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Dissertations / Theses on the topic 'Astrophysical ices'
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Dissly, Richard W. Anicich Vincent G. Anicich Vincent G. Allen Mark Andrew. "Laboratory studies of astrophysical ices /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10312007-083146.
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Dawes, Anita. "Spectroscopic study of photon, ion and electron stimulated molecular synthesis in astrophysical ices." Thesis, University College London (University of London), 2003. http://oro.open.ac.uk/40046/.
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The universe is a vast chemical and physical factory consisting of large collections of stars, gas and dust. Energetic processing of ices and subsequent molecular synthesis in astrophysical environments, including icy Solar System bodies and grain mantles in the interstellar medium, are responsible for the observation of some of the molecular species found in space. Gas phase processes alone cannot explain the reaction mechanisms and the observed abundances of some of these molecules. This thesis reviews the current state of knowledge on solid state molecular synthesis in astrophysical ices and highlights the relevance of this work to understanding the chemical origins of life. The nature and origin of astrophysical ices and their environments is discussed to provide a background for the design and implementation of a new apparatus built to simulate astrophysical environments. An outline is given of the relevant collisional and chemical processes associated with interactions between radiation and matter pertinent to astrochemistry, e.g. ion, photon and electron processing of ices. A detailed description of the design and construction of the new apparatus is given and the theory and instrumentation in the spectroscopic techniques used are discussed. This is followed by a detailed explanation of the experimental procedures implemented at both ion and synchrotron radiation sources. The first results of ion and photon irradiation of H<sub>2</sub>O and CO<sub>2</sub> ices (both pure and binary) using this apparatus are presented and discussed in detail. Ion irradiation is carried out using both reactive and unreactive ions. Reactive carbon ion implantation in pure H<sub>2</sub>O is investigated and the production of CO and CO<sub>2</sub> monitored. Experiments involving both high (100 keV) and low (1 – 5 keV) energy ion irradiation of mixed H<sub>2</sub>O:CO<sub>2</sub> ices are described and the production of H<sub>2</sub>CO<sub>3</sub> (carbonic acid) and CO investigated. The production of CO and CO<sub>3</sub> is described in UV irradiation experiments of mixed H<sub>2</sub>O:CO<sub>2</sub> ices. Particular attention is paid to the infrared band profile of CO in each of the irradiation experiments. The CO band profile shows a great degree of complexity, particularly in the carbon ion implantation experiments in H<sub>2</sub>O. Differences in the types and yields of molecular products formed and their infrared band profiles in ion and photon irradiated ices suggest different chemical and physical processes taking place. Trial experiments of VUV synchrotron photoabsorption experiments of H<sub>2</sub>O and NH<sub>3</sub> ices are also described. Results reveal a blueshift of 20 – 25 nm in the peak absorption of the first excited electronic state, observed in both species, and is attributed to the effect of hydrogen bonding. The thesis ends with suggestions of the possible modifications to the apparatus and plans for future work.
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Bychkova, Anna. "Energetic iοn prοcessing οf arοmatic mοlecules in the sοlid phase". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMC236.
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Dans les nuages denses, les manteaux glacés sont des condensats de petites molécules sur des grains solides. Ces manteaux glacés représentent des sites prometteurs pour certains processus chimiques. Ils sont constamment irradiés et de nouvelles molécules organiques complexes peuvent être ainsi formées. Une fois que les nuages denses se transforment en disque d'accrétion et, éventuellement, en système planétaire, ces manteaux glacés peuvent potentiellement contribuer au réservoir de molécules complexes des planètes. Dans cette thèse, les effets de l'irradiation ionique sur deux molécules aromatiques, la pyridine et le pyrène, ont été étudiés. Les échantillons ont été exposés à une irradiation ionique sur les lignes des accélérateurs du GANIL (Caen, France) et de l'ATOMKI (Debrecen, Hongrie). Leur évolution a été suivie par spectroscopie infrarouge in situ. Il a été constaté que la structure initiale (amorphe ou cristalline) et la température d'irradiation n'affectent pas la section efficace de destruction de la pyridine pure. De plus, il a été observé que la dose locale n'est pas un paramètre clé comme cela était affirmé précédemment. En effet, la destruction du pyrène provoquée par des ions lourds, à partir du carbone, est significativement plus importante que celle provoquée par des ions plus légers comme l'hydrogène et l'hélium pour une même dose locale déposée. Pour les deux molécules, une augmentation significative de la section efficace de destruction a été observée lorsque la concentration des molécules dans la matrice d'eau diminue. Le temps de demi-vie de la pyridine et du pyrène dans les nuages denses a été estimé à environ 13 et 20 millions d'années, respectivement. Cela suggère qu'une fois formées dans ces environnements, ces molécules pourraient survivre et contribuer à la formation planétaire<br>Formed in the dense clouds, icy mantles are condensates of small molecules on solid grains. These icy mantles are promising sites for rich chemical processes, where complex organic molecules can form, as these mantles are continuously exposed to ionizing radiation. Once dense clouds transform into an accretion disc and eventually into a planetary system, these icy mantles may potentially contribute to the reservoir of the complex molecules of the planets.In this thesis, the effects of ion irradiation on two aromatic molecules, pyridine and pyrene were investigated. The samples were exposed to ion irradiation at the GANIL (Caen, France) and ATOMKI (Debrecen, Hungary) ion beam facilities. Their evolution was monitored using in-situ infrared spectroscopy. It was found that the initial structure (amorphous or crystalline) and the irradiation temperature do not affect the destruction cross section of pure pyridine. Additionally, it was observed that the local dose is not a key parameter as previously assumed. Indeed, since the destruction of pyrene caused by heavy ions, starting from C, is significantly greater than that caused by lighter ions such as H and He for the same deposited local dose. For both molecules, a significant increase in the destruction cross section was observed for decreasing molecule concentration in the water matrix. The half-life time of pyridine and pyrene in dense clouds was estimated to be around 13 and 20 millions of years, respectively. This suggests that once formed in these environments, they could survive and contribute to planetary formation
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Holtom, Philip Derek. "Irradiation studies of astrophysical ice analogues." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444790/.
