Orals: Tue, 29 Apr | Room 0.94/95
In search of extraterrestrial life within the solar system, Jupiter’s moon Europa emerges as a promising candidate. Previous observations indicate the existence of a global ocean beneath the moon’s icy shell. To explore the hidden water reservoir, future missions need to penetrate the kilometer-thick ice layer. Within the project line TRIPLE (Technologies for Rapid Ice Penetration and subglacial Lake Exploration), initiated by the German Space Agency at DLR, technologies for such a mission are under development.
Three main components are involved: (i) A retrievable electrothermal drill, also referred to as a melting probe, for penetrating the ice shell and investigating the ice layer. (ii) A miniaturized autonomous underwater vehicle (nanoAUV) for exploring the water reservoir and collecting samples. (iii) An astrobiological laboratory for in-situ examination of samples.
For the melting probe to be able to detect obstacles on its trajectory, safely navigate to the ice-water interface and anchor itself there, it needs a robust forefield reconnaissance system. In this contribution, we present a hybrid forefield reconnaissance system (FRS) that combines sonar and radar. This hybrid approach was selected to utilize the complementary advantages of both sensor systems. Both radar and sonar will be integrated into the melting head. To determine the propagation speed of the electromagnetic waves and to further provide scientific data about the ice stratification, a permittivity sensor is included.
The entire TRIPLE system is to demonstrate its operational capability in an analog terrestrial scenario in the Antarctic. Of particular interest is the Dome C region, as it is expected that subglacial lakes in this area lie beneath a several-kilometer-thick ice shell. The next milestone for addressing this challenge is an intermediate test on the Ekström Ice Shelf. Although the introduced FRS concept was successfully tested on Alpine glaciers, adaptations will be necessary for its integration into the full TRIPLE scenario. In this presentation, we will present the latest developments related to the upcoming campaign.
How to cite: Do, M. G., Audehm, J., Becker, F., Böck, G., Haberberger, N., Helbing, K., Heinen, D., Vossiek, M., Wiebusch, C., and Zierke, S.: Current Developments in the Forefield Reconnaissance System for Melting Probes for the Exploration of Subglacial Lakes with the TRIPLE Project, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18157, https://doi.org/10.5194/egusphere-egu25-18157, 2025.
Ice-melting probes, also called cryobots, are envisioned as a key technology for accessing the subglacial oceans of icy moons, such as Europa and Enceladus, to search for life. These extraterrestrial ice shells, several kilometers thick, are anticipated to include a dense ice layer transitioning to a porous, mushy zone at the ice-water interface, resembling Earth’s sea ice. Despite this, most terrestrial field tests of cryobots have been conducted in glacial ice, which differs significantly from sea ice in structure and composition. However, for mission planning both types of ice need to be considered.
Digital twins and virtual testbeds can be used for the integration of data and forward simulations for design and decision support subjected to the performance of the cryobot. In this contribution, we extend the functionality of the Cryotwin, an in-house digital twin for cryobots [1,2], to assess the influence of porosity on the cryobot’s performance. Our simulation model predicts the cryobot’s melting velocity, efficiency and transit time [3] for the unique thermal and porosity gradients encountered in sea ice. Mimicking a virtual testbed, our model considers an explicit update of the local environment, comprised of porosity, thermal conductivity, heat capacity, and density, while the cryobot moves downward melting into the ice. Porosity will be incorporated into the simulations based on temperature and salinity measurements from sea ice cores. We take salinity and temperature data from the RESICE database [4], which currently provides data from 287 sea ice cores originating from different geospatial locations and seasons, and feed environmental data into the digital twin’s testbed. Further, we use this data to derive the material properties of the local cryo-environment used in the simulation.
This work provides insights into the operation of future cryobots in extraterrestrial environments that comprise both dense and porous ice. With this study, we want to investigate the importance of analogue testing in sea ice, and demonstrate the value add of comprehensive virtualized digital twin infrastructure, to enhance mission readiness for icy moon exploration.
References:
[1] Kowalski et al., Cryotwin – Digital infrastructure for virtually-assisted preparation and analysis of cryo-robotic exploration missions, 84th EAGE Annual Conference & Exhibition (2023) 1 – 5, doi: 10.3997/2214-4609.2023101223.
[2] Bhattacharya et al., Cryotwin: Toward the Integration of a Predictive Framework for Thermal Drilling, ECCOMAS (2024), doi: 10.23967/eccomas.2024.070
[3] Boxberg et al., Ice Transit and Performance Analysis for Cryorobotic Subglacial Access Missions on Earth and Europa, Astrobiology 23 (2023) 1135-1152, doi: 10.1089/ast.2021.007.
[4] Simson et al., RESICE - Reusability-targeted Enriched Sea Ice Core Database - General Information, Zenodo (2024), doi: 10.5281/zenodo.10866347.
How to cite: Bhattacharya, D., Simson, A., and Kowalski, J.: Investigating cryobot performance in realistic ice environments with the Cryotwin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21311, https://doi.org/10.5194/egusphere-egu25-21311, 2025.
Ices are widespread across the solar system, present on the surfaces of nearly all planets and moons. Icy moons, in particular, are of high interest due to their potential habitability, as they can harbor liquid water oceans beneath their icy crust making them prime targets for the upcoming JUICE (ESA) and Europa Clipper (NASA) missions. While space observations suggest that these surfaces are made of granular water ice, the fine-scale structure — such as the size, shape, and distribution of ice grains — remains poorly understood. This raises the question: What is the current state of the ice microstructure on these surfaces?
Various interdependant surface processes interact over large timescales and together alter the microstructure of the icy surfaces. To adress this, we have developed an innovative multiphysics simulation tool, LunaIcy, which integrates the main physics that affect Europa’s ice microstructure and simulates their interactions. This model has already provided valuable insights into Europa's surface, helping to estimate the thermal dynamics, ice cohesiveness/sintering, and crystallinity.
Space observations will greatly benefit from such modeling advancements, which will be essential for a better interpretation of data from the upcoming missions. Multiple other applications for different icy bodies are underway, as we expect that the study of planetary surfaces, much like General Circulation Models for climate science, can greatly benefit from such multiphysical approaches.
How to cite: Mergny, C. and Schmidt, F.: LunaIcy, a Multiphysics Surface Model for the study of icy surfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21520, https://doi.org/10.5194/egusphere-egu25-21520, 2025.
Variations in orbital parameters can change the total amount and spatial distribution of tidal heating within icy satellites, leading to changes in ice shell thickness. These thickness changes are accommodated by the melting and solidification of ice at the ocean/ice interface. During the thickening phase of ice shell evolution, the volumetric change as water freezes into ice, in combination with the volumetric shrinkage of a cooling ice shell, generates overpressure within the subsurface ocean and extensional stresses at the satellite’s surface. During the thinning phase of ice shell evolution, the opposite process may occur, with large compressional stresses generated within the cooling ice shell and underpressure within the subsurface ocean. Fracture penetration, ocean pressurization, and eruptions associated with thickening ice shells have been explored for Europa, Enceladus, and Mimas. However, much less work has been done to understand the behavior of the ice-ocean system when the ice shell thins. Here, we use analytic and numerical models of ice shell evolution to compute the conditions within ice shells and subsurface oceans during the thinning phase of ice shell evolution. We map the conditions under which subsurface oceans may develop underpressure sufficient to initiate decompression boiling and we discuss possible upward transport mechanisms for the vapor generated by this process. We also discuss the implications of our model for the interpretation of compressional tectonic features associated with the stresses generated within thinning ice shells.
