EXOA13
Interstellar ices are not merely passive reservoirs; they act as molecular factories where simple species are transformed into increasing chemical complexity through surface reactions, UV-driven photochemistry, and thermal processing. These icy mantles store and transport volatile material that ultimately becomes incorporated into protoplanetary disks and nascent planets. Understanding how molecules form, evolve, and survive in the solid state is therefore essential for tracing the chemical inheritance of icy bodies in planetary systems.
This session places solid-state chemistry at the center of the molecular inheritance problem, examining how icy grain mantles regulate the chemical inventory ultimately incorporated into forming planetary systems. Key topics include gas–grain chemistry, reaction networks and rates, energetic and thermal processing of ices, volatile transport and reprocessing in disks, and the transmissive and reflective spectroscopic characterization of molecular solids at high resolution. We invite contributions spanning laboratory astrochemistry of ices and organics, chemical modeling, and JWST ice observations in molecular clouds, (proto)planetary systems, icy moons, and comets to develop physico-chemical frameworks that unify chemical networks and constrain the volatile inventories inherited by forming planets.
The presentation covers the topics reported in our recent work published in Nature Rev. Chem. [1]. It covers 50 years of experiments dedicated to simulate radiation and thermally driven processes that occur on icy dust particles in space. The interstellar and protoplanetary ice composition is dominated by water and often contains CO, CO2, CH4, CH3OH, NH3, OCN-, OCS, and probably larger species which await identification. The harsh conditions in space (ultra-high vacuum, cryogenic temperatures, and radiation) are mimicked in the laboratory. UV photons/X-rays/ions impact on the ice covering microscopic pre-cometary dust particles in dense interstellar clouds and protoplanetary disks prior to the formation of cometesimals by agglomeration of the icy dust. Laboratory results show that radiation produces radicals and reactive species changing the initial composition of the ice to form complex organic molecules (COMs) of prebiotic interest (among them are several amino acids, nitrogen-heterocycles related to nucleobases, and sugars). Many of these molecules were also identified in Rosetta comet 67P, and infrared spectra of Ryugu samples delivered by Hayabusa2 are strikingly similar to those of refractory residues retrieved at room temperature after warmup of the irradiated ice [2].
First, recent experimental results on ice properties (density, infrared spectroscopy, optical constants, morphology) supported by DFT calculations will be presented with important updated values of the ice density and infrared band strengths. This allows a proper column density estimation of the various molecular ice components. For instance, the commonly used band strength of water ice was significantly lower than the actual value and did not take into account the variations due to ice temperature. Second, recent results obtained in our laboratory regarding COMs formation by ultraviolet irradiation of interstellar ice analogs will be unveiled. We will propose formation mechanisms of the heterocycles identified in the residues made by ice processing. Another talk by H. Carrascosa will discuss in more detail the important role played by water molecules in the ice chemistry that enables the synthesis of prebiotic species.
References
[1] G. M. Muñoz Caro, H. Carrascosa, & R. Martín-Doménech “Photochemistry of interstellar ice forming complex organic molecules”, 2025, Nature Rev. Chem. 9, 537
[2] J. Mathurin, et al. ¨AFM-IR nanospectroscopy of nanoglobule-like particles in Ryugu
How to cite: Muñoz Caro, G. M., Carrascosa, H., Martín-Doménech, R., Escribano, B., del Burgo, C., Satorre Aznar, M. Á., Cazaux, S., Jiménez Escobar, A., Ciaravella, A., Cecchi-Pestellini, C., and Chen, Y.-J.: Physical properties and photochemistry of interstellar ice analogs furnishing complex organic molecules, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-87, https://doi.org/10.5194/epsc2026-87, 2026.
Complex organic molecules are thought to form on icy dust grains in interstellar environments, through a combination of energetic and non-energetic processes driven by photons, electrons, ions, and atoms. Thanks to the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA), we can now map and characterize ices and gases across various star-forming regions, enhancing our understanding of star formation and chemical evolution.
European large-scale experimental facilities are crucial for interpreting these observations, especially in simulating space-like conditions. In this presentation, I will discuss recent laboratory findings on the formation and stability of prebiotic molecules on ice grain analogs, which mimic the icy surfaces in space. These studies are key to understanding the potential pathways for the origin of life on Earth, and how we can bridge the gap between experimental data and astrochemical theory.
How to cite: Ioppolo, S.: Bridging Laboratory Ice Experiments and Astronomical Observations, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1202, https://doi.org/10.5194/epsc2026-1202, 2026.
In the coldest regions of molecular clouds, carbon and oxygen freeze onto dust grains and react to form icy mantles that play a fundamental role in star and planet formation. These ices establish the initial chemical inventory of emerging protoplanetary disks and seed their chemical complexity. However, the sequential formation pathways of interstellar ices remain poorly constrained. While infrared spectroscopy is a powerful probe of ice chemistry, previous observing facilities lacked both the sensitivity needed to probe ice abundances during the final stages of core collapse and the spatial sampling required to map ice abundances on the same scales (<1000 AU) as gas abundance maps from cloud edge to core.
JWST NIRCam Wide-Field Slitless Spectroscopy (WFSS) now enables such studies. I will present the first cospatial maps of H2O, CO2, and CO ice on scales of hundreds of AU surrounding a Class 0 source within the Chamaeleon I molecular cloud, using 44 sightlines from the JWST ERS programme “IceAge” (PID: 1309). These observations were made possible by a novel data reduction pipeline developed to establish WFSS as a viable and efficient observing mode. Our observations probe ice column densities an order of magnitude higher than previously explored, where correlations between ice species indicate enhanced CO2 formation within CO-rich ice toward the densest sightlines.
I will also present initial results from my JWST Cycle 2 programme “CHEERIO” (PID: 4358), targeting cloud-edge spectra in Cha I. These observations complement the IceAge dataset and extend our view of ice evolution from the diffuse cloud edge to the dense core within a single molecular cloud.
