Organic molecules are widely present in the dense interstellar medium, and many have been synthesized in the laboratory on Earth under the conditions typical for an interstellar environment. Until now, however, only relatively small molecules of biological interest have been demonstrated to form experimentally under typical space conditions. Here we prove experimentally that the condensation of carbon atoms on the surface of cold solid particles (cosmic dust) leads to the formation of isomeric polyglycine monomers (aminoketene molecules). Following encounters between aminoketene molecules, they polymerize to produce peptides of different lengths. The chemistry involves three of the most abundant species (CO, C and NH_3) present in star-forming molecular clouds, and proceeds via a novel pathway that skips the stage of amino acid formation in protein synthesis. The process is efficient, even at low temperatures, without irradiation or the presence of water. The delivery of biopolymers formed by this chemistry to rocky planets in the habitable zone might be an important element in the origins of life.

Abstract The role of H2 in forming interstellar complex organics is still not clear due to the high activation energies required for “non-energetic” association reactions. In this work, we investigated the potential contribution of H2 to the hydrogenated species (HnNCO) formation on dust grains when the “energetic” processing is involved. The goal is to test whether an additional hydrogenation pathway is possible upon UV irradiation of a CO:H2 ice mixture. It is proposed that the electronically excited carbon monoxide (CO*) induced by UV-photons can react with a ground-state H2 to form HCO, ultimately enhancing the production of COMs in ice mantle.

Abstract The electronic spectroscopy of various polycyclic aromatic hydrocarbon (PAH) molecules has been studied in the laboratory at low temperatures using both molecular beam and matrix isolation spectroscopy techniques. While molecular beam spectra can be readily compared to astronomical observations, the band positions measured in Ne and Ar matrices are extrapolated to obtain rather good estimates for the same transitions in the gas phase. Absolute absorption cross sections are determined for gas-phase and matrix spectra by comparing them with calibrated solution spectra. All laboratory results are analyzed and discussed in view of the role that PAHs can play as carriers of the diffuse interstellar bands (DIBs). Our studies suggest that regular neutral PAHs are not responsible for any of the known strong DIBs.

Context. As revealed by high-resolution spectral investigations in the wavelength range between 300 and 400 nm, the interstellar extinction curve does not display any of the sharp electronic absorption bands that are characteristic for large polyatomic molecules, such as polycyclic aromatic hydrocarbons (PAHs), which belong to the most abundant interstellar molecules.

Carbonaceous grains represent a major component of cosmic dust. In order to understand their formation pathways, they have been prepared in the laboratory by gas-phase condensation reactions such as laser pyrolysis and laser ablation. Our studies demonstrate that the temperature in the condensation zone determines the formation pathway of carbonaceous particles. At temperatures lower than 1700 K, the condensation by-products are mainly polycyclic aromatic hydrocarbons (PAHs), that are also the precursors or building blocks for the condensing soot grains. The low-temperature condensates contain PAH mixtures that are mainly composed of volatile 3-5 ring systems. At condensation temperatures higher than 3500 K, fullerene-like carbon grains and fullerene compounds are formed. Fullerene fragments or complete fullerenes equip the nucleating particles. Fullerenes can be identified as soluble components. Consequently, condensation products in cool and hot astrophysical environments such as cool and hot AGB stars or Wolf Rayet stars should be different and should have distinct spectral properties.

Our insight into the structural properties of cosmic dust has been improved by observations at higher spectral resolution and in a wider range of wavelengths However, the formation and processing of main dust components in different astrophysical environments is not yet completely understood Laboratory experiments combined with structural analyses are necessary to get more insight into the formation pathways and chemical-structural modification of solid grains in different astrophysical environments Spectroscopy is a main tool to characterize dust analog materials and to monitor ongoing structural transformations, but provides also the major link to astronomical observations and the tool for identification of cosmic dust properties We review recent laboratory work on cosmic dust analogs, highlighting modern condensation experiments and studies of thermal processing, UV and ion irradiation which have considerably improved our understanding of cosmic dust formation and processing in space In addition, we demonstrate the progress in spectroscopic studies, which have recently widened the spectroscopic database available to modelers and observers, especially at extreme wavelengths and for dust at low temperature