How to cite: Rudolph, M., Rhoden, A., Manga, M., and Walker, M.: Ocean underpressure, subsurface boiling, and the upward transport of water on icy moons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14681, https://doi.org/10.5194/egusphere-egu25-14681, 2025.
Ganymede, the largest moon in the solar system, captivates with its complex geology and potential habitability. ESA's JUICE mission currently focuses on exploring Ganymede [1, 2]. We investigate ray and halo impact craters on its surface, which exhibit diverse morphologies and ejecta materials [3], including bright icy and dark non-ice materials [4, 5] found in various locations on Ganymede. In order to understand stratigraphy of Ganymede’s crust, we investigate formation of ray and halo impact craters using the Z-model [8] and the iSALE 2D, which is a multirheology and multimaterial Hydrocode code [e.g. 9] for numerical simulations.
We mapped ray and halo impact craters using global mosaic created by [10]. Additionally, we incorporate NIMS-derived data on varying water ice abundance, dark non-ice material distribution, and water ice grain sizes as presented in [11], wherever available. For iSALE, the projectile resolution used was 10 cells per projectile radius, corresponding to an impactor size of 1 km. Approximately 120-160 zones were used in the extension zone, with a 5% increase in cell size from one neighboring cell to the next. For Antum, an impactor velocity of 15 km/s was employed.
Excavation depth measurements for different crater types were collected based on [7] and [8] (Z = 3, Z = 4). These measurements reveal that dark ray craters such as Antum and Mir suggest the dark terrain at Marius Regio is relatively thin, not exceeding 2.3 km. In contrast, dark halo craters like Nergal and Khensu on light terrain indicate that excavated dark material originates from depths of ~1.4 km and 2.5 km, respectively, suggesting heterogeneity in the crust and the presence of subsurface dark material. Dark ray craters in light terrain, like Kittu, indicate that dark terrain material originates from a depth of around 2.3 km. From iSALE, for Antum, dark material is ejected furthest followed by bright material, where the dark material is estimated to ~1.3 km thick. These findings support the possibility of rifting contributing to the formation of light terrain wherever dark halo and dark ray craters are present, indicating subsidence of dark material into the subsurface. While bright ray craters imply light terrain formation via tectonic spreading. Our preliminary findings support iSALE modeling results for Antum are consistent with results from Z-model [8].
[1] Grasset et al. (2013), PSS, v. 78, p. 1-21. [2] Stephan et al. (2021), v. 208, p. 105324. [3] Schenk et al., (2004), Cambridge University Press, p. 427 - 456. [4] Hibbitts (2023), Icarus, v. 394, p. 115400. [5] Schenk and McKinnon (1991), Space Science Reviews, v. 60, no. 1, p. 413-455. [6] Kenkmann et al (2014), Journal of Structural Geology, v. 62, p. 156-182. [7] Melosh (1989), Oxford University Press. [8] Maxwell, D. E. (1977), Impact and explosion cratering, 1003–1008. Pergamon Press. [9] Amsden et al. (1980), No. LA-8095), Los Alamos National Lab. (LANL), Los Alamos, NM (United States). [10] Kersten et al. (2022), pp. EPSC2022-450. [11] Stephan et al. (2020), Icarus, v. 337, p. 113440.
How to cite: Baby, N. R., Kenkmann, T., Stephan, K., Wagner, R., Karagoz, O., Das, R., and Hauber, E.: Insights about Stratigraphy and Composition From Ray and Halo Craters on Ganymede, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21586, https://doi.org/10.5194/egusphere-egu25-21586, 2025.
One of the major questions in planetary exploration concerns the habitability of icy moons in the outer Solar System. These bodies can harbor liquid water in substantial amounts over long time-scales, a necessary ingredient for habitable environments. Water on icy moons is located in global oceans in the subsurface, beneath a global ice shell, and/or in local reservoirs within this ice shell. Moreover, some of the satellites, in particular Europa and Enceladus and perhaps also Triton and the largest Moons of Uranus, may provide the ‘right’ chemistry because of an ocean-silicate interface in their interior. The latter allows for rock-water interaction potentially bringing chemical compounds (CHNOPS) in contact with liquid water. Due to tidal friction, which can be an important heat source in the moons’ interiors, energy that drives chemical cycles would be available and sustained over time.
Among the icy moons, Enceladus is a high priority target for planetary explorations due to its high astrobiological potential. Based on the current knowledge from mission data and theoretical modeling, Enceladus provides compelling evidence for the presence of a global ocean, tidal energy as a heat source, hydrothermal processes at the ocean floor, current surface activity and a young surface, as well as possible existence of shallow water reservoirs and complex chemistry. In fact, Enceladus is recommended as the top priority target in ESA’s Voyage 2050 plan covering the science theme “Moons of the Giant Planets” [1], with a subsurface radar sounder in the core payload of such a mission.
Radar sounders are the obvious means to detect and characterize subsurface water reservoirs on icy moons [2]. They can determine the ice-water interface and variations thereof, detect near-surface water reservoirs, study the connection of the ocean with the shallow subsurface/surface, and characterize the layering of the upper ice crust, e.g. snow, ice regolith, or compact ice that can help to understand the past evolution (intensity of jet activity and geological history).
In this study we focus on the scientific goals of a radar sounder at Enceladus. We discuss the ice shell characteristics (thickness and variations, thermal structure, and layering) and their effects on the radar attenuation. We calculate the two-way radar attenuation on Enceladus considering a conductive ice shell covered by a porous thermally insulating surface layer. Our models show that for regions covered by a thick insulating porous surface layer (∼700 m, [3]) a radar signal will not be able to reach the ice-ocean interface. However, for these same regions the high subsurface temperatures caused by a strong insulation due to the thick porous layer increase the likelihood that shallow brines are present [4]. Such brine reservoirs are fundamental to characterize habitable environments in the shallow subsurface, and the potential to directly access them with future measurements is much greater when compared to the accessibility of subsurface oceans [5].
References:
[1] Martins et al. (2024); [2] Benedikter et al., this meeting; [3] Martin et al. (2023); [4] Byrne et al. (2024); [5] Wolfenbarger et al. (2022).
How to cite: Hussmann, H., Byrne, W., Plesa, A.-C., Rückriemen-Bez, T., and Benedikter, A.: Exploring Enceladus: The Science Case for Future Radar Sounder Measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21313, https://doi.org/10.5194/egusphere-egu25-21313, 2025.
