of bio-molecules when exposed to space and Mars-like conditions, and to investigate their mechanisms of resistance or degradation as well as analysing if they are still detectable by the commonly used life detection methods;
To reach these goals, the test samples will be exposed to space vacuum and space radiation, approaching icy-moon specific or planet-specific gaseous and solar environments.
How to cite: de Vera, J.-P. P. and Baqué, M. and the BioSigN team: BioSigN: using an exposure lab on the ISS for preparation of in situ life detection missions and habitability studies, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-114, https://doi.org/10.5194/epsc2024-114, 2024.
Asteroids have been recognised as the parent bodies of most meteorites (Wylie, 1939), and, as a result of bombardment by micrometeorites and interplanetary dust particles, are believed to be surrounded by clouds of ejected surface dust particles (Szalay & Horányi, 2016).
It has recently been postulated by Cohen et al. (2019) that the composition of asteroidal ejecta dust clouds may be determined by the interception of cosmic dust grains by an impact ionisation mass spectrometer aboard a spacecraft conducting a flyby mission (c.f. the Cosmic Dust Analyser aboard Cassini, Srama et al. 2004, or more modern instrumentation, such as the Surface Dust Analyser aboard Europa Clipper, Kempf et al. 2014). The geochemical compositions and abundances of different grains contribute a “fingerprint” identity of an asteroid body, from which the meteorite type most closely linked to the asteroid can be determined.
The approach by Cohen et al. (2019) is generally applicable to asteroid flybys at high velocity regimes (approximately greater than 19 km/s), comparable to that of the planned DESTINY+ flyby mission to asteroid 3200 Phaethon. An extension to this technique, applicable to flyby speeds more typical of dedicated missions to the asteroid belt (e.g. 7-10 km/s), was subsequently proposed by Eckart et al. (2023).
To test the efficacy of the proposed theories, we intend to generate and analyse ensembles of cosmic dust analogues from meteorite samples, which, following metal coating, will be electrostatically accelerated onto laboratory engineering models, or flight spares, of impact ionisation mass spectrometers, such as the Destiny Dust Analyser, to be aboard the DESTINY+ spacecraft (Krüger et al. 2019). The obtained mass spectral datasets will then be statistically analysed both individually and as a cohort in order to identify unique features, which can lead towards the linking of the mass spectra to the original meteorite type/class.
Here we present the latest results and progress in obtaining, characterising, and preparing meteorite samples in order to simulate, within the laboratory, expected data from the impact ionisation mass spectrometry of asteroid dust-clouds aboard flyby spacecraft. The curation of a library of mass spectral data from meteorite mineral phases will largely facilitate the identification of unique meteorite samples and the subsequent tracing of these specimens back to their parent asteroids, providing a deeper insight into the evolution of our solar system.
References
Eckart, L. M., Hillier, J. K., Postberg, F., Marchi, S., & Sternovsky, Z. (2023). Linking meteorites to their asteroid parent bodies: The capabilities of dust analyzer instruments during asteroid flybys. Meteoritics & Planetary Science, 58(10), 1449–1468.
Kempf, S., Altobelli, N., Briois, C., Gru€n, E., Horanyi, M., Postberg, F., Schmidt, J., Srama, R., Sternovsky, Z., and Tobie, G. 2014. SUDA: A Dust Mass Spectrometer for Compositional Surface Mapping for a Mission to Europa International Workshop on Instrumentation for Planetary Missions, p. 7.
Krüger, H., Strub, P., Srama, R., Kobayashi, M., Arai, T., Kimura, H., Hirai, T., Moragas-Klostermeyer, G., Altobelli, N., Sterken, V. J., Agarwal, J., Sommer, M., & Grün, E. (2019). Modelling DESTINY+ interplanetary and interstellar dust measurements en route to the active asteroid (3200) Phaethon. Planetary and Space Science, 172, 22–42.
Srama, R., Ahrens, T. J., Altobelli, N., Auer, S., Bradley, J. G., Burton, M., Dikarev, V. V., et al. 2004. The Cassini Cosmic Dust Analyzer. In The Cassini-Huygens Mission: Orbiter In Situ Investigations, edited by C. T. Russell, 2nd ed., 465–518. Dordrecht: Springer.
Szalay, J. R., and Horányi, M. 2016. The Impact Ejecta Environment of near Earth Asteroids. The Astrophysical Journal 830: L29.
Wylie, C. C. 1939. Where Do Meteorites Come from? Science 90: 264–65.
How to cite: Dewey, P., Hillier, J. K., Postberg, F., Eckart, L. M., Srama, R., and Trieloff, M.: Synthesis and Characterisation of Cosmic Dust Analogue Ensembles from Meteorite Samples , Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1056, https://doi.org/10.5194/epsc2024-1056, 2024.
DESTINY+(Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science) is a future JAXA interplanetary space mission to the active asteroid 3200 Phaethon (Ozaki et al. 2022). The primary scientific payload - the Destiny Dust Analyzer (DDA; Simolka et al. 2024), an impact ionisation mass spectrometer - will assess physicochemical properties of (sub-)micron-sized dust particles emitted by Phaethon. Over the mission duration, DDA will also sample dust particles originating from different environments: lunar, interplanetary, and interstellar. DDA is a time of flight (TOF) impact ionisation mass spectrometer - a successor to Cassini’s Cosmic Dust Analyzer (CDA; Srama et al. 2004), which sampled ice and dust from the Saturnian system - and similar to Europa Clipper’s SUrface Dust Analyzer (SUDA; Kempf et al. in review) that will visit the Jovian moon Europa. These instruments utilise impact ionization; nanometere- to micron-sized dust particles strike the instrument’s target at hypervelocities, ionising chemical species embedded within particles and generating a TOF mass spectrum.
Both for calibration of DDA and the generation of a cationic mass spectral library to characterise the composition of dust in space, laboratory experiments are currently underway using DDA’s engineering model. Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous organic compounds in many different space and planetary environments – e.g. they are a major constituent of carbonaceous chondrites. For this reason, we investigate polypyrrole coated perylene PAH particles prepared in the form of microparticles and accelerate them using a Van de Graaff dust accelerator. Here, we present the first analysis of the cationic TOF mass spectra of such particles accelerated at 750 kV and recorded over an impact speeds range of 3-36 km/s. The spectra successfully exhibit mass line corresponding to the molecular ion [M]+ of perylene at m/z 252 for impact speeds between 3 and 7 km/s. From impact speeds of 9 to 16 km/s, the spectra exhibit a sequence of consecutive mass lines above m/z 45 with mass resolution ∆m ≈ 12-14, sufficient to characterise a homologous series of cations from PAHs. In addition, these spectra also show low mass fragment cations that most likely arise from the coating material of polypyrrole and from target contamination.
Future work will investigate these particles accelerated over higher potential differences up to 2 MV, as well as the mass spectral appearance of other PAHs. This carries relevance not only for DDA, but also for other impact ionisation mass spectrometers onboard future space missions (e.g., SUDA onboard NASA’s Europa-Clipper) that look to sample interplanetary and interstellar dust.
References
Kempf et al. (2024), SUDA: A SUrface Dust Analyser for compositional mapping of the Galilean moon Europa. Space Science Reviews, in review.
Ozaki N et al. (2022), Mission design of DESTINY +: Toward active asteroid (3200) Phaethon and multiple small bodies. Acta Astronaut. 196 , 42–56.
Srama et al. (2004), The Cassini Cosmic Dust Analyser. Space Sci. Rev., 114, 465–518.
Simolka et al. (2024) The DESTINY+ Dust Analyser — a dust telescope for analysing cosmic dust dynamics and composition. Phil. Trans. R. Soc. A 382: 20230199.
How to cite: Khawaja, N., Srama, R., Chan, D., Armes, S., Yanwei, L., Simolka, J., Strack, H., Mocker, A., Hillier, J., Postberg, F., Trieloff, M., Krüger, H., and Hirai, T.: Calibration of Destiny Dust Analyzer (DDA) with Polypyrrole Coated Perylene Microparticles, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1119, https://doi.org/10.5194/epsc2024-1119, 2024.
The search for liquid water in the Solar System is one of the main goals of planetary exploration since it represents the fundamental ingredient for life. Radar instruments have already been successfully employed to detect subglacial lakes in Antarctica and Greenland [1][2] and below the Martian South Pole [3][4]. Radio Echo Sounding technique (RES) consists in sending pulses towards the surface of the investigated body and collecting echoes: parts of the signals come back from the surface, and those that do penetrate the surface are reflected by the electrical discontinuities of the subsurface layers. The intensity of these echoes and their time delay are linked to the material and the position of the reflective interface. RES technique allows a deep study of the interior of celestial bodies to understand how they formed, their characteristics and if they could host any living organisms.
Introduction
In 2030 and 2031 Europa Clipper and JUICE with two radar instruments, REASON and RIME [5][6] will probe Europa, Callisto, and Ganymede to study their characteristics and to search for possible shallow liquid water bodies. These moons are the ideal targets for this type of investigation. From Galileo mission data, we know that they host a liquid water ocean beneath the crust. Their cold icy shell represents the perfect environment for RES surveys because in the frequency band of RIME and REASON (9MHz), cold ice is known to generate a low attenuation of radio waves allowing a deep penetration of the signals. Radars could detect liquid water coming from their inner oceans or caused by the local melting [7], and obtain information about their depth and composition.