This unprecedented statistical sampling within one cloud represents a major advance in constraining interstellar ice chemistry by removing the need to average over chemically distinct environments. The resulting chemically consistent dataset provides powerful new constraints for pre-stellar astrochemical models and opens the door to probing gas–grain interactions, snowline formation, chemical evolution in dense regions, and the broader astrophysical implications of ice chemistry.
How to cite: Smith, Z. and the IceAge: Tracing the ice architecture of the Cha I cloud: Cospatial ice mapping of H2O, CO2 and CO with JWST NIRCam/WFSS, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-210, https://doi.org/10.5194/epsc2026-210, 2026.
Stars and planets form in dense cores within molecular clouds. These cosmic nurseries are where we see the first formation of interstellar ices. Composed mainly of H2O, CO2 and CO, these ice species and their reaction products are the likely precursors to the complex organic molecules (COMs) that enable the development of life on planets such as our own. Yet their origin and evolution, and the survival of the volatile material trapped within them through the violent star formation process, remain poorly understood. This fundamentally limits our ability to determine how molecules of great astrobiological significance are delivered to planetary bodies.
Figure 1: The likely dominant fractionation mechanisms that determine the carbon isotope ratio imprinted in the ice observed in pre- and protostellar environments.
The 12C/13C ratio is a sensitive probe of the physical and chemical conditions under which carbon-bearing ices form and evolve. The initial ratio is set by the distinct origins of the two isotopes: 12C is produced rapidly in massive stars, while a fraction of 12C is converted to it’s weaker counterpart 13C via the CNO cycle in later stellar generations. After injection into the interstellar medium (ISM), fractionation processes enrich or deplete one isotope relative to the other. In star-forming regions the isotope fractionation is driven by a combination of gas-phase and grain-surface processes that dominate during different physical and chemical epochs. For the abundant carbon-bearing ices, CO and CO2, the isotope ratio is therefore thought to preserve a chemical memory of the environment in which they formed, making it a valuable diagnostic of chemical evolution across the star-forming process. Understanding carbon isotope fractionation can shine a light on the inheritance or in-situ formation of molecules during different stages of star and planet formation. If the fractionation patterns established in molecular clouds are preserved through the protostellar phase, they may be inherited by protoplanetary disks and ultimately by planetary bodies. Conversely, if isotope ratios are significantly reprocessed during star formation, they instead reflect local conditions rather than primordial inheritance. Distinguishing between these scenarios has important implications for tracing the chemical origin of complex molecules across evolutionary stages, from cold molecular clouds to protostellar environments and planetary systems.
Figure 2: JWST WFSS observations allow us to obtain spectra along lines of sight towards tens to hundreds of background sources in a single observation.
The unrivalled sensitivity and multiplexing capabilities of The James Webb Space Telescope (JWST), now allows us to probe the chemical environment across star-forming regions with a resolution like never before. I will present 12C/13C ratios derived from JWST NIRCam Wide Field Slitless Spectroscopy (WFSS) observations towards the Chamaeleon I molecular cloud, obtained as part of the Ice Age Early Release Science programme (PID 1309; P.I. M. McClure). Spectra were extracted for 33 background sources along pencil-beam lines of sight through the cloud, in the vicinity of the deeply embedded class 0 protostar Cha MMS1, providing the largest sample of co-spatial ice isotope measurements within a single star-forming region to date. I will examine whether the carbon isotope ratio varies between ice species, whether it shows spatial dependence across the cloud, what this tells us about the chemical evolution across the region, and how the values derived in this study relate to those observed across the broader star and planet formation sequence.
How to cite: Rashman, M., Dickinson, H., Fraser, H., Smith, Z., McClure, M., Noble, J., Demaria, L., and Tsiakaliari, E. and the Ice Age Consortium: Using JWST to Map the Carbon Isotope Ratio in Ice across the Chamaeleon I Molecular Cloud Complex, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-929, https://doi.org/10.5194/epsc2026-929, 2026.
Interstellar ices play a large role in the chemical evolution of prestellar objects. With new data from the James Webb Space Telescope, we have gained new information about ices in different astronomical environments. Astrochemical models are crucial to bridge the gap between the short timescales of chemical reactions and experiments, and the millions of years of evolution of prestellar objects. Surface chemistry in these models is very complicated as a result of the many required parameters to model it. Many of these parameters, such as binding energies and reaction rate coefficients on grains, are often poorly constrained.
I will present our sensitivity analysis to determine the most important chemical parameters to assess which parameters should get priority for new measurements and calculations. Using randomly sampled binding energies, diffusion barriers, energy barriers for reactions, and kinetic desorption and diffusion prefactors, we determined the correlations of the main ice abundances calculated with UCLCHEM, a gas-grain astrochemical code, on each of these parameters.
By running a wide grid of physical conditions (with varying temperature, density, cosmic-ray ionization rate and UV field strength), we find that the main correlations of abundances of many ice species are the diffusion barriers of small radicals such as H, N, CH and CH3. Thus, these should be determined more exactly to further increase the accuracy of astrochemical models, leading to a better understanding and interpretation of observations. I will also demonstrate how machine learning can help us calculate these parameters.
How to cite: Dijkhuis, T., Lamberts, T., Viti, S., and Cuppen, H.: A sensitivity analysis of interstellar ice chemistry in astrochemical models, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1149, https://doi.org/10.5194/epsc2026-1149, 2026.
How to cite: Escribano, B., Carrascosa, H., Martin-Domenech, R., and Muñoz Caro, G.: Photodesorption of SO2 in mixed ices under ultraviolet irradiation, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-143, https://doi.org/10.5194/epsc2026-143, 2026.
Ethylamine (C₂H₅NH₂) has been tentatively detected in the interstellar medium towards G+0.693-
0.027 and Sgr B2 [1], and was identified alongside β-alanine in comet 81P/Wild 2 [2]. As a
potential precursor to alanine through the CH₃CHNH₂ radical [3], understanding the surface
reactivity of ethylamine under interstellar conditions is directly relevant to the question of amino
acid formation in space.
