The Cassini-Huygens mission revealed great complexity in Titan’s atmosphere. Indeed, mass spectrometers onboard Cassini detected the presence of ions of unexpectedly high masses [1]. These macromolecular ions are understood as the precursors of the aerosols abundant at lower altitude with formation mechanisms likely driven by ion chemistry [2]. These precursor molecules probably are polycyclic aromatic (nitrogen bearing) hydrocarbons (PAHs & N-PAHs) identified by their C-H infrared emission signatures [3], compatible with the detected ion mass-to-charge ratios [4]. Chemistry in ionospheres is triggered by UV photons and energetic particles pervading the Solar System. But specific to Titan is its place within Saturn’s magnetosphere where oxygenated ions, sourced from the plumes of Enceladus, were detected. 10 to 100 keV oxygen ions can reach fluxes of ~106 ions.cm-2.s-1 in Titan’s upper atmosphere [5]. Ions typically deposit on Titan between 1200 and 800 km in altitude and mainly loose energy until thermalization by interactions with N2 [6]. Yet a fraction of these ions must interact directly with the organics and contribute to Titan’s complex chemistry. As ion irradiation is known to trigger sputtering, chemical growth and possibly implantation, what is the impact of these processes on Titan’s chemical budget?Titan’s atmospheric chemistry has been historically investigated by subjecting N2:CH4 mixtures to representative energy sources triggering photolysis and radiolysis [7]. The resulting aerosol analogs, called “tholins”, are made of irregular polymeric structures with unsaturation levels indicative of N-PAHs, with infrared features of amines, (iso)cyanides, aliphatic and heteroaromatic groups. Tholins exposed to VUV [8] and plasma [9] irradiation showed erosion on the grains and non-uniform modification of chemical functions. Here, we used N-PAHs as simpler aerosol analogues to investigate and quantify distinct and competing processes triggered by ion irradiation. High resolution mass spectrometry analysis of O+-irradiated adenine (C5H5N5) showed the formation of different families of (HCN)-like polymeric structures of condensed aromatics [10]. During irradiation, sputtering also occurs and expels small molecules to the gas phase, typically HCN, comparable to plasma-driven erosion [11]. But adenine is not fully representative of Titan aerosols as tholins show a range of N/C ratios from 1.5 to 0 [12]. To get a broader picture of oxygen irradiation on a range of representative molecules, we have conducted new experiments on adenine, adenine:chrysene mixtures, bathophenanthroline (C24H16N2) and chrysene (C18H12) with N/C ratios of 1, ~0.2, 0.08 and 0 respectively.Irradiation experiments were performed at the ARIBE beam line coupled to the IGLIAS chamber at GANIL (Caen, France) [13] and at the HUN-REN Institute for Nuclear research (Atomki) in Debrecen (Hungary) with the AQUILA chamber [14] and the Electron Cyclotron Resonance ion source [15]. We used oxygen ions at 10 and 20 keV (for 18O) and at 70 and 108 keV (for 16O) to irradiate samples at 150 or 300 K with maximum fluences of 2x1016 ions/cm2. The experimental rationale varied depending on the process we aimed to quantify: single layers of hundreds of nanometers for sputtering and multiple layers for implantation. In-situ infrared spectroscopy and quadrupole mass spectrometry measurements are performed to track chemical changes and sputtering.Infrared analysis shows the progressive destruction of the initial molecular film, associated to its intact sputtering and to radiolysis followed by sublimation of volatile species [16]. The appearance of new bands allows to identify and quantify abundant radiolytic products, associated with dehydrogenation processes. Samples irradiated with 18O ions were analyzed ex-situ with an 18T-FT-ICR mass spectrometer at the CARMeN Institute (Rouen, France) with a resolution allowing unambiguous detection of implanted 18O. The molecular content of the irradiated samples was analyzed by Laser Desorption Ionization, revealing high molecular complexity with m/z reaching 700.We will present experimental results that provide insights into the heterogeneous processes in Titan’s upper atmosphere. By extracting sputtering yields and destruction cross sections, we provide input for photochemical-microphysical models of Titan’s complex atmosphere. By probing molecular growth through oxygen incorporation into C,H,N material, we investigate an added prebiotic interest for the aerosols sedimenting to the surface. This work can also have implications for outer solar system bodies like Triton, Pluto, Eris and Makemake where oxygen ions of the solar wind and galactic cosmic rays process ices and transient atmospheres of high hydrocarbon content.AcknowledgmentsThis work is supported by the French National Research Agency in the framework of the "Investissements d’avenir” program (ANR-15-IDEX-02) and the generic call for proposals (ANR-22-CE49-0017). The experiments were performed at the Grand Accélérateur National d’Ions Lourds (GANIL) by means of the CIRIL Interdisciplinary Platform, part of CIMAP laboratory, Caen, France. We acknowledge the fundings from ANR IGLIAS grant (ANR-13-BS05-0004) and ANR MIRRPLA grant (ANR-22-EXOR-0012) of the French Agence Nationale de la Recherche and Normandie Region (RIN 50/50). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 871149. We acknowledge the funding from Europlanet’s Transnational Access Pilot programme 2025 (project code 25-EPN-P-5) and from Europlanet’s Transnational Access programme 2026 (project code 26-EPN-38). Access to the CNRS research infrastructure Infranalytics (FR2054) is gratefully acknowledged.References[1] F. J. Crary et al., PSS, 57, 1847-1856 (2009)[2] P. Lavvas et al., Proc. Natl. Acad. Sci. U.S.A., 110, 2729-2734 (2013)[3] M. López-Puertas et al., ApJ, 770, 132 (2013)[4] R. P. Haythornthwaite et al., PSJ, 2, 26 (2021)[5] T. E. Cravens et al., Geophysical Research Letters, 35, 3 (2008)[6] S. Hörst et al., JGR, 113, E10 (2008)[7] M. L. Cable et al., Chem Rev, 112, 1882 (2012)[8] N. Carrasco et al., Nature Astronomy, 2, 489 (2018)[9] A. Chatain et al., Icarus, 345, 113741 (2020)[10] F. Matuszewski et al., Icarus, 445, 116865 (2026)[11] A. Chatain et al., Icarus, 396, 115502 (2023)[12] H. Imanaka et al., PNAS, 107, 12423-12428 (2010)[13] B. Augé et al., Rev. Sci. Instrum., 89, 075105 (2018)[14] R. Rácz et al., Rev. Sci. Instrum., 95, 095105 (2024)[15] S. Biri et al., Eur. Phys. J. Plus, 136, 247 (2021)[16] E. Dartois et al., A&A, 671, A156 (2023)