The intensity of the reflections collected by the radar and the attenuation of radio signals are influenced by the complex value of dielectric permittivity of the ice and the other materials present in the shell. In the case of an interface between two materials i, j the intensity of the echoes, I, caused by the discontinuity in electrical properties is linked to the values of the real part of their permittivity ε_i ,ε_j (Equation1). Signals attenuation is linked to the value of the imaginary part. Liquid water has a permittivity higher than the other materials in the crust, then it causes strong reflections of radio waves. Besides liquid water, the presence of salts in Europa [8] and that of dust in Ganymede could originate features that would be detected by RES, moreover these impurities significantly affect the attenuation of radio pulses. Because of the large number of possible complex scenarios, the stratigraphy obtained by radars is usually difficult to interpret and it would be useful to consider what we could expect in advance making simulations.
Methods
In the Roma Tre laboratory, we collected measurements of dielectric properties of different materials following the methods described in [9]. The trend of permittivity values with temperature of pure ice and ice doped with salts was studied to reproduce the condition of Europa. We also analysed the ice with inclusion of chondrites present in Ganymede spectra [10]. We examined different compositions and temperature profiles given by the literature [7][11] generating possible configurations of Ganymede and Europa subsurface environments. We performed several simulations assuming different scenarios and computed the intensity of the echoes caused by the presence of shallow liquid water bodies and other types of discontinuities.
Results and Conclusions
We can predict, through simulations, signals attenuation and at which depth the radar instruments could detect liquid water bodies depending on the shell temperature and thickness, and on which salt or dust is present. We made hypothesis of different scenarios (Figure1) and performed simulations to see if and how the radar would detect them.
The measurements of permittivity of doped ice in function of the temperature show different regions (Figure2). Until 250K the permittivity of the doped ice is approximately constant, then it rises to higher values and remains constant in the phase of liquid brine (a mixture of salty liquid water and ice) until 270K. After 270K the ice is completely melted, and the real and imaginary part of the permittivity jump to the values of salty liquid water.
The results of the simulation of the waves propagation through doped ice show that the gap in permittivity observed around 250 K causes reflections of the signal (Figure3). These echoes could be detected by the antenna of the radar, only if the signal is slightly attenuated.
This study of the features that electrical discontinuities in the icy crust of Europa and Ganymede would cause in a radar analysis are crucial for the interpretation of real data.
Figure1: Possible scenarios of dielectric discontinuities in the shell of the icy moons. On the right the echo could be caused by the gap in permittivity between ice and liquid brine. On the left it could be cause by the difference in permittivity between two parts of the crust with different salinities.
Figure2: Values of the permittivity of 50mM NaCl doped ice at the frequency of 9MHz in function of the temperature. The upper panel is the real part, the lower panel is the imaginary part. The three zones with different dielectric properties (ice, brine, and liquid) are marked by vertical grey lines.
Figure3: Simulation of the signal propagation through a NaCl doped crust. The main echo is caused by the discontinuity corresponding to the surface (100K), the weaker one (250K) is due to the presence of the brine condition.
References
[1] Siegert, M. J. (2018) In: J. Geol. Soc. Lond. 461, 7–21.
[2] Oswald, G. K. A. et al.(2008) In: J. Glaciol. 54, 94-106.
[3] Orosei, R. et al.(2018) Sci., 361, 490-493
[4] Lauro, S. E. et al.(2020) Nature Astronomy, 5, 63-70
[5] Bruzzone L. et al.(2013) In: IEEE international geoscience and remote sensing symposium-IGARSS.
[6] Blankenship D. et al.(2018) In: 42nd cospar scientific assembly 42: B5-3
[7] Chivers C. J. et al.(2023) In: The Planetary Science Journal
[8] Trumbo,S. et al.(2022) In: The Planetary Science Journal
[9] Brin,A. et al.(2022) In: Icarus
[10] Hibbits, C.A. (2023) In: Icarus
[11] Buffo, J. J. et al.(2021) In: JGR Planets
How to cite: Turchetti, G., Brin, A., Lauro, S., Cosciotti, B., Mattei, E., and Pettinelli, E.: The radar signal propagation through the icy crust of Jovian moons, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1072, https://doi.org/10.5194/epsc2024-1072, 2024.
The surfaces of icy moons are primarily composed of water ice that can be mixed with other compounds, such as carbon dioxide. With the recent JWST observations (Bockelee-Morvan et al. 2024; Villanueva et al. 2023), infrared spectra of Ganymede and Europa’s terrains have been generated with unprecedented resolution, revealing hitherto undetectable variations of the spectral features with the location on the moon. With such high resolution’s data, not only can we identify the species present (in the present case CO2) on the surface, but we can also link their subtle variations to the embedding of the molecule into a host material and/or to energetic processes occurring on the icy moon. The carbon dioxide (CO2) stretching fundamental band observed on Europa and Ganymede appears to be a combination of several bands that are shifting location from one moon to another but also from one terrain to another on the moon itself. We investigated the cause of the observed shift in the CO2 stretching absorption band experimentally. For this purpose, we explored the spectral behavior of CO2 ice by varying the temperature and concentration with respect to water, focusing on the CO2 stretching fundamental band. We analyzed pure CO2 ice and ice mixtures deposited at 10 K under ultra-high vacuum conditions using Fourier-transform infrared (FTIR) spectroscopy and temperature programmed desorption (TPD) experiments. Laboratory ice spectra were compared to JWST observation of Europa's and Ganymede's leading hemispheres. To confirm the assignment of one of the CO2 bands, we simulated IR spectra using density functional theory (DFT) methods, exploring the effect of porosity in CO2 ice. Pure CO2 and CO2-water ice show distinct spectral changes and desorption behaviors at different temperatures, revealing intricate CO2 and H2O interactions. The number of discernible peaks increases from two in pure CO2, referred to as ν3,1 and ν3,2, and to three in CO2-water mixtures, referred to as ν3,1, ν3,2 and ν3,3.
The different CO2 bands were assigned to ν3,1 (2351 cm-1, 4.25 µm) caused by CO2 dangling bonds (CO2 found in pores or cracks) and to ν3,2 (2345 cm-1, 4.26 µm) due to CO2 segregated in water ice, whereas ν3,3 (2341 cm-1, 4.27 µm) is due to CO2 molecules embedded in water ice. The JWST NIRSpec CO2 spectra for Ganymede and for Europa can be fitted with two Gaussians attributed to ν3,1 and ν3,3. For Europa, as shown in Fig.1, ν3,1 is located at lower wavelengths due to a lower temperature. The Ganymede data reveal latitudinal variations in CO2 bands, with ν3,3 dominating in the pole and ν3,1 prevalent in other regions. This shows that CO2 is embedded in water ice at the poles, and it is present in pores or cracks in other regions. Ganymede longitudinal spectra reveal an increase of the CO2 ν3,1 band throughout the day, possibly due to an increase in ice cracks or pores caused by large temperature fluctuations during a day on Ganymede.
References:
Bockelee-Morvan, D., Lellouch, E., Poch, O., et al. 2024, Astronomy & Astrophysics, 681, A27
Villanueva, G., Hammel, H., Milam, S., et al. 2023, Science, 381, 1305
How to cite: Cazaux, S., Schiltz, L., Escribano, B., Muñoz Caro, G., del Burgo Olivares, C., Carrascosa, H., González Díaz, C., Chen, A., Giuliano, M., Caselli, P., and Boshuizen, I.: Characterization of Carbon Dioxide (CO2) on Ganymede and Europa supported by experiments: The effect of temperature, porosity and mixing with water., Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-601, https://doi.org/10.5194/epsc2024-601, 2024.
We present the results of the implantation of energetic sulfur ions in icy samples (H2O:C3H8 and H2O:C3H7OH) in temperature conditions relevant to Europa and other Jovian satellites. The surface of the Jovian moons experiences an intense bombardment of energetic particles, including sulfur ions over a large range of energy[1][2]. Any organic matter emplaced onto the surface from the internal ocean would be processed by this bombardment, with the possibility for sulfur to be included into the resulting products. As a results, the future space missions to the galileans moons (NASA’s Europa Clipper and ESA’s JUICE) may encounter such processed organic matter, which will complicate the characterization of the organic matter from the interior. The MASPEX [3] and SUDA [4] instruments in particular will get the opportunity to characterize the organic matter on Europa’s surface with unprecedented sentitivity and mass resolution.
Here, in temperature conditions relevant to Europa (80 K), we investigate the composition of the organic residues generated by the irradiation of a water:propane ice and a water:propanol ice with a 105 keV S7+ ion beam. Propane is the simplest alkane that can be condensed at a temperature relevant to Europa’s surface, and propanol is the corresponding alcohol. The irradiated samples were slowly warmed up to 300 K to sublimate the volatiles and leave the refractory organic residues. The residues were analyzed with Ultra-High Resolution Mass Spectrometry using two ionization techniques (laser desorption and electrospray).
