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Project Overview: Interest in Near-Earth Asteroids (NEAs) has rapidly grown in recent decades. The motivation is threefold: first, their proximity allows us to discover and investigate small bodies down to the metre-size, thus enhancing our understanding of the mechanisms underlying planetary formation; second, such information is also critical to mitigate their threat of collision with the Earth; third, their near-future exploitation can exponentially expand the natural resources available to humankind.Ground-based observations of thousands of NEAs have revealed the striking diversity existing within this population in terms of physical properties. So far, only a handful of NEAs have been visited by space missions: each of them provided unexpected discoveries and huge steps forward in our understanding of planetary sciences.Following the Near-Earth Space Trekker (NEST) proposal selected by ESA for the Phase 2 of the 2018 Call for a Fast mission, and the Asteroid Nodal Intersection Multiple Encounters (ANIME) proposal which passed the technical and financial screenings of the 2020 ASI Call for future CubeSat missions, here we propose to develop a flexible and modular concept, making use of smallsats and high-TRL available technology for the space exploration of several NEAs. Potential targets include Earth Trojan and other co-orbital asteroids, which are particularly appealing due to the low energetic cost to reach them. In particular, Earth Trojans represent a major gap in our inventory of near-Earth small bodies. Tracking their population size would put strong constraints on the dynamical and cosmochemical theories for the formation and evolution of the inner solar system.International Context: Deep-space smallsats represent a new frontier for the solar system exploration. After the success of the NASA/JPL Mars Cube One (MarCO) mission in 2018 and the launch of ASI LICIACube in November 2021 (currently hosted as piggyback of the NASA DART spacecraft, which will impact the binary NEA Didymos in September 2022), several further deep-space smallsat missions will take place in the next few years, e.g. in the framework of ESA HERA and NASA ARTEMIS I projects.Reference Scenario: Both CubeSat and larger SmallSat platforms are considered, which perfectly address the modularity and flexibility of the proposed mission concept. Multiple identical smallsats (to maximize mission return while minimizing costs and risks) can be launched profiting of the same or separate mission opportunities, and then reach their respective targets using electric propulsion and optimized interplanetary trajectories. Each smallsat will flyby and/or rendezvous multiple NEAs, with encounters at the nodal points.A preliminary selection of the targets has been performed assuming a 12U platform and mission durations capped at 2-3 years, with total ΔV < 3 km/s. We stress that the existence of a large number of sequences with similar performances outlines the strong implementation flexibility of our concept. Indeed, the definitive choice of target NEAs can be easily updated even at relatively late project phases, also considering the exponential growth of NEA discoveries. This gives us a huge flexibility in terms of mission scenarios, which can be adapted to varying constraints in terms of, e.g., launch date, propulsion specifics, mission architecture and duration.Example reference solutions that have been identified include the possibility to reach the Earth’s L4-L5 Lagrange points, using the smallsat payload for the discovery and characterization of Earth Trojan and co-orbital asteroids (especially those with a long synodic period relative to our planet, which are impossible to detect from Earth-based surveys), and to flyby already discovered Earth Trojan asteroids.Considered scientific payload (whose final selection will depend upon the choice of the platform) includes an optical camera, a near-infrared spectrometer, a mass spectrometer and a neutral particle camera, while the onboard transponder will be used to acquire radio science data.Technology Readiness: Mission architecture will rely on flight-proven (TRL 9) COTS and in-house components and scientific payload, using heritage from a number of ongoing (e.g., BepiColombo, LICIACube, …) or under development (e.g., Hera) space missions.Potentially selected components that have flown in the Earth orbital environment only will be appropriately shielded to ensure radiation tolerance to deep-space environment for the whole mission duration.Science and Technology Ambition: We aim to provide new insights into planetary science by characterizing several NEAs presenting peculiar and yet unexplored dynamical and physical properties. Noteworthy, such information will be also relevant for planetary protection purposes, as well as to assess a potential near-future exploitation of asteroid resources.We also aim to validate critical technologies for the exploitation of smallsats in solar system exploration, benefiting from the deep knowhow already gained by our team in designing and managing space missions to NEAs.Our mission concept relies on significant payload heritage and high-TRL available technology, based on our established consortium. Nevertheless, we will consider possible complementary contributions from further national and/or international partners willingly.

Introduction: Ceres is the largest object of the Solar System main belt with a complex geological and chemical history, which experienced extensive water related processes and geochemical differentiation [1]. Ceres’ surface is characterized by dark materials, phyllosilicates, ammonium-bearing minerals, carbonates, water ice, and salts. In addition to a global presence of carbon-bearing chemistry, local concentration of aliphatic organics has been detected by Dawn mission [2]. The mission, thanks to the data collected by the Italian instrument VIR [3], showed clear evidence of a high amount of aliphatic organic material on the surface of Ceres [4, 5, 6]. This has raised new questions about the origin and preservation of this material, especially when considering its high estimated abundance (Fig 1). We started a series of laboratory studies on physicochemical evolution of organic material interacting with minerals thought to be present on Ceres. The goal is to understand the transformations induced on these samples by processing with ultraviolet radiation. Fig. 1 Ceres spectra of the organic-rich area in Ernutet crater (label “Organics”); of a background organic-poor area from a region southeast of Ernutet (label “Background”); and Occator bright material (label “Carbonate”) [4]. Results: In this study, we mixed organic material with a mixture of minerals considered a spectral analog of the Ceres surface. Specifically, we mixed undecanoic acid and solid material made of serpentine, magnetite, carbonate and ammonium bearing montmorillonite with a ratio of 1:80 (organic:mineral). Diffuse FTIR reflectance spectra were acquired in vacuum. Spectra of simulant are resembling the Ceres surface composition (Fig. 2) organic rich area, even if the proportions between the bands of clays, carbonates and organics are not the same as seen on Ceres. We irradiated the sample in the vacuum chamber at room temperature using an UV lamp to simulate the solar radiation. The photon flux was 2.75x1017 ph. cm-2s-1 in the 200-400 nm spectral range as measured through a single monochromator Spectro 320 spectrometer. The simulant was irradiated at increasing fluence up to irradiation time of about 7 hours and the degradation process was monitored in real time with FTIR spectroscopy by measuring the changes in the spectral features (band areas). In Fig. 4 the reflectance spectra of the simulant as prepared and after UV irradiation at 180, 2280, and 21180 s are showed. The bands area of NH3 at 3 μm and aliphatic CH2/CH3 at 3.4 μm are decreasing as the irradiation fluence increases with time. Fig. 2 Average spectrum of Ceres Ernutet organic-rich ares (black) compared to laboratory simulant (blue). Spectra are normalized at 2.6 μm. Each band area, which is proportional to the number of functional groups, was evaluated at different irradiation time and the degradation rate was obtained by fitting the band areas vs irradiation time using an exponential function. This method permits to determine the degradation cross section of each band, which is the probability that chemical bonds are broken by UV radiation. In particular, for the aliphatic band at 3.4 μm it was possible to obtain the degradation cross section of the whole band, 5.85x10-21 cm2. and of every single band component distinguishing between CH2 and CH3 bonds behavior under irradiation. In presence of mineral simulant, the degradation rate of aliphatic compounds extrapolated to the estimated UV flux at the surface of Ceres gives a half-lifetime of 215 days. This result coupled with resurfacing process time scale of million years could justify the absence of detectable organics on most of the Ceres’ surface. However, this result would not be able to explain the presence of organics in the organic-rich area in Ernutet crater. Furthermore, as can be seen from Fig. 3, UV radiation not only degrades the CH bonds but also affects the NH bonds present in the ammoniated silicates. In this latter case the degradation cross section for the whole band is 2.05x10-21 cm2 which is responsible of a less effective photodegradation process giving a degradation half-lifetime of about 613 days. This result also seems to be in contrast with the ubiquity of the presence of ammoniated silicates on Ceres. We have to recall that the experiments reported in this work have been done at room temperature. It is not excluded that photoprocessing at cryogenic temperature typical of Ceres surface can be less effective further reducing the degradation cross sections of CH and NH bonds. Discussion: As showed by VIR, the ammoniated band is ubiquitous on Ceres, which is in contrast with the fact that we expected the ammoniated band to be completely degraded. However, photodegradation acts on the first molecular layers of the surface exposed to the radiation. Furthermore, the visible and near infrared spectra detected by VIR are diffused by the first millimeters of the surface at a depth that cannot be affected by UV radiation. Therefore, the spectra are a combination of processed superficial material and underlying layers of the Ceres surface, which may retain the primitive characteristics of material rich in organic. However, it should be noted that in addition to UV, the surface is constantly bombarded by solar energetic particles (SEP) and galactic cosmic rays (GCR). This radiation also has the effect of breaking chemical bonds such as UV photons, but penetrating meters into the surface can alter deeper layers. These results suggest that there must be a resurfacing mechanism able to expose organic rich material that acts on a much shorter time scale than the geological one. Fig. 3 Diffuse reflectance spectra of the simulant as prepared (0 s) and after UV irradiation at 180, 2280, and 21180 s. Acknowledgements: This work is supported by INAF Main Stream program, grant “Evolution and alteration of organic material on Ceres”. References: [1] De Sanctis et al., 2016, Nature 536, 54–57 [2] Marchi et al., 2019, Nature Astr. 3, 140-145 [3] De Sanctis et al., 2011, Space Science Reviews 163, 329-369. [4] De Sanctis et al., 2017, Science 355, 719-722 [5] Pieters et al., 2018, Meteoritics and Planetary Science 53 (9), 1983-1998 [6] De Sanctis et al., 2019, MNRAS 482 (2), 2407–2421