Context. Terrestrial exoplanets are expected to host secondary, high-metallicity atmospheres derived from the outgassing of volatiles such as N2, CO2, H2O, CH4, and CO. Photochemical organic hazes are likely to form in such environments, significantly impacting both atmospheric observation and planetary habitability. Aims. This study aims to investigate haze formation across representative terrestrial exoplanet atmospheres and assess how CH4 versus CO as the primary carbon source differentially affects haze production rates, particle properties, and chemical complexity. Methods. We conducted six laboratory simulations by exposing the initial gas mixture (a few millibars) to glow discharge at 300 K. Each simulated atmosphere comprises 75% of N2, CO2, or H2O, 10% of each of the other two gases, and 5% of CH4 or CO. We analyzed the gas-phase products using a residual gas analyzer. For solid products, we measured production rates and particle density, determined particle size distributions via atomic force microscopy, identified functional groups using Fourier-transform infrared spectroscopy, and characterized molecular composition with very high-resolution mass spectrometry. Results. Experiments using CH4 produce a wider diversity of gas-phase species and substantially higher haze yields compared to the corresponding CO-based experiments. CO-derived haze particles exhibit a restricted size range (10–80 nm), whereas CH4-derived hazes form denser material with complex functional group signatures and thousands of unique molecular formulas. The pattern of the identified molecular formulas indicates molecular growth pathways linked to detected gaseous precursors such as HCN, CH2O, and C2H4. Conclusions. The atmospheric redox state critically controls haze formation in simulated terrestrial exoplanet atmospheres. CH4 is significantly more effective than CO in initiating organic growth, leading to higher haze production rates and greater chemical complexity. These results provide crucial constraints for exoplanet atmospheric modeling and spectral interpretation, and further support the possibility that reducing atmospheres may facilitate prebiotic organic chemistry relevant to the emergence of life.

Observations of temperate sub-Neptunes suggest active chemical environments, finding evidence of both water vapor and photochemical hazes in their atmospheres. Hazes formed in water-rich atmospheres are chemically complex, containing molecules relevant to prebiotic chemistry, and their strong optical opacity obscures sought-after gaseous molecular absorption features. While many studies have investigated haze formation and properties across diverse atmospheric conditions, little is known about the evolution of these hazes in their environment once formed. In particular, interactions with water can drive hydrolysis reactions that alter haze composition and optical behavior, affecting our interpretations of habitability and observational spectroscopy. Here, we perform hydrolysis experiments on haze analogs of temperate water-rich exoplanets and measure their optical properties. Transmittance measurements from 0.4 to 28.5 μm reveal changes in key functional groups after hydrolysis, along with an overall increase in sample absorbance. We report the derived optical constants for use in observational and modeling studies. Through synthetic atmospheric spectra, we demonstrate the need for physically informed haze optical properties in models, consistent with expected planetary conditions. The increased absorptivity and high imaginary refractive index of hydrolyzed hazes almost completely flatten features in model spectra, presenting critical consequences for atmospheric characterization of water-rich sub-Neptunes.