The analysis of the residue from the irradiation of the water:propane ice shows a very diverse (2000 + unique formulas) organic matter, with heavy molecules (up to m/z>800). We find large numbers of aromatic CH species (Figure 1, left) and oxygen-rich, less aromatic species, depending on the ionization technique used. Organosulfurs are found both in CHS form and CHOS; they are minor both in number and intensity, but demonstrate the possibility of forming organosulfurs in the surface conditions of Europa through sulfur implantation with any organic. [5]
The residue resulting from the water:propanol sample, as seen with laser desorption is very similar, without any noticeable difference between the number and intensity of O-bearing annotations, or aromaticity (Figure 1). Twice as many CHS annotations are found in the water:propanol residue compared to water :propane.
The dose used in our study represents a geologically short time on the surface of Europa (from a few days to a few thousands of year, depending on the region considered). This indicates that the properties of organic precursors may swiftly be erased by radiation processing on the surface. Future work with different doses and precursor species will better constrain how radiation chemistry alters organic signatures on the surface.
[1] J.F. Cooper, et al.,. Icarus, 149(1), 133-159. (2001)
[2] C. Paranicas et al.,., Europa. U. Arizona Press, Tucson, 529 (2009)
[3] Waite Jr, J. H., et al. Space Science Reviews 220.3 (2024): 30.
[4] Goode, W., et al. Planetary and Space Science, 227, 105633. (2023).
[5] Bouquet, A., et al. The Planetary Science Journal, 5(4), 102 (2024).
Fig1 : #C vs DBE (Double Bond Equivalent) of the annotations obtained by Laser Desorption Ionization – Fourier Transform Ion Cyclotron Resonance (LDI-FTICR) applied to the residue of the S-implanted Water :Propane Ice (left) and Water :Propanol Ice (right).
How to cite: Bouquet, A., Pires da Costa, C., Boduch, P., Rothard, H., Domaracka, A., Danger, G., Schmitz, I., Afonso, C., Schmitt-Kopplin, P., Hue, V., Nordheim, T., Ruf, A., Duvernay, F., Napoleoni, M., Khawaja, N., Postberg, F., Javelle, T., Mousis, O., and Tenelanda-Osorio, L.: Implantation of sulfur ions into water-propane and water-propanol ices : formation of refractory organic matter with organosulfurs, and implications for Europa’s surface, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-600, https://doi.org/10.5194/epsc2024-600, 2024.
The plumes of Enceladus contain a non-ice component that originates from aqueous processes occurring within the interior 1,2. The ocean of Enceladus is thought to be connected to the surface across a range of time scales. These processes range from the rapid eruption of cryovolcanic plumes to slow crustal convection on geological timescales3,4. In every case, the system will have a temperature and geochemical evolution as it freezes, with the history of evolution recorded in the sequence of mineral precipitation. Analogously to igneous and metamorphic petrology, we can explore the mineralogy and its context to reconstruct the history of that sample. Most importantly, for astrobiological investigations, the formation and cryo-petrological study of inorganic salts can be used to identify sites of recent exposure on the surface.
Synchrotron X-ray techniques allow fast, high-resolution probing of these systems with X-ray light. By exploring large, multi-component samples with multiple techniques, with variable temperature over time we can reveal many emergent processes that may not be predictable with simple phase diagrams.
We use a combination of synchrotron powder X-ray diffraction (PXRD) and X-ray microtomography (µCT) across multiple beamlines at Diamond Light Source (I11, I12 and DIAD). Using a multi-modal approach, we present an in-situ study of the low-temperature phase behaviour of Na-Cl-HCO3 fluids. We employ K11-DIAD (Dual Imaging and Diffraction) to carry out ‘image-guided diffraction’ on an Enceladus-type sample frozen in real-time. DIAD’s unique capabilities allow us not only to study microstructure down to 1 µm but also to carry out spatially resolved XRD and identify solid phases present.
We present, for the first time, the use of dual imaging and diffraction of a Na-Cl-CO₃ solution frozen in real time in 3 dimensions [Figure 1]. DIAD’s imaged guided diffraction provides spatially-resolved XRD, allowing us to probe different regions of our sample and identify the formation of Na2CO₃ hydrates. We show the influence of carbonate chemistry on the sequence of cryogenic precipitation and the development of complex microstructures. These results provide insights into crustal transport processes and will help with interpreting observational data from upcoming Galilean missions.
[1] Postberg F, Schmidt J, Hillier J, Kempf S, Srama R. A salt-water reservoir as the source of a compositionally stratified plume on Enceladus. Nature 2011; 474: 620–622.
[2] Sekine Y, Shibuya T, Postberg F, Hsu H-W, Suzuki K, Masaki Y et al. High-temperature water–rock interactions and hydrothermal environments in the chondrite-like core of Enceladus. Nat Commun 2015; 6: 8604.
[3] Schoenfeld AM, Hawkins EK, Soderlund KM, Vance SD, Leonard E, Yin A. Particle entrainment and rotating convection in Enceladus’ ocean. Commun Earth Environ 2023; 4: 28.
[4] Vance SD, Journaux B, Hesse M, Steinbrügge G. The Salty Secrets of Icy Ocean Worlds. JGR Planets 2021; 126: e2020JE006736
How to cite: Perera, L., Day, S., Thompson, S., Leonardi, A., and Ahmed, S.: Using synchrotron X-ray diffraction and X-ray tomography to study ocean world cryogeochemistry in 4D., Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1090, https://doi.org/10.5194/epsc2024-1090, 2024.
Vast subsurface oceans buried under kilometers of ice crust have been discovered in our Solar System's icy moons and have sparked worldwide interests in ascertaining their potential habitability. The tell-tale signs that betray their presence on their hosts are mostly related to density and gravitational field measurements. In the case of Saturn’s moon Enceladus however, the Cassini space probe has observed supersonic plumes of water vapour and ice particles spewing from a fractured area of the South Polar Terrain called the "tiger Stripes", with later analysis of their composition confirming the presence of liquid water below the surface. While the plumes mechanisms are now well-understood as a whole, some areas remain unclear such as the link between icy particles nuclei composition and their origin and evolution from the subsurface ocean. As future missions will renew contact with Enceladus and explore its mysteries in the coming decades, we need experimental studies to best prepare for those. These studies will help with mission planning, instruments choice and tests and making sure we will harvest the best scientific return from the observations made. In this paper we present a new experimental setup called the Plumes and Ices Simulation Chamber for Enceladus and icy moonS, or PISCES for short. It is designed to emulate the environmental conditions (pressure, temperature) at the surface and interior of icy moons to experimentally study the processes that occur there using a wide range of sensors and instruments. We first describe the vacuum chamber setup and the range of sensors and instruments it can interface with. To showcase the setup's capabilities, we will then proceed to detail some of the plumes experiments we've run. Using 3D-printed cylindrical channels of various shapes and profiles and mounting them atop a liquid water reservoir placed in the vacuum chamber, we can investigate a wide range of plumes and link the plumes behaviour (vent velocity, temperature or particle size) to subsurface characteristics e.g. wall temperature, width, length or expansion ratio. By steadily increasing the complexity of the models used, we aim to experimentally replicate the icy plumes of Enceladus under analogous conditions using the PISCES setup will be a pioneering achievement this new area of research.
How to cite: Bourgeois, Y. and Cazaux, S.: PISCES: Plumes and Ices Simulation Chamber for Enceladus and icy moonS, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-742, https://doi.org/10.5194/epsc2024-742, 2024.
Introduction
Enceladus, an icy moon of Saturn, has a subsurface ocean with large geysers that originate from hydrothermal vents. A solvent, like liquid water, and a source of energy, such as a hydrothermal vent, are both key elements in creating an environment habitable to life and are involved in theories of its origin [1]. Modelling of the interior of Enceladus suggests its silicate core is composed of undifferentiated material like that found on carbonaceous asteroids and comets [2], which are known to contain amino acids, the building blocks of life [3,4]. Understanding how Enceladus’s sea floor alters will increase the knowledge of the geology surrounding its hydrothermal vents.
Sampling of material from Enceladus’s geysers by the Cassini mission suggests hydrothermal metamorphism is occurring at temperatures of at least 150°C [2]. To better understand hydrothermal processing on Enceladus, we have heated a carbonaceous asteroidal simulant in water at 150°C to study the alteration products that formed.
Methods
CM-E carbonaceous chondrite simulant intended to be representative of the ‘Mighei-like’ carbonaceous (CM) chondrite Murchison was acquired from Space Resource Technologies, with 1.4 cm3 (1.45 g) placed in a 45 ml acid digestion vessel with 22 ml of distilled water and sealed in an inert N2 atmosphere. The vessel was then heated at 150°C for 33 days. The pressure that resulted is calculated to be 6 bars. To study changes in mineralogy, high resolution synchrotron X-ray diffraction (XRD) data was collected at the I11 beamline at Diamond Light Source both for unaltered simulant and the hydrothermally processed simulant. Proportions of different minerals were determined by Rietveld refinement using Topas 4.2. To study the composition of the liquid after hydrothermal alteration, the water from the experiment was extracted with a 450 μm diameter syringe and was analysed by X-ray fluorescence (XRF) using a PANalytical Epsilon3 XL with an Ultralene filter at the Materials Characterisation Laboratory at ISIS Neutron and Muon Source.