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In this thesis the formation of molecular species in cold icy mantles, typical of those in the interstellar medium (ISM) has been studied. The construction of an ultra high vacuum system for the formation and containment of these astrophysical ice analogues is described. The method of preparation of these ices is detailed and analysis methodologies are discussed. VUV spectra of molecular ices (e.g. SO2, CH3NH2, OCS) measured on the UV1 beam line of the Astrid Synchrotron facility at the University of Aarhus in Denmark, are presented. Molecular synthesis (e.g. CO3, CO, H2CO3) induced by ion irradiated CO2/H 2O ices using facilities at Queens University Belfast are also reported. In particular this thesis focuses on the irradiation studies of the binary ice mixture of Methylamine (CH3NH2) and Carbon Dioxide (CO2). The results of irradiation of CH3NH2 and CO2 binary ice mixtures by ultraviolet photons, and electrons are presented. The apparent production of the amino acid - glycine - in our irradiated samples is discussed together with possible production processes.
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Korsmeyer, Julie. "Anthracroronene in Astrophysical Water-Ice Analogs." Scholarship @ Claremont, 2019. https://scholarship.claremont.edu/scripps_theses/1413.
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Polycyclic aromatic hydrocarbons (PAHs) are the most abundant large organic molecules in space. They are thought to be the main contributor to the unidentified infrared (UIR) emission bands from the interstellar medium (ISM) for several reasons: UIR intensities correspond to carbon abundance, indicating the presence of a carbon-based molecule; UIRs are found in extremely harsh environments which means the source must be a stable molecule. The most important evidence is if the bands in mid-infrared (MIR) or 'fingerprint' region match those of PAHs. Through the infrared spectroscopy of matrix-isolated polycyclic aromatic hydrocarbons a compound's unique neutral and ionized vibrational modes can be identified. In this work, the PAH anthracoronene (AntCor, C36H18) is suspended in a matrix of water-ice, irradiated with ultraviolet (UV) light, and then analyzed using Fourier Transform Infrared (FTIR) spectroscopy. AntCor has not been studied in water ice before, and therefore the vibrational transition data collected (i.e. band positions and intensities) has been compared to coronene and anthracene, the parent molecules, and with theoretical predictions made using density functional theory. The data from this work will be incorporated into the NASA Ames PAH IR Database, where it will be applied to astronomical observations of the unidentified infrared emissions of the ISM, as well as observations of infrared absorption features in dense molecular clouds.
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Ding, Jing-Jie. "Irradiation of water ice and astrophysical implication." Caen, 2014. http://www.theses.fr/2014CAEN2056.
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Les glaces sont présentes dans notre système solaire par exemple sur les comètes, les lunes de Jupiter et de Saturne ainsi que sur les objets trans-neptuniens. Dans le milieu interstellaire, ces glaces forment une fine couche à la surface de grains des nuages denses. L’eau (H2O) est la molécule la plus abondante dans ces glaces. Ces glaces sont constamment exposées aux rayons cosmiques, au vent solaire et aux ions piégés dans la magnétosphère des planètes géantes. Les simulations de ce type d’irradiation associées aux observations peuvent nous amener à comprendre la grande variété des processus physicochimiques induits par l’irradiation. Nous avons donc irradié des glaces avec les ions produits par le GANIL afin de simuler les effets des rayons cosmiques pour les ions lourds rapides et les effets du vent solaire pour les ions lents. Les modifications induites sont étudiées par spectroscopie infrarouge dans le domaine 500-5000 cm-1. L’irradiation induite des changements de structure tels que la compaction et l’amorphisation. Plusieurs ions ont été utilisés afin de déterminer la dépendance de ces processus physiques en fonction du pouvoir d’arrêt du projectile. A basse énergie l’implantation d’ions soufre a permis de mesurer le taux de production de l’acide sulfurique H2SO4, molécule observée à la surface d’Europa. La comparaison avec les observations et les mesures de flux des ions soufre à la surface d’Europa amène à penser que le processus d’implantation est primordial pour expliquer la présence de H2SO4 sur cette lune de Jupiter. Finalement, une étude préliminaire sur le rôle de l’interface entre un substrat carboné et une glace de NH3+H2O est présentée<br>Ices can exist in our solar system for example on comets, the moons of Jupiter and Saturn, and trans-Neptunian objects. In the cold interstellar medium, they form thin layers on dust grains. Water (H2O) is the most abundant molecules in those ices, which are continuously exposed to the irradiation by cosmic rays, solar wind, and ions trapped in the magnetosphere of the giant planets. Simulation in the laboratory compared to telescopic observations can provide information to understand the large variety of radiation induced physicochemical processes. Therefore, we simulated the effects of swift heavy ion (cosmic ray analogs) and slow ion (solar wind, magnetosphere ions) irradiation of water ice at different beam lines of the GANIL accelerator facility. Fourier transform infrared spectroscopy (FTIR) was used to analyze the ices. The irradiation induced structural changes of water ice such as amorphization and compaction were studied. The efficiency to amorphize and compact the ice was established as a function of projectile stopping power with several swift heavy ions. Furthermore, by implantation of sulfur ions in water ice, the formation yield of sulfuric acid was measured and found to increase with projectile energy. From comparison to measure sulfur ion fluxes and sulfuric acid concentrations by the Galileo spacecraft, strong evidence was found that H2SO4 on Europa’s surface can be formed by sulfur ion implantation of magnetosphere ions in water ice. Finally, we also performed a first preliminary experiment to study the radiation induced chemistry with a carbonaceous solid substrate covered with a NH3+H2O ice mantle
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SanfeÌlix, Maria Jose Cabrera. "Molecular modelling of water ice in atmospheric and astrophysical environments." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415664.
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Hettlage, Christian. "Lepton production in ice by scattering of astrophysical neutrinos at high energies." Doctoral thesis, [S.l.] : [s.n.], 2005. http://webdoc.sub.gwdg.de/diss/2005/hettlage.
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Muntean, E. A. "Low energy ion irradiation of astrophysical ice analogues : sputtering and molecule formation." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680064.
