scholarly journals Computational studies into urea formation in the interstellar medium

2020 ◽  
Vol 497 (4) ◽  
pp. 5413-5420
Author(s):  
Eren C S Slate ◽  
Rory Barker ◽  
Ryan T Euesden ◽  
Max R Revels ◽  
Anthony J H M Meijer
Keyword(s):  
Interstellar Medium ◽  
Computational Methods ◽  
Radical Reaction ◽  
Closed Shell ◽  
Computational Studies ◽  
Water Ice ◽  
Charged Species ◽  
Ice Shell ◽  
Partial Water

ABSTRACT Formation routes, involving closed shell, radical, and charged species for urea, have been studied using computational methods to probe their feasibility in the interstellar medium. All reactions involving closed shell species were found to have prohibitive barriers. The radical–radical reaction possesses a barrier of only 4 kJ mol−1, which could be surmountable. A charged species based route was also investigated. A barrier of only 8 kJ mol−1 was found in that case, when a partial water ice shell was included.

Experimental and Computational Studies of the Phenyl Radical Reaction with Allene†

2007 ◽  
Vol 111 (29) ◽  
pp. 6881-6889 ◽  
Author(s):  
J. Park ◽  
I. V. Tokmakov ◽  
M. C. Lin
Keyword(s):  
Radical Reaction ◽  
Computational Studies ◽  
Phenyl Radical

scholarly journals Thermal desorption of water ice in the interstellar medium

2001 ◽  
Vol 327 (4) ◽  
pp. 1165-1172 ◽  
Author(s):  
H. J. Fraser ◽  
M. P. Collings ◽  
M. R. S. McCoustra ◽  
D. A. Williams
Keyword(s):  
Interstellar Medium ◽  
Thermal Desorption ◽  
Water Ice

scholarly journals Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets

2018 ◽  
Vol 612 ◽  
pp. A86 ◽  
Author(s):  
Martin Turbet ◽  
Emeline Bolmont ◽  
Jeremy Leconte ◽  
François Forget ◽  
Franck Selsis ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Planetary Science ◽  
Water Ice ◽  
Planetary Evolution ◽  
Ice Surface ◽  
Surface Condensation ◽  
Synchronous Rotation ◽  
Ice Shell

TRAPPIST-1 planets are invaluable for the study of comparative planetary science outside our solar system and possibly habitability. Both transit timing variations (TTV) of the planets and the compact, resonant architecture of the system suggest that TRAPPIST-1 planets could be endowed with various volatiles today. First, we derived from N-body simulations possible planetary evolution scenarios, and show that all the planets are likely in synchronous rotation. We then used a versatile 3D global climate model (GCM) to explore the possible climates of cool planets around cool stars, with a focus on the TRAPPIST-1 system. We investigated the conditions required for cool planets to prevent possible volatile species to be lost permanently by surface condensation, irreversible burying or photochemical destruction. We also explored the resilience of the same volatiles (when in condensed phase) to a runaway greenhouse process. We find that background atmospheres made of N2, CO, or O2are rather resistant to atmospheric collapse. However, even if TRAPPIST-1 planets were able to sustain a thick background atmosphere by surviving early X/EUV radiation and stellar wind atmospheric erosion, it is difficult for them to accumulate significant greenhouse gases like CO2, CH4, or NH3. CO2can easily condense on the permanent nightside, forming CO2ice glaciers that would flow toward the substellar region. A complete CO2ice surface cover is theoretically possible on TRAPPIST-1g and h only, but CO2ices should be gravitationally unstable and get buried beneath the water ice shell in geologically short timescales. Given TRAPPIST-1 planets large EUV irradiation (at least ~103 × Titan’s flux), CH4and NH3are photodissociated rapidly and are thus hard to accumulate in the atmosphere. Photochemical hazes could then sedimentate and form a surface layer of tholins that would progressively thicken over the age of the TRAPPIST-1 system. Regarding habitability, we confirm that few bars of CO2would suffice to warm the surface of TRAPPIST-1f and g above the melting point of water. We also show that TRAPPIST-1e is a remarkable candidate for surface habitability. If the planet is today synchronous and abundant in water, then it should very likely sustain surface liquid water at least in the substellar region, whatever the atmosphere considered.