Ices are the dominant surface material of many Solar system objects, such as comets and trans-Neptunian objects. They are continuously exposed to ion bombardment by solar wind ions and cosmic rays, which trigger secondary ion emission, contributing to the exosphere formation. Laboratory studies demonstrated the effects of energetic processing of ices at low temperature, showing the production of molecules and free radicals of astrophysical interest. Nitrous oxide (N2O) is one of the molecular species observed in star-forming sites, reason why it may be present in the ices covering some minor bodies in the outer Solar system. In the current work, N2O ice at 10 K was irradiated by energetic (MeV/u) multicharged heavy ions (e.g. 105Rh and 140Ba); the sputtered species were detected and analysed by the TOF-PDMS technique (time-of-flight plasma desorption mass spectrometry). Small positive and negative secondary ions were identified: N+, N2+, NO+, O+, and O−. The bombardment also induces production of ion cluster series: (N2)nR$_{m}^+$, (NO)nR$_{m}^+$, (N2O)nR$_{m}^+$, where R = N+, N2+, NO+, N2O+, Om+ (n up to ∼ 10, m = 1−3). Their yield distributions follow the sum of two decreasing exponentials, one fast -F and another slow -S, suggesting a two-regime formation. Most of the yield distributions have the same pair of exponential decay constants, around kF ∼ 1.4 and kS ∼ 0.15 u−1. Based on this behavior, an emission description for aggregates is proposed, useful to understand the processes by which neutral and ionized molecular species are delivery to the gas phase in space.

International audience; N2O and CO2 can be formed in the interstellar space and in ices on the surface of outer solar system bodies, such as Pluto and Triton. Energetic ions can simulate the energy transfer processes that occur by cosmic ray irradiation of interstellar ices, comets, and icy solar system bodies. Proceeding systematic research, pure nitrous oxide (N2O) ice, and nitrous oxide and carbon dioxide (CO2) ice mixture were irradiated at 11 K with MeV-nitrogen (N+) and -xenon (Xe23+) ion beams. The chemical and physical effects induced by ion irradiation on the N2O ice and the N2O:CO2 ice mixture are compared. The formation and dissociation cross sections scale with the electronic stopping power (Se) roughly as σ ∼ a Sen, where n ∼ 3/2. The n power law is helpful for predicting the N2O formation and dissociation cross-sections for other ion beam projectiles and energies; these predictions will allow estimating the effects of the entire cosmic ray radiation field.

Summary Ceres is the largest object in the Solar System main belt. Clearly, Ceres experienced extensive water-related processes and geochemical differentiation and nowadays it is a body with a complex geological and chemical history [1]. Its surface is characterized by dark materials, phyllosilicates, ammonium-bearing minerals, carbonates, water ice, and salts. In addition to a global presence of carbon bearing chemistry, local concentration of aliphatic organics has been detected by Dawn [2]. In this context, we have started a series of laboratory spectroscopy measurements targeted to study the physicochemical interactions between organic material and minerals possibly present on Ceres. The goal is to understand the transformations induced on these samples by ultraviolet radiation, neutral atoms, and fast ions, under experimental conditions that simulate the environment of Ceres. The spectroscopic data obtained in laboratory experiments allow, through the comparison with the observations of the VIR spectrometer aboard the Dawn mission, to clarify the nature and origin of organic material identified on Ceres. Introduction Organic material in the minor bodies of the Solar System is an important component to understand planetary evolution and, eventually, the origin of life. Nevertheless, our knowledge on the subject is still limited. Recently the Dawn mission, thanks to the data collected by the Italian instrument VIR [3], showed clear evidence of a high amount of aliphatic organic material on the surface of Ceres [4, 5, 6] (Fig 1). This evidence has raised new questions about the origin and preservation of this material, especially when considering its high estimated abundance and the mineralogical context. Fig 1 Ceres spectra of the organic-rich area in Ernutet crater (label “Organics”); of a background organic-poor area from a region southeast of Ernutet (label “Background”); and of Occator bright material (label “Carbonate”) [4]. In order to understand the organic chemical species and in particular their abundance on Ceres, laboratory studies were performed [7]. The importance of having a direct comparison between laboratory and remote sensing data can provide a further investigation clues to shed light on the origin and evolution of Ceres. Through this project, we intend to study, through dedicated experiments, the interaction between minerals, water, and organic concerning the environmental conditions of Ceres. Making a synergistic use of complementary and indispensable skills present within INAF (Italian National Institute of Astrophysics) laboratories we investigated a complex issue such as that concerning the origin and preservation of organic molecules on planetary surfaces. Within INAF, complementary and unique realities coexist which, thanks to joint and coordinated work, can give a new interpretation of the physical-chemical processes active on Ceres. Project development and results In this study, we prepare mixtures of materials resembling the Ceres surface composition [8, 9] adding organic molecules in order to: (i) understand how organic molecules behave and eventually degrade on Ceres, in particular, how aliphatic molecules degrade by energetic processing with fast ions (keV-MeV) and UV photons [10, 11]. Moreover, the physico-chemical properties of the materials exposed to a flux of neutral atoms are investigated [12, 13]. (ii) evaluate the interaction between ammoniated minerals and simple organic molecules that may lead to the synthesis of complex compounds. In the presence of ultraviolet (UV) radiation, these minerals present on the surface of Ceres can show photocatalytic effects accelerating the photo-reactions, which generally destroy the original organic molecule and in the synthesis of new complex organic molecules [14]. (iii) evaluate the role of minerals in the protection or degradation of organic compounds. Some studies indicated a fundamental role of clays in the catalysis and preservation of organic materials [15]. Ceres is rich in clays and other hydrated minerals, making the interactions with the observed organics of particular interest. The project is carried out by several INAF institutes and laboratories. In detail: INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali prepared the analog mineral mixtures taking into account the compositional information gained by VIR observations. INAF - Osservatorio Astrofisico di Arcetri subsequently doped the mixture with several organic investigating UV photostability in Ceres analog conditions and the influence of temperature. INAF -Osservatorio Astronomico di Capodimonte studied irradiation with atoms and temperature effect while INAF - Osservatorio Astrofisico di Catania performed irradiation with fast ions. Finally, results of laboratory measurements were compared with data obtained by VIR instrument onboard Dawn mission. AcknowledgementsThis work is support by INAF Main Stream programme, grant 1.05.01.86.08 Evoluzione ed alterazione del materiale organico su Cerere (ref. Maria Cristina De Sanctis). References [1] De Sanctis et al., 2016, Nature 536, 54–57 [2] Marchi et al., Nature Astr., 2019 [3] De Sanctis et al., 2011, Space Science Reviews 163, 329-369. [4] De Sanctis et al., science 2017 355, 719 [5] Pieters et al., 2018, Meteoritics and Planetary Science 53 (9), 1983-1998 [6] De Sanctis et al., 2019, 482 (2), 2407–2421 [7] Vinogradoff et al., 2021 [8] Ferrari et al., 2019, Icarus 321, 522-530 [9]De Angelis et al., 2021 JGR Planets doi: 10.1029/2020JE006696 [10] Baratta et al. 2002, A&A, 384, 343-349 [11] Brucato et al. 2006, A&A, 455, 395-399 [12] Mennella et al. 2003, ApJ, 587, 727-738 [13] Palumbo et al 2004, Ad. Sp. Res., 33, 49-56 [14] Fornaro et al. 2013, Icarus, 226(1), 1068–1085 [15] Fornaro et al 2018, Astrobiology, 18, 989-1007

The James Webb Space Telescope (JWST) is expected to be launched in 2021. The JWST’s science instruments will provide high quality spectra acquired in the line of sight to young stellar objects whose interpretation will require a robust database of laboratory data. With this in mind, an experimental work is in progress in the Laboratory for Experimental Astrophysics in Catania to study the profile (shape, width, and peak position) of the main infrared bands of molecular species expected to be present in icy grain mantles. Our study also takes into account the modifications induced on icy samples by low-energy cosmic ray bombardment and by thermal processing. Here we present some recent results on deuterium hydrogen monoxide (HDO), N-bearing species, and carbon dioxide (CO2).