We present the first experimental study of ethylamine hydrogenation under dark molecular cloud
conditions, performed using the VENUS apparatus at LIRA CY, Cergy Paris Université [4].
Ethylamine and H atoms are co-deposited onto a gold surface held at 10 K inside a UHV chamber
(P ~ 10⁻10 mbar). H atoms are generated by microwave dissociation of molecular hydrogen. After
deposition, a Temperature-Programmed Desorption (TPD) experiment is performed by heating the
surface at 12 K/min, and desorbing species are detected by a quadrupole mass spectrometer (QMS)
operated at 30 eV ionization energy. Products are identified by deconvolving the QMS signal into
contributions from candidate species, each characterized by an independently determined cracking
pattern.
Figure 1 compares the desorption profile at m/z = 30 for pure ethylamine and for ethylamine co-
deposited with H atoms. The strong reduction in signal demonstrates that a significant portion of the
initial ethylamine is consumed upon H-atom exposure. Attempting to fit the co-deposition signal
with ethylamine alone leaves large systematic residuals across multiple m/z channels,
demonstrating the presence of new molecular species.
Figure 2 shows the result of the full deconvolution. The cracking patterns of CH₄, NH₃, CH₃CN,
and CH₃NH₂ were determined by independent pure depositions; that of CH₃CHNH (ethanimine)
was derived directly from the residual signal. The main products identified are CH₄ (desorbing at
~66 K), NH₃ (~90 K), CH₃CN (~129 K), and CH₃CHNH (~135 K), with CH₃NH₂ and HCN as
minor species.
The product distribution reveals a clear selectivity. All identified carbon-containing products either
retain the full C–C–N skeleton of ethylamine (CH₃CHNH, CH₃CN) or result from its complete
fragmentation (CH₄, NH₃). No products retaining only a partial skeleton, such as methylamine
(CH₃NH₂) or ethane, are detected in significant quantities, despite NH₃ and CH₄ being among the
main products. This suggests that single C–C or C–N bond cleavage is not a dominant pathway:
when the carbon skeleton breaks, it breaks entirely.
The observed products are consistent with H abstraction on ethylamine being an accessible
pathway, which would make the CH₃CHNH₂ radical a possible intermediate, but its existence and
the precise reaction mechanism remain to be confirmed. Ongoing quantum chemical calculations
aim to determine the energy barriers along the relevant pathways and establish whether this radical is indeed formed, with direct implications for the proposed role of ethylamine as a precursor to
alanine in interstellar environments.
References: [1] Zeng et al., ApJL 920, L27 (2021) — [2] Glavin et al., Meteoritics & Planet. Sci.
43, 399 (2008) — [3] Förstel et al., ApJ 845, 83 (2017) — [4] Congiu et al., Rev. Sci. Instrum. 91,
12 (2020)
Figures: (1) m/z = 30 desorption profile, pure ethylamine vs. ethylamine + H; (2) Full TPD
deconvolution with identified products.
How to cite: Lorin, M., Dulieu, F., and Wmc, S.: Hydrogenation of ethylamine under interstellar conditions: whenhydrogenation yields unsaturated products, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-355, https://doi.org/10.5194/epsc2026-355, 2026.
Icy grain mantles act as crucial reservoirs for volatile elements and chemical diversity. A major open question regarding their morphology is whether these ices are uniformly mixed or segregated into distinct layers.
This study investigates the chemical and structural evolution of a ternary H₂O:NH₃:CO mixture through laboratory experiments simulating layered and homogeneously mixed ices. We produced mixed and stratified ices using classical isothermal deposition and cooling ramps from 200 K to 10 K, both with and without X-ray irradiation. Depending on the parameters used, the ice evolves into diverse structural, chemical, and thickness configurations. Furthermore, we demonstrate that the CO stretching mode serves as a sensitive probe, reflecting the distinct chemical and structural environments within the ice.
How to cite: Ciaravella, A., Jimenez-Escober, A., Piazzese, F., Cecchi Pestellini, C., and Chen, Y.-J.: Uniformly mixed vs segregated layers: the evolution of H₂O:NH₃:CO ices, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-860, https://doi.org/10.5194/epsc2026-860, 2026.
The volatile composition of icy bodies provides important clues to the chemical inheritance linking molecular clouds, protoplanetary disks, and forming planetary systems. While water ice is generally expected to dominate the volatile inventory of bodies formed in the outer Solar System, observations of comets and trans-Neptunian objects reveal substantial diversity in ice abundances, including unexpectedly high CO-to-water ratios in some objects. Understanding how such CO-rich reservoirs form and evolve is therefore essential for connecting disk ice chemistry with the volatile composition of planetesimals and planets.
In this contribution, I present results of a recent study (Drazkowska 2026) using a one-dimensional disk model including dust coagulation, fragmentation, radial drift, volatile evaporation and recondensation, and planetesimal formation via the streaming instability. In particular, I explore how the disk buildup stage influences the chemical evolution of icy solids and the preservation of volatile-rich reservoirs.
CO-rich pebbles naturally form near the CO snow line due to the cold-finger effect, where outward-diffusing CO vapor recondenses onto drifting grains. This process efficiently enhances the CO ice abundance in solids and occurs regardless of whether disk buildup is included. However, models incorporating the buildup phase produce significantly stronger CO enrichment relative to water in the outer disk, demonstrating that early disk evolution can substantially modify the volatile composition inherited by icy solids. Despite the formation of CO-rich pebbles, smooth disk models do not produce CO-rich planetesimals. This suggests that additional mechanisms are required to retain or trap CO-rich solids.
These results highlight the importance of volatile transport and ice reprocessing in regulating the chemical inheritance of forming planetary systems. In particular, models aiming to connect disk chemistry with cometary compositions and exoplanet atmospheric C/O ratios should account for the disk buildup stage, which can significantly alter the spatial distribution and incorporation of volatile species into solids.
How to cite: Drazkowska, J.: Impact of dust evolution during protoplanetary disk buildup on the CO-to-water ratio of pebbles and planetesimals, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-261, https://doi.org/10.5194/epsc2026-261, 2026.
