Space-Weathering of Solar System Bodies: A Laboratory Perspective

Ionizing radiation exposure on Arrokoth shapes a sugar world

The Kuiper Belt object (KBO) Arrokoth, the farthest object in the Solar System ever visited by a spacecraft, possesses a distinctive reddish surface and is characterized by pronounced spectroscopic features associated with methanol. However, the fundamental processes by which methanol ices are converted into reddish, complex organic molecules on Arrokoth's surface have remained elusive. Here, we combine laboratory simulation experiments with a spectroscopic characterization of methanol ices exposed to proxies of galactic cosmic rays (GCRs). Our findings reveal that the surface exposure of methanol ices at 40 K can replicate the color slopes of Arrokoth. Sugars and their derivatives (acids, alcohols) with up to six carbon atoms, including glucose and ribose-fundamental building block of RNA-were ubiquitously identified. In addition, polycyclic aromatic hydrocarbons (PAHs) with up to six ring units (13C22H12) were also observed. These sugars and their derivatives along with PAHs connected by unsaturated linkers represent key molecules rationalizing the reddish appearance of Arrokoth. The formation of abundant sugar-related molecules dubs Arrokoth as a sugar world and provides a plausible abiotic preparation route for a key class of biorelevant molecules on the surface of KBOs prior to their delivery to prebiotic Earth.

Use of Gaussian-Type Functions for Describing Fast Ion-Matter Irradiation with Time-Dependent Density Functional Theory

The electronic stopping power is an observable property that quantifies the ability of swift ions to penetrate matter to transfer energy to the electron cloud. The recent literature has proven the value of Real-Time Time-Dependent Density Functional Theory to accurately evaluate this property from first-principles, but questions remain regarding the capability of computer codes relying on atom-centered basis functions to capture the physics at play. In this Perspective, we draw attention to the fact that irradiation by swift ions triggers electron emission into the continuum, especially at the Bragg peak. We investigate the ability of Gaussian atomic orbitals (AOC), which were fitted to mimic continuum wave functions, to improve electronic stopping power predictions. AOC are added to standard correlation-consistent basis sets or STO minimal basis sets. Our benchmarks for water irradiation by fast protons clearly advocate for the use of AOC, especially near the Bragg peak. We show that AOC only need to be placed on the molecules struck by the ion. The number of AOC that are added to the usual basis set is relatively small compared to the total number of atomic orbitals, making the use of such a basis set an excellent choice from a computational cost point of view. The optimum basis set combination is applied for the calculation of the stopping power of a proton in water with encouraging agreement with experimental data.

Endogenous CO2 ice mixture on the surface of Europa and no detection of plume activity

Jupiter's moon Europa has a subsurface ocean beneath an icy crust. Conditions within the ocean are unknown, and it is unclear whether it is connected to the surface. We observed Europa with the James Webb Space Telescope (JWST) to search for active release of material by probing its surface and atmosphere. A search for plumes yielded no detection of water, carbon monoxide, methanol, ethane, or methane fluorescence emissions. Four spectral features of carbon dioxide (CO2) ice were detected; their spectral shapes and distribution across Europa's surface indicate that the CO2 is mixed with other compounds and concentrated in Tara Regio. The 13CO2 absorption is consistent with an isotopic ratio of 12C/13C = 83 ± 19. We interpret these observations as indicating that carbon is sourced from within Europa.

Complex organosulfur molecules on comet 67P: Evidence from the ROSINA measurements and insights from laboratory simulations

The ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument aboard the Rosetta mission revolutionized our understanding of cometary material composition. One of Rosetta's key findings is the complexity of the composition of comet 67P/Churyumov-Gerasimenko. Here, we used ROSINA data to analyze dust particles that were volatilized during a dust event in September 2016 and report the detection of large organosulfur species and an increase in the abundances of sulfurous species previously detected in the coma. Our data support the presence of complex sulfur-bearing organics on the surface of the comet. In addition, we conducted laboratory simulations that show that this material may have formed from chemical reactions that were initiated by the irradiation of mixed ices containing H₂S. Our findings highlight the importance of sulfur chemistry in cometary and precometary materials and the possibility of characterizing organosulfur materials in other comets and small icy bodies using the James Webb Space Telescope.

