Thermal desorption of CH4 retained in CO2 ice

TL;DR

This study investigates how CO2 ice can trap methane molecules at temperatures above methane's sublimation point, revealing mechanisms that could explain methane retention in astrophysical environments.

Contribution

It provides experimental evidence on methane retention in CO2 ice at higher temperatures, highlighting structural mechanisms responsible for trapping.

Findings

Methane can be retained in CO2 ice above its sublimation temperature.

Structural properties of CO2 ice influence methane trapping.

Retention mechanisms may explain methane presence in space environments.

Abstract

CO2 ices are known to exist in different astrophysical environments. In spite of this, its physical properties (structure, density, refractive index) have not been as widely studied as those of water ice. It would be of great value to study the adsorption properties of this ice in conditions related to astrophysical environments. In this paper, we explore the possibility that CO2 traps relevant molecules in astrophysical environments at temperatures higher than expected from their characteristic sublimation point. To fulfil this aim we have carried out desorption experiments under High Vacuum conditions based on a Quartz Crystal Microbalance and additionally monitored with a Quadrupole Mass Spectrometer. From our results, the presence of CH4 in the solid phase above the sublimation temperature in some astrophysical scenarios could be explained by the presence of several retaining mechanisms related to the structure of CO2 ice.