A deep understanding of the origin of life requires the physical, chemical, and biological study of prebiotic systems and the comprehension of the mechanisms underlying their evolutionary steps. In this context, great attention is paid to the class of interstellar molecules known as “Complex Organic Molecules” (COMs), considered as possible precursors of prebiotic species. Although COMs have already been detected in different astrophysical environments (such as interstellar clouds, protostars, and protoplanetary disks) and in comets, the physical–chemical mechanisms underlying their formation are not yet fully understood. In this framework, a unique contribution comes from laboratory experiments specifically designed to mimic the conditions found in space. We present a review of experimental studies on the formation and evolution of COMs in the solid state, i.e., within ices of astrophysical interest, devoting special attention to the in situ detection and analysis techniques commonly used in laboratory astrochemistry. We discuss their main strengths and weaknesses and provide a perspective view on novel techniques, which may help in overcoming the current experimental challenges.

)3 Acetylene, C2H2, has been observed in the interstellar medium, mostly around young stellar objects, as well as in molecular clouds and cometary comae, representing an important species of astrophysical interest. In this work, we present a laboratory study of the C2H2 radiolysis at 45 K for three different beams and energies: 1.0 MeV H+ and He+, and 1.0 and 1.5 MeV N+ beams. Fourier transform infrared spectroscopy was used for monitoring the molecular changes induced by the ion processing. Two different sample thicknesses were irradiated; for the thicker one, implantation had occurred. Spectra and absorbance evolutions for the thin and thick films are qualitatively different. Four C2H2 bands are observed at 3225, 1954, 1392, and 763 cm−1. The C2H2 compaction and apparent destruction cross-sections are determined. For the case of the H+ beam, the compaction cross-section dominates. Concerning molecular synthesis by irradiation, New product bands were not observed in the thin ice irradiations; for the thicker film ice, the daughter species CH4, C2H4, C3H6, and C4H4 have been identified and their destruction and formation cross-sections determined. The apparent destruction cross-section was found to be a function of the electronic stopping power (Se) as σd ∝ S$_\mathrm{ e}^{3/2}$. The half-life of the C2H2 bombarded by galactic cosmic rays is estimated. The current findings are a contribution to the understanding of how the molecules synthesized upon irradiation of Interstellar and outer Solar system ices participate to the molecular enrichment and to the physicochemical evolution of the Universe.

A new experimental set-up permitting scale-up and serial internal numbering-up of meso- and micro photocatalytic systems, respectively, was developed to compare their photodegradation efficiency, by using of a commercially avaliable TiO2 (P25), against Rhodamine B (RB) and Methylene Blue (MB) under UV irradiation in water. A circular photocatalytic unit constituted of TiO2 embedded into PDMS was the basic unit of the meso and microchemical reactors. Different volumetric capacity, from 10 μL to 1000 μL, and different flow rates (0.05–1.0 mL min−1) were evaluated to understand the best approach to design a more efficient fixed bed photoreactor for photocatalytic degradation. The multi-photocatalytic microreactor system with the best performace, built-up by plugging six modular microreactor plates (M6), was tested for photooxidition of phenol under UV irradiation, as well. P25 catalyst showed different photodegradation efficiency depending on the photocatalytic meso- and microreactor design and flow parameters. The photocatalytic efficiency for the meso- and microdevices was evaluated by figure-of-merit electrical energy per order (EEO) and apparent quantum yield. The numbered-up M6 system had a lower electrical energy consumption compared with others. The microfluidic device M6 was able to achieve 97% of photodegradation of MB and RB (1.2 10−5 mol L−1) in 1 h compared to 96% conversion of the best mesoreactor in 16 h, while reached a total mineralization of phenol (1.2 10−4 mol L−1) to CO2 and H2O in 6 h.

The term “space weathering” refers to processes that include changes in the physical, chemical, mineralogical, and spectral properties of the surface of asteroids, comets, and some planets and their satellites, such as the bombardment by micrometeorites, solar wind ions, and cosmic rays. In this study, we focus on micrometeorite impacts, which may be the primary contributor to the annual mass flow of material that reaches the surface of such bodies. Studying the processes and effects associated with micrometeorite impacts is fundamental for understanding the evolution of the solar system and its components. From an experimental point of view, it is typically assumed that micrometeorite impacts may be simulated by ns-pulsed lasers and, indeed, many experimental studies have been performed based on such assumption. These studies have the common main goal to understand how micrometeorite impacts may change the physical-chemical and spectral properties of the bombarded surfaces. However, here we perform the first experimental study dedicated to the morphological characterization of the impact craters created by ns-pulsed laser ablation, in order to determine how well ns-pulsed lasers simulate the crater morphology of natural micrometeorite impacts. For this purpose, the laser ablation technique was applied to three different silicates: feldspar, quartz, and jadeite. For each of these minerals, two ablation scenarios have been considered: in air and in water. The craters formed by ns-pulsed laser ablation were characterized, from the morphological point of view, using a profilometer. Using this data we estimated the depth:diameter ratio of each crater. The comparison with literature data shows that the simple craters formed by ns-pulsed laser ablation closely resemble craters formed by natural micrometeorite impacts. In other words, from a morphological point of view, ns-pulsed laser ablation is appropriate for the simulation of micrometeorite impacts. We additionally verified that the value of the depth:diameter ratio does not depend, within errors, on the total number of laser pulses or the repetition frequency, at least within the ranges covered in these experiments: i) between 1 and 1200 laser pulses and ii) between 1 and 10 Hz.

The efficiency of dust formation in a variety of environments is an ongoing topic for discussions, especially if it comes to dust formation in the interstellar medium. Although this possibility is discussed in a wide range of numerical studies, experiments on the formation of dust at low densities and temperatures are mostly lacking. This contribution summarizes the main findings of our low-temperature condensation experiments including the formation of silica, complex silicates with pyroxene and olivine stoichiometry, and of carbonaceous refractory materials. Atomic and molecular species to be expected as products of supernovae shock fronts were produced by laser ablation of silicates and graphite. These species were deposited together with a rare gas on cold substrates representing the surfaces of surviving dust grains in the interstellar medium. After characterizing the precursor species, the rare gas matrix was annealed to induce diffusion and reactions between the initial components. We found the production of amorphous and homogeneous silica and magnesium iron silicates at temperatures of about 12 K in a barrierless reaction as monitored by infrared spectroscopy. The 10 μm band of the low-temperature siliceous condensates shows a striking similarity to the 10 μm band of interstellar silicates. Carbonaceous atoms and molecules can also react without a barrier and form an amorphous or hydrogenated amorphous carbon material. The refractory condensate has properties comparable to fullerene-like carbon grains formed at high temperatures.