Results and Discussion
The CM simulant is a heterogeneous mixture of components meant to recreate textures observed on carbonaceous asteroids [6] and exact proportions of minerals are bound to vary from sample to sample. However, even given this, there are distinct differences between the mineralogy of the simulant used and the CM chondrite it is modelled after (Table 1). CM chondrites are composed mostly of serpentine minerals and tochilinite [5], whereas the simulant used is mostly made out of montmorillonite (Table 1), which lacks Fe and contains more abundant Al, Ca, and Na. Additionally, minerals that are either absent from CM chondrites or occur as terrestrial alteration products, like sulphates, pyrite, hematite, and quartz were present in the simulant (Table 1).
The differences between the simulant and CM chondrites defined the alteration products observed. The altered simulant contains significant amounts of feldspars and sulphates. The feldspars are likely the result of olivine and pyroxene decomposing and reacting with the montmorillonite. The K-feldspar produced is likely adularia, a low temperature hydrothermal mineral [7], while the plagioclase likely resulted as albitization (replacement of feldspar by albite) of adularia, which also occurs under low temperature hydrothermal conditions [8]. Rozenite and epsomite are sulphates in the altered simulant which were likely produced by reactions with gypsum and pyrite and other minerals (e.g., olivine) within the simulant. If CM chondrite material were used, it is likely serpentine and sulphide minerals (e.g., pyrrhotite) would be produced instead, but the breakdown of olivine and pyroxene still would have occurred as observed here.
The water extracted from the autoclave following the experiment was cloudy with small particulates still suspended in it. The particulates could not be separated from the water without significant water loss so were measured alongside the water. The water mixture was found to contain an abundance of Si (Table 2), which may be attributed to sub-mm silica particles. The sizes of these silica particles are unknown, however nanometre Si-rich particles are found in Enceladus’s plumes and other similar hydrothermal environments from a reaction related to clay minerals [9]. The concentration of Si observed here is consistent with that in Saturn’s E-ring, which is produced by Enceladus [9]. However, despite this similarity, no Na was found in the water mixture (Table 2), indicating that any Na present is inside the solid sample, which is dissimilar to Enceladus’s Na-rich ocean. The montmorillonite hydrothermally altered here is chemically different than the material making up Enceladus’s core, however hydrothermal alteration of a clay mineral is likely occurring on Enceladus.
Conclusions
The recreation of hydrothermal processes on Enceladus using CM chondrite simulant resulted in the breakdown of olivine and pyroxene and the production of feldspars. This reaction is likely the result of the CM chondrite simulant containing relatively high aluminium and alkali elements compared to CM chondrite meteorites. The fluid extracted contained sub-mm particulates rich in Si and lacking in Na. The CM simulant is not chemically analogous to the seafloor of Enceladus however its clay rich nature does give it some degree of similarity.
Acknowledgements
We thank Sarah Day and Lucy Saunders for assisting with sample preparation and XRD data collection. We also thank Gavin Stanning and Daniel Nye for use of their XRF and assistance with XRF data collection. We would like to thank Raul Montes for assistance in calculating the pressures produced in this experiment.
References
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How to cite: Jenkins, L., Thompson, S., and Connolly, E.: Simulating with a Simulant: Recreating Hydrothermal Metamorphism on Enceladus, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-451, https://doi.org/10.5194/epsc2024-451, 2024.
The habitability of icy moons in the outer Solar System is linked to their ability to maintain warm subsurface oceans through time, but the mechanisms leading to heat generation in small icy moons are not well constrained. While most heat generation in response to tidal forcing is thought to occur in icy crusts and water oceans, the deformation of chondritic material thought to make up rocky cores and mantles has not previously been studied comprehensively in a laboratory setting under relevant planetary conditions. We experimentally deformed samples of the Kilabo meteorite, an LL6 chondrite, under axial strain rates of 10-5 s-1 and confining pressures up to 100 MPa. We recorded the strength of the material, measured energy dissipation through acoustic emission events, and observed ultrasonic wavespeeds as a function of confining pressure. Our results suggest that dissipative brittle deformation is possible even during isotropic pressurization, as well as at low stresses and strains during nominally “elastic” deformation, due to the porous nature of the material. However, energetic acoustic emission events associated with brittle deformation become less powerful as confining pressure increases. The mechanical behavior of the meteoritic material also evolved as a function of increasing confining pressure: peak strength occurred at 50 MPa confining pressure, and material continuously stiffened as pressure increased. These pressure-dependent properties indicate that larger icy moons could have stiffer, less deformable silicate layers than those found in small icy moons, corresponding to a lower relative contribution of silicate deformation to the bodies’ total heat budgets. Future experiments on carbonaceous chondrites under oscillatory loading conditions are necessary to fully measure the potential magnitude of tidal heating in rocky silicate cores of icy moons.
How to cite: Seltzer, C., O. Ghaffari, H., and Peč, M.: Laboratory investigation of mechanical energy dissipation relevant to rocky interiors of small icy moons, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-569, https://doi.org/10.5194/epsc2024-569, 2024.
Recent interpretations of space observations suggest that the icy moons of Jupiter and Saturn and the dwarf planet Ceres formed by accreting silicates, sulfides, ices and primordial organics. During accretion and differentiation of these icy bodies, the primordial organics reacted with water. We have carried out laboratory experiments at (P,T) conditions relevant to the interiors of icy moons and dwarf planets to investigate the degradation of the organics with water. The goal is to determine the ions that are eventually dissolved in the ocean and the chemical composition and structure of the refractory organics that mix with silicates and sulfides to form the core of these bodies. The primordial organics are analogs made in the Nebulotron. A recent analysis (Lévêque et al., 2024) demonstrated that these organics have elementary and chemical composition close to that of the organic matter found in the Paris meteorite, which is a carbonaceous chondrite, one of less altered CM chondrites. These organic molecules were mixed with water and placed in three different pressuring devices covering a large domain of pressures (up to 2 GPa) and temperatures (at 200°C and 400°C) conditions relevant to the interior of icy bodies.
Gas chromatography has been carried out on sealed capsules reacted in internally heated pressure vessel. In situ Raman spectroscopy and in situ XRD have been carry out on samples pressurized in a Diamond Anvil Cell (DAC). Each device provides complementary information on the evolution of the organic matter solid residues and its byproducts. Gas analyzes and in situ Raman demonstrate that N2 and CO2 are released when OM:H2O mixtures are heated up to 200°C, and CH4 appears at 400°C. Organic matter (OM) evolves towards very condensed PAHs. Being denser than the ocean, that should mix with silicates and sulfides to form a refractory core that further evolves as the temperature raises due to the decay of the long-lived radioactive elements. The primordial OM reacts with water to produce ions which may form carbonates, as observed by our XRD analyzes. These experiments provide potential explanations for the presence of N2 and CH4 in Titan’s atmosphere and for the presence of carbon-rich regions observed at the surface of Ceres, Europa and Ganymede.
How to cite: Lévêque, P., Bollengier, O., Afonso, C., Bujoli, B., Champallier, R., Hertzog, J., Le Menn, E., Marrocchi, Y., Queffelec, C., Schmitz, I., Slodczyk, A., and Sotin, C.: Laboratory experiments on primordial organic degradation at conditions relevant to ocean worlds interiors, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-751, https://doi.org/10.5194/epsc2024-751, 2024.
Results from the Cassini mission at Enceladus revealed the presence of a diverse organic inventory [1,2] in its subsurface ocean as well as ongoing hydrothermal activity at the water-rock interface [3,4]. Ice grains ejected into the plume are thought to contain compounds originating from the depths of the ocean, which are likely linked to hydrothermal (bio)geochemistry, as are other constituents in the vapour phase [1,2,5]. Understanding the nature and effects of hydrothermal activity on Enceladus and other icy ocean worlds (e.g. Europa) is crucial for evaluating the prospects of habitability as well as understanding how potential biosignatures may manifest in spacecraft data. Biosignatures that are present on the ocean floor may be chemically altered by the elevated temperature and pressure conditions in such environments, as well as by salts, mineral catalysts, or other solutes in hydrothermal fluids.