A high-level description of Titan’s wind field is a useful tool for two reasons. First, as a series of simple statements, one can convey succinctly to the public how Titan’s weather differs from that on Earth or Mars, for example. Second, those statements can be mapped to an algorithmic specification (i.e. lines of code) to generate tables or maps of numerical values, and such a program is a much more compact and convenient construct to use in modeling of meteorological or geomorphological processes or in planetary mission design than are tables themselves.
Here I overview such a description, guided by the Huygens descent measurements obtained 20 years ago, subsequent Cassini and groundbased observations, and global circulation model outputs. The most prominent feature to be captured is the seasonal evolution of the stratospheric zonal wind at mid/high latitude (analogous to the jetstream encountered in terrestrial aviation).
Results from this effort may contribute to the next generation of the NASA Titan-GRAM (Global Reference Atmosphere Model) tool.
How to cite: Lorenz, R.: A High-Level Description of Titan’s Winds , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4402, https://doi.org/10.5194/egusphere-egu25-4402, 2025.
Titan, visited by the Huygens probe in 2005, is the only moon in the solar system known to have a dense, nitrogen-rich atmosphere. It is also suspected to possess a subsurface global ocean beneath an ice crust. A striking characteristic of Titan’s atmosphere is the absence of primordial noble gases such as argon, krypton, and xenon. If Titan’s ice content—estimated to be between 30% and 50%—was delivered by volatile-rich planetesimals and solids, it would be expected that these noble gases would have been incorporated into the moon’s hydrosphere during its formation. A plausible explanation for the depletion of these noble gases in Titan’s current atmosphere is their sequestration in clathrate hydrates. This process could have occurred either after the formation of Titan's ice crust or shortly after the moon's accretion, during the “open-ocean” phase, when Titan’s surface was initially liquid.
Our work focuses on modeling the ocean-atmosphere equilibrium during Titan’s early history. To achieve this, we begin with a bulk composition and calculate how volatiles are distributed between the vapor and liquid phases. We take into account the vapor-liquid equilibrium between water and various volatiles, as well as the CO₂-NH₃ chemical equilibrium occurring within the ocean at shallow depths. Additionally, using a statistical thermodynamic model, we explore the potential impact of clathrate formation at the ocean's surface. If the stability conditions for clathrates are met, we investigate how their formation could influence the composition of Titan’s primordial atmosphere. Specifically, we assess the required thickness of the clathrate crust necessary to deplete the primordial atmosphere of noble gases.
Our computations suggest that if Titan's water budget was delivered by icy planetesimals with a comet-like composition, a thick, CO₂- and CH₄-rich primordial atmosphere would form above the ocean. We also highlight that the equilibrium of the primordial hydrosphere leads to a significant depletion of NH₃ in both the atmosphere and the ocean, as it is converted into ions due to the chemical equilibrium with CO₂. Furthermore, we show that a clathrate crust just a few kilometers thick would be sufficient to completely deplete the primordial atmosphere of xenon at 273.15 K. In contrast, to retain most of the krypton in the atmosphere, a much thicker clathrate crust—on the order of tens of kilometers—would be required. Argon, however, is not trapped as efficiently as other noble gases. Our calculations show that argon can only be captured in significant amounts at much lower temperatures, after Titan's surface has cooled.
How to cite: Amsler Moulanier, A., Mousis, O., Bouquet, A., and Trinh, N. H. D.: Clathrate as a noble gas reservoir from the primordial hydrosphere of Titan , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10116, https://doi.org/10.5194/egusphere-egu25-10116, 2025.
Photochemical processes in Titan’s upper atmosphere produce a number of hydrocarbon and nitrile gases which reach their condensation temperatures in Titan’s stratosphere. These ices form around the organic haze particles which give Titan its characteristic orange color. The microphysics of these ice particles was modeled using the Titan mode of PlanetCARMA (based on the Community Aerosol & Radiation Model for Atmospheres). CARMA models the vertical transport, coagulation, nucleation, condensation, and evaporation of particles in a column of atmosphere. Ice composition includes hydrogen cyanide (HCN), benzene (C6H6), diacetylene (C4H2), propane (C3H8), acetylene (C2H2), and ethane (C2H6). CARMA tracks the mass of each ice on the atmospheric particles and calculates a flux of material across the tropopause.
Once in the troposphere, these particles can become seed nuclei for the methane clouds seen from groundbased and Cassini observations. Methane is the only condensable gas abundant enough in Titan’s atmosphere to grow cloud particles to raindrop sizes, which then fall to the surface transporting any haze and ice mass within. The Titan Regional Atmospheric Modeling System (TRAMS) is a fully dynamic, compressible, regional-scale numerical model of Titan’s atmosphere. Coupled to CARMA, TRAMS is used to explore the microphysics and dynamics of Titan’s methane storms. We will report on results from TRAMS simulations of methane clouds and storms to quantify the mass and composition of ices deposited at Titan’s surface and implications for local changes in Titan’s surface albedo.
How to cite: Barth, E. L.: Delivery of Ices to Titan’s Surface within Methane Raindrops, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14316, https://doi.org/10.5194/egusphere-egu25-14316, 2025.
Posters on site: Tue, 29 Apr, 08:30–10:15 | Hall X4
Europa’s geologically young surface, characterised by extensional and subsumption bands, hints at dynamic ice tectonics and active interactions between the moon’s surface and its interior. Potentially, a key driver of this activity is the convection within Europa’s icy shell. Ice shell convection can facilitate and promote the mobility of Europa’s ice surface, the evolution of its topography as well as thermochemical mixing within the shell itself. Yet, critical aspects of Europa’s ice shell, such as its thickness and composition and how these vary across the surface and with depth, remain elusive, limiting our understanding of Europa’s icy dynamics and its surface evolution. In this work, we present state-of-the-art numerical models of convection in an icy shell with composite viscosity, visco-elastic-plastic deformation, and a free-surface top boundary condition using the finite element code ASPECT. We explore a range of ice properties informed by current the literature and find that the ice shell thickness plays a pivotal role in determining the onset, style and longevity of convection. Notably thicker ice shells encourage chaotic convection with high Rayleigh numbers, leading to the formation and peeling of ‘icy slabs’. These results provide new insights into the dynamic behavior of Europa’s icy shell and its implications for surface-interior coupling.
How to cite: Kim, H., Grima, A., and Daly, L.: Cracking Europa’s shell: How ice thickness and convection drive surface-interior dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11947, https://doi.org/10.5194/egusphere-egu25-11947, 2025.
Europa, one of Jupiter's moons, is a prime target in the search for habitability within the solar system (e.g., [1]). While the greatest potential for life lies in the interaction between a hypothesized liquid ocean and the rocky mantle—similar to Earth's deep-sea hydrothermal vents—the outer ice shell also plays a critical role. This shell could either aid in the detection of life or serve as a potential habitat itself.
In both scenarios, the transport of brine liquids is key: at the sub-kilometer-scale ice-ocean interface (localized brine intake) and across the planetary-scale ice shell (global brine transport). Despite the vast differences in spatial and temporal scales, these processes require models that account for the interplay between two phases (solid and liquid), the presence of solutes (salts), and phase changes.