The chemical evolution of interstellar icy grain mantles driven by cosmic rays and secondary electrons plays a pivotal role in the molecular complexity of interstellar environments. While bulk ice chemistry has been extensively studied, the coupled physical and chemical processes occurring at the interface between icy mantles and refractory carbonaceous dust grains remain less understood. In Chuang et al. (2023)[1] and Lee et al. (2026)[2], we have processed high-energy photons, including X-ray and EUV photon, on H2O-covered amorphous carbon. Both results implied that the formation of CO2 bypassed through the intermediate CO phase which is commonly found in ice chemistry. Therefore, in this study, we investigate the effects of energetic electron irradiation on thin H2O ice layers deposited on isotopically labeled amorphous carbon (a-13C) and hydrogenated amorphous carbon (a-13C:H) dust analogues.
To systematically examine whether the CO molecules act as the intermediate products of CO2 formation, irradiation experiments were performed at different temperature ranging from 13 K to 90 K under ultra-high vacuum (UHV) condition. Given that the thermal desorption temperature of CO is approximately 30 K, irradiation above this threshold leads to a lack of CO survival on the dust surface, decreasing the efficiency of CO oxidation to CO2. Via this method, we provide evidence to exclude the necessity of CO molecules in the formation pathway of CO2. These results demonstrate that CO2 formation occurred as long as H2O ice covers the amorphous carbon substrate, crucially providing another chemical pathway to produce CO2 ice in higher-temperature (>30 K) environment within the interstellar clouds.
How to cite: Lee, C.-Y., Lee, J.-Y., Chuang, K.-J., Jäger, C., Chiu, Y.-H., and Chen, Y.-J.: Electron Irradiation of H2O Ice on Amorphous Carbon Films: Temperature Dependence and Interfacial CO2 Formation Pathways, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1347, https://doi.org/10.5194/epsc2026-1347, 2026.
Understanding chemistry in the interstellar medium requires, at the fundamental level, a mechanistic understanding of the various processes taking place. Many steps in the large reaction networks involve photochemical reactions and dissociation plays a particularly important role. From a theoretical standpoint, modelling such processes is challenging due to the highly non-equilibrium nature of the problem. In this presentation, it will be demonstrated how accurate quantum chemistry methods can be used to characterise excited states of key complex organic molecules (e.g. methanol, formaldehyde, formic acid), and how quantum dynamical simulations that solve the time-dependent Schrödinger equation are then able to fully describe dissociation pathways accessible in a given range of wavelengths. Quantitative, wavelength-dependent branching ratios can be automatically obtained for each channel, along with their timescales, which offers valuable information for interstellar chemistry models. Furthermore, a newly developed procedure is also discussed, which allows these same quantum dynamics simulations to be performed in an explicit, atomistic environment. This opens up exciting pathways to fully understand the role of interstellar ices at the atomic and molecular level, and how it affects photochemistry. The overarching goal of this work is to rationalise how chemical complexity builds up in space through the development of high-level theoretical descriptions of key phenomena.
How to cite: Cigrang, L., Lamberts, T., and Worth, G.: Quantum dynamical modelling of photochemistry in space, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-591, https://doi.org/10.5194/epsc2026-591, 2026.
Sulfur chemistry in the interstellar medium has received renewed attention in recent years, driven by long-standing questions about sulfur depletion between diffuse and dense environments and by recent tentative reports of sulfur-bearing organics such as DMS (CH3SCH3) and/or DMDS (CH3SSCH3) in exoplanet atmospheres. These topics highlight the need to better understand how simple sulfur-bearing molecules are processed and transformed into more complex species. In this context, methanethiol (CH3SH), the direct sulfur analogue of methanol (CH3OH), is an excellent starting point for exploring the formation of more complex sulfur-bearing molecules in interstellar ices.
To investigate this chemistry, we performed UV irradiation experiments on pure CH3SH ices under ultra-high-vacuum conditions. The processed ices were monitored by reflection-absorption infrared spectroscopy (RAIRS) and analyzed during warm-up using temperature programmed desorption (TPD), allowing the identification of newly formed species and to evaluate how their abundances change with experimental conditions.
We find that UV photochemistry of CH3SH likely produces radicals such as CH3, CH3S, and CH2SH, which recombine to form a variety of sulfur-bearing complex organic molecules. The detected products include CH3CH2SH, CH3SCH3 (DMS), CH3SSCH3 (DMDS), HSCH2CH2SH, and CH3SCH2SH. We further show that the product yields depend on the ice temperature, thickness, and irradiation time. These results provide new experimental constraints on the solid-state network of sulfur and offer guidance for future searches for sulfur-bearing complex organic molecules in astrophysical environments.
How to cite: Kruczkiewicz, F., Wind, A., and Chuang, K.-J.: Formation of sulfur-bearing complex organic molecules in interstellar ice analogues via UV photochemistry of CH3SH, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1003, https://doi.org/10.5194/epsc2026-1003, 2026.
Astrophysical ices accrete on substrates whose chemical composition vary significantly according to their environment.
In the interstellar medium, ices mantles grow onto dust grains composed of amorphous silicates and carbonaceous materials
[1], while more diverse mineralogical substrates are present in circumstellar regions [2]. On the surfaces of icy moons in
the Solar System, several saline species have been identified [3]; these species are thought to originate from subsurface
oceans, making their characterization essential for inferring the chemistry of these internal water bodies. In this study,
we investigated the interactions between astrochemically relevant molecules and saline substrates through laboratory
experiments. Specifically, we evaluated the adsorption of carbon monoxide and ammonia onto iron salts; the oxidation
states of Fe could indicate the redox conditions of the oceans under the surface. Infrared spectra show the emergence of
spectral profiles reflecting the interactions between ices and salt substrates. Under ultra-high vacuum conditions, while
pure CO typically desorbs at 25–30 K, the new spectral features of CO persisted on the salt substrate up to approximately
180 K, a clear effect of strong chemical interactions. Furthermore, signatures of NH3 remained visible at temperatures
as high as 300 K. These results suggest that saline surfaces significantly enhance the thermal stability of volatile species,
with profound implications for the chemical evolution of icy planetary surfaces and their observations.