Analogue mass spectra, generated in the laboratory using the laser-induced liquid beam ion desorption (LILBID) technique [6], are a useful tool for interpreting impact ionisation mass spectra, as produced by Cassini’s mass spectrometer – the Cosmic Dust Analyzer (CDA). Thus, impact ionisation mass spectra of both hydrothermally processed and unprocessed material in ice grains obtained via spaceborne instruments can be recreated. Given the ubiquity of peptides utilised by all known life on Earth, Khawaja et al. [7] recently investigated the hydrothermal evolution of the simplest tripeptide – triglycine (GGG) - as both a potential biosignature and marker for hydrothermal activity. This work verified significant differences between the spectra of processed and unprocessed GGG, outlining an approach to verify a unique spectral fingerprint as evidence for the former. Here, we briefly discuss the results from the hydrothermally processed GGG, with similarities between the spectra before and after processing compared. We demonstrate that the presence of processed GGG can be elucidated with a two-step process: a) GGG is, in general, identified by the appearance of glycine, diglycine, and GGG peaks, along with common fragments indicative of peptides and N-bearing compounds, and b) processed GGG is identified by the additional presence of unique peaks related to products formed exclusively by the hydrothermal processes. In addition, certain peaks related to compounds not present in the initial solution appear in both spectra – e.g. a peak at m/z 115 in the cation spectrum assigned to diketopiperazine. The potential implications of such results are discussed briefly here and will form the basis of more detailed future investigations. We will apply our methodology used to deduce the presence of hydrothermally processed GGG to peptides of longer chain length and containing different amino acid constituents.
We also examine the influence of salts (NaCl) on the hydrothermal processing of GGG at pH 8.5-10, conditions typical for the ocean-core interface of Enceladus, and the peptide’s appearance in impact ionisation mass spectra. Previous experiments [8-10] have demonstrated that salts can suppress and alter expected organic features in LILBID and, by extension, impact ionisation mass spectrometry. Salinity and acidity are also thought to influence reaction pathways in hydrothermal chemistry [11-13]. This multi-faceted influence of salts presents significant implications for the detection of potential molecular biosignatures from icy ocean worlds with saline oceans (i.e. Enceladus and Europa). The solubility of GGG generally increases with greater departure from a neutral pH (i.e. more acidic or alkaline) and with salinity [14]. This is an important factor that not only influences the detectability of triglycine but also its behaviour as a biomolecule. The role of potential catalytic minerals relevant for the expected seafloor composition of Enceladus is also discussed in this work.
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[7] Khawaja, N. et al. (2024) Phil. Trans. R. Soc. A. 382, 20230201.
[8] Klenner, F. et al. (2020) Astrobiology 20, 1168–1184.
[9] Napoleoni, M. et al. (2023a) ACS Earth Space Chem. 7, 735–752.
[10] Napoleoni, M. et al. (2023b) ACS Earth Space Chem. 7, 1675–1693.
[11] Xia, L. et al. (2020) Chem. Geol. 541, 119581.
[12] Hammerton, J. M. & Ross, A. B. (2022) Catalysts 12, 492.
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How to cite: O'Sullivan, T., Khawaja, N., Hortal Sánchez, L., Napoleoni, M., Bloema, J., Hillier, J., and Postberg, F.: Detecting hydrothermally processed peptides in the mass spectra of ice grains emitted by Enceladus and Europa, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-919, https://doi.org/10.5194/epsc2024-919, 2024.
Introduction: Characterizing the geochemistry of icy ocean worlds such as Europa and Enceladus is a key step to better constrain the habitability of their subsurface oceans. Transition metals with several oxidation states, such as iron, may be tracers of the oxidation state of icy ocean moon interiors. Their detection, and the characterization of their oxidation states, in Europa’s or Enceladus’ ice grains would provide valuable new data about the geochemistry of both the subsurface oceans and surface processes. Indeed, ice grains are ejected from both moons either in plumes and/or by micrometeorite bombardment, and their analysis can give valuable insight into the composition of subsurface liquid reservoirs. Impact ionization mass spectrometers such as the SUrface Dust Analyzer (SUDA; Kempf et al. 2024) onboard the upcoming Europa Clipper mission can analyze ejected ice grains and detect ocean-derived salts therein.
Methods: To determine if SUDA-type mass spectrometers are capable of detecting iron in different oxidation states, we recorded analogue mass spectra using the Laser Induced Liquid Beam Ion Desorption (LILBID), a technique shown to accurately reproduce data of spaceborne impact ionization mass spectrometers probing ocean worlds (e.g., Postberg et al. 2009, Klenner et al. 2019). Here, we measured Fe2+ and Fe3+ sulfates and chlorides with LILBID, thus determining the mass spectral appearances of these salts as if encased in ice grains from Europa or Enceladus and detected by SUDA-type instruments.
Results: Our results show that impact ionization mass spectrometers can detect and differentiate ferrous (Fe2+) from ferric (Fe3+) ions in both cation and anion modes owing to their tendency to form distinct ionic complexes with characteristic spectral features (Napoleoni et al. 2024). Peaks bearing Fe3+, such as [Fe3+ (OH)2]+ and [Fe3+ (OH)a Clb]- are particularly important for discriminating between the two oxidation states of iron in the sample and even allow quantification of the two species.
Implications for Europa Clipper. This study indicates that SUDA could be a useful tool for the characterization of the oxidation state of the subsurface ocean of Europa by quantification of iron-bearing salts in Europa’s ice grains. In both our analogue experiments and future SUDA mass spectra, the intensities of Fe-bearing ions of different oxidation states and the isotope distribution patterns are informative features that can be used to determine the presence and oxidation state of iron-bearing compounds. The recorded LILBID mass spectra complement a spectral library (Klenner et al. 2022) providing analogue data for SUDA onboard Europa Clipper and potential future Enceladus missions.
Implications for the geochemistry of ocean worlds. The recorded LILBID mass spectra could allow the detection of iron (a key element for life) and the characterization of its oxidation state on the surfaces of icy moons, and potentially from their subsurface oceans (Figure 1). We draw implications for the pH values and oxidation state of Europa’s and Enceladus’ subsurface oceans for difference cases of (non) detection and characterization of iron in ice grains, considering both surface ejecta and plume ice grains. Such characterization of the geochemistry of Europa or Enceladus could be used to test and further develop different models of redox chemistry in their oceans (Ray et al. 2021). It could also have important implications for hydrothermal processes and potential metabolic pathways, such as iron reduction metabolisms (Roche et al. 2023), that may be used by possible extant life in icy moons’ oceans.
Figure 1. Simplified interpretations of the (non) detection and characterization of iron in ice grains from ocean worlds with SUDA-type instruments. From Napoleoni et al., 2024. Three scenarios are considered: (a) detection of Fe(II)-dominated grains; (b) detection of significant Fe(III) in ice grains; (c) no Fe detection. In addition to iron, the detection of aluminum ions (Al3+) in ice grains would support a salt source from an acidic ocean composition. In both scenarios (a) and (b), the case of ice grains originating from a plume (i.e., fresh surface material) is distinct from ice grains originating from the surface, where older material has likely undergone oxidation. In the case of surface material, the age of this material may be constrained by investigating its surface appearance, including geological features.
References
Kempf et al. (2024) Space Science Reviews, in review.
Klenner et al. (2019) Rapid Commun. Mass Spectrom., 33(22), 1751-1760
Klenner et al. (2022) Earth and Space Science, 9(9), e2022EA002313
Napoleoni et al. (2024) The Planetary Science Journal, 5(4), 95
Postberg et al. (2009) Nature, 459, 1098
Ray et al. (2021) Icarus, 364, 114248
Roche et al. (2023) International Journal of Astrobiology, 22(5), 539-558
How to cite: Napoleoni, M., Hortal Sánchez, L., Khawaja, N., Abel, B., Glein, C., Hillier, J. K., and Postberg, F.: Detecting Fe (II) and Fe (III) in Ice Grains with Mass Spectrometry: Implications for the Geochemistry and Habitability of Europa and Enceladus, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-974, https://doi.org/10.5194/epsc2024-974, 2024.
Carbonaceous organic matter (COM), between 20 and 50%, is needed to model the rocky core of icy bodies (Neri et al, 2020, Reynard & Sotin. 2023), and account for their mass, moment of inertia, and density as measured by the Cassini, Galileo and Juno missions. However, the effects of temperature and pressure on COM at conditions of the rocky cores (up to ~7 GPa and 1300 K) have not been taken into account in these preliminary models. We present an experimental characterization of the evolution of COM at elevated temperature and pressure to describe its density evolution during thermal evolution of icy bodies. Carbonaceous organic matter undergoes important transformations both in terms of composition and structure when subjected to an increase in temperature and pressure. These transformations are characterized by the loss of heteroatoms (O, H, N, S) and a structural rearrangement which lead to a variation of density from 1200 kg/m3 at 300 K to 2300kg/m3 at 1300 K.
We first performed determinations of the ambient temperature compressibility of COM analogs using diamond anvil cell experiments. Kerogens and glassy carbons were used as analogs of COM. Second, we adapted the Vitrimat kinetic model of kerogen chemical and density evolution as a function of temperature and time (Burnham 2019). This modification accounts for chemical evolution determined on samples heated at temperatures of 473-723 K for times ranging from seconds to 100 days, and at various pressures (0.2-2.5 GPa). Combining these two studies allows us to describe the density evolution of COM as a function of time, temperature and pressure, assuming it behaves like kerogens.
Thermo-chemical evolution models are coupled with this equation to determine the time evolution of the density structure of icy bodies and compare it with available observations. In addition to density evolution of COM in the core, heteroatoms are released as volatiles (mainly H2O, CO2, CH4). They may form new species in the core (carbonates) and the high-pressure ice level (clathrates), reach the ocean, and be released to the upper ice level, then to space. Models will also provide estimates of volatile fluxes and formation of new compounds on the density structure.