Temperate sub-Neptune and terrestrial exoplanets could contain large inventories of water in various phases, such as water-dominated atmospheres or even oceans. Observations have shown that many exoplanets, including water worlds, likely contain photochemically generated hazes. Haze particles are a key source of organic matter and may impact the evolution or origin of life; their optical properties are imperative for interpreting observations through theoretical atmospheric modeling. Modelers have thus far assumed haze optical properties that may not represent hazes under sub-Neptune and terrestrial atmospheric conditions. Often orbiting close to M dwarf stars, these planets receive large amounts of radiation, especially during flaring events, which may accelerate atmospheric escape and affect atmospheric compositions. Critically, it remains unknown how stellar flaring affects hazes and the subsequent transmission spectra of sub-Neptune and terrestrial exoplanets. Here, we present optical constants of experimentally generated sub-Neptune haze analogs before and after UV irradiation across a broad wavelength range (0.5-8 mu m). We find that UV irradiation alters haze optical constants, which become generally more absorbing in this wavelength range, which we hypothesize is due to our sample containing more oxygen-rich absorbing bands postirradiation. We use Virga and PICASO to simulate transmission spectra of potentially hazy water-dominated planets GJ 1214b and LHS 1140b, accounting for irradiated haze layers in their atmospheres. For our GJ 1214b CH4-rich haze modeled case, we see a difference in the N-H feature at 2.6 mu m in the resulting transmission spectrum between irradiated and unaltered haze that should be observable within current JWST capabilities. Broadly, we demonstrate the importance of using more representative optical constants, as they have an impact on current and future atmospheric composition interpretations.

Complex organic molecules have been found in many space environments like meteorites and comets. There, they are subjected to various forms of radiation (photons, electrons, ions), opening the question of their behavior and chemical evolution, which may have played a crucial role in chemical processes of astrobiological interest. In this study, we investigate the irradiation of adenine (C5H5N5) with oxygen and neon ions. The free parameters of the experiments include varying energies (30-70 keV), temperatures (150, 300 K), sample thicknesses (138-554 nm), and ion fluences (0.69-5 x 1015 ions cm-2). In situ IR spectroscopy reveals the appearance of C equivalent to N and N=C=N bands indicating the formation of new species. Ex situ ultra-high-resolution mass spectrometry shows the formation of new complex organic molecules that far exceed the molecular mass of adenine. These macromolecules show great chemical diversity and can be expressed as (HCN)zR families, where z can reach 14 and R can be Cx, Hx, Nx, NxHy, CxHy or CxNy. In total, nearly 100 individual families have been identified, 28 of which can be found in every irradiated sample. Their aromaticity equivalent is higher than that in other N-rich samples such as Titan tholins and HCN-polymers, corresponding to polycyclic aromatic nitrogen-bearing hydrocarbons. The high amount of nitrogen in these molecules indicates a very efficient incorporation of nitrogen in the solid phase during the irradiation of adenine. The ease with which complex organic matter forms through irradiation highlights the relevance of these species in space environments.

Pluto possesses a thin atmosphere primarily composed of N _2 , with minor constituents including CO and CH _4 . Photochemical processes generate distinct haze layers as observed by the New Horizons spacecraft. However, the mechanisms governing haze formation, as well as the composition and physical properties of the hazes, remain poorly constrained. Due to Pluto’s highly eccentric orbit and obliquity, its surface temperature and atmospheric composition undergo substantial seasonal variations, but it is unclear how such seasonal variations impact the chemical pathways and efficiency of haze formation in Pluto’s atmosphere. To address this, we conducted a laboratory simulation of Pluto’s atmospheric photochemistry, in which N _2 /CH _4 /CO gas mixtures with CH _4 concentrations varying from 0.1% to 5% were exposed to a glow discharge to initiate photochemical reactions. Gas-phase composition was monitored in situ using a residual gas analyzer, while the solid-phase products were characterized by atomic force microscopy, a gas pycnometer, infrared spectroscopy, and very-high-resolution mass spectrometry to determine particle sizes, density, and composition, respectively. Our results show that increasing the CH _4 mixing ratio significantly enhances the yield of gas and solid products. Under low CH _4 conditions, nitrogen is primarily incorporated into solids as cyanide groups, whereas CH _4 -rich conditions favor the formation of amino groups, greatly promoting nitrogen incorporation into organic solids. These findings not only shed light on how seasonal variations into Pluto’s atmosphere composition influence haze formation pathways, but also provide critical parameters to interpret observational data and to improve photochemical and microphysical models of planetary hazes.

In Titan’s atmosphere, the chemistry of simple hydrocarbons (e.g., CH _4 and C _2 H _2 ) and nitrogen bearing species (e.g., N _2 and CN) represents an important link between molecular species and the ubiquitous organic haze that gives Titan its characteristic orange hue. Here we present a new search for two previously undetected molecules, triacetylene (C _6 H _2 ) and the gas phase dicyanoacetylene (C _4 N _2 ), using the Echelon-Cross-Echelle Spectrograph instrument on board the Stratospheric Observatory for Infrared Astronomy aircraft. We do not detect these two molecules but determine upper limits for their mixing ratios and column abundances. We find the 3 σ upper limits on the uniform volume mixing ratio (VMR) above 100 km for C _6 H _2 to be 4.3 × 10 ^−11 , which is lower than the photochemical model predictions. This new upper limit suggests that the growth of linear molecules is inhibited. We also put a strict upper limit on the uniform VMR for gas phase C _4 N _2 above 125 km to be 1.0 × 10 ^−10 . This upper limit is well below the saturation mixing ratio at this altitude for C _4 N _2 and greatly limits the feasibility of C _4 N _2 forming ice from condensation.

