Carbonaceous extraterrestrial matter is observed in a wide variety of astrophysical environments. Spectroscopic signatures reveal a large variety of chemical structure illustrating the rich carbon chemistry that occurs in space. In order to produce laboratory analogues of the carbonaceous cosmic dust, a new chemical reactor has been built in the Laboratoire de Photophysique Moléculaire. It is a low pressure flat burner providing flames of premixed hydrocarbon/oxygen gas mixtures, closely following the model system used by the combustion community. In such a device the flame is a one-dimensional chemical reactor offering a broad range of combustion conditions and sampling which allows production of many and various by-products. In the present work, we have studied the effect of ion irradiation (200-400 keV), at the Laboratorio di Astrofisica Sperimentale in Catania, on several samples, ranging from strongly aromatic to strongly aliphatic materials. Infrared and Raman spectra were monitored to follow the evolution of the films under study, and characterize the irradiation process-induced modifications.

Polycyclic aromatic hydrocarbons (PAHs) and related aromatic materials are thought to be the most abudant class of organic carbon in the universe, being present in virtually all phases of the ISM, and abundant in carbonaceous meteorites and asteroid and comet dust. The basic PAH skeleton is proposed to have formed in outflows of carbon rich stars, and isotopic measurements of extraterrestrial graphitic carbon is consistent with this notion. However, functionalized aromatics bearing oxygen atoms, aliphatic domains, and deuterium enrichments have been extracted from meteorites and more recently been measured in IDPs and Stardust retuned comet samples. Exposure of remnant circumstellar PAHs to energetic processing at low temperature in the presense of H2O is the most parsimonious explanation for these observations.

We will present laboratory infrared spectra of various aromatic species and PAH cations in solid H2O under conditions relevant for comparsion to absorptions attributed to PAHs observed towards objects embedded in dense clouds. In addition, we shall describe the reactions of PAHs under these conditions in the lab when they are exposed to energetic processing. Finally, we will propose a mechanism, and make specific predictions regarding the structures and distribution of deuterium that should be observed in extraterrestrial samples if low temperature ice radiation chemistry is playing a role in the formation of the molecules seen in Solar System materials.

For over three decades tholins have been synthesized from mixtures of the cosmically abundant gases CH4, C2H6, NH3, H2O, HCHO, N2, and H2, previously in the Laboratory for Planetary Studies at Cornell University and in recent years at NASA Ames Research Center. The tholin synthesized by UV light or spark discharge on sequential and non-sequential pyrolysis GC-MS revealed hundreds of compounds, and on hydrolysis produced a large number of amino acids including racemic protein amino acids. Optical constants have been measured of many of the tholins, tholins produced from a condensed mixture of water and ethane at 77 K, poly HCN, and Titan tholin produced on electrical discharge through a mixture of 90% N2 and 10% CH4. Its optical constants were measured from soft x-rays to microwave for the first time.

Here we report the absorption properties of Titan tholin that is produced in the temperature range 135 to 178 K where tholins are produced by magnetospheric charged particles, then pass through lower temperature at 70 K and finally to the ground at 95 K. While descending to the ground, it gets coated and processed on the way by other sources of energy such as long UV and cosmic rays. It is therefore expected that the stable products of CH4 photolysis react with Titan tholin to recycle the CH4 supply in Titan's atmosphere. Furthermore, the reactions of gaseous C2H6 with the reactive materials on the surface of the tholin could incorporate atmospheric C2H6 into the tholin and therefore might reduce the deposition rate of C2H6 onto the ground of Titan.

The UV irradiation of interstellar/circumstellar ice analogs is known to lead to the formation of organic compounds such as amino acids and maybe nucleobases. In this work, the mechanisms of formation and distribution of amino acids, chosen as tracers for the organic compounds formed in such experiments, are studied and compared with meteoritic data.

The aim of this work is to study the chemistry of the irradiation of frozen solutions of HCN. This compound has been detected in comets and other icy bodies. The CN group might have made its first appearance in the early stages of chemical evolution. Therefore, is behavior under irradiation at low temperature is relevant for chemical evolution studies and icy bodies.

Icy bodies in space are being irradiated continuously by ionizing radiation. Therefore, the transformation of organic molecules trapped in extraterrestrial ices might have been possible. This work studied a bulk irradiation of a mixture of some constituents of cometary nuclei. The results show that the formation of different compounds, among them ammonia, carbon dioxide, amines, ureas, free amino acids, and oligomeric material, yields carboxylic acids, amino acids, and purines upon hydrolysis.