Within the terrestrial and extraterrestrial cryosphere research community, two-phase flow models have been independently developed. They describe processes such as mushy layer dynamics (e.g., [3]) and, more recently, global ice shell behavior involving pure water ice (e.g., [4]). Established models are often derived from a common system of conservation laws, but a variety of different simplifying assumptions makes it challenging to compare and connect them consistently.
In this work, we present a unified framework for deriving process models applicable to different scales, from mushy layers to global ice shells. We begin by outlining the homogenized conservation laws for mass, momentum, energy, and solute (salt), operating under the assumption of equilibrium solidification.
Subsequently, we perform a scaling analysis to develop two-phase flow models tailored to both planetary-scale ice shells and sub-kilometer-scale mushy layers, which represent the ice-ocean interface. These derived models will be systematically compared to existing published models, with a particular focus on addressing the equilibrium thermochemistry problem in the context of the significant pressure variations encountered across planetary ice shells.
References:
[1] Coustenis & Encrenaz et al., 2013. [2] Nisbet and Sleep, 2001. [3] Katz and Worster, 2008, [4] Kalousova et al., 2018.
How to cite: Terschanski, B., Rückriemen-Bez, T., Plesa, A.-C., and Kowalski, J.: A journey across scales: Two-phase models for Europa’s icy mantle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18900, https://doi.org/10.5194/egusphere-egu25-18900, 2025.
Icy moons and their cryo-/hydrospheres are central to the search for subsurface habitable environments in the solar system (e.g., [1]). While the structure of internal ice and liquid water layers varies with the moon’s size, an outer ice shell is a common feature. Smaller moons, like Europa, typically have a thin ice shell overlaying a liquid ocean, whereas larger moons, like Ganymede, possess a thicker ice shell, burying the ocean deeper beneath the surface. The outer ice layer is particularly significant: it is the most accessible for exploration, serves as a conduit between the surface and subsurface ocean, and may itself harbor niches for life. Understanding its thermal and dynamic state is essential for interpreting mission data and assessing astrobiological potential.
In this work, we compare thin (10–40 km, e.g., Europa) and thick (50–200 km, e.g., Ganymede) ice shells, focusing on their impact on thermal and dynamic properties. We model ice shell dynamics using the GAIA convection code [2], building on recent studies [3,4] to incorporate temperature-dependent thermal conductivity (k), temperature- and pressure-dependent thermal expansivity ($\alpha$), and a complex rheology. We also examine tidal heating, a significant factor for Europa [5].
Our analysis explores various ice grain sizes, which influence the viscosity—a critical parameter for ice shell dynamics. Key model outputs that can be tested with future measurements include elastic thickness, brittle-to-ductile transition, boundary heat flux, and potential formation of brines. Furthermore, scaling laws relating heat loss and convection vigor, as well as the creep mechanism that dominates the deformation help us to characterize the ice shell dynamic regime (i.e., conductive, weakly convective, or highly convective). By distinguishing dynamic regimes, we aim to advance our understanding of icy worlds, the heat and material transport through their icy shells, and their potential for habitability.
References:
[1] Coustenis & Encrenaz et al., 2013. [2] Hüttig et al., 2013. [3] Carnahan et al. 2021. [4] Harel et al. 2020. [5] Tobie et al., 2003.
How to cite: Rückriemen-Bez, T. and Plesa, A.-C.: Icy realms compared: Global ice shell dynamics of Ganymede and Europa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17397, https://doi.org/10.5194/egusphere-egu25-17397, 2025.
The Jupiter moons Ganymede and Europa are prime targets for icy moons exploration by ESA’s JUICE and NASA’s Europa Clipper missions [1,2]. Future measurements by JUICE and Europa Clipper will provide key information about the ice shell structure and the depth of the subsurface oceans of these moons. While the ocean itself is the largest water body beneath the surface, liquid brine reservoirs may be present locally within the ice shell, in the shallow subsurface. These reservoirs may represent niches for habitability that may provide ideal targets for exploration because of their location close to the surface.
Evidence for the presence of shallow water reservoirs within the ice shell of Europa has been presented in a recent study that performed detailed geomorphological-structural investigations of Menec Fossae [3]. The observed tectonic activity in this region on Europa could be related to a shallow water pocket located close to the surface that would explain the observed overall topography of this area in addition to the presence of specific geological features such as chaos terrain and double ridges.
On Ganymede, possible past cryovolcanic activity was suggested in a few isolated spots on the surface, the so-called “scalloped depressions” (“paterae”), which have been interpreted as possible caldera-like features [4] and could be potentially sourced from shallow water bodies. While the low-resolution data currently available prevents a precise characterization, age estimates, and composition of these regions, future measurements by JUICE will reveal the origin and formation mechanism of Ganymede’s paterae.
In this work, we perform numerical modeling of the outer ice shell of Ganymede and Europa to test the expected gravity and topography signatures of shallow water bodies. We vary the size and location beneath the surface of such reservoirs. Moreover, since the composition and physical state (i.e., liquid state or solidified state) of such reservoirs is poorly constrained but affects the density in these regions, we test different values for density anomalies. In our models, we assume that these reservoirs are located within the conductive part of the ice shell, close to the surface. In order to quantify the effect of large-scale dynamics on the gravity and topography signal induced by shallow density anomalies, we test scenarios in which the entire ice shell is purely conductive (no additional density anomalies) and cases where the deeper ice shell is convective (additional density anomalies due to solid-state convection).
Our models will provide scenarios that can be tested with current data, where resolution permits, and help to interpret future measurements. This will help us to locally constrain the structure of the ice shell and determine the presence of shallow water bodies in the subsurface of Ganymede and Europa.
References:
[1] Grasset et al. (2013), PSS. https://doi.org/10.1016/j.pss.2012.12.002
[2] Pappalardo et al. (2024), SSR. https://doi.org/10.1007/s11214-024-01070-5
[3] Matteoni et al. (2023), JGR: Planets. https://doi.org/10.1029/2022JE007623
[4] Stephan et al. (2021), PSS. https://doi.org/10.1016/j.pss.2021.105324
How to cite: Maia, J., Matteoni, P., Plesa, A.-C., Rückriemen-Bez, T., Postberg, F., and Hussmann, H.: Gravity and topography signatures of shallow water bodies in the subsurface of Europa and Ganymede, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21003, https://doi.org/10.5194/egusphere-egu25-21003, 2025.
Ice is omnipresent in our Solar System: on Earth, on different planetary bodies, and on icy moons in the outer Solar System. Quite a number of those icy bodies feature subglacial water reservoirs under global ice shells, some of which may even host cryo-habitats. In addition, on the moons Europa and Enceladus the ocean is thought to be in contact with the rocky interior leading to water-rock processes potentially similar to the ones at the ocean floor on the Earth and making these two bodies highly relevant targets for planetary exploration. Space exploration missions, such as JUICE and Europa Clipper missions which are currently on their way to the Jupiter system, will allow us to further characterize cryo-environmental conditions on icy moons. Lander missions are likely to follow should a high habitability potential be identified. In order to prepare for both the interpretation of data acquired by Europa Clipper and JUICE, and for the design of future lander missions, it is of crucial importance to exploit any possible synergy between the various cryosphere research communities.