In Titan's atmosphere, the chemistry of small hydrocarbons and nitriles represent an important link from molecular species to the ubiquitous organic haze that gives Titan its characteristic yellow color. Here we present a new search for two previously undetected molecules, triacetylene (C_6H_2) and the gas phase dicyanoacetylene (C_4N_2), using the Echelon-Cross-Echelle Spectrograph (EXES) instrument aboard the SOFIA (Stratospheric Observatory For Infrared Astronomy) aircraft. We do not detect these two molecules but determine upper limits for their mixing ratios and column abundances. We find the 3σ upper limits on the uniform volume mixing ratio (VMR) above 100 km for C_6H_2 to be 4.3×10^-11 which is lower than the photochemical model predictions. This new upper limit suggests that the growth of linear molecules is inhibited. We also put a strict upper limit on the uniform VMR for gas phase C_4N_2 above 125 km to be 1.0×10^-10. This upper limit is well below the saturation mixing ratio at this altitude for C_4N_2 and greatly limits the feasibility of C_4N_2 forming ice from condensation.

The Cassini-Huygens mission revealed that energetic (1 – 1000 keV) water ions (OHx+, x = 0,1,2), originating from Enceladus' geysers, precipitate in Titan's upper atmosphere where molecules reaching a mass-to-charge (m/z) of several thousand atomic mass units have been detected. These aerosol embryos, that were not expected at such high altitudes, have been attributed to polycyclic aromatic (nitrogen bearing) hydrocarbons (PANHs) that would result from the ionization and dissociation of the major atmospheric compounds, N2 and CH4 by solar photons [1].A fraction of the Enceladus’ water ions must collide with Titan’s macromolecules but the impact on the atmospheric chemistry is unclear. Do the ions trigger the formation of more complex organic species, maybe including oxygen? Do they sputter some organic material back into the gas phase? Since aerosols sediment towards the surface, the formation of complex oxygenated molecules in the upper atmosphere would add a new dimension with strong exobiological implications to the carbon / nitrogen / hydrogen chemistry endogenous to Titan.Titan’s photochemistry has inspired many to simulate these conditions in the laboratory [2]. The complex organic compounds resulting from photolysis or radiolysis of N2/CH4 mixtures have been deemed “tholins” and numerous studies have attempted to characterize their properties. Infrared spectroscopy has shown that the tholins chemical functions include primary and secondary amines, (iso)cyanides, carbodiimides, aliphatic and heteroaromatic groups. Exact mass Fourier transform mass spectrometry (FT-MS) has demonstrated that their constituent molecules extent to ~500 Da and have unsaturation levels consistent with high degrees of both cyclization and aromaticity, favoring PANH-type structures.Despite the important literature on tholins, the chemical evolution of nitrogen-rich organics upon interaction with energetic particles has been largely unexplored. One study simulated in the laboratory how vacuum ultraviolet irradiation affects the tholins optical properties as probed by infrared spectroscopy [3]. This work provided evidence that photochemistry could deplete the sensitive primary and secondary amine functions while preserving nitrogen-bearing functionalities that are more strongly bound, such as tertiary amines, imines and nitriles. Adenine (C5H5N5) is a simple heterocyclic aromatic molecule that has been identified in Titan’s tholins [4]. Infrared spectroscopy of adenine samples irradiated by photons, electrons or ions over a wide energy range shows its destruction as well as the formation a solid residue probably of macromolecular nature [5,6]. However, neither the molecular content of the organic residue or the sputtering into the gas phase have been investigated so far.In this work, we have irradiated under ultra-high vacuum thin film samples of adenine. Adenine was deposited homogeneously in several hundred nm thin layers onto MgF2 or ZnSe windows [10]. Irradiation experiments were performed either at the ARIBE beam line at GANIL (Caen, France), at the SIDONIE isotope separator (Orsay, France) or at the HUN-REN Institute for Nuclear research (Atomki) in Debrecen, Hungary [7,8,9]. Adenine samples were irradiated with either Ne𝑞+, O𝑞+, OH𝑞+ or H2O𝑞+ at various energies from 10 to 70 keV, temperatures (150, 300 K), and fluences (up to 2x1015 ions.cm−2). Infrared absorption spectra of the adenine samples were obtained in situ during the irradiation with a FTIR spectrometer while the residual gas in the experimental chamber was measured with in-situ quadrupole mass spectrometry, analyzing the material that was sputtered into the gas phase during irradiation. The molecular content of the soluble phase of the irradiated samples was obtained with a very high-resolution mass spectrometer at the Institut de Planétologie et d’Astrophysique de Grenoble (France).We show that the energetic ion irradiation of the samples leads to their destruction, through both chemical processes forming new species in the solid phase and sputtering into the gas phase. The macromolecules detected in the solid phase far exceed the molecular mass of adenine, reaching up to m/z 500. They show great chemical diversity and can be expressed as (HCN)z-R families, where z can reach 17 and R can be C, H, N, NH, CH or CN. In total, nearly 100 individual families have been identified, 28 of which can be found in every irradiated sample. Their aromaticity equivalent is higher than that in other N rich samples such as Titan tholins and HCN-polymers, corresponding to polycyclic aromatic nitrogen-bearing hydrocarbons. A number of small adenine fragments, including N2, nitriles and hydrocarbons, are sputtered into the gas phase, throughout the irradiations. Larger species like intact adenine are only detected at the on-set of the irradiations.These experimental results suggest that ion deposition in Titan’s atmosphere may play a role in the rapid molecular growth occurring at high altitudes and should be considered in photochemical-microphysical models. AcknowledgmentsThis work is supported by the Programme National de Planétologie (PNP), the French National Research Agency in the framework of the "Investissements d’avenir” program (ANR-15-IDEX-02) and the generic call for proposals (ANR-22-CE49-0017). The experiments were performed at the Grand Accélérateur National d’Ions Lourds (GANIL) by means of the CIRIL Interdisciplinary Platform, part of CIMAP laboratory, Caen, France. We acknowledge the fundings from ANR IGLIAS grant ANR-13-BS05-0004 of the French Agence Nationale de la Recherche. INGMAR is a IAS-IJCLab facility funded by the French Programme National de Planétologie (PNP), Faculté des Sciences d’Orsay, Université Paris-Sud (Attractivité 2012), P2IO LabEx (ANR-10-LABX-0038) in the framework Investissements d’Avenir (ANR-11-IDEX-0003-01). We acknowledge the funding from Europlanet 2024 RI (under the grant agreement No 871149). References[1] V. Vuitton et al., In : Titan After Cassini-Huygens, 157 (2024)[2] M. L. Cable et al., Chem Rev, 112, 1882 (2012)[3] N. Carrasco et al., Nature Astronomy, 2, 489 (2018)[4] J. A. Sebree et al., Astrophys. J., 865, 133 (2018)[5] O. Poch et al., Icarus, 242, 50 (2014)[6] G. S. Vignoli Muniz et al., Astrobiology, 17, 298 (2017)[7] B. Augé et al., Rev. Sci. Instrum., 89, 075105 (2018)[8] N. Chauvin et al., Nucl. Instrum. Meth. A, 521, 149 (2004)[9] S. Biri et al., Eur. Phys. J. Plus, 136, 247 (2021)[10] K. Saïagh et al., Planet. Space Sci., 90, 90 (2014)