Processing of methane and acetylene ices by galactic cosmic rays and implications to the color diversity of Kuiper Belt objects

Kuiper Belt objects exhibit a wider color range than any other solar system population. The origin of this color diversity is unknown, but likely the result of the prolonged irradiation of organic materials by galactic cosmic rays (GCRs). Here, we combine ultrahigh-vacuum irradiation experiments with comprehensive spectroscopic analyses to examine the color evolution during GCR processing methane and acetylene under Kuiper Belt conditions. This study replicates the colors of a population of Kuiper Belt objects such as Makemake, Orcus, and Salacia. Aromatic structural units carrying up to three rings as in phenanthrene (C14H10), phenalene (C9H10), and acenaphthylene (C12H8), of which some carry structural motives of DNA and RNA connected via unsaturated linkers, were found to play a key role in producing the reddish colors. These studies demonstrate the level of molecular complexity synthesized of GCR processing hydrocarbon and hint at the role played by irradiated ice in the early production of biological precursor molecules.

Evaluation of morpho-physiological responses and genotoxicity in Eruca sativa (Mill.) grown in hydroponics from seeds exposed to X-rays

Due to its potential applications in cultivated plants, ionizing radiation (IR) and its effect on organisms is increasingly studied. Here we measured the effects of ionizing radiation on Eruca sativa by analyzing plants from irradiated seeds (1 and 10 Gy) grown in hydroponics. We measured several morpho-physiological traits and genotoxicity. Radiation stress induced a noticeable variability of the morpho-physiological traits highlighting decreased plant vigor. Shoot length and leaf number were significantly higher in 1 Gy-treated samples, whereas root length was significantly higher in 10 Gy treated plants. Stomata number significantly increased with IR dose, whereas both pigment and Rubisco content decreased under radiation stress. Phenol content significantly increased in 1 Gy treated samples, otherwise from total antioxidants, which were not different from control. Most results could find a feasible explanation in a hormesis-like pattern and in a decreased plant vigor under radiation stress. IR induced genotoxic damage, evaluated by ISSR markers, in 15 day old leaves; specifically, a severe decrease in the genome template stability was observed. However, a partial recovery occurred after 2 weeks, especially under the lowest dose (i.e., 1 Gy), suggesting that DNA damage detection and repair mechanisms are active. Pigment content and genotoxic damage may serve as proxies for evaluating plant responses to IR stress, since they show univocal dose-dependent trends. The use of more checkpoints for analyses and more doses over a wider range, as well as the focus on different metabolites, could help elucidate plant response in terms of morpho-physiological changes.

Nitrile regio-synthesis by Ni centers on a siliceous surface: implications in prebiotic chemistry

By means of quantum chemistry (PBE0/def2-TZVPP; DLPNO-CCSD(T)/cc-pVTZ) and small, but reliable models of Polyhedral Oligomeric Silsesquioxanes (POSS), an array of astrochemically-relevant catalysis products, related to prebiotic and origin of life chemistry, has been theoretically explored. In this work, the heterogeneous phase hydrocyanation reaction of an unsaturated CC bond (propene) catalyzed by a Ni center complexed to a silica surface is analyzed. Of the two possible regioisomers, the branched iso-propyl-cyanide is thermodynamically and kinetically preferred over the linear n-propyl-cyanide (T = 200 K). The formation of nitriles based on a regioselective process has profound implications on prebiotic and origin of life chemistry, as well as deep connections to terrestrial surface chemistry and geochemistry.

Indirect X-ray photodesorption of 15N2 and 13CO from mixed and layered ices

X-ray photodesorption yields of 15N2 and 13CO are derived as a function of the incident photon energy near the N (~ 400 eV) and O K-edge (~ 500 eV) for pure 15N2 ice and mixed 13CO:15N2 ices. The photodesorption spectra from the mixed ices reveal an indirect desorption mechanism for which the desorption of 15N2 and 13CO is triggered by the photo-absorption of respectively 13CO and 15N2. This mechanism is confirmed by the X-ray photodesorption of 13CO from a layered 13CO/15N2 ice irradiated at 401 eV, on the N 1s -> π* transition of 15N2. This latter experiment enables to quantify the relevant depth involved in the indirect desorption process, which is found to be 30 - 40 ML in that case. This value is further related to the energy transport of Auger electrons emitted from the photo-absorbing 15N2molecules that scatter towards the ice surface, inducing the desorption of 13CO. The photodesorption yields corrected from the energy that can participate to the desorption process (expressed in molecules desorbed by eV deposited) do not depend on the photon energy hence neither on the photo-absorbing molecule nor on its state after Auger decay. This demonstrates that X-ray induced electron stimulated desorption (XESD), mediated by Auger scattering, is the dominant process explaining the desorption of 15N2 and 13CO from the ices studied in this work.

