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Gelos astrofísicos (formados pela água, entre outras moléculas) atuam como um catalisador e um reservatório de espécies carbonáceas, ambas com grandes implicações para a astrobiologia. Neste trabalho, nós estudamos a formação de nanoestruturas de gelo astrofísico encontradas no meio interestelar, tendo uma folha de grafeno como substrato catalisador, utilizando-se a técnica de dinâmica molecular clássica para modelar esses ambientes astrofísicos. Para isso, projetou-se dois sistemas: o primeiro composto por grafeno e e o segundo composto por grafeno, e . Inicialmente construiu-se uma caixa de simulação onde a área foi delimitada pelo grafeno cuja altura variava de 4, 6, 8 e 10 nm. As moléculas foram distribuídas uniformemente por toda a caixa. A técnica de dinâmica molecular provou ser uma ferramenta promissora para entender o fenômeno da adsorção de moléculas no substrato, permitindo-nos perceber que a distribuição aleatória de moléculas no sistema interfere com a estrutura geométrica formada por uma nanoestrutura de gelo. Este estudo nos permite compreender, do ponto de vista nanométrico, a influência de alguns parâmetros físico-químicos, no que tange a formação das nanoestruturas de gelos astrofísicos, como o número de ligações de hidrogênio, o tamanho inicial da caixa de simulação, e sua densidade durante o processo de congelamento

Here we present experimental results on the irradiation of ethanol ice (CH3CH2OH) by broadband soft X-rays to simulate the effect processing of organic-rich astrophysical ices by space radiation. This molecule was detected in the interstellar medium in molecular clouds like Sagittarius B2 and towards nebulas like Orion KL. The experiments were performed at the Brazilian Synchrotron Facility LNLS/CNPEM, at Campinas, SP. The frozen sample was analyzed in-situ by infrared spectroscopy (IR) in a simulated astrophysical environment at different radiation fluences. The results show the formation of several new molecular species such as CO2, CO, H2O, CH4, CH3(CO)CH3 (acetone), and CH3COOH (acetic acid). We determined the effective destruction cross-section of ethanol (~1×10-18 cm2) and the formation cross-sections of the daughter species with values between 0.5 to 3.4×10-18 cm2. The chemical equilibrium phase of ice was characterized and desorption yield induced by X-rays was determined (0.13 molecules photon-1). The result helps us to understand the photolysis induced by X-rays in organic-rich ices in space environments.

Gelos astrofísicos ricos em H2O (água) estão sempre expostos a radiações ionizantes no espaço, assim como a eventuais mudanças de temperatura. Seus estudos em laboratório permitem compreender seus comportamentos e mudanças químicas, além de permitir a quantificação de parâmetros físico-químicos importantes do próprio gelo. No presente trabalho, uma amostra de gelo de água a 12 K foi irradiada por raios-X moles na linha de luz SGM do LNLS/CNPEM até atingir o equilíbrio químico, e em seguida, foi aquecida até 220 K. Utilizando espectroscopia infravermelha (IR), mapeamos a evolução química da amostra e quantificamos a produção do seu principal produto, a molécula de H2O2. O estudo tem implicações na química das regiões de formação estelar, bem como em regiões frias do sistema solar.

A molécula de CH3OH é uma das espécies orgânicas mais abundantes no meio interestelar e importante precursor de espécies pré-bióticas. Nesse trabalho estudamos sua sobrevivência em um cenário típico de estrela jovem, na presença de um campo de radiação ultravioleta (UV) entre 91.2 – 205 nm. Para isso usamos o código de transferência radiativa RADMC-3D para calcular os perfis de densidade e intensidade média de fótons em toda parte do modelo. Através desses resultados, usamos a seção de choque de destruição do CH3OH na região do ultravioleta para calcular sua taxa de fotodissociação e tempo de meia vida. Concluímos que no interior do disco, a molécula pode sobreviver intacta e ser liberada para a fase gasosa por processos não-térmicos. Porém no envelope, a fotodissociação é predominante, podendo formar espécies como HCOOCH3, HOCH2CHO e CH3CH2OH.

Neste trabalho, estudamos a estabilidade da molécula de glicina na sua forma zwiteriônica cristalina, conhecida como a-glycina (+NH3CH2COO-) a duas temperaturas (14 e 300 K), sob a ação de íons rápidos, simulando ambientes espaciais na presença de raios cósmicos pesados. Para tanto, a meia vida da glicina bombardeada no meio interestelar (nuvens densas) foi estimada, sendo 1.1 x 104 anos (300 K) e 1.6 x 103 anos (14 K). No sistema solar, os valores foram de 1.2 x 103 anos (300 K) e 2.8 x 103 anos (14 K). O estudo da estabilidade da glicina, nesses ambientes, traz à tona questões sobre o papel dessa molécula na química pré-bióticana Terra, para auxiliar nas descobertas sobre a origem da vida como a conhecemos.

Our groups in Brazil, France and Italy have been active, among others in the world, in performing experiments on physical-chemical effects induced by fast ions colliding with solids (frozen gases, carbonaceous and organic materials, silicates, etc.) of astrophysical interest. The used ions span a very large range of energies, from a few keV to hundreds MeV. Here we present a summary of the results obtained so far on the formation of oxidants (hydrogen peroxide and ozone) after ion irradiation of frozen water, carbon dioxide and their mixtures. Irradiation of pure water ice produces hydrogen peroxide whatever is the used ion and at different temperatures. Irradiation of carbon dioxide and water frozen mixtures result in the production of molecules among which hydrogen peroxide and ozone. The experimental results are discussed in the light of the relevance they have to support the presence of an energy source for biosphere on Europa and other icy moons in the outer Solar System.