Improvements of density determinations of COM analogs will provide accurate models for predicting the density and thermal evolutions compatible improved determinations of internal structures of icy moons from the JUICE and future Europa Clipper and Dragonfly missions, and observation of dwarf planets by JWST.
Burnham, A. K. Kinetic models of vitrinite, kerogen, and bitumen reflectance. Organic Geochemistry 131, 50-59 (2019). https://doi.org/https://doi.org/10.1016/j.orggeochem.2019.03.007
Néri, A., Guyot, F., Reynard, B. & Sotin, C. A carbonaceous chondrite and cometary origin for icy moons of Jupiter and Saturn. Earth and Planetary Science Letters 530, 115920 (2020). https://doi.org/https://doi.org/10.1016/j.epsl.2019.115920
Reynard, B. & Sotin, C. Carbon-rich icy moons and dwarf planets. Earth and Planetary Science Letters 612, 118172 (2023). https://doi.org/https://doi.org/10.1016/j.epsl.2023.118172
How to cite: Delarue, C., Reynard, B., and Sotin, C.: Density of carbonaceous organic matter in icy bodies, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-424, https://doi.org/10.5194/epsc2024-424, 2024.
Context. Europa, similar to the other Galilean Moons, is constantly being bombarded by energetic particles coming from Jupiter’s magnetosphere. This energetic bombardment would inevitably alter the organic species that could be on Europa’s surface, whether exogenic or coming from the internal ocean. One type of relevant particles that take part of this bombardment is sulfur ions provided by Io’s volcanic activity, which are highly reactive [1].
Goals. Future space missions to the Jovian satellites (Europa Clipper, JUICE) will try to analyze organics on Galilean moons’ surface to understand better the composition of their inner ocean. Because these organics will likely be processed by sulfur ions and other energetic particles, it will be necessary to study how they survive in that environment and what possible products the bombardment could yield. Methanol is one of the species of interest; being the simplest and most abundant alcohol found in the Solar System [2], and having been potentially detected coming from Enceladus’ ocean [3][4].
Experimental method. We formed ices of pure CH3OH and mixtures with water (H2O:CH3OH 2:1) in conditions of temperature relevant to Europa (80K) in the ICA chamber at HUN-REN ATOMKI, Debrecen, Hungary [5]. We irradiated them with a sulfur ion beam using S+ with energy of 290 keV, and then heated slowly (0.5 K/min) to room temperature. After that, we collected the refractory organic residues for future UHRMS (Ultra-High Resolution Mass Spectrometry) analysis, following a protocol previously used successfully by our group to demonstrate the formation of organosulfur in conditions relevant to Europa [6]. During the whole process, we used FTIR (Fourier-Transform Infrared Spectroscopy) to monitor the deposit, the destruction under irradiation of the initial mixture, and the appearance of new features associated to radiation chemistry products.
Results. Post-irradiation FTIR spectra (Figure 1) show the formation of the usual products of radiation chemistry of organics in ice [7], like CO2, CO and CH4 (with the presence of CO and CH4 being a strong indicator of trapping, since one would expect those species to desorb at 80K), but we don’t see signs of sulfur species being created. This is to be expected given the relative low number of sulfur ions being implanted in regards of the thickness of the ices, and that is why we will need to look at the residue with UHRMS techniques that will allow us to see even the smallest traces of sulfur products. We also monitored the decay of the CH3OH bands at 2830 cm-1 (CH3 stretching), 1126 cm-1 (CH3 rocking) and the 2700―3200 cm-1 interval (CH3 stretching) to calculate the cross-section of destruction of methanol in a water matrix for each layer deposited (Figure 2), taking values of band strength from the literature [8]. For the H2O:CH3OH 2:1 mixture, we obtain σdes (10-15cm2) = 18.4 +/- 5.9, which agrees with similar values of irradiation of methanol with oxygen ions of comparable energies [9].
Figure 1: FTIR spectrum of pure methanol ice before irradiation (red) and after receiving a total fluence of 8.47·1015 ions/cm2 (blue). This was a background deposition experiment where we kept depositing at the same time as we were irradiating.
Figure 2: Column density vs Fluence obtained from the methanol band at 2830 cm-1 for the third layer of the layered deposit of the H2O:CH3OH 2:1 mixture.
Next steps. The organic refractory residues implanted with sulfur that we collected presented a clear distinction in color: the one coming from irradiation of pure CH3OH was orange/brown, while the residues from the H2O:CH3OH 2:1 mix looked transparent. Now they will be taken to a facility equipped with an FTICR (Fourier-Transform Ion Cyclotron Resonance) mass spectrometer for UHRMS analysis using two ionization techniques (laser desorption and electrospray). The result will be compared to previous works of this group [6] to identify trends in properties of the resulting organic matter (aromaticity, inclusion of oxygen…), including formation of organosulfurs.
Acknowledgements. This work was supported by CNES, focused on the JUICE mission. This work was also supported by the Programme National de Planétologie (PNP) of CNRS-INSU cofunded by CNES. We acknowledge support from CNRS Ingéniérie as part of the DERCI Programme (European Research and International Cooperation Directorate). We acknowledge support from the French government under the France 2030 investment plan, as part of the Initiative d'Excellence d'Aix-Marseille Université—A*MIDEX AMX-21-PEP-032. We acknowledge funding from the Europlanet Society through the Trans National Access Program. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº 871149. This work has also received support from the European Union and the State of Hungary; co-financed by the European Regional Development Fund through grant GINOP-2.3.3-15-2016-00005.
References
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How to cite: Carrasco-Herrera, R., Bouquet, A., Danger, G., Noble, J., Herczku, P., Juhász, Z., Sulik, B., Rajta, I., Vajda, I., and Lakatos, G.: Irradiation of CH3OH ices with a sulfur ion beam: implications for Europa’s surface organics, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-367, https://doi.org/10.5194/epsc2024-367, 2024.
The subsurface oceans of Enceladus and Europa are presumably the most habitable places in the solar system beyond Earth, and may host extant life [1]. Putative molecular biosignatures could be transported from the ocean to the surface, where they would be detectable by spaceborne instruments such as the SUrface Dust Analyzer (SUDA [2]) onboard Europa Clipper [3]. Indeed, recent laboratory experiments [4,5] showed that SUDA-type mass spectrometers could detect molecular biosignatures in ejected ice grains, with lipids providing some of the most notable and characteristic spectral fingerprints. Lipids (i.e., cell membrane-derived organic compounds based on carbon-carbon chains) are some of the most robust molecular biosignatures that could be detected on ocean worlds [6,7,8]. Ubiquitous in all life on Earth, lipids are considered as universal biomarkers of life [9] thanks to their effective membrane-forming properties even under geochemically hostile conditions [10] - a feature that is expected to be upheld in extraterrestrial environments. Lipids are therefore prime targets for life detection missions on ocean worlds.
Spaceborne impact ionization mass spectrometers such as SUDA could directly analyze fresh ocean material that may contain lipids among other organics [4,5,11,12]. However, the performance of such spaceborne instruments strongly relies on analogue data obtained from laboratory experiments. The calibration of spaceborne mass spectrometers can be achieved by using Laser Induced Liquid Beam Ion Desorption (LILBID), a well-established method which allows the simulation of ejected ice grains’ mass spectra. Many LILBID spectra have already been recorded to complement an expanding reference database [13] for Europa Clipper and other missions to ocean worlds. However, environmental samples from terrestrial locations analogous to icy moons have never been analyzed with LILBID so far, although they allow a more realistic assessment of the detection capabilities of spaceborne instruments as compared to experiments with prepared synthetic samples of well-defined compositions. Specifically, natural ice analogues from polar locations offer some of the most realistic representations of icy moons as these ices are subject to similar environmental conditions, leading to complex biochemical compositions that include extremophilic ecosystems - which could be the case for surface or plume ice samples from icy moons.
Here we present the first analysis of natural ice analogues with LILBID combined with a detailed analysis of lipid biomarkers. With support from the Instituto Antártico Uruguayo, ice samples were collected from key locations in the Collins (a.k.a. Bellinghausen) Glacier on King George Island, Antarctica, with several environmental conditions (including intense UV radiation, saline aerosols, low temperature) analogous to specific processes on ocean worlds. Our analytical study includes (1) Gas Chromatography coupled to Mass Spectrometry (GC-MS), which is a well-established, standardized and optimized technique already used on King George Island for the detailed examination of lipids [14] and (2) LILBID analyses providing SUDA-type mass spectra of the same samples. Combining these two analytical methods allows a novel assessment of the detectability of lipid biomarkers from icy moon analogues with spaceborne instrumentation. Preliminary results including the first data of each analytical technique will be presented, as well as future steps of sample processing and analysis. Overall, this work will highlight the possible limitations that spaceborne dust analyzers can potentially encounter when dealing with complex-matrix samples, and will allow to acquire a more profound knowledge of potential lipid biomarkers that could be encountered by SUDA onboard Europa Clipper.