Carbonaceous materials have been prepared by laser-induced pyrolysis of a mixture of hydrocarbons (C2H2, C2H4, and benzene) under different conditions. We have investigated the soluble and insoluble part of the condensed carbon powders with several techniques, such as UV/VIS and IR spectroscopy, mass spectroscopy, gas chromatography combined with mass and IR spectrometry and high-performance liquid chromatography (HPLC) in order to obtain information on the total content and composition of the extracted soluble part and on the influence of the soluble component on the spectroscopic properties of the condensed carbon nanopowder. It has been found that the extract contains more than 64 different polycyclic aromatic hydrocarbons (PAHs). The most abundant PAH molecules are those containing 3–5 rings. The total amount of aromatic soluble components depends on the temperature in the condensation zone whereas the ratio between high- and low-mass PAHs is influenced by both, the temperature and the precursor gases. IR spectroscopic investigations of the extract have shown partial hydrogenation of PAHs leading to the formation of CH2 groups, at the edge of PAH molecules. The IR spectral properties of the carbonaceous materials and of the PAHs are influenced by the adsorption process.

The absorption spectra of the olivine particles of different Mg/Fe content were measured in the infrared spectral region between 5 and 100 mu m, while the particles were continuously cooled down to 10 K. Measurements independently carried out on different samples of synthetic forsterite, natural olivine, and synthetic fayalite at laboratories in Kyoto and Jena. The positions of the olivine infrared bands were measured for these samples in detail at up to seven individual temperatures in the interval between 300 K and 10 K. According to the different widths of the olivine bands in different wavelength regions, spectral resolutions of 2, 1, 0.5, 0.25, 0.2, and 0.125 cm(-1) were used in order to measure the band positions with high accuracy. While in general the band positions and their temperature-dependent shift agree very well for the Kyoto and Jena samples, the positions of some very strong bands differ, which is probably a consequence of different particle shapes. For the two long-wavelength forsterite bands at 49 and 69 mu m, the sharpening and strengthening of the bands were quantified. The widths of these bands differ for the Kyoto and Jena samples, which is discussed in terms of different crystal quality and particle coagulation of the samples. Our new data can be used to derive dust temperatures from the observed peak positions for crystalline silicate dust in circumstellar regions.

CO2 laser induced co-pyrolysis of toluene and iron pentacarbonyl in the presence of an ethylene sensitizer was used to produce iron-carbon nanostructures containing cementite Fe3C as the major component. The passivated Fe-C nanocomposites were characterized by several complementary analytical methods. Good agreement is found between the results of X-ray diffraction, Mössbauer spectroscopy and high-resolution transmission electron microscopy techniques which show that besides cementite, iron, and iron oxides, traces of other carbides are also present. Specific morphological aspects of the nanograins encased in a mostly disordered and quasi-amorphous carbon matrix are revealed. The simultaneous presence of rather small crystallites (mean diameter between 3–6 nm), identified as possible Fe3C/α-Fe and iron oxide (maghemite/magnetite) phases and of single-phase larger crystallites (10–13 nm mean diameter), identified as Fe3C is illustrated. Raman spectroscopy seems to confirm maghemite as the iron oxide phase present in the iron-carbon nanopowders. The level of oxidation mainly induced by powder passivation is roughly estimated by FTIR spectroscopy and leads to iron oxide contents between 11–17 wt. %. The catalytic role of iron nanoparticles in the pyrolyzed system is addressed in connection with nanocarbon samples obtained in the absence of an iron donor.

Because amorphous carbon grains are considered among the main components of cosmic dust, the characterization of their physical and chemical properties in the laboratory is needed to explain the data obtained by the astronomical observations. Material produced by laser pyrolysis of acetylene in the laboratory has been analyzed in the 4000-500 cm(-1) (2.5-20 mum) region of the infrared spectrum. It is believed that this material serves as analogue to the cosmic dust. The obtained spectra have been compared to IRAS and ISO infrared spectroscopic data.

We report the discovery of carbonates in the Planetary Nebulae NGC 6302 and NGC 6537 (Kemper et al. 2002). In the ISO LWS spectra far-infrared features have been identified with calcite and dolomite by comparison with laboratory spectra of these minerals. This is the first time that carbonates have been identified outside the solar system. In a follow-up study (Kemper et al., in prep.) a detailed analysis of the mineral composition of the dust in NGC 6302 is presented.

We describe the current state and future of the WWW Jena-Petersburg database of optical constants (JPDOC) that also contains references to papers and links to internet resources related to measurements or calculations of the optical constants of materials of astronomical interest. The most important part of the JPDOC are data measured in broad wavelength ranges and partly at low temperatures in the Jena Laboratory. To demonstrate the use of these data, we show as examples infrared refractive indices of crystalline and amorphous magnesium silicates, spinel, and hydrogenated amorphous carbon and calculate the absorption cross-sections of small particles composed of these materials.