Space Weathering: Processing Velocities in Organic Materials as a Function of Electron Beam Energies-Solar Electron Erosion Rate Application

Samples of α-glycine (α-GLY; 230-350 nm) were irradiated in laboratory as a function of electron beam energies (0.25, 0.50, and 1.00 keV) at room temperature (293-295 K). The evolution of α-glycine irradiation process was monitored in real time by infrared spectroscopy (Fourier transform infrared - FTIR), through specific spectral bands: 2610, 2124, 1410, and 1333 cm^-1. A phenomenological model is proposed to describe the column density decay when thick organic samples are processed by ionizing beams. The α-glycine radiolysis has exhibited transient and stationary modes in such thickness films. The first stage is mainly described by one exponential decay, whereas the latter foremost decays linearly; compaction processes have been neglected; glycine dissociation and sputtering processes are assumed to be responsible for the damage caused by the electron beam impact through the solid film. The second (stationary) stage is due to equilibrium between a partially shielded bulk radiolysis and sputtering of protective layers. The decay rates are measured for the transient and stationary modes and allow determining the processing velocity of the samples as a function of the electron beam energy. Finally, the model is applied to space weathering to find out the typical sputtering rate of organic compounds on the surface of astrophysical analogs with no protection layers attacked by solar wind (SW) electrons at ≈1 AU. Although the velocity of processing materials in SW has natural competing effects, such as regolith overturn by impacts of micro- and macrometeorites and downslope motion of material that is unstable due to changes in the geopotential of the airless bodies (e.g., asteroid 101955 Bennu), these competing processes are not included in the simulations presented here.

Irradiation of Phenylalanine at 300 K by MeV Ions

Phenylalanine (Phe) is an amino acid that has been identified in carbonaceous meteorites; its formation mechanism in space is unknown, and its radioresistance has been the subject of investigation. This work aims at studying, in the laboratory, the Phe radiolysis by cosmic analogues. The Phe destruction rate, at 300 K, is measured for H, He, and N ion beam irradiation in the 0.5 to 2 kinetic MeV range. Fourier transform infrared (FTIR) spectroscopy was employed to monitor the molecular degradation as a function of fluence. The Phe apparent destruction cross-section, σ^ap_d, which includes radiolysis and sputtering processes, is determined to be proportional to the electronic stopping power, S_e. The measured parameter D₀ = 14.3 ± 2.2 eV/molec in the relationship, and σdap = S_e/D₀ is interpreted as the mean absorbed dose necessary to dissociate or eject a Phe molecule. The Phe half-life in the interstellar medium is predicted to be about 10 million years, H⁺ ions the main destructive cosmic ray constituent.

X-Ray induced desorption and photochemistry in CO ice

We report an investigation of X-ray induced desorption of neutrals, cations and anions from CO ice. The desorption of neutral CO, by far the most abundant, is quantified and discussed within the context of its application to astrochemistry. The desorption of many different cations, including large cations up to the mass limit of the spectrometer, is observed. In contrast, the only desorbing anions detected are O- and C-. The desorption mechanisms of all these species are discussed with the aid of their photodesorption spectrum. The evolution of the X-ray absorption spectrum shows significant chemical modifications of the ice upon irradiation, which along with the desorption of large cations gives a new insight into X-ray induced photochemistry in CO ice.

First-Principles Simulations of Biological Molecules Subjected to Ionizing Radiation

Ionizing rays cause damage to genomes, proteins, and signaling pathways that normally regulate cell activity, with harmful consequences such as accelerated aging, tumors, and cancers but also with beneficial effects in the context of radiotherapies. While the great pace of research in the twentieth century led to the identification of the molecular mechanisms for chemical lesions on the building blocks of biomacromolecules, the last two decades have brought renewed questions, for example, regarding the formation of clustered damage or the rich chemistry involving the secondary electrons produced by radiolysis. Radiation chemistry is now meeting attosecond science, providing extraordinary opportunities to unravel the very first stages of biological matter radiolysis. This review provides an overview of the recent progress made in this direction, focusing mainly on the atto- to femto- to picosecond timescales. We review promising applications of time-dependent density functional theory in this context.