[1]Jones, A. P. ”Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry.” Royal
Society Open Science 3.12 (2016).
[2] Keller, L. P., et al. ”Identification of iron sulphide grains in protoplanetary disks.” Nature 417.6885 (2002): 148-150..
[3] Carlson, R. W., et al. ”Europa’s surface composition.” Europa 283 (2009).
[4] Napoleoni, Maryse, et al. ”Probing the oxidation state of ocean worlds with SUDA: Fe (II) and Fe (III) in ice grains.” The
Planetary Science Journal 5.4 (2024): 95.
How to cite: Piazzese, F., Jimenez-Escobar, A., Cecchi-Pestellini, C., Mangione, A., Ferrante, F., and Ciaravella, A.: Adsorption of CO and NH3 on iron salts in space-like conditions: implications for icy moonssurface chemistry and observations, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-951, https://doi.org/10.5194/epsc2026-951, 2026.
Comets are frozen remnants from our solar system’s birth, 4.6 billion years ago. Comparing their composition with that found in planet-forming disks surrounding young solar analogues (104 — 106 years old) provides a diagnostic of the evolutionary processes that can shape planetary systems. Moreover, it allows the tracing of chemical signatures from parental molecular clouds to planets, bridging the gap between interstellar chemistry and planetary formation (Ceccarelli C., et al., 2023, Mumma M. J., & Charnley S. B.).
Nevertheless, systematic comparisons between protostellar environments, disks, and comets remain scarce, often limited to a few target selections (e.g., Drozdovskaya M.et al., 2019; Bianchi E., et al., 2019).
In this work, we present the first statistical analysis of [CH3CN]/[CH3OH] abundance ratios across a diverse sample, including 13 comets, 24 low-mass hot corinos, and 6 planet-forming disks. This statistical approach allows us to identify whether inconsistencies are present in existing datasets and provides a more comprehensive view of the various stages of planet formation (Lippi M., et al., 2024).
While we observe significant variations of the [CH3CN]/[CH3OH] abundance ratios within the planet-forming disk sample – most likely driven by evolutionary processes – in comets and hot corinos this ratio shows a remarkable similarity (see Figure 1). This suggests that the transition from protostellar envelopes to cometary bodies is driven by a consistent chemistry that converges over time, even when material is continuously reprocessed.
Figure 1: Comparison of the [CH3CN]/[CH3OH] abundance ratio in hot corinos, Class 0 to Class II disks, and comets.
References: Ceccarelli, C., Codella, C., Balucani, N., et al. 2023, in Astronomical Society of the Pacific Conference Series, Vol. 534, Protostars and Planets VII; Mumma M. J., Charnley S. B., Annual Review of Astronomy and Astrophysics, 2011, 49, 471-524; Drozdovskaya, M. N., van Dishoeck, E. F., Rubin, M., Jørgensen, J. K., & Al- 470; Bianchi, E., Codella, C., Ceccarelli, C., et al. 2019, MNRAS, 483, 1850; Lippi M., Podio L., Codella C., Faggi S., De Simone M., Villanueva G. L., Mumma M. J., Ceccarelli C., The Astrophysical Journal, 2024, 970.
How to cite: Lippi, M., Podio, L., Codella, C., Cordiner, M., Walsh, C., Ceccarelli, C., Giani, L., Booth, A., Faggi, S., Villanueva, G. L., Biver, N., and Bockelee-Morvan, D.: Tracing the Evolution of the [CH3CN/CH3OH] Ratio From Protostars to Comets, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-602, https://doi.org/10.5194/epsc2026-602, 2026.
The role of water in the chemistry of interstellar ices
H. Carrascosa1, G. M. Muñoz Caro1, C. Del Burgo Olivares1, Y. –J. Chen2
Centro de Astrobiología (CAB, CSIC-INTA), Ctra de Ajalvir, km 4, Torrejón de Ardoz, 28850, Madrid, Spain.
Department of physics, National Central University, Zhongli District, Taoyuan City, Taiwan.
Experiments performed under simulated interstellar conditions have shown the formation of a full variety of complex organic molecules (such as sugars, heterocycles, amides, etc.) from irradiation of ice samples. As water is, by far, the most abundant molecules in ice mantles in the interstellar medium, most of the species present in ice mantles will be surrounded by water molecules. Understanding the role of water is therefore essential to predict the conditions and environmental situations where certain species will be favoured.
It is well known that the presence of water determines the chemistry in specific directions, which can be drastically different from the chemistry without water. For example, methanol ice forms formaldehyde readily under UV radiation. Formaldehyde is a very reactive species, which polymerises, forming a polymer called polyoxymethylene (POM). However, in the presence of water, formaldehyde molecules are solvated by water molecules, and the formation of POM is highly inhibited [1].
We have experimentally studied the role of water in two different ice mixtures: 1) H2O:NH3:CH3OH and 2) H2O:H2S. Experiments were carried out using a high vacuum chamber, cooled down with liquid nitrogen and submitted to UV radiation with a deuterium lamp. After simultaneous deposition and irradiation, ice samples were warmed up to room temperature. A methanol extract of the organic residue at room temperature, was analysed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (HPLC-MS) equipments, to identify and quantify the molecules remaining in the organic residues. The composition and abundances of the detected molecules were compared in experiments with different water ratios [2].
Several works have already studied the formation of organic molecules in H2O:NH3:CH3OH ice mixtures ([3] and references therein). There is a full variety of organic species detected from UV irradiation of this ice samples. The experimental procedure prior to chromatographic analyses is designed in each work depending on the family of species of interest. Sugars, amino acids, or heterocycles are among the species which have been detected. We have not carried out any pretreatment of the samples, to avoid any induced chemistry after the extraction of the sample from the simulation chamber. GC-MS analyses have revealed that N-heterocycles are favoured over O-heterocycles, and we have investigated the role of water toward this chemistry [4].
