Photon and thermal processing of CH3NH2-bearing ices. Synthesis of prebiotic species at low temperature (such as formamide, ethylamine, and methylcyanide), and N-heterocycles during warm up.

<p>Hexamethylentetramine has drawn a lot of attention due to its potential to produce prebiotic species. This work aims to gain a better understanding in the chemical processes concerning methylamine under astrophysically relevant conditions. In particular, this work deeps into the formation of N-heterocycles in interstellar ice analogs exposed to UV radiation, which may lead to the formation of prebiotic species.</p> <p>Experimental simulations of interstellar ice analogs were carried out in ISAC. ISAC is an ultra-high vacuum chamber equipped with a cryostat, where gas and vapour species are frozen forming ice samples. Infrared and ultraviolet spectroscopy were used to monitor the solid phase, and quadrupole mass spectrometry served to measure the composition of the gas phase. The variety of species detected after UV irradiation of ices containing  methylamine revealed the presence of 12 species which have been already detected in the ISM, being 4 of them typically classified as complex organic molecules: formamide (HCONH<sub>2</sub>), methyl cyanide (CH<sub>3</sub>CN), CH<sub>3</sub>NH and CH<sub>3</sub>CHNH. Warming up of the irradiated CH<sub>3</sub>NH<sub>2</sub>-bearing ice samples lead to the formation of trimethylentriamine (TMT), a N-heterocycle precursor of HMT, and the subsequent synthesis of HMT at temperatures above 230 K.</p>

Theoretical Determination of Binding Energies of Small Molecules on Interstellar Ice Surfaces

The adsorption of a series of atoms and small molecules and radicals (H, C, N, O, NH, OH, H2O, CH3, and NH3) on hexagonal crystalline and amorphous ice clusters were obtained via classical molecular dynamics and electronic structure methods. The geometry and binding energies were calculated using a QMHigh:QMLow hybrid method on model clusters. Several combination of basis sets, density functionals and semi-empirical methods were compared and tested against previous works. More accurate binding energies were also refined via single point Coupled Cluster calculations. Most species, except carbon atom, physisorb on the surface, leading to rather small binding energies. The carbon atom forms a COH2 molecule and in some cases leads to the formation of a COH-H3O+ complex. Amorphous ices are characterized by slightly stronger binding energies than the crystalline phase. A major result of this work is to also access the dispersion of the binding energies since a variety of adsorption sites is explored. The interaction energies thus obtained may serve to feed or refine astrochemical models. The present methodology could be easily extended to other types of surfaces and larger adsorbates.

MgO surface lattice phonons observation during interstellar ice transition

Relevant information on the origins of the solar system and the early evolution of life itself can be derive from systematic and controlled exploration of water ice here on Earth. Therefore, over the last decades, a huge effort on experimental methodologies has been made to study the multiple crystal ice phases, which are observed outside our home–gravitational–potential. By employing (100)–oriented MgO lattice surface as a microcantilever sensor, we conducted the first ever study on the dynamics of the Structural Phase Transition at 185 K in water ice by means of coherent elastic scattering of electron diffraction. We estimate the amount of phonons caused by this transition applying precise quantum computing key tools, and resulting in a maximum value of 1.23 ± 0.02. Further applications of our microcantilever sensor were assessed using unambiguous mapping of the surface stress induced by the c($$4 \times 2$$ 4 × 2 ) → p($$3 \times 2$$ 3 × 2 ) Structural Phase Transition of the interstellar ice formulated on the Williamsom–Hall model. This development paves the way and thus establishes an efficient characterization tool of the surface mechanical strains of materials with potential applications arising from interstellar ice inclusive glaciers to the wide spectrum of solid–state physics.

Radicals in prebiotic chemistry

Radical chemistry is tightly interwoven in proposed prebiotic synthetic pathways, reaction networks and geochemical scenarios that have helped shape our understanding of how life could have originated. Gas-phase prebiotic reactions involving electric discharge, vapour ablation by asteroidal and cometary impacts as well as ionising radiation all produce radicals that facilitate complex molecular synthesis. Reactions in the solid phase which are responsible for astrochemical syntheses can also take place through radicals produced via irradiation of protoplanetary/interstellar ice grains and dust particles. Aqueous-phase radical chemistry affords further molecular complexity promoting the production of precursors for the synthesis of biopolymers thought important for the emergence of life. Radical chemistry appears to be a common thread amongst all kinds of prebiotic investigations, and this Review aims to bring attention to a few selected examples. Some important historical studies and modern developments with respect to prebiotic chemistry are summarised through the lens of radical chemistry.