A long-standing problem in interstellar chemistry is how molecules can be maintained in the gas phase at the extremely low temperatures in space. Photodesorption has been suggested to explain the observed cold gas in cloud cores and disk mid-planes. We are studying the UV photodesorption of ices experimentally under ultra high vacuum and at astrochemically relevant temperatures (15 – 27 K) using a hydrogen discharge lamp (7-10.5 eV). The ice desorption during irradiation is monitored using reflection absorption infrared spectroscopy and the desorbed species using mass spectrometry. We find that both the UV photodesorption rates and mechanisms are highly molecule specific. CO photodesorbs without dissocation from the surface layer of the ice. N2, which lacks dipole allowed electronic transitions in the range of the lamp, does not photodesorb. CO2 desorbs through dissociation and subsequent recombination from the top few layers of the ice. At low temperatures (15 – 18 K) the derived photodesorption rates are ~ 10−3 for CO and CO2 and < 2 × 10−4 for N2 ice per incident photon.

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.

To understand the origin of protein/nucleic acid based life as we know it on Earth, we must “follow” the nitrogen. Because of its unique hydrogen bonding characteristics, nitrogen is the key element in catalytic and/or informational proteins and nucleic acids essential to cell function and reproduction. We present evidence that HCN is the original source of prebiotic protein and nucleobase nitrogen. We also present chemically rational models supporting the radical hypothesis that the polymerization of HCN yields ab initio mundi prebiotic protein and polynucleobase macromolecules of sufficient size and complexity to allow the spontaneous generation of pre-RNA World biopolymers capable of catalysis and information transfer.

Laboratory simulation of interstellar grain processing is a unique tool to better understand the nature and evolution of cosmic dust. In recent years this approach has been crucial to outline a new model of evolution of the aliphatic component of organic matter in the interstellar medium. Here, the results of a recent laboratory research on processing of nano-sized carbon particles by H atoms under simulated dense medium conditions are discussed. The experiments show that the formation of C-H bonds in the aliphatic CH2 and CH3 functional groups does not take place, while the activation of a band at 3.47 μm, due to the C-H stretching vibration of tertiary sp3 carbon atoms, is observed. These results indicate that the assumption about inhibition of aliphatic C-H bond formation in interstellar dense clouds is correct. Moreover, they suggest that carbon grains responsible for the interstellar aliphatic band at 3.4 μm in diffuse regions can contribute to the absorption observed at 3.47 μm in dense clouds.

A wide variety of organic compounds have been found in carbonaceous chondrites and comets, which suggests that extraterrestrial organic compounds could have been an important source of the first terrestrial biosphere. In the Greenberg model, these organic compounds in the small bodies were originally formed in interstellar dusts (ISD) in dense clouds by the action of cosmic rays and ultraviolet light. We irradiated a frozen mixture of methanol, ammonia and water with high-energy heavy ions from an accelerator (“HIMAC” in NIRS, Japan) to simulate the action of cosmic rays in dense clouds. Racemic mixtures of amino acids were detected after hydrolysis of the irradiation products. A mixture of carbon monoxide, ammonia and water also gave such complex amino acid precursors with large molecular weights. When such amino acid precursors were irradiated with circular polarized UV light from a synchrotron, enantiomeric excesses were detected. The yield of amino acids was not largely changed between, before, and after CPL-irradiation. The present results suggest that the seed of homochirality of terrestrial amino acids were originally formed in interstellar space.

Large laser sparks created by a single shot of a high-power laser system were used for the laboratory simulation of the chemical consequences of high-energy-density events (lightning, high-velocity impact) in planetary atmospheres, e.g., the early Earth's atmosphere.

It is important to say that the formaldehyde and hydrogen cyanide have been detected in the interstellar medium through resonance spectrum emission. Here I describe a way to produce uracil in interstellar space.

The idea that some nitrogen bases, such as adenine and guanine, are easily formed and can be found in interstellar space is should not be rejected. In fact, they have been found in the soluble fraction of some ancient meteors. It is possible that the “seed” of life had its origin in space, and thanks to Earth conditions, a synergistic interaction ocurred and allowed life to spring forth on our planet.

Good evening. I'd like to invite you to join me on a journey that could be entitled “Full Circle: Star Ferry to Stardust”. “Star Ferry” represents Hong Kong, my home town, and especially its university - Hong Kong University - as I knew it during the years of World War II. “Stardust” refers to our gathering here to report on our research on possible organic chemistry in space.