Role of Suprathermal Chemistry on the Evolution of Carbon Oxides and Organics within Interstellar and Cometary Ices

ConspectusLaboratory-based experimental astrochemistry regularly entails simulation of astrophysical environments whereby low-temperature condensed ices are exposed to radiation from ultraviolet (UV) photons or energetic charged particles. Here, excited atoms/radicals are generated that are not in thermal equilibrium with their surroundings (i.e., they are nonthermal, or suprathermal). These species can surpass typical reaction barriers and partake in unusual chemical processes leading to novel molecular species. Often, these are uniquely observable under low-temperature conditions where the surrounding ice matrix can stabilize excited intermediates that would otherwise fall apart. Fourier-transform infrared (FTIR) spectroscopy is traditionally utilized to monitor the evolution of chemical species within ices in situ during radiolysis. Yet, the characterization and quantification of novel species and radicals formed within astrophysical ices is often hindered since many of these cannot be synthesized by traditional synthetic chemistry. Computational approaches can provide fundamental vibrational frequencies and isotopic shifts to help aid in assignments alongside infrared intensities and Raman activities to quantify levels of production. In this Account, we begin with a brief history and background regarding the composition and radiation of interstellar ices. We review details of some of the early work on carbon oxides produced during the radiolysis of pure carbon dioxide ices and contention around the carrier of an absorption feature that could potentially be a product of radiation. We then provide an overview of current and emerging experimental methodologies and some of the chemistries that occur via nonthermal processes during radiolysis of low-temperature ices. Next, we detail computational approaches to reliably predict vibrational frequencies, infrared intensities, and Raman activities based on our recent work. Our focus then turns to studies on the formation of complex organics and carbon oxides, highlighting those aided by computational approaches and their role in astrochemistry. Some recent controversies regarding assignments alongside our recent results on the characterization of novel carbon oxide species are discussed. We present an argument for the potential role of carbon oxides within cometary ices as parent molecular species for small volatiles. We provide an overview of some of the complex organic species that can be formed within interstellar and cometary ices that contain either carbon monoxide or carbon dioxide. We examine how Raman spectroscopy could potentially be leveraged to help determine and characterize carbon oxides in future experiments as well as how computational approaches can aid in these assignments. We conclude with brief remarks on future directions our research group is taking to unravel astrochemically relevant carbon oxides using combined computational and experimental approaches.

Quantum Chemical Cluster Studies of Cation-Ice Reactions for Astrochemical Applications: Seeking Experimental Confirmation

ConspectusInterstellar clouds and the outer reaches of protostellar and protoplanetary systems are very cold environments where chemistry is limited to processes that have little or no reaction barrier (in the absence of external energy input). This account reviews what is known about cation-ice reactions, which are not currently incorporated in astrochemical network models. Quantum chemical cluster calculations using density functional theory have shown that barrierless reactions can occur when gas phase cations such as HCO⁺, OH⁺, CH₃⁺, and C⁺ are deposited on an icy grain mantle with energies commensurate with other gas phase species. When cations react with molecules on ice surfaces, the pathways and products often differ significantly from gas phase chemistry due to the involvement of water and other molecules in the ice. The reactions studied to date have found pathways to abundant and important astromolecules such as methanol, formic acid, and carbon dioxide that are very favorable and may be more efficient pathways than gas phase processes. Other products that can be produced include glycolonitrile, its precursors, and related isocyanide compounds. This account describes for the first time ice surface reactions between the carbon cation, C⁺, and two common astromolecules, methanol (CH₃OH) and formic acid (HCOOH), which can yield precursors to glyoxal, hydroxyketene, vinyl alcohol, and acetaldehyde. The quantum chemical methodology used to explore reaction surfaces is also used to predict both vibrational and electronic spectra of reactant and product ices, which offers guidance for possible experimental studies of these reactions. While theoretical calculations indicate that cation-ice reactions are efficient and offer novel pathways to important astrochemical compounds, experimental confirmation would be very welcome. Cations and ice-covered grain mantles are certainly present in cold astrophysical environments. The account concludes with a discussion of how cation-ice reactions could be incorporated into reaction network models of the formation and destruction of molecules in interstellar clouds and protoplanetary systems. Further studies will involve characterizing additional rcactions and more extensive treatment of the most important cation-ice reactions to better ascertain reaction branching outcomes.