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The work presented in this thesis is an experimental investigation into the sputtering of oxygen and water ice by 4 ke V ions under conditions existing in the Interstellar Medium (ISM). This work is divided into two main parts : 1) sputtering of oxygen ice by singly and doubly charged ions He+, Ar+, C+, N+ ,0, C2+, N2+ and 0 2+ and 2) sputtering of water ice by C+, N+, 0+, C2+, N2+ and 0 2+. The experimental sputter yield obtained for both oxygen and water ice is compared with those from a theoretical obtained model and found to be in reasonable agreement within the experimental errors. For oxygen and water ice, deposited at 10 K, the refractive index was experimentally determined and found to have values of 1.285 and 1.282 respectively that are in good agreement with previous results. In the case of oxygen ice the sputtering yields are at least nine times larger compared to that of water ice. For water ice the doubly charged ions have, the same sputtering yield ,as the singly charged ions within the experimental errors. In the case of oxygen ice the doubly charged ions have the same sputtering yield as the singly charged ions, except 0+ and 0 2+, where 0 2+ has a significantly lower sputtering yield.
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Dupuy, Rémi. "Photon and electron induced desorption from molecular ices Spectrally-resolved UV photodesorption of CH4 in pure and layered ices The efficient photodesorption of nitric oxide (NO) ices : a laboratory astrophysics study X-ray photodesorption from water ice in protoplanetary disks and X-ray-dominated regions." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS068.
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L’excitation électronique de molécules condensées sur des surfaces froides (10-100 K) peut mener à la désorption de certaines de ces molécules. Ce processus fondamental a des conséquences dans de nombreuses disciplines, dont deux ont guidé ce travail : l’astrochimie et la dynamique du vide dans les accélérateurs. La désorption induite par photons et électrons est étudiée pour des films amorphes de molécules condensées (glaces) telles que CO, H2O, NO ou CH4. Un objectif de cette thèse est la quantification de la désorption des différentes espèces, et d’explorer les paramètres pouvant affecter l’efficacité du processus. Le second objectif est de déterminer l’évolution et la relaxation des excitations électroniques initiales et par quel mécanisme cela mène à la désorption. La photodésorption est étudiée au LERMA en utilisant le rayonnement synchrotron dans la gamme du VUV (5-14 eV) et des X mous (520-600 eV). Cela permet d’obtenir une information spectrale cruciale pour la compréhension des mécanismes et pour l’implémentation dans les modèles. La désorption induite par les électrons est étudiée au CERN dans la gamme d’énergie 150-2000 eV. Les résultats obtenus étendent les données de photodésorption UV disponibles et permettent de déterminer la pertinence de la désorption par les électrons ou les rayons X pour l’astrochimie. Des progrès sont faits dans la compréhension des mécanismes, notamment sur le rôle du transport d’énergie ou de particules depuis l’intérieur de la glace vers la surface, ou sur la désorption indirecte. Un nouveau dispositif expérimental a aussi été mis en place au LERMA pour des expériences de désorption par laser et de spectroscopie laser, permettant d’obtenir l’énergie interne et cinétique des molécules désorbées<br>The deposition of energy in the form of electronic excitations in molecules condensed on cold surfaces (10-100 K) can lead to the desorption of some of these molecules. This basic surface science process has consequences in a variety of fields, two of which are of concern here : astrochemistry and vacuum dynamics. Photon and Electron-Induced desorption are studied in this manuscript for thin films of condensed molecules (ices), e.g. CO, H2O, NO or CH4. The first objective is to obtain a quantification of the desorption of the various desorbing species, and to look for the parameters that affect the efficiency of the process. The second objective is to understand the mechanisms of evolution and relaxation of the initial electronic excitations that lead to desorption. Photon-induced desorption is studied at LERMA using synchrotron radiation in the VUV range (5-14 eV) and soft X-ray range (520-600 eV). This allows to obtain spectrally-resolved information, which is crucial both for model implementation and fundamental understanding of the mechanisms. Electron-induced desorption is studied at CERN in the 150-2000 eV range. The results expand the available data on UV photodesorption and allow to determine the relevance of electron or X-ray desorption for astrochemistry. Progress has also been made on the understanding of mechanisms, particularly on the role of energy or particle transport from the bulk to the surface of the ice, on indirect desorption, or on the desorption of ions in the soft X-ray range. A new experimental set-up has also been developed at LERMA for laser desorption and laser spectroscopy experiments, allowing quantum-state and kinetic energy resolved measurements of desorbed molecules
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Mastrapa, Rachel Michelle Elizabeth. "Water ice and radiation in the solar system." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290041.
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Infrared detection of water ice phase can reveal the temperature and radiation history of a surface. In this dissertation, I will describe and quantify the process of amorphization of crystalline ice through lab experiments and computer simulations. I will then show how these measurements can be applied to ground based observations. The amorphous phase of solid water forms at temperatures less than 130 K, and converts to crystalline ice at 135 K in an exothermic and irreversible reaction. The amorphous and crystalline phases have distinctive spectra in the infrared. However, ion irradiation of crystalline water ice in the lab makes the infrared spectrum indistinguishable from that of amorphous ice. If the process of amorphization can be quantified, the model can be applied to various planetary surfaces, using an estimate of the temperature and the radiation environment. This work sheds light on the physical processes behind amorphization. I will show that the irradiation of crystalline ice does not create the amorphous phase of ice, but produces a sample that is spectrally indistinguishable from amorphous water ice. The changes in the spectral features are caused by the breaking of OH and hydrogen bonds among other processes. The temperature dependence of this process is a function of the ability of free hydrogen and oxygen to reform the crystalline lattice.
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Accolla, Mario. "Experimental Investigation on the Morphology of Interstellar Ice Analogues." Phd thesis, Université de Cergy Pontoise, 2010. http://tel.archives-ouvertes.fr/tel-00609347.