Water ice exists on many objects in space. The most abundant icy species, among them water, are present in the icy satellites of the outer Solar System giant planets. The nuclei of comets, which are mainly composed of water ice, give another example of its abundance. In the interstellar medium (ISM), ice mantles, formed by molecular species sticking on dust grains, consist mainly of water ice. All these objects are exposed to ionizing radiation like ions, UV photons, and electrons. Sputtering of atoms, molecules, ions, and radicals from icy surfaces may populate and maintain exospheres of icy objects in the Solar System. In other respects, ionized hydrides such as OH+, H2O+, and H3O+ have been detected in the gas phase in star-forming regions. Interactions with cosmic rays could be an additional explanation to the current models for the formation of those species. In fact, laboratory simulations showed that the main components of the sputtered ionic species from water ice are oxygen hydrides. In this work, water ice targets were irradiated at several temperatures (10-200 K) by 90 keV O6+ ions, yielding an electronic stopping power of about 12 eV/A, when the nuclear stopping power is comparable to the electronic stopping power. Sputtering of secondary ions after bombardment of the ice target was analyzed by time-of-flight mass spectrometry (TOF-SIMS). Besides hydrogen ions (H+, H2+, H3+), also O+, O2+, OH+, (H2O)+, and clusters of (H2O)nH+ with n = 1-8 are emitted. Our results show a progressive yield decrease with increasing temperature of all of the detected species. This is related to the structure of the ice: the ionic sputtering yield for crystalline ice is much lower than for an amorphous ice. For instance, amorphous ice at 10 K exhibits a yield of the order of 2 × 10-6 secondary (H2O)nH+ hydride ions/projectile (with n = 1-8). As the temperature is increasing toward the phase transition to crystalline ice, the yields decrease by about one order of magnitude.

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We present a novel experimental study on solid CH2DOH pure and in astrophysical relevant mixtures. Solid samples were accreted under ultra high vacuum conditions at 17 K and were analyzed by mid-infrared transmission spectroscopy. Refractive index, density, and mid-IR band strength values were measured for pure solid CH2DOH. The refractive index was also measured for CH2DOH:H2O, CH2DOH:CO, and CH2DOH:CH3OH mixtures. For all samples, the thermal evolution of the main band profile was studied. We used the interference laser technique (He Ne laser, λ = 543.5 nm) to measure the samples thickness and a numerical method to measure the refractive index starting from the amplitude of the interference curve. We obtained the ice density through the Lorentz-Lorenz relation. To calculate the band strength values we used the linear fit of the integrated band intensities with respect to the column densities. Samples deposited at 17 K were warmed up to their sublimation temperature. Spectra were taken at selected temperatures to study their thermal evolution. The results are discussed in view of their relevance for the interpretation of astronomical IR spectra.

Astronomical observations towards star-forming regions have revealed the presence of molecules with the N-O bond such as NO, N2O, and HNO. These species are considered potential precursors of prebiotic molecules. Thus, understanding nitrogen and oxygen chemistry may help us to better understand the origin and evolution of prebiotic molecules in space. However, species with the N-O bond are poorly studied and laboratory works on the effects induced on them by solar wind and galactic cosmic rays are still scarce. For this, we wanted to study the effects of ion bombardment on molecules with the N-O bond. We focus here on N2O ices and NO2:N2O4 = 1:1 ice mixtures (at 16 and 50/60 K) irradiated with 200 keV protons. Infrared transmission spectroscopy (8000-500 cm-1; 1.25-20 μm) was used to analyse the samples. Irradiation of N2O ices and NO2:N2O4 ice mixtures produces comparable effects independent of the irradiation temperature, NO being the main product. Moreover, we show that the maximum amount of N2O and N2O4 destroyed by irradiation, at the highest dose reached in our experiments, is equal to about 98 and 70 {{ per cent}}, respectively. The dose range covered in the experiments has been compared with the astrophysical time-scale of surface processing in space, showing that irradiation of N2O and NO2:N2O4 mixtures can produce, within 105-108 yr, amounts of solid NO ice detectable towards star-forming regions by the James Webb Space Telescope.

The majority of basaltic objects in the main belt are dynamically connected to Vesta, the largest differentiated asteroid known. Others, due to their current orbital parameters, cannot be easily dynamically linked to Vesta. This is particularly true for all the basaltic asteroids located beyond 2.5 au, where lies the 3:1 mean motion resonance with Jupiter. In order to investigate the presence of other V-type asteroids in the middle and outer main belt (MOVs) we started an observational campaign to spectroscopically characterize in the visible range MOV candidates. We observed 18 basaltic candidates from TNG and ESO - NTT between 2015 and 2016. We derived spectral parameters using the same approach adopted in our recent statistical analysis and we compared our data with orbital parameters to look for possible clusters of MOVs in the main belt, symptomatic for a new basaltic family. Our analysis seemed to point out that MOVs show different spectral parameters respect to other basaltic bodies in the main belt, which could account for a diverse mineralogy than Vesta; moreover, some of them belong to the Eos family, suggesting the possibility of another basaltic progenitor. This could have strong repercussions on the temperature gradient present in the early Solar System, and on our current understanding of differentiation processes., 15 pages, 4 figures, accepted for pubblication to MNRAS

In recent years several small V-type asteroids have been identified in the main belt. Most of them belong to the Vesta's dynamical family (“Vestoids”) but an increasingly large number appears to have no link with it (“non-Vestoids”). V-types have also been found within the population of Near Earth Asteroids (NEAs) and they are linked to the Howardite–Eucrite–Diogenite meteorites (HEDs). Several questions on Vesta, the V-types, and the HEDs are still unsolved. Among them, probably the most important is whether all basaltic objects do come from Vesta or not. To help answer to this and similar questions, recent studies have focused on the analysis of the visible-near infrared (Vis-NIR; 0.4–2.5 μm) spectroscopic and mineralogical properties of large samples of V-types. The objectives are to highlight similarities and differences among V-types belonging to different subclasses, increase the number of available Vis-NIR spectra for under numbered subclasses, and compare these spectra with laboratory data. In this last case, we also considered the data from ion irradiation experiments performed on different samples of Eucrites, to simulate the effects of space weathering. The data analysis shows that although most of the V-type asteroids in the inner main belt do have a surface composition compatible with an origin from Vesta, this seems not to be the case for V-types in the middle and outer main belt (MOVs). For these asteroids, a number of physical and dynamical parameters point to an origin other than Vesta. The space weathering effects are evident for all V-type subclasses, except for the V-type NEAs where they are only moderate. In this case, the laboratory experiments support the idea that the current NEAs spectral properties could be due to a balance between space weathering and rejuvenative processes triggered by close encounters with terrestrial planets. Finally, we have applied the same Vis-NIR analysis to all HEDs with available spectra in the RELAB database, including those Eucrite meteorites which present anomalous oxygen isotopic composition and/or petrologic characteristics when compared to the rest of the HEDs. These “anomalous” Eucrites show some Vis-NIR differences with respect to the rest of Eucrites. This is an interesting point to be further investigated once more spectra of anomalous HEDs will be available.

Asteroid surface space weathering has been investigated both observationally and experimentally, mostly focusing on the effects on the visible–near infrared (VNIR, 0.4–2.5 μm) spectral range. Here we present laboratory near-ultraviolet (NUV, 200–400 nm) reflectance spectra of ion irradiated (30–400 keV) silicates and meteorites as a simulation of solar wind ion irradiation. These results show that the induced alteration can reproduce the spread observed in the VNIR vs. NUV slope diagram for S-type asteroids. In particular, the well-known spectral reddening effect induced in the VNIR range is accompanied by a less known but stronger bluing effect at NUV wavelengths. Such trend was previously identified by Hendrix and Vilas (Hendrix, A.R., Vilas, F. [2006]. Astron. J., 132, 1396–1404) but only based on the comparison between observations and laboratory spectra of lunar materials. We attribute the NUV bluing, analogously to the VNIR reddening, to the formation of iron nanoparticles accompanied by structural modifications (amorphization) of surface silicates. We expect the evidence of weathering processes in the NUV part of spectra before these effects become observable at longer wavelengths, thus searching for the space weathering effects in the NUV range would allow establishing the extent of space weathering for very young asteroidal families. It will be important to include in future studies the NUV range both in the observations of specific classes of objects (e.g., the Vestoids) and in the laboratory spectra of meteorites and terrestrial analogues before and after space weather processing.