In this work, we experimentally simulate the methanol (CH3OH) ice behavior (12 K) through the bombarded by fast electrons (4.9 keV) in an attempt to simulate radiation chemistry induced by radiation in space environments. The sample analysis by infrared spectroscopy reveals the appearance of new species, including CO2, CO, H2O, and CH4, during the sample bombardment. We have quantified the effective destruction cross-section of methanol (5.5 × 10-19 cm2) and determined the formation cross-section for these newly produced species. Additionally, we have characterized the chemical equilibrium (CE) phase, which becomes evident at higher fluences. We have also calculated molecular abundances and assessed the desorption yield induced by fast electrons within the same sample. Furthermore, we estimated the timescale required to achieve chemical equilibrium in specific astrophysical environments impacted by electrons. This study significantly contributes to our comprehension of electron bombardment behavior in astrophysical ices and allows for meaningful comparisons with organic-rich ices in space environments

Methanol (CH3OH) is one of the most abundant organic molecules in astrophysical environments. It has been found in cold regions such as surfaces of comets, ices near young stellar objects and protoplanetary disks, as well as in the gas phase in different regions in space. In this work, we experimentally simulate the methanol ice and its behavior when irradiated by broadband soft X-rays. The experiments were performed at the Brazilian Synchrotron Facility LNLS/CNPEM, employing a broadband photon beam (6 to 2000 eV). The frozen sample was analyzed in situ by infrared spectroscopy (IR) in simulated astrophysical at different radiation fluences. The results show the formation of several new species such as CO2, CO, H2O and CH4 during the photolysis CH3OH ice by soft X-rays. We determined effective destruction and formation cross-section, as well as the chemical equilibrium fluence (FE) and desorption yields. The timescale to reach chemical equilibrium in some astrophysical environments with soft X-rays were estimated. The result helps us to understand the photolysis induced by X-rays in organic-rich ices in space environments.

AbstractDespite the extensive search for glycine (NH2CH2COOH) and other amino acids in molecular clouds associated with star-forming regions, only upper limits have been derived from radio observations. Nevertheless, two of glycine''s precursors, formic acid and acetic acid, have been abundantly detected. Although both precursors may lead to glycine formation, the efficiency of reaction depends on their abundance and survival in the presence of a radiation field. These facts could promote some favoritism in the reaction pathways in the gas phase and solid phase (ice). Glycine and these two simplest carboxylic acids are found in many meteorites. Recently, glycine was also observed in cometary samples returned by the Stardust space probe.The goal of this work was to perform theoretical calculations for several interstellar reactions involving the simplest carboxylic acids as well as the carboxyl radical (COOH) in both gas and solid (ice) phase to understand which reactions could be the most favorable to produce glycine in interstellar regions fully illuminated by soft X-rays and UV, such as star-forming regions. The calculations were performed at four different levels for the gas phase (B3LYP/6-31G*, B3LYP/6-31**, MP2/6-31G*, and MP2/6-31**) and at MP2/6-31** level for the solid phase (ice).The current two-body reactions (thermochemical calculation) were combined with previous experimental data on the photodissociation of carboxylic acids to promote possible favoritism for glycine formation in the scenario involving formic and acetic acid in both gas and solid phase. Given that formic acid is destroyed more in the gas phase by soft X-rays than acetic acid is, we suggest that in the gas phase the most favorable reactions are acetic acid with NH or NH2OH. Another possible reaction involves NH2CH2and COOH, one of the most-produced radicals from the photodissociation of acetic acid. In the solid phase, we suggest that the reactions of formic acid with NH2CH or NH2CH2OH are the most favorable from the thermochemical point of view. Key Words: Interstellar molecules—Interstellar environments—Abiotic organic synthesis—Extraterrestrial organic compounds—Prebiotic chemistry. Astrobiology 11, 883–893. [ABSTRACT FROM AUTHOR]

Titan, the largest satellite of Saturn, has an atmosphere chiefly made up of N2and CH4and includes traces of many simple organic compounds. This atmosphere also partly consists of haze and aerosol particles which during the last 4.5 gigayears have been processed by electric discharges, ions, and ionizing photons, being slowly deposited over the Titan surface. In this work, we investigate the possible effects produced by soft X-rays (and secondary electrons) on Titan aerosol analogs in an attempt to simulate some prebiotic photochemistry. The experiments have been performed inside a high vacuum chamber coupled to the soft X-ray spectroscopy beamline at the Brazilian Synchrotron Light Source, Campinas, Brazil. In-situ sample analyses were performed by a Fourier transform infrared spectrometer. The infrared spectra have presented several organic molecules, including nitriles and aromatic CN compounds. After the irradiation, the brownish-orange organic residue (tholin) was analyzed ex-situ by gas chromatographic (GC/MS) and nuclear magnetic resonance (1H NMR) techniques, revealing the presence of adenine (C5H5N5), one of the constituents of the DNA molecule. This confirms previous results which showed that the organic chemistry on the Titan surface can be very complex and extremely rich in prebiotic compounds. Molecules like these on the early Earth have found a place to allow life (as we know) to flourish. [ABSTRACT FROM AUTHOR]