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Spectroscopic observations of cold and dense interstellar clouds show the presence of "dirty ice" mantles on dust grains, mainly composed by water molecules. These ices are enriched by the presence of other simple species that are either formed by surface reactions or accreted from the gas phase. While there is quite a general consensus that interstellar water ice is mainly amorphous, its morphology (porous or compact) still remains poorly known. Morphology is important due to its influence both on the catalytic efficiency of grain surfaces and on the release to the grain of the fraction of the formation energy of species, as shown by laboratory simulations of molecular hydrogen formation. Ice porosity may be identified through the weak infrared absorption features (~ 2.7 μm) showing the presence of dangling bonds on the pore surface. To our knowledge, there has been to date no detection of such absorptions in the infrared spectra of interstellar ices, perhaps suggesting that they may have a compact nature. It has been already investigated that interstellar porous ice may be compacted by the transient heating of stellar radiation and cosmic ray bombardment. In this thesis I report an experimental work, performed using FORMOLISM (the experimental apparatus at the University of Cergy-Pontoise - France), that shows relevant changes in the ice morphology following atomic hydrogen exposure. In particular, it is shown that a thin highly porous ice film is gradually changed into a more compact structure. This is probably due to the transient heating caused by the energy released to the ice during H2 formation. Such a process may also produce in the interstellar space compact amorphous ice mantles concurrently with the other envisaged processes. Moreover, I have experimentally analyzed the morphology of the just formed water ice. Analysing one of the possible mechanism of water formation (the pathway H + O2) under conditions mimicking those found in a molecular cloud, we have found that the water just synthesized has a non-porous structure. Indeed, the layers of water formed in this way show the kinetic characteristics typical of a compact (non-porous) ice, as for instance the D2 TPD peak position.
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Modica, Paola. "From astrophysics to astrobiology : significance of laboratory organic residues from photo-irradiation of cosmic ice analogs." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112329/document.
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Les expériences de laboratoire ont montré que la photo-irradiation ultraviolette d'analogues de glaces astrophysiques suivie de leur réchauffement à température ambiante mène à la formation de résidus organiques réfractaires. Ces résidus, solubles dans l'eau, consistent en un riche mélange de composés organiques incluant entre autres des acides aminés, molécules potentiellement importantes pour la chimie prébiotique. Ces résidus sont considérés comme des analogues de la matière organique réfractaire que l'on pense être synthétisée sur les grains de poussière dans les nuages moléculaires et/ou dans les disques protoplanétaires, produit de l'évolution des glaces, et qui pourra être accrétée plus tard en comètes ou en astéroïdes et finalement délivrée sur la Terre primitive. Ainsi, l'étude de ces analogues, produits dans des conditions astrophysiques pertinentes, représente un outil efficace pour explorer les processus à l'origine de la formation des molécules organiques complexes dans le Système Solaire et en particulier la possible introduction d'excès énantiomériques dans les molécules chirales.Ce travail de thèse est consacré à l'étude de ces résidus organiques, leur caractérisation et les applications astrophysiques de ces résultats. Nous avons utilisé différentes techniques d'analyse comme la chromatographie en phase gazeuse couplée à la spectrométrie de masse (GC MS, classique et multidimensionnelle), la spectrométrie de masse par résonnance cyclotronique ionique à transformée de Fourier (FT ICR MS) ou encore la spectroscopie infrarouge. Nous avons mesuré les excès énantiomériques induits dans cinq acides aminés par irradiation de nos analogues avec de la lumière UV polarisée circulairement (UV CPL) et insérons nos résultats dans le cadre d'un scénario astrophysique cohérent pour expliquer l'origine des excès énantiomériques observés dans les acides aminés météoritiques. Nous avons étudié le contenu en acides aminés de la météorite de "Paris" et montré des similarités avec la distribution en acides aminés de nos résidus organiques. Nous avons également produit des analogues plus réalistes de grains interstellaires en incluant une surface silicatée, afin de tester l’effet potentiel de cette surface sur la formation et la nature des résidus organiques. Enfin, nous effectuons une discussion générale à propos de la pertinence de ces résultats dans le contexte astrophysique et soulignons le possible lien entre astrochimie et chimie prébiotique<br>Laboratory experiments have shown that ultraviolet photo-irradiation of astrophysical ice analogs and their following warm-up until room temperature lead to the formation of refractory organic residues. These residues consist of rich mixtures of organic compounds, including amino acids, which have a potential importance for prebiotic chemistry. They are considered as analogs of the organic refractory materials that are thought to be synthesized on dust grains in molecular clouds and/or in protoplanetary disks, as a product of ices evolution, and that could be later accreted into comets and asteroids and eventually be delivered to the early Earth. Hence, the study of these analogs, produced under astrophysically relevant conditions, represents a valid tool to investigate the processes at work for the origin of complex organic molecules in the Solar System and in particular the possible introduction of enantiomeric excesses in chiral molecules. This PhD work is devoted to the study of these laboratory organic residues, their characterization and the astrophysical applications of the results. We used different analytical techniques such as gas chromatography mass spectrometry (GC MS, classical and multidimensional), Fourier transform ion cyclotron resonance mass spectrometry (FT ICR MS), and infrared spectroscopy. We measured the enantiomeric excesses induced in five chiral amino acids by UV circularly polarized light (UV CPL) irradiation of our analogs and insert our result in a coherent astrophysical scenario for the origin of the enantiomeric excesses observed in meteoritic amino acids. We studied the amino acid content of the Paris meteorite and evidence some similarities with the distribution of the amino acids in our organic residues. We also produced more realistic analogs of interstellar grains, including a silicate surface, to test the potential effect of such a surface on the formation and nature of organic residues. Finally, we discuss the significance of these results in the astrophysical context and the possible relationship between astrochemistry and prebiotic chemistry
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Dai, Wei. "Gas trapping in amorphous water ice: A theoretical and experimental approach." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284175.