Figure 1: chromatogram of a H2O:CH3OH:NH3 ice mixture. Gaussian profiles for each of the identified species are shown. Note that there are no O-heterocycles, as a consequence of the chemistry induced by the presence of ammonia, and the chemical properties of the O-H groups provided by photodissociation of water and methanol molecules.
The fate of sulphur in the interstellar medium is still unclear. Several authors have pointed out to the formation of long sulphur chains as sulphur reservoirs in the interstellar medium [5, 6, 7]. However, H2S has not been detected in ice mantles, suggesting that, if present, its abundance will be low compared to water. Consequently, H2S molecules will not be in close contact in ice mantles. Experiments were made with H2O:H2S ice samples in different ratios. If sulphur ends up forming chains, there must be an efficient mechanism which brings together sulphur atoms, making it possible to react and producing covalent S-S bonds. This mechanism has been elucidated [2] and will be presented here. In our experiments, water enhances the formation of octaedric sulphur by a factor of ~100. Water molecules play a key role, forming covalent bonds with sulphur intermediates that favours subsequent S-addition reactions. Some of these intermediates have been detected in the organic residue, which served to complete the chemical pathway to the formation of sulphur chains in a water environment.
In brief, we show strong evidence for the need of a water-rich ice environment in the photosynthesis of sulphur allotropes up to S8, and provide a reaction scheme that also requires the presence of water for the N-heterocycles formation.
Figure 2: mechanism of sulphur formation in two steps. First, water molecules favour the formation of S-SO3 species, which is required to elongate sulphur chains. 2) when sulphur chains are long enough, they will make an intramolecular reaction producing sulphur cycles. Alternatively, A’ shows a chemical pathway by which molecules could not elongate more, producing different species that were also detected in the chromatographic analyses.
[1] Schutte, W., Allamandola, L. J., and Sandford, S. A., 1993, Icarus, 104, 118-137.
[2] Del Burgo Olivares, C., Carrascosa, H., Muñoz Caro, et al., 2026, submitted to A&A.
[3] Muñoz Caro, G. M., Carrascosa, H., Martín-Doménech, R., 2025, Nat. Rev. Chem, 9, 537-552.
[4] Del Burgo Olivares, C., Carrascosa, H., Muñoz Caro, G. M., et al., 2026, submitted.
[5] Cazauz, S., Carrascosa, H., Muñoz Caro, G. M., et al. 2022 A&A 657, 1-12.
[6] Carrascosa, H., Muñoz Caro, G. M., Martín-Doménech, R. et al. 2024, MNRAS, 533, 1, 967-978
[7] Herath, A., McAnally, M., Turner, A. M., et al. 2025, Nat. Comm. 16, 5571.
How to cite: Carrascosa de Lucas, H., Muñoz Caro, G. M., del Burgo Olivares, C., and Chen, Y. J.: The role of water in the chemistry of the interstellar medium, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-90, https://doi.org/10.5194/epsc2026-90, 2026.
Ribose is a key biomolecule in the context of the RNA world hypothesis and prebiotic chemistry, yet the photochemistry of carbohydrates remains significantly less explored than that of amino acids or nucleobases. In this work, a theoretical investigation of the excited-state dynamics of β-D-ribopyranose following ultraviolet (UV) excitation using non-adiabatic molecular dynamics simulations is presented.
Several electronic structure approaches of different accuracy and computational cost were employed and compared, including CASSCF, MRSF-TDDFT, and OM2/MRCISD. To enable simulations with the MRSF-TDDFT method, a new interface between the ABIN molecular dynamics package and the OpenQP electronic structure program was developed. The suitability of the individual methods for non-adiabatic dynamics simulations of sugar-like systems was critically evaluated.
The simulations provide insight into the low-lying excited states of ribose, the topology of the relevant potential energy surfaces, and the dominant relaxation pathways following UV excitation. The excited-state dynamics reveal ultrafast relaxation to the ground state accompanied by competing photochemical processes, including pyranose ring opening, bond dissociation, and return to the initial closed-ring structure.
These findings suggest that β-D-ribopyranose can efficiently dissipate absorbed UV energy under the investigated conditions, accompanied by competing reactive and non-reactive relaxation pathways. This work contributes to the understanding of saccharide photochemistry under extraterrestrial conditions and provides a comparison of electronic structure methods for non-adiabatic molecular dynamics simulations of biologically relevant carbohydrate molecules.
How to cite: Vosovičová, K., Slavíček, P., Lamberts, T., and Janoš, J.: Ribose Photochemistry in Space: Non-adiabatic Reaction Pathways, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-694, https://doi.org/10.5194/epsc2026-694, 2026.
Introduction
Future missions to Enceladus will aim to characterise the chemical composition of its subsurface ocean by sampling material ejected through the south polar plumes, as well as surface ice near the plume vents. A primary scientific objective of such missions is the detection of prebiotic organic molecules as potential biosignatures of extant or extinct life. However, correctly distinguishing true biosignatures from organics produced via abiotic processes remains a critical interpretive challenge.
At the surface of Enceladus, radiation from Saturn's magnetosphere is a driver of molecular destruction and synthesis within the ice phase. Ions and electrons from magnetospheric plasmas are well established as agents of chemical change on the icy surfaces of Solar System moons, including Europa, Ganymede, and Enceladus itself. Water-group ions dominate the Saturnian magnetospheric ion population at the orbit of Enceladus, with H₂O⁺ ions alone accounting for over 60% of the ion flux (Johnson et al. 2008; Tokar et al. 2008, 2009).
Our previous work (Richards et al. 2025) demonstrated that such radiation can produce simple inorganic species (e.g., CO, NH₄⁺, OCN⁻) as well as prebiotically relevant organics such as formamide (HCONH₂) and acetaldehyde (CH₃CHO). The radiolytic products were formed within Encealdus timescales of a few tens of hours within a plume, or a few years on the icy surface; short enough to make discrimination between subsurface-sourced and abiotically formed molecules extremely difficult.