References
[1] Hand, K. P., Carlson, R. W., & Chyba, C. F. (2007). Energy, chemical disequilibrium, and geological constraints on Europa. Astrobiology, 7(6), 1006-1022.
[2] Kempf et al. SUDA: A SUrface Dust Analyser for compositional mapping of the Galilean moon Europa. Space Science Reviews, in review.
[3] Howell SM and Pappalardo RT. NASA’s Europa Clipper—a Mission to a Potentially Habitable Ocean World. Nat Commun 2020;11(1):1311.
[4] Dannenmann M, Klenner F, Bönigk J, et al. Toward Detecting Biosignatures of DNA, Lipids, and Metabolic Intermediates from Bacteria in Ice Grains Emitted by Enceladus and Europa. Astrobiology 2023;23(1):60–75.
[5] Klenner, F., Bönigk, J., Napoleoni, M., Hillier, J., Khawaja, N., Olsson-Francis, K., ... & Postberg, F. (2024). How to identify cell material in a single ice grain emitted from Enceladus or Europa. Science Advances, 10(12), eadl0849.
[6] Bywaters K, Stoker CR, Batista Do Nascimento N, et al. Towards Determining Biosignature Retention in Icy World Plumes. Life 2020;10(4):40.
[7] Jebbar M, Hickman-Lewis K, Cavalazzi B, et al. Microbial Diversity and Biosignatures: An Icy Moons Perspective. Space Sci Rev 2020;216(1):10.
[8] Carrizo D., de Dios-Cubillas A., Sánchez-García L., López I., & Prieto-Ballesteros O. Interpreting molecular and isotopic biosignatures in methane-derived authigenic carbonates in the light of a potential carbon cycle in the Icy Moons. Astrobiology 2022, 22(5):552-567.
[9] Georgiou CD and Deamer DW. Lipids as Universal Biomarkers of Extraterrestrial Life. Astrobiology 2014;14(6):541–549.
[10] Finkel PL, Carrizo D, Parro V, & Sánchez-García L., An Overview of Lipid Biomarkers in Terrestrial Extreme Environments with Relevance for Mars Exploration. Astrobiology 2023; ast.2022.0083.
[11] Klenner F, Postberg F, Hillier J, et al. Analog Experiments for the Identification of Trace Biosignatures in Ice Grains from Extraterrestrial Ocean Worlds. Astrobiology 2020a;20(2):179–189.
[12] Napoleoni M, Klenner F, Khawaja N, et al. Mass Spectrometric Fingerprints of Organic Compounds in NaCl-Rich Ice Grains from Europa and Enceladus. ACS Earth Space Chem 2023;7(4):735–752.
[13] Klenner, F., Umair, M., Walter, S. H., Khawaja, N., Hillier, J., Nölle, L., ... & Postberg, F. (2022). Developing a laser induced liquid beam ion desorption spectral database as reference for spaceborne mass spectrometers. Earth and Space Science, 9(9), e2022EA002313.
[14] Carrizo D., Sánchez-García L., Menes R. J., García-Rodríguez F. Discriminating sources and preservation of organic matter in surface sediments from five Antarctic lakes in the Fildes Peninsula (King George Island) by lipid biomarkers and compound-specific isotopic analysis. Sci. Tot. Environ. 672, 657-668.
How to cite: Hortal Sánchez, L., Napoleoni, M., L. Finkel, P., Carrizo, D., Khawaja, N., Sánchez-García, L., Parro, V., and Postberg, F.: Detection of molecular biosignatures in polar ices with mass spectrometry: implications for Europa Clipper, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-835, https://doi.org/10.5194/epsc2024-835, 2024.
Saturn’s icy moon Enceladus is a prime target in the search for extraterrestrial life in our Solar System. Its subsurface ocean fulfils essential criteria for life as we know it on Earth: liquid water [1], organic chemistry [2, 3] and a potential energy source from hydrothermal activity induced by tidal heating [4, 5]. At its south pole, ice grains form from the ocean and are ejected through cracks in the ice shell, transporting the ocean water to space where it can be detected by flyby missions [6, 7].
The Cosmic Dust Analyzer (CDA) [8], an impact ionization mass spectrometer onboard the Cassini-Huygens spacecraft, analyzed the composition of single ejected ice grains, providing insights into the composition of the moderately salty and alkaline ocean [4, 6, 7]. Interpretation of CDA data was aided by complementary analogue experiments with a Laser Induced Liquid Beam Ion Desorption Mass Spectrometer (LILBID-MS) that simulates impact ionization with laser desorption [9]. The LILBID technique can also predict the mass spectral appearance of bacterial biosignatures in ice grains detected by future impact ionization mass spectrometers [10, 11]. However, past experiments have not considered the influence of ambient environmental conditions on the growth of putative extraterrestrial cells and the biosignatures they produce.
To be enclosed in ice grains, cells have to be present at the ocean surface [2]. Thus, they either need to grow in proximity to the ice-ocean interface or be transported upwards from deeper habitats. Here, we investigate the first scenario of viable cells at the ocean surface, represented by Rhodonellum psychrophilum, an alkaliphilic psychrophile, as a model organism.
At its surface, the ocean is likely stratified by a thin salt-depleted layer with NaCl concentrations of 0.05 M [6, 12] and pH 9-11 [7, 13, 14]. This lies within the range of the optimal growth conditions for R. psychrophilum: 0 – 0.1 M NaCl and pH 10 [15]. Water temperatures reach the freezing point at the ice-ocean interface, ca. -0.1 °C for an aqueous 0.05 M NaCl solution, and increase by approximately 2 °C over the stratified layer [12]. Although optimal growth of R. psychrophilum occurs at 5 °C, it can sustain temperatures down to 0 °C [15]. As a strictly aerobic chemoheterotroph, it would rely on transport of radiolytic oxygen from the irradiated icy surface [16] and organic carbon from hydrothermal sites at the ocean floor [2, 3].
We first grew R. psychrophilum at 6 °C in its optimal growth medium (R2-A medium [15]) adjusted to pH 10 with Na2CO3 to demonstrate its suitability as a representative of putative alkaliphilic cells in Enceladus’ ocean. In ongoing experiments, we now aim to set up the culture in an Enceladus ocean water simulant based on CDA data and existing models of the ocean that consists of the following inorganic compounds: 0.05 M NaCl, 0.01 M KCl, up to 0.1 M Na2CO3 (variable for pH adjustment), 0.002 M Na3PO4, 0.001 M SiO2, and 0.001 M NH3 [4, 6, 7, 13, 14, 17, 18, 19]. Organic carbon, sulfur and additional nitrogen sources will first be supplied by the addition of R2-A medium but finally substituted by organic compounds detected in the ocean [2, 3, 18]. We will incubate R. psychrophilum in the dark at 6 °C to obtain optimal biomass yield [15] and at 0 °C to simulate growth in surface waters. Finally, the cells will be analyzed by LILBID-MS to predict their mass spectral appearance in ejected ice grains.
Cultivating bacteria in simulated Enceladus ocean water will illustrate its potential for supporting life and yield biosignatures reflective of authentic environmental settings, increasing the predictive power of biosignature detection experiments.
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How to cite: Dannenmann, M., Ackley, M., Burr, D., Olsson-Francis, K., and Postberg, F.: Growing a putative inhabitant of Enceladus’ ocean surface, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-973, https://doi.org/10.5194/epsc2024-973, 2024.
Icy moons with a liquid subsurface ocean, such as Europa7 and Enceladus16, are prime candidates in the search for extraterrestrial life. For future spaceflight missions, the identification of biosignatures with onboard mass spectrometers (MS) will be essential. NASA and ESA’s Cassini-Huygens spacecraft, which passed nearby to Enceladus and sampled ice grains from the icy moon’s cryovolcanic plume using low resolution impact ionization mass spectrometry, has already identified a variety of organic material originating from the moon’s subsurface ocean6,11. In upcoming missions, such as NASA’s Europa Clipper, the use of higher resolution mass spectrometers will be crucial for clearer identification of organic compounds5,13.
The Planetary Sciences group at Freie Universität Berlin is specialized in simulating mass spectra obtained from ice grains in space by a Laser Induced Liquid Beam Ion Desorption Mass Spectrometer (LILBID-MS)17. Such experiments have proven capable of accurately identifying and quantifying biomolecules in a water-ice matrix, such as amino acids, peptides, sugars, and fatty acids from within cells4, while distinguishing between molecular patterns with biotic or abiotic origins8. They have also demonstrated how to identify cell material from within a single pure-water ice grain emitted from Enceladus or Europa9. However, there are still gaps in our knowledge of to what extent salts affect the spectrometric fingerprints of biosignatures.