In Titan's atmosphere, the chemistry of simple hydrocarbons (e.g., CH4 and C2H2) and nitrogen bearing species (e.g., N2 and CN) represents an important link between molecular species and the ubiquitous organic haze that gives Titan its characteristic orange hue. Here we present a new search for two previously undetected molecules, triacetylene (C6H2) and the gas phase dicyanoacetylene (C4N2), using the Echelon-Cross-Echelle Spectrograph instrument on board the Stratospheric Observatory for Infrared Astronomy aircraft. We do not detect these two molecules but determine upper limits for their mixing ratios and column abundances. We find the 3 sigma upper limits on the uniform volume mixing ratio (VMR) above 100 km for C6H2 to be 4.3 x 10-11, which is lower than the photochemical model predictions. This new upper limit suggests that the growth of linear molecules is inhibited. We also put a strict upper limit on the uniform VMR for gas phase C4N2 above 125 km to be 1.0 x 10-10. This upper limit is well below the saturation mixing ratio at this altitude for C4N2 and greatly limits the feasibility of C4N2 forming ice from condensation.

Super-Earths and sub-Neptunes are the most common exoplanets, with a “radius valley” suggesting that super-Earths may form by shedding sub-Neptunes’ gaseous envelopes. Exoplanets that lie closer to the super-Earth side of the valley are more likely to have lost a significant fraction of their original H/He envelopes and become enriched in heavier elements, with CO _2 gaining in abundance. It remains unclear which types of haze would form in such atmospheres, potentially significantly affecting spectroscopic observations. To investigate this, we performed laboratory simulations of two CO _2 -rich gas mixtures (with 2000 times solar metallicity at 300 and 500 K). We found that under plasma irradiation organic hazes were produced at both temperatures, with a higher haze production rate at 300 K, probably because condensation occurs more readily at lower temperature. Gas-phase analysis demonstrates the formation of various hydrocarbons, oxygen- and nitrogen-containing species, including reactive gas precursors like C _2 H _4 , CH _2 O, and HCN, for haze formation. The compositional analysis of the haze particles reveals various functional groups and molecular formulas in both samples. The 500 K haze sample has larger average molecular sizes, a higher degree of unsaturation with more double or triple bonds present, and higher nitrogen content incorporated as N–H and C=N bonds, indicating different haze formation pathways. These findings not only improve the haze formation theories in CO _2 -rich exoplanet atmospheres but also offer important implications for the interpretation of future observational data.