The life-cycle of cosmic dust grains is far from being understood and the origin and evolution of interstellar medium (ISM) grains is still under debate. In the ISM, the cosmic dust destruction rate is faster than the production rate by stellar sources. However, observations of ISM refractory matter suggest that to maintain a steady amount of cosmic grains, some supplementary production mechanism takes place. In this context, we aimed to study possible re-formation mechanisms of cosmic grains taking place at low temperature directly in the ISM. The low temperature condensation of carbonaceous materials has been investigated in experiments mimicking the ISM conditions. Gas-phase carbonaceous precursors created by laser ablation of graphite were forced to accrete on cold substrates (T about 10 K) representing surviving dust grains. The growing and evolution of the condensing carbonaceous precursors have been monitored by MIR and UV spectroscopy under a number of experimental scenarios. It is demonstrated, for the first time, the possibility to form ISM carbonaceous grains in "situ". The condensation process is governed by carbon chains that first condense into small carbon clusters and finally into more stable carbonaceous materials, which structural characteristics are comparable to the material formed in gas-phase condensation experiments at very high temperature. We also show that the so-formed fullerene-like carbonaceous material is transformed into a more ordered material under VUV processing. The cold condensation mechanisms here discussed can give fundamental clues to fully understand the balance between the timescale for dust injection, destruction and re-formation in the ISM., 15 pages, 12 figures - accepted for publication in ApJS

We have studied the photodesorption of monolayer coverage of water ice coating amorphous carbon by 193 nm photons. We found that the column density of water decreases exponentially with fluence during irradiation at 120 K and obtain a desorption cross-section of (7.4±0.5)×10–19 cm2. We estimate the lifetime for photodesorption to be ∼14 h for average solar activity at the sub-solar point on the Moon. The photodesorbed molecules, based on other experiments, are expected to be slower than the escape velocity and to be re-adsorbed on the surface, contributing to water migration. For comparison, we determine the effect of 4 keV He+ on water-coated Apollo 16 soil (65901) under similar experimental conditions. We find a sputtering cross-section of (1.2 ±0.4)×10–16 cm2. We calculate that photodesorption by solar UV is four orders of magnitude more effective than sputtering by the solar wind in causing migration of adsorbed water on the lunar surface.

Inter- and circumstellar ices comprise different molecules accreted on cold dust particles. These icy dust grains provide a molecule reservoir where particles can interact and react. As the grain acts as a third body, capable of absorbing energy, icy surfaces in space have a catalytic effect. Chemical reactions are triggered by a number of possible processes; (i) irradiation by light, typically UV photons from the interstellar radiation field and Ly-α radiation emitted by excited hydrogen, but also X-rays, (ii) bombardment by particles, free atoms (most noticeably hydrogen, but also N, C, O and D-atoms), electrons, low energy ions and cosmic rays, and (iii) thermal processing. All these effects cause ices to (photo)desorb, induce fragmentation or ionization in the ice, and eventual recombination will make molecules to react and to form more and more complex species. The effects of this solid state astrochemistry are observed by astronomers; nearly 180 different molecules (not including isotopologues) have been unambiguously identified in the inter- and circumstellar medium, and the abundances of a substantial part of these species cannot be explained by gas phase reaction schemes only and must involve solid state chemistry. Icy dust grains in space experience different chemical stages. In the diffuse medium grains are barely covered by molecules, but upon gravitational collapse and darkening of the cloud, temperatures drop and dust grains start acting as micrometer sized cryopumps. More and more species accrete, until even the most volatile species are frozen. In parallel (non)energetic processing can take place, particularly during planet and star formation when radiation and particle fluxes are intense. The physical and chemical properties of ice clearly provide a snapshotroot to characterize the cosmological chemical evolution. In order to fully interpret the astronomical observations, therefore, dedicated laboratory experiments are needed that simulate dust grain formation and processing as well as ice mantle chemistry under astronomical conditions and in full control of the relevant parameters; ice morphology (i.e., structure), composition, temperature, UV and particle fluxes, etc., yielding parameters that can be used for astrochemical modeling and for comparison with the observations. This is the topic of the present manuscript. Laboratory experiments simulating the conditions in space are conducted for decades all over the world, but particularly in recent years new techniques have made it possible to study reactions involving inter- and circumstellar dust and ice analogues at an unprecedented level of detail. Whereas in the past “top-down scenarios” allowed to conclude on the importance of the solid state for the chemical enrichment of space, presently “bottom-up approaches” make it possible to fully quantify the involved reactions, and to provide information on processes at the molecular level. The recent progress in the field of “solid state laboratory astrophysics” is a consequence of the use of ultra high vacuum systems, of new radiation sources, such as synchrotrons and laser systems that allow extensions to wavelength domains that long have not been accessible, including the THz domain, and the use of highly sensitive gas phase detection techniques, explicitly applied to characterize the solid state such as fluorescence, luminescence, cavity ring-down spectroscopy and sophisticated mass spectrometric techniques. This paper presents an overview of the techniques being used in astrochemical laboratories worldwide, but it is incomplete in the sense that it summarizes the outcome of a 3-day workshop of the authors in November 2012 (at the Observatoire de Meudon in France), with several laboratories represented, but not all. The paper references earlier work, but it is incomplete with regard to latest developments of techniques used in laboratories not represented at the workshop.

International audience; The radiolysis of pure N2O ice at 11 and 75 K by 90 MeV 136Xe23 + ion irradiation has been studied by Fourier-transformed infrared spectroscopy (FTIR). Six daughter molecular species have been observed: NO2, (NO)2, N2O3, N2O4, N2O5, and O3. The chemical evolution of the new molecules formed in the sample was followed by the measurement of the column densities of the precursor and products as a function of the beam fluence. This procedure allows the determination of their formation and dissociation cross-sections. Other processes monitored by FTIR were sublimation (non-existent at 11 K, but present at 75 K) and ice compaction by the ion beam. Comparison between results obtained for the 11 and 75 K ices shows that formation and destruction cross-sections are higher (for light products) or much higher (for heavy products) at 75 K. This enhancement of chemical activity at higher temperature should not be attributed to higher projectile ionization rate but rather to a higher mobility of the radiolysis products in an ice undergoing slow sublimation. Although N2O ice has not yet been observed in space, it is reasonable to expect its occurrence since N and O are very abundant and reactive. Furthermore, if this ice is actually absent, the knowledge of the chemical–physical processes induced by ion irradiation on N2O ice at low temperature is necessary to explain its depletion.

Among main belt asteroids, V-types belonging to Vesta's dynamical family are known as `Vestoids' while those lying outside Vesta's family as `non-Vestoids'. V-types have also been found within the population of Near Earth Asteroids (NEAs). Several questions on Vesta, the V-types, and the Howardite-Eucrite-Diogenite meteorites are still unsolved, such as the genesis of each class/subclass, their evolution and mutual relationship, and the existence of other basaltic parent bodies. We present new NIR (0.8-2.4 μm) spectroscopic observations of seven non-Vestoids, carried out at the Telescopio Nazionale Galileo (TNG - INAF). We derived a number of spectral parameters (BI and BII centres, band separations, and BI slopes) and compared them with available spectra of V-types belonging to different subclasses (102 V-types in total), to highlight possible spectral differences useful to shed light on the questions mentioned above. We also considered the data from ion irradiation experiments performed on different samples of eucrites, simulating space weathering effects. Net discrepancies are seen for the BI slope distributions: NEAs show a distribution strongly different from all other V-type subclasses. Ion irradiation experiments induce strong effects on BI slope values and, as irradiation proceeds, the BI slope of eucrites quickly increases, changing the overall aspect of their VIS-NIR spectra (0.4-2.5 μm). Space weathering may explain the whole range of spectral slopes observed for all V-type subclasses. An exception is represented by NEAs, where moderate space weathering effects are evidenced. We propose that this is due to tidal perturbations exposing `fresh' unweathered surface grains during close encounters with the Earth, as previously found for Q-type NEAs.

Since many years, the Laboratory for Experimental Astrophysics in Catania (Italy) has given a contribution to a number of experiments with the aim to investigate the physico-chemical effects induced by fast ions irradiating astrophysical relevant materials. Here, we review some of the most recent results, namely irradiation of mixtures of solid CO and S-bearing molecules. In the interstellar medium, two or more icy compounds can coexist to form ice mantles on grains in two different forms: either they can be mixed together or form separated layers (ice segregation). Thus experiments have been performed with targets prepared at low T (15–20 K) both by a co-deposition of a mixture of two gas compounds (CO and SO2 or H2S) and with targets prepared by deposition of CO ices on a previously deposited SO2 or H2S layer. Samples have been irradiated with 200 keV protons with the aim of simulating a cosmic ion bombardment of interstellar ices. The results show that new chemical species are formed; in particular, OCS and CS2. The astrophysical relevance of the results is discussed.