During their lifetime, cosmic dust silicates suffer from a continuous processing by annealing, cosmic ray and UV irradiation, destruction and possibly also interstellar recondensation. Since the discovery that a significant proportion of stardust silicates leaves their star in crystalline form, the question arose as to why the interstellar silicate dust component does not show any indication of crystallinity. Amorphization due to ion irradiation is one possible explanation for the effect. In this paper, the results of irradiation experiments of submicrometre-sized clinoenstatite (MgSiO3) particles with 400 keV Ar+ and 50 keV He+ ions are presented. The irradiation doses have been varied between 1 x 10(16) and 1 x 10(18) ions/cm(2) for He+ ions and 1 x 10(14) up to 5 x 10(14) ions/cm(2) for Ar+ ions. These doses are comparable to those values that an interstellar silicate grain should be exposed to during its average life-time of 4 x 10(8) years. Threshold values for amorphization have been amounted to 1 x 10(17) and 3 x 10(14) ions/cm(2) for 50 keV He+ and 400 keV Ar+ ions. Besides the structural changes in the microcrystallites morphological modifications in the grains, but no change of the chemical composition are found. Conclusions of potential astrophysical relevance have been drawn.

. Silicate grains in space have attracted recently a wide interest of astrophysicists due to the increasing amount and quality of observational data, especially thanks to the results obtained by the Infrared Space Observatory. The observations have shown that the presence of silicates is ubiquitous in space and that their properties vary with environmental characteristics. Silicates, together with carbon, are the principal components of solid matter in space. Since their formation, silicate grains cross many environments characterised by different physical and chemical conditions which can induce changes to their nature. Moreover, the transformations experienced in the interplay of silicate grains and the medium where they are dipped, are part of a series of processes which are the subject of possible changes in the nature of the space environment itself. Then, chemical and physical changes of silicate grains during their life play a key role in the chemical evolution of the entire Galaxy. The knowledge of silicate properties related to the conditions where they are found in space is strictly related to the study in the laboratory of the possible formation and transformation mechanisms they experience. The application of production and processing methods, capable to reproduce actual space conditions, together with the use of analytical techniques to investigate the nature of the material samples, form a subject of a complex laboratory experimental approach directed to the understanding of cosmic matter. The goal of the present paper is to review the experimental methods applied in various laboratories to the simulation and characterisation of cosmic silicate analogues. The paper describes also laboratory studies of the chemical reactions undergone and induced by silicate grains. The comparison of available laboratory results with observational data shows the essential constraints imposed by astronomical observations and, at the same time, indicates the most puzzling problems that deserve particular attention for the future. The outstanding open problems are reported and discussed. The final purpose of this paper is to provide an overview of the present stage of knowledge about silicates in space and to provide to the reader some indication of the future developments in the field.

The study of the crystalline-to-amorphous transition of silicates triggered by ion irradiation is useful for the understanding of the structural modification of interstellar dust grains. We focused our experiments on the mineral enstatite (MgSiO3), an essential part of the polycrystalline silicate dust. Within our studies He+-, Li+-, Ne+- and Ar+-ions with energies between 50 and 400 keV were used. Irradiations were carried out at 70 K. The samples were analyzed by transmission electron microscopy in combination with electron diffraction and infrared reflection spectroscopy. It was found, that the number of displacements necessary to amorphize enstatite is higher for lower ion masses. The amorphization threshold increases from 0.3 to about 5 dpa in the case of 400 keV Ar+- and 50 keV He+-ions, respectively. This can be explained by the dilution of the collision cascades with decreasing ion mass and with an in situ annealing process with enhanced ratio between electronic and nuclear energy loss, respectively.

Carbonates on large Solar System bodies like Earth and Mars1,2 (the latter represented by the meteorite ALH84001) form through the weathering of silicates in a watery (CO3)2- solution. The presence of carbonates in interplanetary dust particles and asteroids (again, represented by meteorites) is not completely understood, but has been attributed to aqueous alteration on a large parent body, which was subsequently shattered into smaller pieces. Despite efforts3,4,5, the presence of carbonates outside the Solar System has hitherto not been established6,7. Here we report the discovery of the carbonates calcite and dolomite in the dust shells of evolved stars, where the conditions are too primitive for the formation of large parent bodies with liquid water. These carbonates, therefore, are not formed by aqueous alteration, but perhaps through processes on the surfaces of dust or ice grains or gas phase condensation. The presence of carbonates which did not form by aqueous alteration suggests that some of the carbonates found in Solar System bodies no longer provide direct evidence that liquid water was present on large parent bodies early in the history of the Solar System8.