Previous laboratory studies have quantified the radiolytic destruction of Enceladean ice analogues and the formation of radiolytic products using various forms of ionising radiation, including keV electrons, high-energy oxygen ions, X-rays, and Lyman-α photons (Bergantini et al. 2014, Bründl et al. 2026, Pilling et al. 2019, Rachid et al. 2020). Key parameters extracted from these studies include the effective destruction cross-section, σ (cm²), a probabilistic measure of molecular destruction by radiolysis or sputtering, and analogous formation cross-sections for radiolytic products. They also include the G-value, which describes the number of molecules formed or destroyed per 100 eV of energy deposited into the target. This study aims to quantify these parameters under irradiation by water-group ions in the energy range of tens of keV.
Methodology
Experiments were performed using the AQUILA chamber at the HUN-REN Institute for Nuclear Research, described in detail by Rácz et al. (2024). The AQUILA consists of an ultrahigh-vacuum chamber operating at a base pressure of a few 10⁻⁹ mbar, equipped with a cryogenically cooled sample holder hosting a ZnSe deposition substrate. Astrophysical ice analogues are deposited via background condensation of gas mixtures dosed into the chamber. The facility also hosts a dedicated electron cyclotron resonance ion source (ECRIS; Biri et al. 2021), which delivers keV ion beams to the sample at 45° to the surface normal. Chemical and structural changes to the ice are monitored in situ using mid-infrared transmission absorption spectroscopy (Bruker V70v; 4000–650 cm⁻¹; 1 cm⁻¹ resolution).
Ice analogues composed of H₂O, CO₂, CH₄, and NH₃ were deposited to thicknesses exceeding 300 nm onto the pre-cooled (20 K) substrate, then warmed to 70 K to better represent Enceladean surface conditions (Spencer & Nimmo 2013). In separate experiments, ices were exposed to five water-group ion beams: 10 keV O⁺, 45 keV O³⁺, 10 keV OH⁺, 15 keV OH⁺, and 15 keV H₂O⁺. Infrared spectra were acquired at regular fluence intervals throughout each irradiation run.
From the resulting spectra, we derive: (i) effective destruction cross-sections for the parent ice constituents; (ii) formation cross-sections for selected radiolytic products; and (iii) G-values (molecules destroyed or formed per 100 eV deposited). Together, these parameters provide a quantitative description of radiation chemistry relevant to the surface environment of Enceladus, and constitute input for models seeking to distinguish abiotic chemistry from genuine biosignatures in future Enceladus mission data. The results of this analysis will be presented during the conference.
Acknowledgements
This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 871149.
References
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How to cite: Richards, G., Mifsud, D., Rácz, R., Kovács, S. T. S., Sulik, B., Pearson, V., Morgan, G., Patel, M. R., Sheridan, S., McCullough, R. W., Biri, S., Herczku, P., Mason, N. J., and Juhász, Z.: Water-group ion radiation chemistry of Enceladean surface ice analogues: Quantifying cross-sections and G-values, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-903, https://doi.org/10.5194/epsc2026-903, 2026.
For accurate interpretation of JWST ice spectra, radiative transfer models are required. These models need optical constants which are derived from laboratory experiments. Within the Optical Analysis Setup for Interstellar Spectroscopy (OASIS), interstellar environments are simulated by forming ice at low temperatures (10 K) within an ultra-high vacuum chamber (1E-8 mbar). Using background deposition, the real refractive index is measured as the ice grows in the chamber. Refractive index curves are calculated from the data, giving a refractive index from 250 nm up to 800 nm in a single experiment. Pure and binary ices are formed at different temperatures, allowing for the study of porosity behaviour across different temperature regimes. Different mixing ratios of binary ices such as water and carbon dioxide are studies to observe the behaviour of the real refractive index. We find similar values as previously reported and expand the explored parameter space of different mixing ratios at different temperatures.
How to cite: Heinsohn Huala, M., Santhan, R., and Chuang, K.-J.: Broadband UV–Visible Refractive Index Measurements for Astrophysics and Planetary Science, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-898, https://doi.org/10.5194/epsc2026-898, 2026.
We investigate how the infrared absorption profile of the solid-state CO stretching mode reflects the chemical and structural environments produced during ice growth under astrophysically relevant conditions. Using two complementary deposition protocols, classical isothermal codeposition at 12 K and a temperature-decreasing ramp that simulates accretion during grain cooling, we produce a set of mixed and layered CO ices containing
H2O, NH3, CH4, CO2, and CH3OH. The resulting laboratory CO spectra are decomposed into a library of Gaussian components, each associated with a specific chemical and structural microenvironment. Within this framework, variations in the CO line profile can be related to differences in ice structure and local chemical composition. We apply this laboratory-based approach to JWST observations of two molecular cloud sight lines and one protoplanetary disc.
How to cite: Cecchi-Pestellini, C., Aslam, R., Ciaravella, A., Jiménez-Escobar, A., and Chen, Y.-J.: How interstellar ice growth shapes the CO band, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1137, https://doi.org/10.5194/epsc2026-1137, 2026.
IR irradiation has been suggested to steer interstellar ice evolution, including molecular orientation, restructuring, and even desorption, complicating the spectral interpretation of James Webb Space Telescope (JWST) ice observations [1, 2, 3]. However, the role of the substrate beneath the ice layer has not been fully investigated. In particular, silicate dust grains, which also exhibit strong vibrational transitions at ~22 and 9.7 um, are expected to actively absorb photons in the IR range and participate in energy dissipation, vibrational coupling, and surface reactions at the ice–dust interface.
In this work, we irradiate H2O-coated amorphous olivine-like (MgFeSiO4) dust analogs on a ruthenium (Ru) substrate using the free-electron IR laser at the HFML-FELIX facility in Nijmegen to study the vibrational excitation and subsequent energy transfer. The selected IR laser wavelengths are 9.7 and 21.9 µm to resonantly excite silicates with and without H2O ice coverage. The silicate-ice samples, cryogenically cooled to 10.5 K, are prepared by background deposition and monitored by a Bruker FTIR Spectrometer (VERTEX 80v) during stepwise IR irradiation up to 240 sec. The IR-induced spectral changes are further quantified as a function of photon fluence. Complementary, the potential desorption signals are recorded by a Hiden QMS (HAL/3F 501 PIC).
