Temperature programed desorption of water ice from the surface of amorphous carbon and silicate grains as related to planet-forming disks

TL;DR

This study investigates how water ice desorbs from amorphous carbon and silicate grains in planet-forming disks, revealing the influence of dust/ice ratios and grain composition on desorption kinetics, which impacts understanding of small body evolution.

Contribution

First laboratory analysis of temperature-programmed desorption of water ice mixed with carbon and silicate grains, highlighting the effects of dust/ice ratio and grain type on desorption behavior.

Findings

Desorption kinetics depend on dust/ice mass ratio.

Water binds differently to silicate versus carbon grains.

Results link grain structure to ice desorption processes.

Abstract

Understanding the history and evolution of small bodies, such as dust grains and comets, in planet-forming disks is very important to reveal the architectural laws responsible for the creation of planetary systems. These small bodies in cold regions of the disks are typically considered as mixtures of dust particles with molecular ices, where ices cover the surface of a dust core or are actually physically mixed with dust. Whilst the first case, ice-on-dust, has been intensively studied in the laboratory in recent decades, the second case, ice-mixed-with-dust, present uncharted territory. This work is the first laboratory study of the temperature-programmed desorption (TPD) of water ice mixed with amorphous carbon and silicate grains. We show that the kinetics of desorption of H2O ice depends strongly on the dust/ice mass ratio, probably, due to the desorption of water molecules from a large surface of fractal clusters composed of carbon or silicate grains. In addition, it is shown that water ice molecules are differently bound to silicate grains in contrast to carbon. The results provide a link between the structure and morphology of small cosmic bodies and the kinetics of desorption of water ice included in them.