Titan, Saturn’s largest satellite, maintains an atmosphere composed primarily of nitrogen (N _2 ) and methane (CH _4 ) that leads to complex organic chemistry. Some of the nitriles (CN-bearing organics) on Titan are known to have substantially enhanced ^15 N abundances compared to Earth and Titan’s dominant nitrogen (N _2 ) reservoir. The ^14 N/ ^15 N isotopic ratio in Titan’s nitriles can provide better constraints on the synthesis of nitrogen-bearing organics in planetary atmospheres as well as insights into the origin of Titan’s large nitrogen abundance. Using high signal-to-noise ratio (>13), disk-integrated observations obtained with the Atacama Large Millimeter/submillimeter Array Band 6 receiver (211–275 GHz), we measure the ^14 N/ ^15 N and ^12 C/ ^13 C isotopic ratios of acetonitrile (CH _3 CN) in Titan’s stratosphere. Using the NEMESIS, we derived the CH _3 CN/ ^13 CH _3 CN ratio to be 89.2 ± 7.0 and the CH _3 CN/CH _3 ^13 CN ratio to be 91.2 ± 6.0, in agreement with the ^12 C/ ^13 C ratio in Titan’s methane and other solar system species. We found the ^14 N/ ^15 N isotopic ratio to be 68.9 ± 4.2, consistent with previously derived values for HCN and HC _3 N, confirming an enhanced ^15 N abundance in Titan’s nitriles compared with the bulk atmospheric N _2 value of ^14 N/ ^15 N = 168, in agreement with chemical models incorporating isotope-selective photodissociation of N _2 at high altitudes.

Temperate sub-Neptune exoplanets could contain large inventories of water in various phases, such as water worlds with water-rich atmospheres or even oceans. Both space-based and ground-based observations have shown that many exoplanets likely also contain photochemically generated hazes. Haze particles are a key source of organic matter and may impact the evolution or origin of life. In addition, haze layers could provide a mechanism for lower-atmospheric shielding and ultimately atmospheric retention. Often orbiting close to M dwarf stars, these planets receive large amounts of radiation, especially during flaring events, which may strip away their atmospheres. M dwarf stars are known to have higher stellar activity than other types of stars, and stellar flares have the potential to accelerate atmospheric escape. In this work, we present the results from laboratory investigations of UV radiation effects simulating two different stellar flare energies on laboratory-produced exoplanet hazes made under conditions analogous to water-world atmospheres. We find that both simulated flares altered the overall transmittance and reflectance of the hazes, and higher-energy “flares” make those alterations more pronounced. On a larger scale, these laboratory-made hazes show potential signs of degradation over the simulated flaring period. Our results provide insight into the effects that stellar flaring events have on potential exoplanet haze composition and the ability for water-world-like exoplanets to retain their atmospheres.

Many sub-Neptune and super-Earth exoplanets are expected to develop metal-enriched atmospheres due to atmospheric loss processes such as photoevaporation or core-powered mass loss. Thermochemical equilibrium calculations predict that at high metallicity and a temperature range of 300–700 K, CO _2 becomes the dominant carbon species, and graphite may be the thermodynamically favored condensate under low-pressure conditions. Building on prior laboratory findings that such environments yield organic haze rather than graphite, we measured the transmittance spectra of organic haze analogs and graphite samples and computed their optical constants across the measured wavelength range from 0.4 to 25 μ m. The organic haze exhibits strong vibrational absorption bands, notably at 3.0, 4.5, and 6.0 μ m, while graphite shows featureless broadband absorption. The derived optical constants of haze and graphite provide the first data set for organic haze analogs formed in CO _2 -rich atmospheres and offer improved applicability over prior graphite data derived from bulk reflectance or ellipsometry. We implemented these optical constants into the Virga and PICASO cloud and radiative transfer models to simulate transit spectra for GJ 1214b. The synthetic spectra with organic hazes reproduce the muted spectral features in the near-infrared observed by Hubble and general trends observed by JWST for GJ 1214b, while graphite models yield flat spectra across the observed wavelengths. This suggests haze features may serve as observational markers of carbon-rich atmospheres, whereas graphite’s opacity could lead to radius overestimation, offering a possible explanation for superpuff exoplanets. Our work supplies essential optical to infrared data for interpreting observations of CO _2 -rich exoplanet atmospheres.