The mutual phenomena between Jupiter and Saturn's satellites occur every half orbital period of these planets, when the Earth and the Sun cross their equatorial plane. At Physics and Astronomy Department of Catania University the events between Jupiter's satellites have been observed during the 1973, 1979, 1985/86, 1991, 1997 and 2009 campaigns and the ones between Saturn's satellites during the 1980/81 and 1995 campaigns. An overview of the main results obtained since 1973 is presented.

We present the results of observational campaigns of asteroids performed at Asiago Station of Padova Astronomical Observatory and at M.G. Fracastoro Station of Catania Astrophysical Observatory, as part of the large research programme on Solar System minor bodies undertaken since 1979 at the Physics and Astronomy Department of Catania University. Photometric observations of six Main-Belt asteroids (27 Euterpe, 173 Ino, 182 Elsa, 539 Pamina, 849 Ara, and 984 Gretia), one Hungaria (1727 Mette), and two Near-Earth Objects (3199 Nefertiti and 2004 UE) are reported. The first determination of the synodic rotational period of 2004 UE was obtained. For 182 Elsa and 1727 Mette the derived synodic period of 80.23+/-0.08 h and 2.981+/-0.001 h, respectively, represents a significant improvement on the previously published values. For 182 Elsa the first determination of the H-G magnitude relation is also presented., 19 pages, 11 figures, accepted for publication in Planetary and Space Science

Ices in the solar system are observed on the surface of planets, satellites, comets and asteroids where they are continuously subordinate at particle fluxes (cosmic ions, solar wind and charged particles caught in the magnetosphere of the planets) that deeply modify their physical and structural properties. Each incoming ion destroys molecular bonds producing fragments that, by recombination, form new molecules also different from the original ones. Moreover, if the incoming ion is reactive (H+, On+, Sn+, etc.), it can concur to the formation of new molecules. Those effects can be studied by laboratory experiments where, with some limitation, it is possible to reproduce the astrophysical environments of planetary ices. In this work, we describe some experiments of 15–100 keV H+ and He+ implantation in pure sulfur dioxide (SO2) at 16 and 80 K and carbon dioxide (CO2) at 16 K ices aimed to search for the formation of new molecules. Among other results we confirm that carbonic acid (H2CO3) is formed after H-implantation in CO2, vice versa H-implantation in SO2 at both temperatures does not produce measurable quantity of sulfurous acid (H2SO3). The results are discussed in the light of their relevance to the chemistry of some solar system objects, particularly of Io, the innermost of Jupiter's Galilean satellites, that exhibits a surface very rich in frost SO2 and it is continuously bombarded with H+ ions caught in Jupiter's magnetosphere.

In recent years several small basaltic V-type asteroids have been identified all around the main belt. Most of them are members of the Vesta dynamical family, but an increasingly large number appear to have no link with it. The question that arises is whether all these basaltic objects do indeed come from Vesta. To find the answer to the above questioning, we decided to perform a statistical analysis of the spectroscopic and mineralogical properties of a large sample of V-types, with the objective to highlight similarities and differences among them, and shed light on their unique, or not, origin. The analysis was performed using 190 visible and near-infrared spectra from the literature for 117 V-type asteroids. The asteroids were grouped according to their dynamical properties and their computed spectral parameters compared. Comparison was also performed with spectral parameters of a sample of HED meteorites and data of the surface of Vesta taken by the VIR instrument on board of the Dawn spacecraft. Our analysis shows that although most of the V-type asteroids in the inner main belt do have a surface composition compatible with an origin from Vesta, this seem not to be the case for V-types in the middle and outer main belt., Comment: 18 pages, 4 figures, tables in appendix A

The life cycle of the population of interstellar polycyclic aromatic hydrocarbon (PAH) molecules depends partly on the photostability of the individual species. We have studied the dissociative photoionization of two ethynyl-substituted PAH species, namely, 9-ethynylphenanthrene and 1-ethynylpyrene. Their adiabatic ionization energy and the appearance energy of fragment ions have been measured with the photoelectron photoion coincidence (PEPICO) spectroscopy technique. The adiabatic ionization energy has been found at 7.84 +/- 0.02 eV for 9-ethynylphenanthrene and at 7.41 +/- 0.02 eV for 1-ethynylpyrene. These values are similar to those determined for the corresponding non-substituted PAH molecules phenanthrene and pyrene. The appearance energy of the fragment ion indicative of the loss of a H atom following photoionization is also similar for either ethynyl-substituted PAH molecule and its non-substituted counterpart. The measurements are used to estimate the critical energy for the loss of a H atom by the PAH cations and the stability of ethynyl-substituted PAH molecules upon photoionization. We conclude that these PAH derivatives are as photostable as the non-substituted species in HI regions. If present in the interstellar medium, they may play an important role in the growth of interstellar PAH molecules., Comment: Accepted for publication in Astrophys. J. on 1 August 2015, 19 pages, 6 figures, 1 table

International audience; We present new results for ion irradiation experiments performed on fragments of the Tagish Lake (TL) meteorite. These experiments were focused on (a) quantifying the effect of the solar wind on spectral reflectance and (b) identifying the parent bodies of TL within the Asteroid Belt and or Jupiter Trojans. In the visible and near-infrared, we observe a flattening and brightening of the reflectance with progressive irradiation; in the mid-infrared, we observe a small shift towards longer wavelengths of the main emission feature at 10 mu m consistent with what is observed in silicates, likely caused by amorphization. We evaluated possible parent bodies for Tagish Lake by comparing its total reflectance in the visible and spectral changes in the 0.4-25 mu m range with available measurements for main belt asteroids and Jupiter Trojans (asteroid data includes measurements from the WISE, SMASS and Spitzer surveys as well as IRTF observations). The low reflectance of TL compared to asteroid albedos shows that TL-like bodies are very rare among Jupiter Trojans (\textless0.02% of the total population) and that they exist in a very small proportion (\textless4.5% of the total population) among main belt asteroids, where only one asteroid, 368 Haidea, was found to match both TL's spectrum and reflectance. Additionally, TL-like bodies would be preferentially located in the outer Asteroid Belt (2.85-3.3 AU) further away from the Sun than the average current location of most Ch- and Cgh-types, these objects being the likely parent bodies of CM-type chondritic meteorites. It thus appears that the location of both meteorite groups (TL and CM) must be different, with TL having formed further away from the Sun than CMs. We find that there are by far more parent bodies of CM than TL-like meteorites, which still remains to be understood. (C) 2013 Elsevier Inc. All rights reserved.

Context. Several objects in the Solar System like Europa, Ganymede and Callisto have frozen surface (main component: H2O). The associated thickness is bigger than the penetration depth of the relevant projectile ions. Additionally, other species such as H2O2, SO2 and CO2 have been detected on these surface. The formation mechanisms of these molecules are still under discussion.\ud \ud Aims. We present new experimental results on the implantation of 13Cq+ (q = 2, 3) ions at an energy of 30 keV in water ice at low temperatures (15 and 80 K). Experiments with multiply charged ions at energies of tens of keV are particularly relevant to simulating the complexity of the irradiation environment to which the surfaces of the icy moons in the outer solar system are exposed.\ud \ud Methods. The experiments were performed at the low energy ion beam facility ARIBE of GANIL in Caen (France). 30 keV 13Cq+ (q =\ud 2, 3) ions have been used to bombard solid H,2O surface which were frozen at 15K and 80K. Fourier Transform Infrared Spectrometer (FTIR) was used to analyze the sample in the 5000 - 600 cm-1 (2-16.7 μm) region with a spectral resolution of 1 cm-1.\ud \ud Results. The results of our experiments indicate that implantation produces 13CO2 with yields in the range of 0.32-0.57 molecules ion-1. This yield seems to be independent of the temperature of the ices in the range studied. We have estimated the time scale necessary to accumulate by implantation of magnetospheric carbon ions the observed quantity of carbon dioxide on the surface of Europa, a Jovian moon. This time scale is of the order of 1.0-1.3x104 yrs which is higher than that evaluated for carbon dioxide production by other relevant processes.\ud \ud Conclusions.We conclude that although a relevant quantity of CO2 can be formed by carbon ion implantation, this is not the dominant formation mechanism at Europa.