In the past, terrestrial and extraterrestrial cryosphere research mostly developed as independent research fields whereas synergies may shed light on both fields. In fact, close cooperation across different cryosphere research communities is a necessary prerequisite for designing future planetary exploration missions. An in-depth knowledge of similarities and differences between ice regimes on Earth and hypothesized physical regimes on icy moons will pave the way for optimized information retrieval from mission data and allow to effectively orchestrate terrestrial analogue field test, lab experiments, and model-based design for lander technology development. An accessible database that provides information on available datasets, e.g., regarding activities at terrestrial analogue sites, dedicated lab experiments or ice properties is not available to date or maintained by the community.
The International Space Science Institute (ISSI) team ‘Bridging the gap: From terrestrial to icy moons cryospheres’ [1] started its work in 2023 and brings together scientists and engineers with different terrestrial and extra-terrestrial cryosphere expertise. The overall goal of the project is to make knowledge hidden in the vast amounts of existing data from different cryosphere research groups accessible to the community. This should be achieved by consolidating information from existing data sets into comprehensive, moderated open access compilations. More specifically, the team focusses on two types of data compilations, namely
- a collection of experimental and theoretical work regarding ice properties along with their implicit assumptions and ranges of applicability, and
- a compilation of published work conducted at terrestrial analogues sites along with their relevance for icy moons exploration.
Here, we will introduce the project and its rationale, and describe our approach to selecting and compiling the data. Most importantly, we will show how the community can contribute to and benefit from the data collection.
Acknowledgement: This research was supported by the International Space Science Institute (ISSI) in Bern, through ISSI International Team project #23-589 Bridging the gap: From terrestrial to icy moons cryospheres.
References: [1] https://teams.issibern.ch/icymoonscryospheres/
How to cite: Kowalski, J., Plesa, A.-C., Boxberg, M., Buffo, J., Fox-Powell, M., Kalousová, K., Kerch, J., Llorens, M.-G., Montagnat, M., Motahari, S., Rückriemen-Bez, T., Schroeder, D., Simson, A., Sotin, C., Stephan, K., Terschanski, B., Tobie, G., and Wolfenbarger, N. S.: Ice Data Hub - A Crowdsourced Approach to Compile Terrestrial Analog and Ice Property Data for Icy Moons Exploration Activities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21709, https://doi.org/10.5194/egusphere-egu25-21709, 2025.
Since the very first observations of the Moon, radars have been more and more employed as payloads of planetary exploration missions, in various operational modes like altimeters, SARs or radar sounders. Especially radar sounders provide unique measurement capabilities for the subsurface exploration of planetary bodies, as demonstrated by the MARSIS and SHARAD instruments and planned for the REASON [1] and RIME [2] instruments of the Europa Clipper and Juice missions, aimed on the exploration of Jupiter’s icy moons. Radar sounders are nadir-looking sensors that transmit pulsed electromagnetic radiation that propagates through the subsurface due to its relatively low frequency. Each dielectric discontinuity in the ground material reflects part of the signal towards the radar. The analysis of the recorded echoes provides crucial information on the subsurface structure and composition. Despite the capability of achieving good performances, the abovementioned instruments are limited by the almost omnidirectional antenna characteristic of dipole antennas that are commonly used because of the large antenna size at low frequencies. Due to the omnidirectional characteristic, surface clutter, i.e., spurious signals from off-nadir directions, is collected that potentially masks the signal of interest coming from subsurface layers in nadir direction, thus hindering the subsurface data interpretation.
To overcome those limitations, we investigate the feasibility and potential of a distributed radar sounder satellite configuration for an Enceladus mission scenario, in the frame of an ESA study. Distributed radar sounding configurations have been already proposed for Earth Observation of icy regions (e.g., the STRATUS concept [3]). Such a formation flying satellite configuration allows for synthesizing a large antenna array that potentially provides the following advantages with respect to a traditional radar sounding configuration: 1) suppress the surface clutter through beamforming techniques, 2) increase the signal to noise ratio, 3) possibility of exploiting interferometric techniques for subsurface DEM generation and clutter interpretation, and 4) possibility of performing 3D tomographic imaging of the subsurface.
We present an analysis of a distributed HF-band radar sounder for the subsurface exploration of Enceladus including 1) a science case derivation, 2) orbit and formation implications, 3) radar operational concepts, 4) instrument and satellite system architecture implications, and 5) performance assessment. The formation consists of up to 7 satellites, one complex mother satellite (~1.5 tons) implementing the radar signal transmission and other power and mass demanding functionalities (e.g., communication, down-link, data storage, on-board processing), and the other satellites (~200 kg) implementing transponder functionalities that receive the radar echoes and forward it to the mother satellite in a MirrorSAR [4] configuration. A main criticality is the strongly perturbed gravitational environment at Enceladus [5] posing challenges on the orbits and the formation flying capabilities. Potential orbit and formation concepts are presented as well as a performance assessment for the subsurface sounder exploration of Enceladus based on the envisioned satellite formation, attenuation and backscatter models, different operational concepts, and different beamforming approaches.
References:
[1] Blankenship et al., 2009. [2] Bruzzone et al., 2013. [3] Bruzzone et al., 2021. [4] Krieger et al., 2017. [5] Benedikter et al., 2022.
How to cite: Benedikter, A., Plesa, A.-C., Matar, J., Hussmann, H., Nagai, M., Otto, T., Parihar, T., Byrne, W., Rückriemen-Bez, T., Rodrigues-Silva, E., Krieger, G., and Rodriguez-Cassola, M.: A Distributed Radar Sounder Concept for Subsurface Exploration of Saturn's Moon Enceladus: Feasibility and Potential, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21319, https://doi.org/10.5194/egusphere-egu25-21319, 2025.
The presence of an ocean beneath the Enceladus’ ice shell makes this Saturnian moon a high priority target for future planetary exploration [1]. Water jets that have been observed at the south pole by NASA’s Cassini mission [2] are thought to originate from the ocean and provide a direct window into the subsurface composition [3]. These jets generate a highly porous material that, due to its low thermal conductivity, affects the thermal state of the ice shell.
The analysis of pit chains on the surface of Enceladus indicates that locally the porous layer can be as thick as 700 m [4]. Such a thick porous layer can locally increase the temperature of the ice shell, leading to a low viscosity. This may promote solid-state convection in regions where the ice shell is covered by such a layer, whereas regions with thin porous layers could be characterized by conductive heat transport. Moreover, due to its effect on the ice shell temperature, the porous layer can strongly attenuate the signal of radar sounders that have been proposed to investigate the Enceladus’ subsurface [5, 6].