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The solar system began with the collapse of a dense molecular cloud, which is rich in atoms, dust grains and diverse molecules. The complexity of different physical and chemical processes which happened during the formation of the early solar system constitute a major topic within our scientific community, even though a complete model of the solar nebula including all such processes has not been constructed. This thesis deals with some of these chemical and physical processes and consists of two phases. In the first phase of my work, I have studied the heating of water-ice grains during infall into the solar nebula from the surrounding collapsing cloud. The investigations in this phase extend previous studies (Lunine et al., 1991) in two aspects. Firstly, we revise the previous grain heating model. The calculations for large fluffy grains (up to 10μm) are conducted. Secondly, we explicitly incorporate terms associated with various exothermic and endothermic reactions which contribute to the thermal evolution of the grains in our computation. By tracking the threshold temperatures reached as a function of grain size, density and infall velocity, we are able to quantify the evolution of infalling interstellar grains. Once the volatiles were brought in by the ice grains, codeposition of diversed volatiles on the surface of refractory grains happened in the cold solar nebula region. Disk dynamical evolution leads to a background temperature below 50K at distance beyond 20AU. Studies have shown that amorphous water ice forms at this temperature range. Amorphous ice can volumetrically absorbs a large amount of volatiles. My work in the second phase consists of investigations of amorphous water ice, especially its property of trapping various volatiles under conditions well outside the stability field of the condensed phases of the volatiles. A statistical thermodynamical model has been established. It is used to predict fractional abundances of trapped volatiles in different temperature and pressure conditions. Our investigations involve both theoretical and experimental studies.
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Pope, Shelly Kay. "Laboratory measurements of the single-scattering properties of ammonia ice crystals." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185372.
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This work presents scattering measurements and photographs of ammonia ice crystals grown at temperatures from 130 to 180 Kelvins. The prime candidate for the material making up the visible clouds of Jupiter and Saturn is ammonia ice. Spacecraft observations of these planets have constrained the single-scattering properties of the cloud particles. To further investigate the nature of these particles, ammonia ice crystals were grown under conditions simulating the atmosphere of Jupiter and Saturn. The experimental apparatus used to make these measurements includes a glass-walled cylindrical chamber which permits measurement of the scattered light over a wide range of scattering angles and a temperature control system which uses a liquid nitrogen reservoir combined with heaters. The chamber is illuminated by a tungsten lamp through a rapidly spinning filter/polarizer wheel which yields measurements of intensity and linear polarization in each of three colors. A photographic record of the crystals is obtained with a microscope objective, and six linear array detectors measure the scattered light. A variety of crystal shapes and phase functions were seen. A representative selection of scattering measurements and photographs are presented. The data do not resemble theoretical calculations for ammonia cubes, tetrahedra, or octahedra. They do appear similar to microwave analog measurements of the scattering properties of a mix of particle shapes as well as of fluffy particles. The ammonia measurements fall into two groups: one has wavelength-dependent polarization and for size parameters up to about seven the scattering properties can be fit by Mie theory. The second group has wavelength-independent phase functions, implying size parameters of 10 to 50, and has a characteristic signature of polarization varying from -10% to +10%. The data can be used to rule out some models for Jupiter's and Saturn's atmospheres and to guide future modelling efforts. For Jupiter, models with a cloud of ammonia crystals of size parameter equal to about 5 (in the red) are suggested. For Saturn, a model is suggested that has a thin layer of small ammonia crystals (in the Mie range) over a thicker ammonia cloud with the wavelength-independent polarization that is characteristic of larger crystals.
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Benson, Jennifer Lynn. "Properties of Water Ice Clouds over Major Martian Volcanoes Observed by MOC." University of Toledo / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1163799718.
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Déry, Francis. "Interannual and intraseasonal variability of the ice cover in the Gulf of Saint Lawrence, 1963-1990." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56975.
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Using a dataset of weekly ice cover in the Gulf of St. Lawrence, the intraseasonal and interannual variabilities of the mean ice cover fraction were investigated over the Gulf and six of its subregions for the 1963-90 period. Climatological seasonal cycles were calculated by averaging the weekly ice cover fraction means over the sampling period. The interannual variability was investigated using seasonal and monthly means. The major findings are the positive trend of the seasonal means and the prominence of variability at the interdecadal scale (12-15 yr).<br>Relationships with runoff, monthly surface air temperature, monthly air circulation, autumnal water salinity and temperature profiles, and particular climatic events are investigated to determine the major causes of the variability.<br>From the original 83-cell grid data, the monthly-averaged icefields of the Gulf were calculated and their maps generated for the months of January, February, March, April and May for every sample year.
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Poteet, Charles Allen. "Characterizing Dust and Ice Toward Protostars in the Orion Molecular Cloud Complex." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1341606610.
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Whitehead, Samuel Robert. "On the Properties of Ice at the IceCube Neutrino Telescope." Thesis, University of Canterbury. Physics and Astronomy, 2008. http://hdl.handle.net/10092/1529.
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The IceCube Neutrino Telescope is designed to detect high energy neutrinos with a large array of photomultiplier tubes placed deep within the Antarctic ice. The way that light propagates through the ice needs to be modelled accurately to enable the paths of charged particles to be reconstructed from the distribution of their Cerenkov radiation. Light travelling through even the purest of ice will undergo scattering and absorption processes, however the ice in which IceCube is embedded has optical properties that vary significantly with depth which need to be accurately modelled. Currently, simulation of the muon background using the current ice model is unable to fully replicate experimental data. In this thesis we investigate a potential method of improving on the current generation of ice models. We introduce thin, highly absorbing layers into the current description of the detection medium and investigate the effect on the simulation of muon tracks in IceCube. We find that better agreement between simulation and data can be seen in the occupancy of optical modules, through the introduction of such absorptive layers into the existing ice layers.
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Chan, Ngai Ham. "Stability of Planetary Rotation." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11684.
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This thesis focuses on the long-term rotational stability of the Earth and terrestrial planets. One important class of perturbation is a reorientation of the solid planet with respect to a rotation pole that remains fixed in an inertial frame. These motions are driven by mass redistribution within or on the surface of the planet (e.g. glaciation, mantle convective flow). Long-term changes in the orientation of the rotation pole are called True Polar Wander (TPW).<br>Earth and Planetary Sciences
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Schmitt, Bernard. "La Surface de la glace structure, dynamique et interactions, implications astrophysiques /." Phd thesis, Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37601091r.
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Joliat, Julien. "Modélisation des processus de piégeage, par la glace d'eau et les clathrates hydrates, de petites molécules d'intérêt astrophysique." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2023. http://www.theses.fr/2023UBFCD053.