Context. Several molecular species have been observed as frozen gases in cold environments such as grains in the interstellar/circumstellar medium or icy objects in the outer solar system. Because N2 and O2 are homonuclear, symmetric molecules are not easily observed. It is therefore relevant to find indirect methods to prove their presence from astronomical observations. Aims. Here we investigate one of the possible indirect methods, namely the formation of specific molecules by cosmic ion bombardment of ices in astrophysical environments that contain O2 and N2. The observation of these molecules in astronomical environments could act as a trojan horse to detect the presence of frozen molecular oxygen and/or nitrogen. Methods. We have conducted ion bombardment experiments of frozen O2 ,H 2O and their mixtures with N2 at the laboratories of CIMAP-GANIL at Caen (France) and LASp at Catania (Italy). Different ions ( 13 C 2+ ,A r 2+ and H + ) and energies (30–200 keV) have been used. Results. We have found that 13 CO2 is formed when carbon ions are implanted in ices containing H2 Oa nd/or O2. Ozone and nitrogen oxides (NO, N2O, NO2) are formed in the studied ices containing O2 and N2 with different relative abundances. Conclusions. We suggest that ozone and nitrogen oxides are present and have to be searched for in some specific environments such as dense clouds in the interstellar medium and the surfaces of Pluto, Charon and Triton. Their observation could demonstrate the presence of molecular oxygen and/or nitrogen. A possible interest for the observations of atmospheres in exo-planetary objects is also discussed.

International audience; We present new irradiation experiments performed on the enstatite chondrite Eagle (EL6) and the mesosiderite Vaca Muerta. These experiments were performed with the aims of (a) quantifying the spectral effect of the solar wind on their parent asteroid surfaces and (b) identifying their parent bodies within the asteroid belt. For Vaca Muerta we observe a reddening and darkening of the reflectance spectrum with progressive irradiation, consistent with what is observed in the cases of silicates and silicate-rich meteorites such as OCs and HEDs. For Eagle we observe little spectral variation, and therefore we do not expect to observe a significant spectral difference between EC meteorites and their parent bodies. We evaluated possible parent bodies for both meteorites by comparing their VNIR spectra (before and after irradiation) with those of ∼400 main-belt asteroids. We found that 21 Lutetia (Rosetta's forthcoming fly-by target) and 97 Klotho (both Xc types in the new Bus-DeMeo taxonomy) have physical properties compatible with those of enstatite chondrite meteorites while 201 Penelope, 250 Bettina and 337 Devosa (all three are Xk types in the Bus-DeMeo taxonomy) are compatible with the properties of mesosiderites.

We present novel measurements of the refractive index, density and integrated band strengths of mid-infrared features of solid N 2 O at 16 K and of NO 2 and N 2 O 4 in two frozen NO 2 :N 2 O 4 mixtures deposited at 16 and 60 K. The refractive index and density measurements were performed also for frozen O 2 deposited at 16 K. In this case, the integrated band strength values could not be determined since O 2 is a homonuclear molecule and therefore its fundamental mode is not infrared active. The solid samples were analysed by infrared spectroscopy in the 8000÷800 cm −1 range. The sample thickness was measured by the interference curve obtained using a He–Ne laser operating at 543 nm. The refractive index at this laser wavelength was obtained, by numerical methods, from the measured amplitude of the interference curve. The density values were obtained using the Lorentz–Lorenz relation. Integrated band strength values were then obtained by a linear fit of the integrated band intensities plotted versus column density values. The astrophysical relevance of these novel measurements is briefly discussed.

Vacuum-Ultraviolet (VUV) radiation is responsible for the photo-processing of simple and complex molecules in several terrestrial and extraterrestrial environments. In the laboratory such radiation is commonly simulated by inexpensive and easy-to-use microwave-powered hydrogen discharge lamps. However, VUV flux measurements are not trivial and the methods/devices typically used for this purpose, mainly actinometry and calibrated VUV silicon photodiodes, are not very accurate or expensive and lack of general suitability to experimental setups. Here, we present a straightforward method for measuring the VUV photon flux based on the photoelectric effect and using a gold photodetector. This method is easily applicable to most experimental setups, bypasses the major problems of the other methods, and provides reliable flux measurements. As a case study, the method is applied to a microwave-powered hydrogen discharge lamp. In addition, the comparison of these flux measurements to those obtained by O2 actinometr...

Planets and their moons are constantly subjected to irradiation from both their respective planetary magnetospheres and the solar wind. Energetic particles (electrons, protons and ions) in such radiation may induce complex chemistry within the icy mantles of such bodies, producing many organic compounds. Such processes can be simulated in laboratory experiments. In this report we present recent results from experiments exploring both molecular synthesis and the morphology of such ices.The morphology of any ice may be characterised by IR and Vacuum Ultra-Violet (VUV) spectroscopy. The latter is particularly useful for studying ices in which infrared inactive molecules like oxygen (O2) are common. We have shown that oxygen forms dimers in typical planetary ices and that, in contrast to previous analysis, many of the chemical reactions within the ice involve such dimer (and larger cluster) chemistry. We also present the results of a series of experiments that explore electron, proton and ion irradiation on Solar System relevant ices such as carbon dioxide (CO2) at different temperatures. Infrared spectra recorded before and after irradiation are used to identify and quantify molecules formed in such irradiation, e. g. ozone. These experiments show that the morphology of the ice plays a critical role in the chemistry.

Ion implantation experiments were carried out on amorphous (30 K) and crystalline (80 K) solid CO2 using both reactive (D(+), H(+)) and non-reactive (He(+)) ions, simulating different irradiation environments on satellite and dust grain surfaces. Such ion irradiation synthesized several new species in the ice including ozone (O3), carbon trioxide (CO3), and carbon monoxide (CO) the main dissociation product of carbon dioxide. The yield of these products was found to be strongly dependent upon the ion used for irradiation and the sample temperature. Ion implantation changes the chemical composition of the ice with recorded infrared spectra clearly showing the coexistence of D3h and C2v isomers of CO3, for the first time, in ion irradiated CO2 ice.

We investigate via infrared spectroscopy the synthesis of CO2 by ultraviolet irradiation (6.41 eV) of amorphous carbon covered with solid O2 at 21 K. Oxidation occurs at the O2-carbon interface promoted by photon excitation or dissociation of O2 molecules. The CO2 production is linear with photon fluence with a yield of 3.3 ± 0.3 × 10–5 CO2 photon–1; the yield does not decrease at high fluences (at least up to 2 × 1019 photons cm–2) since CO2 is not photodissociated at this photon energy. Replacing oxygen with water ice did not produce CO2 since H2O does not dissociate at this photon energy. The CO2 synthesis process discussed in this Letter does not require H2O or CO and may be important in cold astrophysical environments where O2 could be locally segregated on carbonaceous grains, such as in molecular clouds and icy objects in the outer solar system.

We report the synthesis of carbon dioxide on an amorphous carbon-13 substrate coated with amorphous water ice from irradiation with 100 keV protons at 20 K and 120 K. The quantitative studies show that the CO{sub 2} is dispersed in the ice; its column density increases with ion fluence to a maximum value (in 10{sup 15} molecules cm{sup -2}) of {approx}1 at 20 K and {approx}3 at 120 K. The initial yield is 0.05 (0.1) CO{sub 2} per incident H{sup +} at 20 (120) K. The CO{sub 2} destruction process, which limits the maximum column density, occurs with an effective cross section of {approx}2.5 (4.1) Multiplication-Sign 10{sup -17} cm{sup 2} at 20 (120) K. We discuss radiation-induced oxidation by reactions of radicals in water with the carbon surface and demonstrate that these reactions can be a significant source of condensed carbon dioxide in interstellar grains and in icy satellites in the outer solar system.