The complexity and origin of organic matter in carbonaceous chondrites has been a topic of interest for over 60 years1. This organic matter has been studied through the bulk, the Insoluble Organic Matter (IOM) and the Soluble Organic Matter (SOM) using different analytical techniques.The procedures for extracting the soluble fraction significantly influence the quantity and diversity of extracted organic matter, thereby impacting the interpretation of the data in terms of origin and evolution. They vary depending on the analytical approach (targeted or untargeted) and the analytical instruments used for the characterization2–4.So far, most of the work done on the analysis of organic matter from carbonaceous chondrites has focused on targeted approaches. For example, numerous studies have worked on the optimization of the extraction of water-soluble organic matter (such as amino acids, sugars, nucleobases…) usually extracted with boiling water and acid hydrolysis and then analysed by gas chromatography coupled to mass spectrometry (GC-MS)5–7. Other studies have worked on the solvent-soluble organic matter for the characterization of specific hydrocarbons and aromatics, also using GC-MS8,9. In 2010, Schmitt Kopplin et al. studied the influence of the extracting solvent on the resulting molecular diversity of the SOM using Ultra-High Resolution Mass Spectrometry, and were able to conclude that methanol was the most efficient extracting solvent10. No other untargeted study has focused on the impact of the extracting protocol since then. Similar conclusions can be drawn regarding the elemental and isotopic analysis of the SOM, that have mostly been studied using targeted approaches6,11,12. Untargeted elemental and isotopic analysis applied to SOM was used by Becker & Epstein in 198113, and was never systematically applied to other SOM extracts since then.In the present work, our objective is to implement an untargeted workflow to carry out comprehensive analyses of the soluble organic matter using mass spectrometry techniques.Firstly, to better understand the influence of chemical extraction on the resulting SOM, we are optimizing different parameters of the extraction procedure (pH, grain size, extraction time, solvent, etc.) and characterizing the resulting soluble organic fractions using a sample of Murchison (ME 2644 #23.13) allocated by the Field Museum. With Orbitrap Ultra-High Resolution Mass Spectrometry, we can assess qualitative information on the molecular diversity and mass distribution of the sample. Thus, the high mass resolution of this instrument (100 000 at m/z = 400) enables to conduct family analysis and to look for polymerization patterns14. We also aim to develop a new method to characterize the SOM with an Elemental Analyzer – Isotope Ratio Mass Spectrometry (EA-irMS). This technique will provide quantitative information on the elemental (%C, %N…) and isotopic (13C/12C, 15N/14N…) compositions of the sample, enabling comparisons with previous data on IOM and bulk compositions.With this untargeted workflow of combined analyses, we will provide new insights into the molecular diversity, mass distribution, and elemental composition of the SOM of carbonaceous chondrites. Later on, we will apply these procedures on CM chondrites having experienced various degrees of alteration. This will enable systematic comparison of the effect of post-accretion processes (aqueous alteration and thermal process) on the organic complexity. Moreover, having an optimized and standardized extraction procedure to characterize the SOM as a whole is important for working on pristine samples such as those from Bennu and Ryugu. [1] H. Studier, M., Hayatsu, R. & Anders, E. Origin of organic matter in early solar system—V. Further studies of meteoritic hydrocarbons and a discussion of their origin. Geochim. Cosmochim. Acta 36, 189–215 (1972).[2] Naraoka, H. et al. Soluble organic molecules in samples of the carbonaceous asteroid (162173) Ryugu. Science 379, eabn9033 (2023).[3] Gardinier, A. et al. Solid state CP/MAS 13C NMR of the insoluble organic matter of the Orgueil and Murchison meteorites: quantitative study. Earth Planet. Sci. Lett. 184, 9–21 (2000).[4] Cody, G. D., Alexander, C. M. O. & Tera, F. Solid-state (1H and 13C) nuclear magnetic resonance spectroscopy of insoluble organic residue in the Murchison meteorite: a self-consistent quantitative analysis. Geochim. Cosmochim. Acta 66, 1851–1865 (2002).[5] Martins, Z., Modica, P., Zanda, B. & d’Hendecourt, L. L. S. The amino acid and hydrocarbon contents of the Paris meteorite: Insights into the most primitive CM chondrite. Meteorit. Planet. Sci. 50, 926–943 (2015).[6] Hilts, R. W., Herd, C. D. K., Simkus, D. N. & Slater, G. F. Soluble organic compounds in the Tagish Lake meteorite. Meteorit. Planet. Sci. 49, 526–549 (2014).[7] Simkus, D. N. et al. New insights into the heterogeneity of the Tagish Lake meteorite: Soluble organic compositions of variously altered specimens. Meteorit. Planet. Sci. 54, 1283–1302 (2019).[8] Kalpana, M. S., Babu, E. V. S. S. K., Mani, D., Tripathi, R. P. & Bhandari, N. Polycyclic aromatic hydrocarbons in the Mukundpura (CM2) Chondrite. Planet. Space Sci. 198, 105177 (2021).[9] Cronin, J. R. & Pizzarello, S. Aliphatic hydrocarbons of the Murchison meteorite. Geochim. Cosmochim. Acta 54, 2859–2868 (1990).[10] Schmitt-Kopplin, P. et al. High molecular diversity of extraterrestrial organic matter in Murchison meteorite revealed 40 years after its fall. Proc. Natl. Acad. Sci. 107, 2763–2768 (2010).[11] Krishnamurthy, R. V., Epstein, S., Cronin, J. R., Pizzarello, S. & Yuen, G. U. Isotopic and molecular analyses of hydrocarbons and monocarboxylic acids of the Murchison meteorite. Geochim. Cosmochim. Acta 56, 4045–4058 (1992).[12] Huang, Y., Aponte, J. C., Zhao, J., Tarozo, R. & Hallmann, C. Hydrogen and carbon isotopic ratios of polycyclic aromatic compounds in two CM2 carbonaceous chondrites and implications for prebiotic organic synthesis. Earth Planet. Sci. Lett. 426, 101–108 (2015).[13] Becker, R. H. & Epstein, S. Carbon, hydrogen and nitrogen isotopes in solvent-extractable organic matter from carbonaceous chondrites. Geochim. Cosmochim. Acta 46, 97–103 (1982).[14] Isa, J. et al. Aqueous Alteration on Asteroids Simplifies Soluble Organic Matter Mixtures. Astrophys. J. Lett. 920, L39 (2021).