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Dans ce travail de thèse, des simulations à l'échelle moléculaire ont permis de modéliser le piégeage, éventuellement sélectif, de molécules légères par des systèmes glacés (glace cristalline hexagonale et clathrates hydrates), à des températures et pressions typiques de certains corps du Système Solaire (tels qu'Encelade et Titan). L'objectif fondamental est de mieux comprendre comment, en favorisant le piégeage de certaines espèces par rapport à d'autres, la structure moléculaire de la glace peut influencer la composition de la phase fluide environnante. Des simulations Monte Carlo ont été effectuées dans l'ensemble grand canonique (GCMC). Ces simulations sont parfaitement adaptées au calcul des isothermes et des énergies d'adsorption, observables pouvant faire l'objet de comparaisons avec les résultats expérimentaux disponibles. En particulier, le piégeage de petites molécules d'alcool a été modélisé sur la glace hexagonale, ainsi que, pour la première fois, le piégeage d'un mélange n-butanol/acide acétique, en différentes proportions. La sélectivité du piégeage de mélanges N2 -- CH4 dans les clathrates hydrates de Titan a également été étudiée en détail. Ces résultats, en très bon accord avec les données expérimentales, ouvrent la voie à des travaux de modélisation de la sélectivité du piégeage d'autres fluides mixtes, par d'autres formes d'eau solide, telle que la glace amorphe<br>In this work, molecular-scale simulations have been used to model the trapping, possibly selective, of small molecules by icy systems (hexagonal crystalline ice and clathrate hydrates), at temperatures and pressures typical of certain bodies in the Solar System (such as Enceladus and Titan). The main objective is to gain a better understanding of how, by favoring the trapping of certain species over others, the molecular structure of ice can influence the composition of the surrounding fluid phase. Monte Carlo simulations have been carried out in the grand canonical ensemble (GCMC). These simulations are perfectly suited for calculating adsorption isotherms and adsorption energies, observables that can be compared with available experimental results. In particular, the trapping of small alcohol molecules has been modeled on hexagonal ice, as well as, for the first time, the trapping of a mixture of n-butanol/acetic acid in different proportions. The selectivity of trapping mixtures of N2 -- CH4 in Titan's clathrate hydrates has also been characterized in detail. These results, in excellent agreement with experimental data, pave the way for modeling the selectivity of trapping other mixed fluids by other forms of solid water, such as amorphous ice
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Grisolle, Florence. "Les condensats saisonniers de Mars : étude expérimentale de la formation et du métamorphisme de glaces de CO2." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-01010519.
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Chaque année sur Mars, en automne et hiver, une partie importante de l'atmosphère passe de l'état gazeux à solide. Ce condensat, principalement du CO2 solide, s'accumule au sol sous forme de neige, givre ou glace. Cela se produit aux plus hautes latitudes, où les températures baissent suffisamment grâce à la nuit polaire pour provoquer ces dépôts qui disparaissent au retour du soleil au sortir de l'hiver. Les mécanismes de formation de ces glaces, leurs propriétés microphysiques ou encore leur évolution durant la nuit polaire puis avec l'insolation sont encore peu connus. Au cours de cette thèse un dispositif expérimental a été créé pour former et étudier en laboratoire des glaces de CO2 de différentes textures, en conditions analogues à Mars. Le dispositif permet de suivre et contraindre plusieurs paramètres thermodynamiques, observer visuellement l'évolution de l'échantillon et le caractériser spectralement. Les résultats amélioreront la compréhension du cycle du CO2 et les données acquises par les sondes spatiales martiennes.
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Beise, Jakob. "In-situ calibration device of firn properties for Askaryan neutrino detectors." Thesis, Uppsala universitet, Högenergifysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-452702.
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Simulations have demonstrated that high-energy neutrinos (E > 1017 eV) are detected cost-efficiently via the Askaryan effect in ice, where a particle cascade induced by the neutrino interaction produces coherent radio emission that can be picked up by antennas installed below the surface. A good knowledge of the near surface ice (aka firn) properties is required to reconstruct the neutrino properties. In particular, a continuous monitoring of the snow accumulation (which changes the depth of the antennas) and the index-of-refraction profile are crucial for an accurate determination of the neutrino's direction and energy. 14 months of data of the ARIANNA detector on the Ross Ice Shelf, Antarctica, are presented where a prototype calibration system was successfully used to monitor the snow accumulation with unprecedented precision of 1 mm. Several algorithms to extract the time differences of direct and reflected (off the surface) signals (D'n'R time difference) from noisy data (including deep learning) are explored. This constitutes an in-situ test of the neutrino vertex distance reconstruction using the D'n'R technique which is needed to determine the neutrino energy. Additionally, an in-situ calibration system is proposed that extends the radio detector station with a radio emitter to continuously monitor the firn properties by measuring D'n'R time difference. In a simulation study the station layout is optimized and the achievable precision is quantified.
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Beise, Jakob. "Measurement of the snow accumulation in Antarctica with a neutrino radio detector and extension to the measurement of the index-of-refraction profile." Thesis, Uppsala universitet, Högenergifysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-437647.
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High-energy neutrino physics offers a unique way to investigate the most violent phenomena in our universe. The detection of energies above E > 1017 eV is most efficient using the Askaryan effect, where a neutrino-induced particle shower produces coherent radio emission that is detectable with radio antennas. By using radio techniques large volumes can be covered with few stations at moderate cost exploiting the large attenuation length of radio in cold ice. Key to the reconstruction of the neutrino properties visa precise and continuous monitoring of the firn properties. In particular the snow accumulation (changing the absolute depth of the antennas thus the propagation path of the signal) and the index-of-refraction profile are crucial for the neutrino energy and direction reconstruction. This work presents an in-situ calibration design that acts as an detector extension by adding additional emitter antennas to the station design to continuously monitor the firn properties by measuring the direct and reflected signals (D’n’R). In a simulation study the optimal station layout is determined and the achievable precision is quantified. Furthermore 14 months of data from an ARIANNA station at the Ross Ice Shelf, Antarctica, are presented where a prototype of this calibration system has been successfully installed to monitor the snow accumulation with unprecedented precision of 1 mm. Several algorithms, including deep learning algorithms, to compute the D’n’R time difference from radio traces are considered.
