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.

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 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.