The chirality of amino acids in extraterrestrial materials may provide an insight into the origin of the essential l-enantiopure amino acids in the terrestrial biosphere. In 2020, the Hayabusa2 mission succeeded in bringing back surface materials from the C-type asteroid (162173) Ryugu to the Earth. Amino acids were one of the targeted organic molecules to be studied in the Ryugu samples. To analyze the various structural isomers of amino acids, which were expected to be present, from the limited amount of the returned samples, the development of a highly-sensitive and selective analytical method was necessary. In the present study, a three-dimensional high-performance liquid chromatography (3D-HPLC) system has been developed for the enantioselective determination of five proteinogenic and three non-proteinogenic amino acids in the Ryugu samples, in which amino acids in the sample were separated by reversed-phase, anion-exchange and enantioselective columns after the fluorescence derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiozole. The applicability of the analytical system to the extraterrestrial samples was evaluated by analyzing several types of carbonaceous meteorites before applying the system to the Ryugu samples. In the analysis of the Ryugu samples, all of the target amino acids were successfully determined quantitatively. Non-proteinogenic amino acids including 2-amino-n-butyric acid, isovaline and norvaline, rarely present in the terrestrial environment, were found as almost racemic mixtures with 47.1 to 55.2%l.

The James Webb Space Telescope (JWST) has begun its scientific mission, which includes the atmospheric characterization of transiting exoplanets. Some of the first exoplanets to be observed by JWST have equilibrium temperatures below 1,000 K, which is a regime where photochemical hazes are expected to form. The optical properties of these hazes, which control how they interact with light, are critical for interpreting exoplanet observations, but relevant experimental data are not available. Here we measure the density and optical properties of organic haze analogues generated in water-rich exoplanet atmosphere experiments. We report optical constants (0.4 to 28.6 μm) of organic haze analogues for current and future observational and modelling efforts covering the entire wavelength range of JWST instrumentation and a large part of Hubble. We use these optical constants to generate hazy model atmospheric spectra. The synthetic spectra show that differences in haze optical constants have a detectable effect on the spectra, impacting our interpretation of exoplanet observations. This study emphasizes the need to investigate the optical properties of hazes formed in different exoplanet atmospheres and establishes a practical procedure for determining such properties. The reported optical properties of organic hazes produced in water-rich exoplanet atmospheres differ from those in nitrogen-rich atmospheres. Such differences have a detectable effect on the spectra, impacting interpretation of JWST observations.

The discovery of heavy organic anions by in situ measurements using Cassini’s CAPS Electron Spectrometer (ELS) in Titan’s ionosphere was an unexpected result of the Cassini mission (Coates et al, 2007, Waite et al, 2007); a complete reconsideration of chemical processes in this enigmatic atmosphere was necessary as a result. These negative ions can be associated with complex hydrocarbon and nitrile processes which are linked to haze formation at lower altitudes. Cassini’s CAPS ELS observed negative ions during Titan encounters at altitudes below 1400 km. The ions can reach masses over 13,000 amu/q (Coates et al., 2009), while recurring peaks in the mass spectra can be used to identify different mass groups as reported by Coates et al. (2007) and Wellbrock et al. (2013, 2019). Studying density and mass trends of these groups helps to identify controlling factors of the production and destruction mechanisms, and ultimately to improve our understanding of how organic macromolecules can be produced by naturally occurring abiotic processes. In this study we examine the effects different solar zenith angle conditions might have on both the light and heavy negative ion mass groups, and consider the role of processes such as photodetachment and dissociative electron attachment. We also compare the negative ion data with RPWS electron measurements and discuss the possible implications associated with the above processes.