Quantum chemical study on the formation of isopropyl cyanide and its linear isomer in the interstellar medium

2020 ◽  
pp. 1-11
Author(s):  
Keshav Kumar Singh ◽  
Poonam Tandon ◽  
Alka Misra ◽  
Shivani ◽  
Manisha Yadav ◽  
...  
Keyword(s):  
Amino Acids ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Dark Cloud ◽  
Water Ice ◽  
Hydrocarbon Radicals

Abstract The formation mechanism of linear and isopropyl cyanide (hereafter n-PrCN and i-PrCN, respectively) in the interstellar medium (ISM) has been proposed from the reaction between some previously detected small cyanides/cyanide radicals and hydrocarbons/hydrocarbon radicals. n-PrCN and i-PrCN are nitriles therefore, they can be precursors of amino acids via Strecker synthesis. The chemistry of i-PrCN is especially important since it is the first and only branched molecule in ISM, hence, it could be a precursor of branched amino acids such as leucine, isoleucine, etc. Therefore, both n-PrCN and i-PrCN have significant astrobiological importance. To study the formation of n-PrCN and i-PrCN in ISM, quantum chemical calculations have been performed using density functional theory at the MP2/6-311++G(2d,p)//M062X/6-311+G(2d,p) level. All the proposed reactions have been studied in the gas phase and the interstellar water ice. It is found that reactions of small cyanide with hydrocarbon radicals result in the formation of either large cyanide radicals or ethyl and vinyl cyanide, both of which are very important prebiotic interstellar species. They subsequently react with the radicals CH2 and CH3 to yield n-PrCN and i-PrCN. The proposed reactions are efficient in the hot cores of SgrB2 (N) (where both n-PrCN and i-PrCN were detected) due to either being barrierless or due to the presence of a permeable entrance barrier. However, the formation of n-PrCN and i-PrCN from the ethyl and vinyl cyanide always has an entrance barrier impermeable in the dark cloud; therefore, our proposed pathways are inefficient in the deep regions of molecular clouds. It is also observed that ethyl and vinyl cyanide serve as direct precursors to n-PrCN and i-PrCN and their abundance in ISM is directly related to the abundance of both isomers of propyl cyanide in ISM. In all the cases, reactions in the ice have smaller barriers compared to their gas-phase counterparts.

The aromaticity of verdazyl radicals and their closed-shell charged species

2018 ◽  
Vol 42 (24) ◽  
pp. 19987-19994 ◽  
Author(s):  
Rashid R. Valiev ◽  
Anna K. Drozdova ◽  
Pavel V. Petunin ◽  
Pavel S. Postnikov ◽  
Marina E. Trusova ◽  
...  
Keyword(s):  
Current Density ◽  
Closed Shell ◽  
Induced Current ◽  
Charged Species ◽  
Verdazyl Radicals

The aromaticity of fourteen 3-oxo-verdazyl (1–8) and Kuhn verdazyl (9–14) radicals with different substituents has been investigated computationally using the gauge-including magnetically induced current-density (GIMIC) method.

scholarly journals The quest of chirality in the interstellar medium

2020 ◽  
Vol 633 ◽  
pp. A49
Author(s):  
Y. Ellinger ◽  
F. Pauzat ◽  
A. Markovits ◽  
A. Allaire ◽  
J.-C. Guillemin
Keyword(s):  
Interstellar Medium ◽  
Gas Phase ◽  
Propylene Oxide ◽  
Density Functional ◽  
Energy Scale ◽  
Potential Candidate ◽  
Structural Constraints ◽  
Water Ice ◽  
Rotational Spectra ◽  
Complex Organic Molecule

Context. All but one complex organic molecule (COM) detected so far in the interstellar medium (ISM) are achiral; propylene oxide (c-C2H3O)-CH3 is the only exception to this. Finding other chiral species is a priority for astrobiology to progress in the understanding of the emergence of life. Whatever the conditions of their formation, i.e., gas phase or grain chemistry, the detection relies on rotational spectra. This means that, if adsorbed after formation in the gas phase or directly formed on the icy grains, these COMs must escape in the gas phase as free flyers to be detectable. Aims. Learning the lesson drawn from the only observation of a chiral compound and considering the structural constraints imposed to a molecule to be chiral, we look at what species could satisfy these conditions and be potential targets for a radio astronomy search in the ISM gas phase. Methods. This question was addressed by combining two complementary approaches that rely on density functional theory. The structure, energetics, and spectroscopic parameters of each potential candidate were determined using molecular calculations. The propensity for a molecule to remain trapped on the ice coating of the grains was evaluated by numerical simulations making use of a solid state periodic model. Results. Replacing the -CH3 group on rigid propylene oxide by -CN, -CCH, -NH2, -OH, or -HCO gives oxirane daughter molecules whose adsorption energies divide into two classes: below and above the adsorption energy of H2O on solid water-ice ~13.5 kcal mol−1. Conclusions. The best chiral candidate would be a rigid molecule for an easier determination of its radio spectra. This molecule would be composed of a central carbon linked to one hydrogen and three different chemical groups as simple as possible. If not the most stable isomer, this candidate should be as close as possible on the energy scale, possess a significant dipole moment, and be less strongly attached to the ice than H2O itself.

