# Synthesis of complex organic molecules in soft x-ray irradiated ices

## TL;DR

This study investigates the chemical evolution of ice mixtures irradiated with soft X-rays, identifying prebiotic molecules and their potential release into the gas phase in space environments.

## Contribution

It provides new insights into the formation and desorption of complex organic molecules in space ice analogs under soft X-ray irradiation.

## Key findings

- Identification of nitrogen-bearing molecules such as OCN-, NH4+, HNCO, CH3CN, HCONH2.
- Detection of desorbing species including methyl isocyanate and possible prebiotic molecules.
- Estimation of gas-phase enrichment of organics in protoplanetary disks.

## Abstract

We study the chemical evolution of H2O:CO:NH3 ice mixtures irradiated with soft X-rays, in the range 250-1250 eV. We identify many nitrogen-bearing molecules such as e.g., OCN-, NH4+ , HNCO, CH3CN, HCONH2, and NH2COCONH2. Several infrared features are compatible with glycine or its isomers. During the irradiation, we detected through mass spectroscopy many species desorbing the ice. Such findings support either the infrared identifications and reveal less abundant species with not clear infrared features. Among them, m/z = 57 has been ascribed to methyl isocyanate (CH3NCO), a molecule of prebiotic relevance, recently detected in protostellar environments. During the warm up after the irradiation, several infrared features including 2168 cm-1 band of OCN-, 1690 cm-1 band of formamide, and the 1590 cm-1 band associated to three different species, HCOO-, CH3NH2 and NH3+CH2COO survive up to room temperature. Interestingly, many high masses have been also detected. Possible candidates are methyl-formate, (m/z = 60, HCOOCH3), ethanediamide (m/z = 88, NH2COCONH2), and N-acetyl-L-aspartic acid (m=z = 175). This latter species is compatible with the presence of the m/z = 43, 70 and 80 fragments. Photo-desorption of organics is relevant for the detection of such species in the gas-phase of cold environments, where organic synthesis in ice mantles should dominate. We estimate the gas-phase enrichment of some selected species in the light of a protoplanetary disc model around young solar-type stars.