Photodesorption of Water Ice from Dust Grains and Thermal Desorption of Cometary Ices Studied by the INSIDE Experiment

Abstract

A new experimental set-up INterStellar Ice-Dust Experiment (INSIDE), was designed for studying cosmic grain analogues represented by ice-coated carbon-and silicate-based dust grains. In the new instrument, we can simulate physical and chemical conditions prevailing in interstellar and circumstellar environments. The set-up combines ultrahigh vacuum and low temperature conditions with infrared spectroscopy and mass spectrometry. Using INSIDE, we plan to investigate physical and chemical processes, such as adsorption, desorption, and formation of molecules, on the surface of dust/ice samples. First experiments on the photodesorption of water ice molecules from the surface of silicate and carbon grains by UV photons revealed a strong influence of the surface properties on the desorption yield, in particular in the monolayer regime. In the second experiment, the thermal desorption of cometary ice analogues composed of six molecular components was studied for the first time.Co-desorption of CO2 and CH3OH with O2 indicates that at high O2 concentrations in cometary or interstellar ices "heavy" ice molecules can be partly trapped in O2 and release to the gas phase much earlier than expected. This effect could explain astronomical detections of complex organic molecules in cold dense interstellar clouds.

Constraining the detectability of water ice in debris disks

“…In addition, recent laboratory experiments have demonstrated trapping of water molecules on porous silicate grains at 200 K (above the desorption temperature of H 2 O ice; Potapov et al 2018a;Potapov et al 2018b). First experiments on the UV photosputtering of water ice molecules from the surface of porous silicate and carbon grains by UV photons showed an influence of the surface properties on the photosputtering yield, in particular in the monolayer regime (Potapov et al 2019).…”

Ice Coverage of Dust Grains in Cold Astrophysical Environments

“…Compared to molecular solids, there is a handful of studies of the physics and chemistry on the surface of dust grain analogs. We refer to recent papers on the formation [17,18] and desorption [19] of molecules. Summarising the findings of previous studies, it has been shown that (i) the efficiency of molecule formation depends on the morphology of the grain surface, (ii) the binding energies of species can be quite different for different grain surfaces and on the grain surfaces compared to molecular solids, (iii) functional groups and atoms of the grain surface can participate directly in surface reactions, (iv) the grain surface has a catalytic effect, (v) desorption kinetics and yields of volatile molecules are different for different grain surfaces and compared to molecular solids, (vi) water molecules can be trapped on the grain surface at temperatures above the desorption temperature of water ice.…”

Dust/ice mixing in cold regions and solid-state water in the diffuse interstellar medium

“…In addition to these studies, there are studies on physical-chemical processes, such as formation, desorption, and diffusion of molecules, on the surface of cosmic dust analogues: amorphous carbon grains, atomic carbon foils, graphite, amorphous silica, and amorphous and crystalline silicate grains. The reader can find examples of and references to these experimental studies in recent papers [4][5][6][7][8][9] .Concerning ice-mixed-with-dust, this is a new direction of research started very recently by us [10][11][12] . One of the conclusions of our previous study of the optical constants of dust/ice mixtures 11 was that differences between measured constants and constants calculated using effective medium approaches show that a mathematical mixing (averaging) of the optical constants of water ice and silicates for the determination of the optical properties of silicate/ice mixtures can lead to incorrect results.…”