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Mangold, Nicolas. "Rhéologie du pergélisol de Mars : applications géomorphologiques et structurales ; conséquences sur l'origine des contraintes compressives." Phd thesis, Université Joseph Fourier (Grenoble), 1997. http://tel.archives-ouvertes.fr/tel-00740850.
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La planète Mars est pourvue d'un climat glaciaire et d'un pergélisol riche en glace. Le comportement mécanique du pergélisol est affecté par la présence de la glace. L'objectif de cette étude est (1) de mesurer expérimentalement la viscosité de mélanges glace-roche analogues au pergélisol et (2) d'appliquer ces résultats à la rhéologie du pergélisol, la tectonique et la morphologie. Des implications climatiques et tectoniques sont obtenues à partir de l'étude de glaciers rocheux et des rides compressives. Les résultats expérimentaux établissent que le mélange glace-roche se déforme de manière visqueuse pour des proportions de glace en volume, donc des porosités, supérieures à 28%. La déformation est cassante pour des proportions de glace inférieures à 28%. Ainsi, lorsque la porosité du pergélisol est élevée, celui-ci est ductile avec une résistance nettement inférieure aux niveaux fragiles. La profondeur à laquelle la déformation ductile du pergélisol peut s'effectuer est limitée par la porosité. La déformation visqueuse du pergélisol s'observe en surface sous la forme de glaciers rocheux situés dans les régions de latitude 35 à 50° où les températures sont actuellement d'environ -60°C. A partir des données de rhéologie et d'observations morphologiques, nous montrons que ces glaciers rocheux ont pu se former sur des durées de l'ordre du milliard d'années et des températures invariablement froides. Aucun réchauffement climatique important n'a pu survenir au cours de l'évolution récente de la planète, soit depuis environ 2 Ga. Les "rides" martiennes sont des structures compressives interprétées comme des chevauchements enracinés à faible profondeur. A partir d'observations structurales d'une part et des résultats expérimentaux d'autre part, nous montrons (1) que ces structures sont enracinées sur un niveau de décollement à environ 1.5 km de profondeur et (2) que ce niveau correspond à un interface ductile dû à la glace du sous-sol. Enfin nous développons le problème de la nature du champ de compression à l'origine des rides. En utilisant les observations, les méthodes de datation par cratères et les modèles de refroidissement de la planète, nous arrivons à la conclusion que la déformation compressive est générée par la contraction thermique globale de la planète.
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Jasinghege, Don Prasanna Deshapriya. "Spectrophotometric properties of the nucleus of the comet 67P/Churyumov-Gerasimenko observed by the ROSETTA spacecraft." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC007/document.
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Cette thèse s'inscrit dans le cadre de la mission spatiale Rosetta et porte sur les propriétés spectrophotométriques de la comète 67P/Churyumov-Gerasimenko à l’aide de l’instrument OSIRIS. Cet instrument est composé de deux caméras pour les observations du noyau et de la coma de la comète. Elles permettent d’acquérir des images avec des filtres qui opèrent dans la gamme du proche UV au proche IR. Dans un premier temps, j'ai analysé les courbes spectrophotométriques des taches claires qui sont apparues sur le noyau de la comète. Une étude comparative de celles-ci grâce aux données du spectro-imageur VIRTIS a ainsi permis de constater que les taches claires sont liées à la glace de H2O. Dans un second temps, j’ai entrepris une étude spectrophotométrique de la région Khonsu, qui a mis en évidence les variations saisonnières de la pente spectrale de différents terrains. Par la suite, j’ai élargi mon analyse des taches à tout le noyau de la comète. J’ai détecté plus de 50 taches claires dues à la présence de glace de H2O et j’ai produit une carte pour repérer leurs emplacements sur le noyau, afin d’étudier plus en détail leur répartition et leur évolution au cours de temps. Ceci m’a permis d’identifier quatre types de taches regroupés en fonction de leur morphologie et de constater qu'elles sont dues à différentes sources d'activité cométaire<br>This thesis is based on the spectrophotometric properties of the comet 67P/Churyumov-Gerasimenko, using the OSIRIS instrument of Rosetta space mission. Composed of two scientific cameras to observe the nucleus and the coma of the comet, OSIRIS images are acquired with multiple filters, that span the near-UV to near-IR wavelength range. They were used to study the spectrophotometric curves of the exposed bright features that appeared on the surface of the cometary nucleus, leading to a comparative study, that was carried out in collaboration with the VIRTIS spectro-imager aboard Rosetta, that demonstrated, that these exposures are related to H2O ice, using its absorption band located at 2 microns. The thesis further details a spectrophotometric study of the Khonsu region in the southern latitudes of the comet, where the seasonal variation of the spectral slope of different types of terrains is explored. Finally, the results of an extended survey of exposed bright features are presented. More than 50 individual features are presented under four morphologies along with an albedo calculation, suggesting that different activity sources are responsible for their appearance on the nucleus
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Dissly, Richard William. "Laboratory studies of astrophysical ices." Thesis, 1995. https://thesis.library.caltech.edu/4343/1/Dissly_rw_1995.pdf.
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NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
This thesis reports the results of three laboratory studies, each concerned with some aspect of ices in an astrophysical environment, presented as independent papers:
1. Molecular hydrogen is the most abundant molecule in interstellar space, and is therefore of central importance to the physics and chemistry of that environment. Experiments simulating the codeposition of molecular hydrogen and water ice on interstellar grains demonstrate that amorphous water ice at 12 K can incorporate a substantial amount of H2, up to a mole ratio of H2/H2O = 0.53. We find that the physical behavior of ~80% of the hydrogen can be explained satisfactorily in terms of an equilibrium population, thermodynamically governed by a wide distribution of binding site energies. Such a description predicts that gas phase accretion could lead to mole fractions of H2 in interstellar grain mantles as high as 0.3. Accretion of gas phase H2 onto grain mantles, rather than photochemical production of H2 within the ice, could be a general explanation for recent observations of frozen H2 in interstellar ices. The possibility of interstellar grains that are rich in H2 could strongly affect our understanding of grain surface chemistry and gas-grain interactions.