Such salt concentrations are highly relevant for the ocean and surface of icy moons, where potential biosignatures might be found in water or ice with salinity levels similar to or greater than that of Earth’s oceans. On Enceladus, the ocean contains salt concentrations ranging from 0.07 - 0.3 M NaCl, dependent on depth and ocean layer2,12. On Europa, the abundance and composition of salts in the ocean is not well defined, but existing estimates suggest that the ocean is dominated by NaCl and MgSO4 3. Previous research indicates that the total hydrosphere of Europa contains ∼0.6 M of total dissolved salts14, ranging from 0.01 M MgSO4 and NaCl in less salty ocean waters10 to 2.4 M in mantle pore fluids or localized hyper-saline regions15. Biosignatures entrained in ice grains originating from these regions of Europa or Enceladus would contain far higher salinity levels than have previously been studied, and these levels of salinity are known to interfere with the visibility of organics in mass spectral data1,8, 18, 19.
This research project studies how salinity levels and various types of salts comparable to those found on the icy moons may affect mass spectral biosignature readings. To achieve this, the psychrophilic extremophile Sphingopyxis alaskensis is submerged in water-based solutions with salt concentrations similar to that of Enceladus and Europa. The mass spectra of the cells are then measured using MS laboratory instruments to determine what biosignatures might be detectable in single salt-rich ice grains that contain cell material.
Understanding how salts affect the way cell material is presented in mass spectral data is conducive to the identification of organic biosignatures in future spaceflight missions, such as Europa Clipper. This research project will help to strengthen our understanding of biosignature detection, enhancing the capability of spaceborne instruments to detect the presence or absence of biosignatures with high confidence.
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How to cite: Ackley, M., Dannenmann, M., Napoleoni, M., Klenner, F., Bönigk, J., Olsson-Francis, K., and Postberg, F.: Detecting cellular biosignatures from single salt-rich ice grains emitted from Enceladus or Europa, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1081, https://doi.org/10.5194/epsc2024-1081, 2024.
Introduction: Analysis of micrometer-sized ice grains emitted from Saturn’s moon Enceladus revealed that the moon’s subsurface ocean represents a potentially habitable place in the Solar System. The ocean is salty, with comparable salinity to Earth’s oceans [1]. However, salt concentrations in individual grains sourced from the ocean can vary drastically [2], probably due to the segregation of individual salts upon freezing [3]. The ocean contains a diverse complement of organic compounds [4,5] and likely interacts with the moon’s rocky core through hydrothermal reactions at the seafloor [6]. Recent work demonstrates that traces of bacterial life, if entrapped and preserved in the ice grains, would be detectable [7].
One important aspect for the preservation of organic structures, or even cells, is the phase state (crystalline, glassy, or some mixture of both) of the ice grains. Although organic structures and cells tolerate tiny micrometer-sized crystals in their vicinity [8], glassy phases can favor preservation of these compounds [9].
While the largest amount of glassy phases on Enceladus are found in the active regions around the moon’s south pole [10], freshly emitted material appears to be predominantly crystalline [11]. These phase states of the grains are ultimately linked to their formation conditions, i.e. liquid-solid phase transitions.
Salt-rich ice grains on Enceladus are believed to form via flash-freezing of ocean droplets [1], with fast freezing rates being favorable for the formation of glassy phases [12]. The freezing rates of these grains are not well constrained, but calculations indicate that the grains may freeze within 1 ms after droplet formation [13], meaning they would freeze within the first cm above the water table [14].
Methods: To better understand the formation of crystalline and/or glassy phases upon freezing of ice grains from Enceladus’s ocean, we performed Differential Scanning Calorimetry (DSC) experiments with aqueous solutions of NaCl, KCl, Na2CO3, NaHCO3, NH4OH, Na2HPO4, K2HPO4, as well as mixtures of these compounds. The same technique was recently applied to Mars by studying brines of single salt perchlorate compositions [15]. Measured salt concentrations in our experiments covered the range of estimated concentrations of these compounds in Enceladus’s ocean [1,14,16]. We determined the degree of supercooling and the degree of vitrification of the samples (volumes varied from 4 to 40 μL) over a wide range of cooling rates, from as low as 10 K/min up to ~1000 K/min via drop-quenching into liquid nitrogen (flash freezing). We then modeled the freezing process of these solutions and associated mineral formation using the thermodynamic aqueous chemistry software PHREEQC [17] to support our DSC experiments.
Results and Conclusions: Between 0.3 and ~10 percent of the total ice grain volume should form a glassy state upon freezing from Enceladus’s subsurface ocean, strongly correlated with the freezing rate and the salt concentration of individual grains. Organic structures, or potentially cells, are more likely to be preserved in rapidly freezing grains with high concentrations of salts because these grains have a higher degree of vitrification than salt-poor grains.
Significant supercooling is expected to occur during flash-freezing of ice grains from a salty ocean on Enceladus. Upon freezing, the crystallization of minerals appears to follow a particular sequence.
Our experiments and models are an important step toward understanding the formation and structure of ice grains and their capability for preserving organics and cells. Newly derived data will inform future Enceladus models and is relevant to other icy worlds with subsurface water reservoirs, such as Jupiter’s moon Europa or dwarf planet Ceres.
References:
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How to cite: Klenner, F., Fifer, L. M., Journaux, B., Bravenec, A. D., and Catling, D. C.: Toward a Better Understanding of Ice Grain Formation from Enceladus’s Salty Ocean, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-657, https://doi.org/10.5194/epsc2024-657, 2024.
Introduction: Enceladus’s erupting plume likely originates from a subsurface ocean, and thus represents an avenue for revealing the ocean composition. The plume composition was measured by two mass spectrometers on Cassini during flythroughs of the plume. These measurements currently provide our best means of estimating Enceladus’s ocean chemistry and the moon’s potential to host life. The Cosmic Dust Analyzer (CDA; Srama et al. 2004) measured the composition of ice grains in the plume and Saturn’s E ring, finding a variety salts (including biologically useful phosphate) and organic molecules that could be hydrothermal, primordial, or possibly biological in origin (e.g., Postberg et al. 2018, 2023; Khawaja et al. 2019). The Ion and Neutral Mass Spectrometer (INMS; Waite et al. 2006) analyzed the gases in the plume and detected CO2, NH3, H2, CH4 and HCN, which suggests conditions in the ocean are likely favorable for chemotrophy (e.g., methanogenesis) and possibly prebiotic chemistry (e.g., Waite et al. 2017, Peter et al. 2023).
Motivation: However, the relative abundances of key molecules in the plume may be quite different in the ocean due to fractionating processes during eruption (Fifer et al. 2022). The effects of fractionation are important when considering how the plume gas represents (or misrepresents) the abundances of gases in the ocean. For instance, condensation of water vapor onto the icy walls of the tiger stripe fissures can cause gases like CO2 to have much higher abundances (relative to water) in the plume than in the ocean (Glein et al. 2015; Glein & Waite 2020; Fifer et al. 2022). In a competing fractionation, the differential exsolution of gases from Enceladus’s ocean will tend to enrich water vapor in the plume relative to other gases (Fifer et al. 2022). While CDA in situ measurements suggest that the ocean’s pH is ~8.5 – 10.5 (e.g., Postberg et al. 2009, Postberg et al. 2023), studies to account for fractionation and estimate ocean gas content and pH from the plume measurements have produced a wide range of possible ocean compositions, with pH ~6–13 (e.g., Marion et al. 2012; Glein et al. 2015). Thus, quantifying fractionation in the plume gas during eruption can better determine the ocean composition.
Here, we used laboratory experiments to constrain a key fractionation process: the exsolution of gases at the liquid-gas interface.
Methods: In a stainless steel vessel at 0°C, we added pure water or saline solutions and degassed them under vacuum. We then introduced a single gas (e.g., CO2) and allowed it to dissolve to equilibrium. We monitored the headspace pressure and partially evacuated the headspace gas, driving gas exsolution in an analogous process to how the plumes may form from a water-filled fissure on Enceladus. We can calculate a mass transfer coefficient associated with exsolution by monitoring the increasing headspace pressure during exsolution and deriving the concentration remaining in solution. We also used a stir bar to investigate the effects of stirring or mixing on exsolution.
Results: We find a positive linear correlation between stir rate and mass transfer coefficient for CO2 (Figure 1) consistent with previous experiments investigating gas transfer in water (Nishimura et al. 1991). Notably, our mass transfer coefficients are comparable to those derived for ocean-atmosphere exchange on Earth (Broecker & Peng 1982). In trials using a 0.2 NaCl solution, we found a reduction in the mass transfer coefficient of CO2 by ~25% compared to pure water, which is larger than in previous studies (~10%) for CO2 diffusion in NaCl solutions (Zhang et al. 2015).
Figure 1: Mass transfer coefficient for CO2 exsolution from pure water as a function of stir rate in solution.
Conclusions: We find that the mass transfer coefficient of CO2 strongly depends on the rate of stirring. For Enceladus’s plume formation, this means that an observed flux of erupting gas could originate from either a well-mixed ocean with low gas concentrations or a poorly-mixed ocean with higher gas concentrations. Therefore, it is important to quantify the degree of mixing in the surface ocean where the plume gas is likely sourced.
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How to cite: Fifer, L., Toner, J. D., Ford, K., Mousseau, B., Klenner, F., and Catling, D. C.: Measuring Exsolution Rates of Gases in a Laboratory Analog for Enceladus Plume Formation, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1314, https://doi.org/10.5194/epsc2024-1314, 2024.