Here, we use the geodynamical code GAIA [7] to investigate the effects of a porous layer on the thermal state and dynamics of Enceladus’ ice shell. Using the resulting thermal state we calculate the associated two-way radar attenuation at each location within the ice shell. We test different values of the ice shell thickness (5 – 35 km, [8]), porous layer thickness (d = 0 – 750 m), and its thermal conductivities (k = 0.1 – 0.001 Wm-1K-1 [9,10]). To account for chemical impurities within the ice shell we test a “low” loss scenario that considers a pure water ice shell and a “high” loss case that assumes a homogeneous mixture of water ice and chlorides in concentrations extrapolated from the particle composition of Enceladus’ plume [5].
Our results show that the porous layer thickness and its distribution have a first order effect on the thermal state and dynamics of the ice shell. Regions covered by a thick porous layer are characterized by a warm ice shell temperature and thus a lower viscosity, becoming more prone to convect. The vigor of convection depends on both the temperature-dependent ice shell viscosity and the temperature difference across the ice shell. While a thick porous layer would result in a low ice shell viscosity, thus increasing the convection vigor, such thick porous layers lead to an almost isothermal ice shell, due to their strong insulation, which, in turn, decreases the convection vigor. As discussed in a recent study that only investigated a purely conductive ice shell [6], the high temperatures may lead to the formation of shallow brines detectable by radar measurements.
References:
[1] Choblet et al. (2021); [2] Porco et al. (2006); [3] Postberg et al. (2009); [4] Martin et al. (2023); [5] Souček et al. (2023). [6] Byrne et al. (2024); [7] Hüttig et al., (2013); [8] Hemingway & Mittal (2019); [9] Seiferlin et al. (1996); [10] Ferrari et al. (2021).
How to cite: DeMers, E., Byrne, W., and Plesa, A.-C.: The Effects of a Porous Layer on the Dynamics and Two-way Radar Attenuation of Enceladus’ Ice Shell, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21724, https://doi.org/10.5194/egusphere-egu25-21724, 2025.
Jupiter’s moon Europa is one of the prime targets for planetary exploration due to its high astrobiological potential. Slightly smaller than Earth’s moon, Europa harbors a liquid water ocean beneath an ice shell. The thickness of Europa’s ice shell is poorly constrained and values of less than 1 km to up to 90 km have been suggested in previous studies (e.g., Billings and Kattenhorn, 2005, Vilella et al., 2020). Ice-penetrating radars on NASA’s Europa Clipper (REASON, Blankenship et al., 2024) and ESA’s JUICE (RIME, Bruzzone et al., 2013) missions aim to determine the thickness of Europa's ice shell. Recent studies have suggested that constraints on the thickness of Europa’s ice shell can be obtained through the detection of eutectic interfaces, defined as the depth where brine becomes thermodynamically stable in the ice shell (Schroeder et al., 2024). In fact, previous studies have shown that the detection of eutectic horizons within an ice shell is likely easier than detecting the ice-ocean interface, given their shallower depths and therefore lower total signal attenuation (Kalousova et al., 2017, Soucek et al., 2023, Byrne et al., 2024). The depth of the eutectic interfaces depends on the thermal state of the ice shell, which is closely linked to the ice shell viscosity and large-scale dynamics (Kalousova et al., 2017). As suggested by previous authors (Kalousova et al., 2017, Schroeder et al., 2024), detection of eutectic interfaces therefore represents a promising strategy to constrain the thermophysical properties of the ice shell through characterization of its convective pattern.
In this study we use the geodynamic code GAIA (Hüttig et al., 2013) to investigate the ice shell dynamics on Europa. We vary the ice shell thickness and ice shell viscosity that largely affect the convection pattern and in particular the number of hot upwellings and cold downwellings that can develop. In our models, the viscosity is temperature dependent and follows an Arrhenius law. We choose a reference value for the viscosity at the ice-ocean interface and vary this over several orders of magnitude between the different models. Once a simulation has reached a statistical (quasi-)steady state, we determine the eutectic pattern by identifying the depths of the eutectic temperature. We treat this sequence of eutectic depths as a signal and identify the peaks of each local maxima (or peak) in the signal. The number of local maxima in the simulation is used to estimate the global number of convection cells in the ice shell.
Our preliminary results show a close relation between the number of plumes that develop in the ice shell of Europa and the viscosity at the ice-ocean interface. By increasing the number and complexity of our simulations, we aim to derive so-called scaling laws that will relate the convection structure with the viscosity and thickness of Europa’s ice shell. This will provide a framework that will help to interpret the detection of eutectic interfaces in future radar measurements in the context of large-scale dynamics of the deep ice shell.
How to cite: Byrne, W., Plesa, A.-C., Hussmann, H., Wolfenbarger, N., Schroeder, D., and Steinbruegge, G.: Constraining the Viscosity of Europa’s Ice Shell from Eutectic Interfaces in Geodynamic Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-652, https://doi.org/10.5194/egusphere-egu25-652, 2025.
Enceladus is one of the few objects in our Solar System that probably harbors a habitable environment. This makes it a highly interesting target for planetary exploration and the European Space Agency (ESA) has decided to send its large mission (L4) to Enceladus. With the active regions located at the South pole of the moon a polar orbit is most desirable for revealing the mechanism that powers the jets and to perform a chemical analysis of the material ejected from the deep interior of Enceladus. We carried out a comprehensive numerical integrations of spacecraft orbits, with the aim to find suitable candidate orbits for a future mission to Enceladus. All the relevant perturbations caused by mainly Saturn, as well as the Sun, Jupiter, and the other moons of the Saturn system, and also solar radiation pressure, are taken into account. We have considered the higher degree and order Stokes coefficients of Enceladus’ and Saturn’s gravity fields provided in Park et al. 2024. Furthermore, we performed a grid search to identify suitable orbits in inertial space by varying orbital parameters such as semi-major axis (330 to 420 km), inclination (40° to 120°) and longitude of ascending node. Moderately inclined orbits (inclination between 45° and 60°) covering the equatorial and mid-latitude regions of Enceladus were found to be stable from several months up to years. In contrast, the more useful polar mapping orbits were found to be extremely unstable due to the so-called “Kozai mechanism”, which causes the spacecraft to impact the moon’s surface within a few days. However, an example of a highly inclined orbit was found with inclination of approximately 76°, which had an orbital life time of 13 days. A longer mission duration in this orbit would require correction maneuvers every few days. This would provide coverage of the tiger stripes region and allow for a near-global characterization of the surface. We also determined the delta-v that would be necessary to maintain such an orbit over a mission duration of several months.
How to cite: Parihar, T., Hussmann, H., Stark, A., Wickhusen, K., Oberst, J., and Galas, R.: Search for low altitude polar orbits for future Enceladus missions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18662, https://doi.org/10.5194/egusphere-egu25-18662, 2025.
In light of the growing interest in the composition and habitability of the ocean beneath the icy crust of Enceladus, we revisit the basic hypotheses behind the formation of the prominent Tiger Stripes fault system on Enceladus’ south pole. This study revolves around the formation of new fractures assuming the existence of the first one, considering two distinct physical scenarios.