Analytical methodology to evaluate the Terrestrial Weathering of Libyan Desert Glasses and Darwin Glasses after their formation

Libyan Desert Glasses (LDGs) and Darwin Glasses (DGs) are impact glasses produced by the impact of an extraterrestrial body into the Earth million years ago. LDGs were formed in the Libyan Desert (Africa) and DGs in Tasmania (Australia). From their formation, they have suffered terrestrial weathering processes due to their interaction with the environment. This is the first work that has evaluated their weathering processes according to their composition, the surrounding environment, and the climate. An innovative methodology based on the leaching of organic and inorganic ions and chemical modeling simulations was employed. Inductively coupled plasma-mass spectrometry (ICP-MS), ionic chromatography (IC), and solid-phase microextraction (SPME), and head space (HS) injections coupled to gas chromatography and mass spectrometry (GC-MS) detection were used. As a result, soluble organic compounds such as oxalates, n-hexadecanoic acid, and 4-chlorobenzalacetone were detected. The inorganic ions suffered a similar process, going inside the body of glasses and precipitating the corresponding salts when water evaporated. As these compounds are polar, they were probably transported by infiltration waters from outside the glasses, remaining inside in the pores, cavities, or cracks of the glasses during thousands of years. In the case of the DGs, it could be observed that under the oxidizing conditions of the terrestrial atmosphere, sulfides present in some samples transformed into sulfates. Finally, this methodology could be applied in other extraterrestrial materials discovered in deserts, ice fields, or in locations with great living activity like those of Tasmania.

Compaction and Destruction Cross-Sections for α-Glycine from Radiolysis Process via 1.0 keV Electron Beam as a Function of Temperature

Glycine is an amino acid that has already been detected in space. It is relevant to estimate its resistance under cosmic radiation. In this way, a sublimate of glycine in α-form on KBr substrate was exposed in the laboratory to a 1.0 keV electron beam. The radiolysis study was performed at 40 K, 80 K, and 300 K sample temperatures. These temperatures were chosen to cover characteristics of the outer space environment. The evolution of glycine compaction and degradation was monitored in real time by infrared spectroscopy (Fourier-transform infrared) by investigation in the spectral ranges of 3500-2100, 1650-1200, and 950-750 cm^-1. The compaction cross-section increases as the glycine temperature decreases. The glycine film thickness layer of ∼160 nm was depleted completely after ∼15 min at 300 K under irradiation with ∼1.4 μA beam current on the target, whereas the glycine depletion at 40 K and 80 K occurred after about 4 h under similar conditions. The destruction cross-section at room temperature is found to be (13.8 ± 0.2) × 10^-17 cm², that is, about 20 times higher than the values for glycine depletion at lower temperatures (<80 K). Emerging and vanishing peak absorbance related to OCN^- and CO bands was observed in 2230-2100 cm^-1 during the radiolysis at 40 K and 80 K. The same new IR bands appear in the range of 1600-1500, 1480-1370, and 1350-1200 cm^-1 after total glycine depletion for all temperature configurations. A strong N-H deformation band growing at 1510 cm^-1 was observed only at 300 K. Finally, the destruction cross-section associated to tholin decay at room temperature is estimated to be (1.30 ± 0.05) × 10^-17 cm². In addition, a correlation between the formation cross-sections for daughter and granddaughter molecules at 300 K is also obtained from the experimental data.

Detection of ammonia on Pluto's surface in a region of geologically recent tectonism

We report the detection of ammonia (NH3) on Pluto's surface in spectral images obtained with the New Horizons spacecraft that show absorption bands at 1.65 and 2.2 μm. The ammonia signature is spatially coincident with a region of past extensional tectonic activity (Virgil Fossae) where the presence of H2O ice is prominent. Ammonia in liquid water profoundly depresses the freezing point of the mixture. Ammoniated ices are believed to be geologically short lived when irradiated with ultraviolet photons or charged particles. Thus, the presence of NH3 on a planetary surface is indicative of a relatively recent deposition or possibly through exposure by some geological process. In the present case, the areal distribution is more suggestive of cryovolcanic emplacement, however, adding to the evidence for ongoing geological activity on Pluto and the possible presence of liquid water at depth today.