By targeting the resonant vibrational mode of both silicates and water ice at 9.7 µm, the experimental results show significant processing of the silicate dust grain, as evidenced by a decrease in the peak intensity of the Si-O stretching mode at 1060 cm-1. In addition, irradiation at 9.7 µm is also shown to induce clear spectral changes in the water OH stretching mode at 3330 cm-1, indicative of water restructuring and desorption from the silicate surface. For irradiation at 21.9 µm, which exclusively resonates with silicate dust analogs, the results show a characteristic water restructuring feature in the water OH stretching mode, suggesting vibrational energy transfer from the silicate grain to the ice mantle.
How to cite: Holmen, C., Jäger, C., Cuppen, H., Ioppolo, S., and Chuang, K.-J.: IR Irradiation on Interstellar H2O Icy Silicate Grains: from Dust Vibrational Excitation to Ice Structural Change , Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1058, https://doi.org/10.5194/epsc2026-1058, 2026.
Ices in embedded protostellar disks provide one of the earliest observable records of the volatile material available for planet formation, but their interpretation is complicated by the surrounding infalling envelope. In particular, it remains unclear whether infrared ice absorption features observed toward highly inclined Class 0/I systems primarily trace disk ices or envelope ices. We investigate this question using RADMC-3D radiative transfer models of parameterized disk+envelope structures. We introduce three cases for each model to separate the intrinsic disk-ice signal from the effects of envelope scattering and thermal emission, as well as envelope ice absorption. We find that the H$_2$O 3 $\mu$m and CO$_2$ 4.3 $\mu$m bands are strongly affected by the envelope because they lie in a scattering-dominated wavelength regime. In contrast, the CO$_2$ 15.2 $\mu$m band is dominated by more direct thermal emission and remains a more robust tracer of disk ices across most parameter variations. Other ice features in between show behavior that reflect their absorption and scattering opacities at their respective wavelengths. Disk contribution ratios in the observed ice optical depths are the highest for the extracted spectra from the disk center, and decrease as one moves farther away in each direction. Surprisingly, apertures located outside the disk show signatures from the ices in the disk, showcasing the impact of scattering. We confirm that $\sim70^\circ$ is the critical angle for the best view of ices in the disk for short wavelength features. Moreover, our results show that the inferred disk contribution depends strongly on envelope infall rate, disk mass, size and vertical extent. Higher envelope infall rate results in higher envelope contribution, bringing disk contribution to almost non-existent at ^{-5} M_\odot{\rm yr}^{-1}$ for the scattering-dominated bands, while for the 15 $\mu$m feature disk contribution still stays significant. Meanwhile, higher disk mass does not necessarily result in higher disk contribution to the ice absorption features. Grain size distribution, especially in the envelope, may also significantly alter the contribution ratios since they are an important factor in determining absorption and scattering opacities. We then proceed to reveal the ice inventory in the ‘Butterfly Star’ IRAS04302, and reveal spatial distribution of its ice features with an empirical approach before performing detailed radiative transfer modeling.
How to cite: Kacan, D., van 't Hoff, M., Tychoniec, Ł., Tabone, B., McClure, M., van Dishoeck, E., and Smith, Z.: Ices in Young Embedded Disks, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1288, https://doi.org/10.5194/epsc2026-1288, 2026.
Young stars emit a large amount of X-rays that can penetrate deep into protoplanetary disks, reaching the inner and more shielded regions. In the interaction of X-ray photons with ices, it produces ionisation of core electrons of the atoms forming part of the molecules. The ionisation of an inner-shell electron is followed by Auger decays for light elements [1]. The decay of the Auger stimulates the emission of an electron. The injection of these electrons into the ice produces multiple ionisations that dominate the chemistry [2].
In this study, we investigate the role of the photon energy of X-rays on a realistic ice mixture H2O:CO:NH3 at 10 K. To elucidate the dependence of the X-ray energy photons on the induced chemistry, we irradiated the ice sample with X-rays at different energies, scanning from 250 up to 900 eV, increasing the photon energy by a few eV after each irradiation step.
The results indicate that variation of the column density of different components of the ice strongly depends on the X-ray absorption profile of the sample at each energy. We observe a sharp variation of the column densities at ~300, ~400, and ~550 eV corresponding to the C, N, and O X-ray absorption edges, respectively. Comparison of the experimental edges, measured during X-ray irradiation, with the literature values reveals discrepancies with the atomic values, giving information about the chemical environment of the absorber (e.g., if C is bonded with O).
Comparing the destruction/formation yields measured in our experiments indicates that the energy of the photons is not a determining factor in the chemical network but only the total energy deposited in the ice through ionisations produced by secondary electrons. In addition, these experiments also show clues about a possible contribution of the substrate to the ice chemistry through the electron emitted from the surface of the substrate to the ice.
[1] Y-J. Chen, A. Ciaravella, G. M. Muñoz Caro, C. Cecchi-Pestellini, A. Jimenez-Escobar, K.-J. Juang, and T.-S. Yih, 2013, ApJ, 778, 162
[2] A. Jiménez-Escobar, Y.-J. Chen, A. Ciaravella, C.-H. Huang, G. Micela, and C. Cecchi-Pestellini, 2016, ApJ, 820, 25.
How to cite: jimenez Escobar, A., Cecchi-Pestellini, C., Ciaravella, A., Chen, Y.-J., Lee, C.-Y., Chiu, Y.-H., Mangione, A., Piazzese, F., and Muñoz Caro, G. M.: Soft X-Ray Irradiation of realisticIce Analogs: The Role of Absorption Edges and Secondary Electrons, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-374, https://doi.org/10.5194/epsc2026-374, 2026.