In the first one, we expand the idea by Hemingway et al.[1]. First, we approximate the ice crust by a Kirchhoff plate to obtain a fourth-order ordinary differential equation modeling the deformation of the plate. The solution of this equation is obtained by the method of variation of parameters providing us with a function describing the plate’s response to different surface load distributions. By investigating the solution profiles for both the approximated point load [1] and the more realistic distributed load [2] and employing the criterion for the maximal bending moment of the plate, we find that the maxima correspond to the positions of the new fracture. Our results indicate that while simple point load approximation quite accurately predicts new fracture positions for a reasonable estimate of the elastic shell thickness, the more realistic load model implies a thinner crust more consistent with observations [3].
In the second scenario, we couple the mechanical Kirchhoff plate problem with damage mechanics [4] which allows us to model the formation of the crack due to periodic tidal loading rather than distributed surface mass. We compare the results of these two scenarios and discuss their implications both for the formation hypotheses and the structural constraints on the ice shell thickness.
This research was supported by the Czech Science Foundation under Grant No. 25-16801S.
[1] Douglas J. Hemingway, Maxwell L. Rudolph, and Michael Manga. Cascading parallel fractures on Enceladus. Nature
Astronomy, 4(3):234–239, 2020
[2] Ben S. Southworth, Sascha Kempf, and Joe Spitale. Surface deposition of the Enceladus plume and the zenith angle of
emissions. Icarus, 319:33–42, 2019
[3]Ondřej Čadek, Gabriel Tobie, Tim Van Hoolst, Marion Massé, Gaël Choblet, Axel Lefèvre, Giuseppe Mitri, Rose-Marie
Baland, Marie Běhounková, Olivier Bourgeois, et al. Enceladus’s internal ocean and ice shell constrained from cassini
gravity, shape, and libration data. Geophysical Research Letters, 43(11):5653–5660, 2016
[4] Ravindra Duddu, Stephen Jiménez, and Jeremy Bassis. A non-local continuum poro-damage mechanics model for hydrofracturing of surface crevasses in grounded glaciers. Journal of Glaciology, 66(257):415–429, 2020
How to cite: Piláriková, B., Souček, O., and Southworth, B. S.: Modeling of fault initiation in the ice shell of Enceladus, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9877, https://doi.org/10.5194/egusphere-egu25-9877, 2025.
Titan’s atmosphere is one of the most complex environments in the solar system. The intense photochemistry of the main atmospheric gases (N2 & CH4) drives a rapidly expanding molecular growth of organic species that terminates with the formation of photochemical hazes. However, many aspects of this atmosphere remain elusive: observations with the Cassini-Huygens space mission reveal that Titan’s upper atmosphere is temporally variable through unidentified mechanisms, while the processes driving the gas to haze transition are largely unknown due to the lack of constraints on the haze microphysical properties in the upper atmosphere. Here we discuss observations obtained with the Cassini UltraViolet Imaging Spectrograph (UVIS) from 2004 to 2017 that provide a detailed view of the upper atmosphere. Spectra from the FUV detector reveal the dominance of emissions from the de-excitation of molecular and atomic nitrogen, resonant scattering of Lyman-a photons by atomic hydrogen and scattering by the atmospheric gases and the photochemical haze. We use detailed forward models of the observed emissions to characterize the upper atmosphere and get constraints on the abundance profiles (and their variability) of the N2, CH4 and H gases and the microphysical properties of the haze particles. Our results demonstrate that the observed gaseous emissions closely follow a temporal evolution throughout the Cassini mission that is consistent with the solar-cycle variability, while the haze scattering observations reveal marked differences between the evening and morning terminators. We discuss the implications of our retrievals on the thermal structure of the upper atmosphere and the haze microphysical growth.
How to cite: Lavvas, P., Hoover, D., Le Guennic, N., and Koskinen, T.: An updated view of Titan’s upper atmosphere from Cassini/UVIS airglow observations: Constraints on atmospheric structure and haze., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8107, https://doi.org/10.5194/egusphere-egu25-8107, 2025.
Seasonal Variability of Stratospheric H₂O on Titan
Titan is Saturn’s largest moon and one of the most complex Earth-like bodies in our Solar system. It hosts a thick, complex atmosphere with weather systems [1], rich C-N-H photochemistry [2], and unique surface features such as lakes of methane [3]. The presence of organic hazes and oxygen-bearing molecules in the atmosphere make Titan astrobiologically important and provides an analogous natural laboratory to study pre-biotic Earth [4] and exoplanets with similar climates. Understanding Titan’s atmosphere is also pertinent to inform NASA's Dragonfly mission set to arrive in 2034 [5].
Water vapour is an important, yet poorly understood presence in Titan’s atmosphere. It plays a vital role in distributing oxygen molecules, which are otherwise scarce, throughout the planet to form species such as CO, CO2 and H2CO [2]. Water vapour was first detected in Titan’s atmosphere in 1998 by the Infrared space Observatory [6]. Since then, only a handful of studies from Herschel [7], CIRS [8] and the INMS [9] instruments have provided observations. Due to modelling difficulty and its low abundances, there is limited information on seasonal, global and vertical abundances of Titan’s H2O with research focusing on averages and single measurements.
146 far-IR observations acquired by CIRS on-board the Cassini spacecraft were analysed to form the first-reported global picture of H2O abundances in Titan’s stratosphere across its 13-year mission, improving on previous studies. Using the most recent photochemical model [2] as an a priori in the NEMESIS radiative transfer modelling tool [10] and a new method of applying parameterised gaussian cross-sections [11] to fit the poorly understood hazes, we present results showing the seasonal variability of water vapour at pressures of ~ 0.1-10 mbar. We discuss our results and its implications, and compare our findings to previous work.
References: [1] N.A. Teanby et al. (2017) Nat. Commun. 8, 1586. [2] V. Vuitton et al. (2019) Icarus 324, 120-190. [3] M. Mastrogiuseppe et al. (2019) Nat. Astron. 3, 535-542. [4] D.W. Clarke and J.P. Ferris (1997) Orig. Life Evol. Biosph. 27, 225-248. [5] J.W. Barnes et al. (2021) Planet. Sci. J. 2, 130. [6] A. Coustenis et al. (1998) A&A 336, 85-89. [7] R. Moreno et al. (2021) Icarus 221, 753-767. [8] V. Cottini et al. (2012) Icarus 220(2), 855-862. [9] J. Cui et al. (2009) Icarus 200, 581-615. [10] P.G.J. Irwin (2008) J. Quant. Spec. Radiat. Transf. 109, 1136–1150. [11] N.A. Teanby (2007) Math Geol, 39, 419–434. [12] S. Bauduin et al. (2018) Icarus, 311, 288-305.
How to cite: Ford, J., Teanby, N., Irwin, P., Nixon, C., and Wright, L.: Seasonal Variability of Stratospheric H2O on Titan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3741, https://doi.org/10.5194/egusphere-egu25-3741, 2025.