Rationalising pKa shifts in Bacillus circulans xylanase with computational studies

2016 ◽  
Vol 18 (44) ◽  
pp. 30305-30312 ◽  
Author(s):  
Kela Xiao ◽  
Haibo Yu
Keyword(s):  
Molecular Mechanism ◽  
Computational Methods ◽  
Bacillus Circulans ◽  
Computational Studies ◽  
Wild Type ◽  
Pka Shifts ◽  
Bacillus Circulans Xylanase ◽  
Key Residues

Molecular mechanism for pKa shifts for the key residues in wild-type and mutants of BcX based on three different computational methods.

Icy Moon Ice-Salt Measurements for Dielectric and Thermal Properties

2020 ◽  
Author(s):  
Robert Frampton
Keyword(s):  
Thermal Properties ◽  
Relative Permittivity ◽  
Laboratory Data ◽  
Dual Frequency ◽  
Water Ice ◽  
Temperature Range ◽  
Salt Mixtures ◽  
Ground Penetrating ◽  
Sodium Sulfates ◽  
Ice Shell

<p>The REASON ground penetrating radar (GPR) on Europa Clipper and the RIME GPR on JUICE will produce radargrams for Europa to determine the nature and depth of the ice overlying a putative ocean. The REASON radar is dual frequency, 9 MHz and 60 MHz, and the RIME frequency is 9 MHz. The surface temperature of Europa is between 50 and 100 Kelvin. At 9 MHz, the REASON GPR could map relative permittivity to about 30 km with a resolution of 150 m. These two GPRs may be able to spot pockets of water within the ice shell that could serve as a passageway for chemicals between the surface and the ocean below. The upper ice crust is expected to contain magnesium and sodium sulfates, and perhaps calcium sulfate [J. Moore, 1999].</p><p>To fill this gap in knowledge about the properties of the ice crust on Europa, we will make laboratory measurements of the relative permittivity (complex dielectric coefficient using impedance spectroscopy) and thermal properties (thermal conductivity and specific heat) of ice-salt mixtures at 9 and 60 MHz, over the temperature range 50 to 100 Kelvin, for the ice-salt mixtures given in Table X. This Table was provided by Kevin Collins (UCF). We do not plan to include any dust content in these ice-salt mixtures. These laboratory data may assist in the interpretation of future radargrams from RESSON and RIME</p><p> </p><p>   TABLE 1, Europan ice-salt specimens for electrical and thermal property measurements.</p><div><strong>Experiment Number</strong><strong>Salt Species</strong><strong>Salt Concentration (wt. %)</strong><strong>Physical Texture</strong>1Sulfuric acid hydrate5Dispersed in particulate ice2Magnesium sulfate5Dispersed in particulate ice3Magnesium chloride5Dispersed in particulate ice4Sodium chloride5Dispersed in particulate ice5Magnesium sulfate1Dispersed in particulate ice6Magnesium sulfate10Dispersed in particulate ice7Magnesium sulfate25Dispersed in particulate ice8Magnesium sulfate + sulfuric acid hydrate5 (each)Dispersed in particulate ice9Magnesium sulfate5Solid block10Magnesium sulfate5Layered structure</div><p> </p><p>We are planning also to make similar measurements of the electrical and thermal properties of ice on Titania (moon of Uramus), over temperature range of 60 to 90 Kelvin, and at 9 MHz. The surface of Titania is mainly water ice, with some frozen carbon dioxide and possibly salts. We will devise a table of salt-ice mixtures that is appropriate for Titania, based on available information on surface content.</p>

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