2. Photochemical models of Triton's atmosphere predict ethylene (C2H4) as a primary product of methane photodissociation, formed at a high enough level that it should be readily observable as a surface condensate in [...] years, yet it has not been observed. Ultraviolet photolysis experiments on C2H4 ice were done to simulate its irradiation on Triton's surface. Our results show that C2H4 ice is readily dissociated by radiation of wavelengths [...], with C2H4 ice as a primary product. Dilution in an inert N2 matrix does not affect the photochemical yield of C2H4, suggesting that the reaction C2H4 [...] C2H2 is unimolecular. Quantum yields for both the destruction of C2H4 and the formation of C2H2 are discussed, as functions of both irradiation wavelength and dilution in N2 ice. Applying these results to Triton, we find that the ambient UV flux reaching Triton's surface is more than adequate to prevent the build-up of an ethylene ice layer.
3. Thermal models of icy satellite surfaces that allow the scattering and absorption of incident sunlight at significant depths predict an enhancement of subsurface temperatures over the mean surface temperature known as the solid-state greenhouse effect. We verify that a solid-state greenhouse can readily be produced in a bed of evacuated glass beads, used as a crude analog for the surface of an icy body. Measurements of the thermal and radiative properties thought to govern the size of this temperature enhancement confirm that it can be reasonably predicted from these parameters.
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Lee, Huan-Cheng, and 李桓誠. "A.Theoretical investigation of C(3P) + SiH4 reaction B.Formation of amide polymers via carbonyl-amino group linkages in energetically processed ices of astrophysical relevance." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7e8xde.
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碩士<br>國立東華大學<br>化學系<br>105<br>In the dissertation, the reaction of C(3p) + SiH4 is investigated by combining electronic structure and statistical calculations. The reaction was found to from an initial a van der Waals complex in the entrance channel, intersystem crossing (ISC) from the triplet to the singlet potential surface. The study provides insight on the molecular level and shed light on the non-adiabatic reaction dynamics of silicon, which is distinct from isovalent carbon systems. On both triplet and singlet surface, we use CCSD/cc-pVTZ to optimize complexes, intermediates, transition states and products. Energies are further calculated by CCSD/CBS with CCSD/cc-pVTZ zero-point energy correction. The statistical RRKM theory is employed in calculating rate constant and evolution of concentration with time. The major product at triplet pathways is predicted to be Si-CH3 and at singlet pathways, HSi-CH2.
The formation of organic amide polymers via carbonyl–amino group linkages in carbon monoxide and ammonia bearing energetically processed ices of astrophysical relevance is investigated with one carboxyl group and an increasing number of amine moieties starting with formamide (45 u), urea (60 u), and hydrazine carboxamide (75 u). The second group consists of species with two carboxyl (58 u) and up to three amine groups (73 u, 88 u, and 103 u). The formation and polymerization of these linkages from simple inorganic molecules via formamide und urea toward amide polymers is discussed in an astrophysical and astrobiological context. Our results show that long chain molecules, which are closely related to polypeptides, easily form by energetically processing simple, inorganic ices at very low temperatures and can be released into the gas phase by sublimation of the ices in star-forming regions. Our experimental results were obtained by employing reflectron time-of-flight mass spectroscopy, coupled with soft, single photon vacuum ultraviolet photoionization; they are complemented by theoretical calculations. We use b3lyp/cc-pVTZ to optimize neutral and ionic 2-oxo-2-triazylacetaldehyde and N-formylhydrazinecarboxamide. Energies are calculated by CCSD/CBS with b3lyp/cc-pVTZ zero-point energy correction. The ionization energies are obtained by taking the energy difference between corresponding neutral and ionic species. The result is compared with experiments.
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Hettlage, Christian [Verfasser]. "Lepton production in ice by scattering of astrophysical neutrinos at high energies / vorgelegt von Christian Hettlage." 2005. http://d-nb.info/979983738/34.
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Harris, Pauline. "A search for gamma ray burst neutrinos using the Radio Ice Cherenkov Experiment : a thesis submitted in partial fulfilment of the requirements for the degree of Doctorate of Philosophy at the University of Canterbury, Christchurch, New Zealand /." 2008. http://hdl.handle.net/10092/2166.
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"The Effect of Rayleigh-Taylor Instabilities on the Thickness of Undifferentiated Crust on Kuiper Belt Objects like Charon." Master's thesis, 2013. http://hdl.handle.net/2286/R.I.17885.
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abstract: In this thesis I model the thermal and structural evolution of Kuiper Belt Objects (KBOs) and explore their ability to retain undifferentiated crusts of rock and ice over geologic timescales. Previous calculations by Desch et al. (2009) predicted that initially homogenous KBOs comparable in size to Charon (R ~ 600 km) have surfaces too cold to permit the separation of rock and ice, and should always retain thick (~ 85 km) crusts, despite the partial differentiation of rock and ice inside the body. The retention of a thermally insulating, undifferentiated crust is favorable to the maintenance of subsurface liquid and potentially cryovolcanism on the KBO surface. A potential objection to these models is that the dense crust of rock and ice overlying an ice mantle represents a gravitationally unstable configuration that should overturn by Rayleigh-Taylor (RT) instabilities. I have calculated the growth rate of RT instabilities at the ice-crust interface, including the effect of rock on the viscosity. I have identified a critical ice viscosity for the instability to grow significantly over the age of the solar system. I have calculated the viscosity as a function of temperature for conditions relevant to marginal instability. I find that RT instabilities on a Charon-sized KBO require temperatures T > 143 K. Including this effect in thermal evolution models of KBOs, I find that the undifferentiated crust on KBOs is thinner than previously calculated, only ~ 50 km. While thinner, this crustal thickness is still significant, representing ~ 25% of the KBO mass, and helps to maintain subsurface liquid throughout most of the KBO's history.<br>Dissertation/Thesis<br>M.S. Astrophysics 2013