Titan’s organic chemistry has been partly revealed from Cassini-Huygens and recent ground-based observations so far, but the full degree of its complexity is not yet fully understood (e.g. Coustenis, 2021; Nixon, 2024). Several hydrocarbons and nitriles have already been detected in the atmosphere and their seasonal variations studied in particular by the CIRS instrument aboard Cassini. Other minor species have been detected from the ground mainly in the millimeter range or space-borne observatories like ISO (Coustenis et al., 1998). These results have been included in photochemically models (Lavvas et al. 2008, and this work) that have also predicted the presence of other minor species, among which some have infrared transitions in the 5-25-micron spectral range, like cyanopropyne (CH3C3N) and isobutyronitrile (i-C3H7CN).
Jacquemart et al. (2025) have derived absorption cross-sections at room temperature for these two non-cyclic organic molecules from laboratory spectra recorded in the 495-505 cm-1 and 510-570 cm-1 spectral ranges, respectively, with a spectral resolution of 0.01 cm-1 and 0.056 cm-1 and have proposed them for the 2024 update of the HITRAN database. In this group, we have started an observing campaign using the TEXES thermal infrared imaging spectrometer at the Infrared Telescope Facility (Mauna Kea Observatory) to monitor the infrared signatures of hydrogen cyanide (HCN) and cyanoacetylene (HC3N), along with acetylene (C2H2 and C2HD). In addition, we have been searching for C4H3N and C4H7N in the 20-micron region. High resolution spectra of Titan have been obtained in September 2022 in the following spectral ranges: (1) 498-500 cm-1 (C2HD, HC3N, search for C4H3N); (2) 537-540 cm-1 (C2HD, search for C4H7N); (3) 744-749 cm-1 (C2H2, HCN); (4) 1244-1250 cm-1 (CH4). As a first application, we used the retrieved spectra in a radiative transfer code to simulate observations of Titan’s stratosphere acquired using the Texas Echelon Cross Echelle Spectrograph (TEXES at the Infrared Telescope Facility (IRTF, Mauna Kea Observatory). We discuss preliminary results and perspectives, among which estimated upper limits of 3×10-9 for CH3C3N and 3×10-7 for isobutyronitrile in Titan’s stratosphere.
In the future, we plan to use the TEXES instrument in conjunction with other larger telescopes in order to optimize the search range and to acquire detection or upper limits for some of these new molecules.
References
- Coustenis, A., 2021. “The Atmosphere of Titan”. In Read, P. (Ed.), Oxford Research Encyclopedia of Planetary Science. Oxford University Press. doi:https://doi.org/10.1093/acrefore/9780190647926.013.120
- Nixon, C. A., 2024. The Composition and Chemistry of Titan’s Atmosphere. ACS Earth and Space Chemistry 2024 8 (3), 406-456. DOI: 10.1021/acsearthspacechem.2c00041
- Coustenis, A., Salama, A., Lellouch, E., Encrenaz, Th., Bjoraker, G., Samuelson, R. E., de Graauw, Th., Feuchtgruber, H., Kessler, M. F., 1998. Evidence for water vapor in Titan’s atmosphere from ISO/SWS data. Astron. Astrophys. 336, L85-L89.
- Lavvas, P., Coustenis, A., Vardavas, I. M., 2008. Coupling photochemistry with haze formation in Titan's atmosphere. Part I: Model description. Plan. Space Sci. 56, 27-66.
- Jacquemart, D., et al. 2025. Near- and mid-infrared spectroscopy of isobutyronitrile and cyanopropyne: absorption cross-sections for quantitative detection in astrophysical objects. JQSRT, submitted.
How to cite: Coustenis, A., Encrenaz, T., Jacquemart, D., Greathouse, T. K., Lavvas, P., Tremblay, B., Soulard, P., Krim, L., Giles, R., and Guillemin, J.-C.: Search for cyanopropyne and isobutyronitrile in Titan with TEXES, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7144, https://doi.org/10.5194/egusphere-egu25-7144, 2025.
Dragonfly is a relocatable lander that will explore Titan in the mid-2030’s [1]. It is equipped with the Dragonfly Mass Spectrometer (DraMS) instrument to investigate Titan chemistry at geologically diverse locations. DraMS’ gas chromatography-mass spectrometry (GCMS) mode will investigate organic molecule diversity and look for potential molecular biosignatures in surface samples. In this mode, solid samples are thermally volatized or chemically derivatized in a pyrolysis oven. The evolved components are concentrated on a chemical injection trap during the whole duration of the thermal or chemical treatment of the sample. The adsorbed compounds are then desorbed by flash-heating the trap for a rapid injection into the chromatographic column. The role of the column is to separate the different components so that they can be detected and identified with the mass spectrometer.
DraMS-GC is composed of two independent injection traps. At least one of them is necessarily composed of Tenax for its performances and heritage, but the chemical adsorbent in the other trap may be different. Despite its overall performance, Tenax has shown some contamination that challenges the interpretation of the origin of the molecules. This has been widely documented on the Sample Analysis at Mars (SAM) instrument onboard Mars Science Laboratory (MSL) mission [2],[3],[4],[5]. Both Carbograph and Carbotrap adsorbents have been considered as an alternative, but the former was abandoned due to its low mechanical resistance to vibration.
Desorption performance was evaluated for various chemical compounds mimicking the ones expected in future Titan samples, such as linear alkanes, fatty acid methyl esters, amines, amides, amino acids and nucleobases. Some of these were derivatized beforehand using N,N-dimethylformamide dimethyl acetal (DMF-DMA), as they will be on DraMS-GC.
The desorption temperature and the flash-heat duration have to be optimized for each adsorbent to ensure the best efficiency within the mission constraints. While the optimal desorption temperature for Tenax is 280°C, Carbotrap requires at least 300°C to significantly desorb most compounds. At the highest temperature tested (350°C), alkanes up to C26 can be desorbed from Carbotrap. Results also showed a greater increase in desorption efficiency by extending the flash-heat duration from 10 to 40 seconds rather than by increasing its temperature alone (for example from 280 to 300°C).
Moreover, DraMS-GC must be able to detect a potential enantiomeric excess in the samples since this could be a bioindicator. Thus, some homochiral compounds are studied using a chiral chromatographic separation. Preliminary results show adsorption and desorption processes on Carbotrap do not induce a significant racemization of those compounds.
The final choice for the nature of the adsorbent and the operating conditions will consider those results along with the strong constraints on the power available to reach and maintain the optimal desorption temperature.
[1] J.W. Barnes et al., 2021, Planet. Sci. J.
[2] D.P. Glavin et al., 2013, J. Geophys. Res. Planets
[3] C. Freissinet et al., 2015, J. Geophys. Res. Planets
[4] A. Buch et al., 2019, J. Geophys. Res. Planets
[5] K.E. Miller et al., 2015, J. Geophys. Res. Planets
How to cite: Abello, A., Freissinet, C., Govekar, T., Buch, A., Casalinho, J., Szopa, C., and Trainer, M.: Selection of the chemical adsorbents and operating conditions for the injection traps onboard the Dragonfly Mass Spectrometer Gas Chromatograph, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10910, https://doi.org/10.5194/egusphere-egu25-10910, 2025.