Context. In the past few decades, several tens of main belt asteroids have been found to exhibit basaltic surface composition, similar to the one of Vesta and basaltic Howardite, Eucrite, and Diogenite achondrite meteorites (HEDs). Most of these objects (V-types) belong to the Vesta dynamical family. Several questions on the relationship between Vesta, V-types, and HEDs are still unresolved. In particular, Vesta is spectroscopically bluer than most V-types. Aims. To date, it has not yet been understood whether these spectral differences are due to space weathering, similar to what has been observed for OC meteorites and S-type asteroids. To test this hypothesis, ion irradiation experiments were performed on different samples of eucrites to simulate the effects of space weathering on Vesta and V-types by solar wind ions. Methods. Eucrite meteorites were analyzed before and after different stages of ion irradiation by VIS-NIR reflectance spectroscopy (0.4–2.5 μm). We used different ions (Ar + ,C + ) with different energies (from 60 to 200 keV) to weather the samples. Results. Ion irradiation was observed to alter the spectral properties of eucrite meteorites, inducing progressive reddening and darkening of the irradiated samples. Different eucrite samples (Bereba and Dar Al Gani 684) show different reddening behaviors. Because they are patchy, reddening also varied between different parts of the same meteorite. Moreover, for both meteorites, irradiation effects are much faster (∼100 times) for C + than for Ar + ions. Conclusions. Comparing the laboratory spectra of eucrites before and after different stages of ion irradiation with those of V-types, it turns out that the slope spread shown by V-type asteroids can be explained by space weathering. These results provide new clues to the connection between Vesta, V-types, and HEDs, and are also useful in the context of the NASA Dawn mission to Vesta.

Context. Recent mid-infrared spectroscopic observations of Pluto and Triton suggest a wide distribution of H2O ice into surface regions containing more volatile species such as N2 ,C H4, and CO. This disagrees with the common idea that because of their typical surface temperature, water should not be involved in volatile transport processes, standing easily segregated from the more volatile species. Aims. We analyse infrared H2O band profiles when water is diluted in solid matrices dominated by methane, carbon monoxide, and/or molecular nitrogen. We also show the results of temperature-related diffusion processes of solid N2 into H2O ice deposited at different temperatures. Finally, we analyse ion irradiation effects for some of the mixtures considered. Methods. Solid samples were analysed by infrared (1.0‐16.0 µm) transmission and reflectance spectroscopy at different temperatures (15‐150 K), before and after ion irradiation with 200 keV protons. Results. When water is highly diluted in solid matrices, the profile of its near-infrared bands is strongly modified. Two narrow bands appear around 1.89 µm and 1.39 µm instead of the well known pure water ice bands at 2 µm and 1.5 µm, respectively. Furthermore, the peak position and width of the 1.89 and 1.39 µm bands depend on the initial mixture water is embedded in. The intensity of these bands decreases after ion irradiation. Conclusions. Since the mixtures considered closely resemble the surface composition of trans-Neptunian objects, experiments here discussed show that the bands around 1.89 µm and 1.39 µm are appropriate to investigating the presence of diluted water regions on their surface. In fact, the irradiation dose required for a significant decrease in their intensity would be accumulated on a timescale larger than the timescale for resurfacing processes on the surfaces of trans-Neptunian objects. Results shown here will contribute in a strong way to the interpretation of New Horizons near-infrared observations.

Context. Chemical models predict the presence of S-bearing molecules such as hydrogen sulfide (H2S) in interstellar icy grain mantles in dense molecular clouds. Up to now only two S-bearing molecules, namely sulfur dioxide (SO2) and carbonyl sulfide (OCS), have been detected in the solid phase towards young stellar objects (YSOs), while upper limits for solid H2S have been reported towards the same lines of sight. The estimated abundance of S-bearing molecules in icy grain mantles is not able to account for the cosmic S abundance. Aims. In this paper we studied the effects of ion irradiation on different icy targets formed by carbon monoxide (CO) and SO2 or H2S as mixtures and, for the first time, as layers. Methods. We carried out several irradiation experiments on ices containing SO2 or H2S mixed or layered with CO. The samples were irradiated with 200 keV protons in a high-vacuum chamber (P < 10 −7 mbar) at a temperature of 16‐20 K. IR spectra of the samples were recorded after various steps of irradiation and after warm-up. Results. We have found that the column density of H2 Sa nd SO2, as well as CO, decreases after irradiation, and the formation of new molecular species is observed. In the case of CO:SO2 samples, OCS, sulfur trioxide (SO3), ozone (O3), and carbon dioxide (CO2 )a re the most abundant species formed. In the case of CO:H2S samples the most abundant species formed are OCS, SO2, carbon disulfide (CS2), hydrogen persulfide (H2S2), and CO2. The profile of the OCS band formed after irradiation of the CO:H2S mixture compares well with the profile of the OCS band detected towards the high mass YSO W33A. Conclusions. Our results show that on a time scale comparable to the molecular cloud lifetime, the column density of H2S is strongly reduced and we suggest that this could explain the failure of its detection in the solid phase in the lines of sight of YSOs. We suggest that the solid OCS and SO2 detected in dense molecular clouds are formed after ion irradiation of icy grain mantles.

In this paper, we report on the results of experimental studies of the irradiation of pure water ices using 2 keV 13C+ and 13C2+ ions. Studies have been carried out at two temperatures (30 and 90 K) and the influence of the different morphologies at these temperatures has also been studied. With singly charged ions, the formation of 13CO2 was observed to be a strongly dependent upon morphology and showed a weaker dependence upon temperature. With doubly charged ions, the dependence upon temperature was significantly stronger. This is explained by enhanced production of reactive species resulting from the additional potential energy contained within the doubly charged ions. Increased temperature provides mobility to these species which may then yield additional 13CO2.

Ices, silicates and carbonaceous materials have been detected in several astrophysical environments such as interstellar molecular clouds, comets, and planetary surfaces. These solids are continuously exposed to ion irradiation and UV photolysis. Our knowledge on the properties of solids and molecules and on the modification induced by fast ions (keV-MeV) and UV photons is mainly based on laboratory experiments and on the comparison of experimental results with observations. Here we will give a few examples of the role of laboratory experiments to our understanding of the physical and chemical properties of ices in space.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO A origem da vida ainda é uma questão aberta na ciência. Dentre as possíveis respostas, a panspermia é uma alternativa amplamente discutida. Ao investigar esta possibilidade, o desenvolvimento de modelos que descrevam o comportamento de moléculas interagindo com raios cósmicos são de extrema importância. Para esta finalidade, filmes finos de diferentes espessuras de bases nitrogenadas - adenina, citosina, guanina e timina - foram depositados sobre pastilhas de ZnSe para serem irradiados por elétrons de 1,0 e 0,50 keV. A adenina foi irradiada sob diferentes temperaturas. Após cada irradiação parcial, a espectroscopia óptica na região do infravermelho (FTIR) foi usada para monitorar as modificações nas características espectrais. Observou-se que a seção de choque de destruição das bases nitrogenadas irradiadas é aproximadamente 10 elevado a -16 cm quadrados e, para a adenina, este valor aumenta para temperaturas baixas. Com base nos dados obtidos de glicina, o tempo de meia vida de adenina pura processada por vento solar a 1 UA estimado é de cerca de 40 dias. A seção de choque varia muito pouco quando as espessuras dos filmes são aumentadas de 10 para 30 nm, e os valores encontrados para as quatro bases seguem a ordem: citosina, adenina, guanina e timina, respectivamente, da menos para a mais radioresistente. Para melhor compreender o significado dos resultados experimentais, previsões foram obtidas com o algoritmo CASINO-estendido e apresentam bom acordo se radiólise e sputtering são considerados. The origin of life is still an open question in science. Among the possible answers, panspermia is a widely discussed alternative. To investigate this possibility, the development of models that describe the behavior of molecules interacting with cosmic rays is extremely important. For this purpose, thin films of different thicknesses of nitrogenous bases - adenine, cytosine, guanine, and thymine - were deposited on ZnSe disks to be irradiated by 1.0 and 0.50 keV electrons. Adenine was irradiated under different temperatures. After each partial irradiation, optical spectroscopy in the infrared region (FTIR) was used to monitor changes in spectral characteristics. It is observed that the destruction cross sections of irradiated nitrogenous bases are approximately 10 raised to -16 square cm and, for adenine, this value increases at low temperatures. In comparition to glycine data, the estimated half-life of pure adenine when processed at 1 au by the solar wind is about 100 days. The cross section varies very little when the film thicknesses are increased from 10 to 30 nm, and the bases follow the order: cytosine, adenine, guanine and thymine, respectively, from the least to the most radioresistant. To better analyze the experimental data, they are compared with predictions obtained with the CASINOextended algorithm. They are in good agreement if radiolysis and sputtering are considered.