A vacuum ultraviolet photoionization study on the formation of methanimine (CH2NH) and ethylenediamine (NH2CH2CH2NH2) in low temperature interstellar model ices exposed to ionizing radiation

Methylamine (CH3NH2) and methanimine (CH2NH) represent essential building blocks in the formation of amino acids in interstellar and cometary ices. In our study, by exploiting isomer selective detection of the reaction products via photoionization coupled with reflectron time of flight mass spectrometry (Re-TOF-MS), we elucidate the formation of methanimine and ethylenediamine (NH2CH2CH2NH2) in methylamine ices exposed to energetic electrons as a proxy for secondary electrons generated by energetic cosmic rays penetrating interstellar and cometary ices. Interestingly, the two products methanimine and ethylenediamine are isoelectronic to formaldehyde (H2CO) and ethylene glycol (HOCH2CH2OH), respectively. Their formation has been confirmed in interstellar ice analogs consisting of methanol (CH3OH) which is ioselectronic to methylamine. Both oxygen-bearing species formed in methanol have been detected in the interstellar medium (ISM), while for methanimine and ethylenediamine only methanimine has been identified so far. In comparison with the methanol ice products and our experimental findings, we predict that ethylenediamine should be detectable in these astronomical sources, where methylamine and methanimine are present.

Extraterrestrial prebiotic molecules: photochemistryvs.radiation chemistry of interstellar ices

Photochemistry and radiation chemistry of interstellar ices lead to the synthesis of prebiotic molecules which may be delivered to planets by meteorites and/or comets.

Glycine formation in CO2:CH4:NH3 ices induced by 0-70 eV electrons

Glycine (Gly), the simplest amino-acid building-block of proteins, has been identified on icy dust grains in the interstellar medium, icy comets, and ice covered meteorites. These astrophysical ices contain simple molecules (e.g., CO₂, H₂O, CH₄, HCN, and NH₃) and are exposed to complex radiation fields, e.g., UV, γ, or X-rays, stellar/solar wind particles, or cosmic rays. While much current effort is focused on understanding the radiochemistry induced in these ices by high energy radiation, the effects of the abundant secondary low energy electrons (LEEs) it produces have been mostly assumed rather than studied. Here we present the results for the exposure of multilayer CO₂:CH₄:NH₃ ice mixtures to 0-70 eV electrons under simulated astrophysical conditions. Mass selected temperature programmed desorption (TPD) of our electron irradiated films reveals multiple products, most notably intact glycine, which is supported by control measurements of both irradiated or un-irradiated binary mixture films, and un-irradiated CO₂:CH₄:NH₃ ices spiked with Gly. The threshold of Gly formation by LEEs is near 9 eV, while the TPD analysis of Gly film growth allows us to determine the "quantum" yield for 70 eV electrons to be about 0.004 Gly per incident electron. Our results show that simple amino acids can be formed directly from simple molecular ingredients, none of which possess preformed C-C or C-N bonds, by the copious secondary LEEs that are generated by ionizing radiation in astrophysical ices.

Electron-induced origins of prebiotic building blocks of sugars: mechanism of self-reactions of a methanol anion dimer

Reactions of methanol dimers in interstellar medium driven by low energy irradiation may lead to prebiotic precursors.

A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules

Complex organic molecules such as sugars and amides are ubiquitous in star- and planet-forming regions, but their formation mechanisms have remained largely elusive until now. Here we show in a combined experimental, computational, and astrochemical modeling study that interstellar aldehydes and enols like acetaldehyde (CH3CHO) and vinyl alcohol (C2H3OH) act as key tracers of a cosmic-ray-driven nonequilibrium chemistry leading to complex organics even deep within low-temperature interstellar ices at 10 K. Our findings challenge conventional wisdom and define a hitherto poorly characterized reaction class forming complex organic molecules inside interstellar ices before their sublimation in star-forming regions such as SgrB2(N). These processes are of vital importance in initiating a chain of chemical reactions leading eventually to the molecular precursors of biorelevant molecules as planets form in their interstellar nurseries.

AstRoMap European Astrobiology Roadmap

The European AstRoMap project (supported by the European Commission Seventh Framework Programme) surveyed the state of the art of astrobiology in Europe and beyond and produced the first European roadmap for astrobiology research. In the context of this roadmap, astrobiology is understood as the study of the origin, evolution, and distribution of life in the context of cosmic evolution; this includes habitability in the Solar System and beyond. The AstRoMap Roadmap identifies five research topics, specifies several key scientific objectives for each topic, and suggests ways to achieve all the objectives. The five AstRoMap Research Topics are • Research Topic 1: Origin and Evolution of Planetary Systems • Research Topic 2: Origins of Organic Compounds in Space • Research Topic 3: Rock-Water-Carbon Interactions, Organic Synthesis on Earth, and Steps to Life • Research Topic 4: Life and Habitability • Research Topic 5: Biosignatures as Facilitating Life Detection It is strongly recommended that steps be taken towards the definition and implementation of a European Astrobiology Platform (or Institute) to streamline and optimize the scientific return by using a coordinated infrastructure and funding system.

Electrons, excitons and hydrogen bonding: electron-promoted desorption from molecular ice surfaces

Desorption of benzene from methanol and diethyl ether ices during irradiation with 250 eV electrons is reported and compared with our previous work on benzene/water ices to highlight the role of hydrogen bonding in excitation transport.

Non-thermal ion desorption from an acetonitrile (CH3CN) astrophysical ice analogue studied by electron stimulated ion desorption

Non-thermal desorption by electron impact constitutes an important route by which neutral and ionic fragments from simple nitrile-bearing ices may be delivered back to the gas-phase of astrophysical environments, contributing to the production of more complex molecules.

Leaf anatomy and photochemical behaviour of Solanum lycopersicum L. plants from seeds irradiated with low-LET ionising radiation

Plants can be exposed to ionising radiation not only in Space but also on Earth, due to specific technological applications or after nuclear disasters. The response of plants to ionising radiation depends on radiation quality/quantity and/or plant characteristics. In this paper, we analyse some growth traits, leaf anatomy, and ecophysiological features of plants of Solanum lycopersicum L. "Microtom" grown from seeds irradiated with increasing doses of X-rays (0.3, 10, 20, 50, and 100 Gy). Both juvenile and compound leaves from plants developed from irradiated and control seeds were analysed through light and epifluorescence microscopy. Digital image analysis allowed quantifying anatomical parameters to detect the occurrence of signs of structural damage. Fluorescence parameters and total photosynthetic pigment content were analysed to evaluate the functioning of the photosynthetic machinery. Radiation did not affect percentage and rate of seed germination. Plants from irradiated seeds accomplished the crop cycle and showed a more compact habitus. Dose-depended tendencies of variations occurred in phenolic content, while other leaf anatomical parameters did not show distinct trends after irradiation. The sporadic perturbations of leaf structure, observed during the vegetative phase, after high levels of radiation were not so severe as to induce any significant alterations in photosynthetic efficiency.

Radiation processing of formamide and formamide:water ices on silicate grain analogue

Lyman-α (121.6 nm) photon and 1 keV electron-beam irradiation of pure HCONH2 (FA) ice and H2O:HCONH2 ice mixtures on high-surface-area SiO2 nanoparticles have been investigated with FT-IR spectroscopy and temperature programmed desorption (TPD). Lyman-α photolysis of pure amorphous FA ice grown at 70 K and crystalline FA ice produced by annealing to 165 K gives spectral signatures between 2120 and 2195 cm(-1) that we assign primarily to OCN(-) and CO. The OCN(-) and CO yields are ∼25% less abundant for crystalline FA ice. Photon and electron processing also produces H2 that is released from the ice between ∼90 and 140 K. A decrease in the H2 TPD peak is seen for irradiated crystalline HCONH2 ice. Lyman-α photolysis of H2O:HCONH2 mixed ices increases OCN(-) and CO production, suggesting a catalytic role of H2O. Also, for pure FA, 1 keV electron irradiation slightly increases the yield of OCN(-), while CO decarboxylation is selectively prevented. CO is also not produced in H2O:HCONH2 ices upon electron irradiation. Dissociative ionization, direct dissociative excitation, and dissociative electron attachment (DEA) channels are accessible in the Lyman-α (121.6 nm) photon and 1 keV electron-beam energy range. DEA energetically favors OCN(-) and H(-) formation, with the latter leading to H2 formation. The FA fragment product identities, yields, and branching ratios are considerably different relative to the gas phase and depend upon the radiation type, ice structure, and the presence of SiO2 nanoparticles. The latter may increase ion-electron recombination and radical recombination rates. The main products observed suggest very different condensed-phase dissociation channels from those reported for gas-phase dissociation. Formation of ions/products from FA is not negligible upon Lyman-α photolysis or electron irradiation, both of which could process ices in interstellar regions as well as in Titan's atmosphere.

Hydrogenation processes from hydrogen peroxide: an investigation in Ne matrix for astrochemical purposes

Hydrogenation processes of hydrogen peroxide leading to the formation of water.