Amorphous water ice and its ability to trap gases

New experimental studies of ice grain ejection by massive gas flow, implications to comets, Enceladus, Triton and Mars

“…The new experimental studies on thin (up to 200 µm) ice layers confirmed our previous findings (Bar-Nun et al 1987) on ice grain ejection during the annealing of gas-laden amorphous ice and during its transformation into cubic ice. A massive gas flow, from the interior, breaks the ice structure and is imbedded in the amorphous ice, to be released from it during its annealing and transformation to cubic ice as seen in Figure 1.…”

“…Bar-Nun et al 1987;Laufer et al 2013). In the case of 100 µm layer of frozen CO 2 covered by a 200 µm thick layer of amorphous ice, upon uniformly warming up the sample, ice grains and jets of gas were measured by a quadrupole mass filter (MS), at a msec time resolution; (2) Few cm thick gas laden amorphous ice layers were formed in a one of its kind machine (Bar-Nun et al 2003).…”

Thermally induced mixing of water dominated interstellar ices

“…[22][23][24] Hence to facilitate accurate modelling of ISM processes, a detailed characterization of the adsorption and desorption of astrophysically relevant molecules from H 2 O covered surfaces is essential. Despite considerable attention in the literature given to the thermal desorption of simple volatiles detected in H 2 O-rich ices, [25][26][27][28][29][30][31][32][33] the desorption of more complex saturated molecules, such as C 2 H 5 OH, has yet to be explored. We have therefore used reflection absorption infrared spectroscopy (RAIRS) and temperature programmed desorption (TPD) to investigate the adsorption and desorption of C 2 H 5 OH from various thicknesses of amorphous solid water (ASW) grown on an underlying highly oriented pyrolytic graphite (HOPG) surface at 98 K. The exact composition of interstellar dust grains is still not accurately known and depends on the astrophysical environment.…”

“…36,37 The interaction between H 2 O ice films and astrophysically relevant gas-phase molecules, and the subsequent annealing of these model interstellar ices, has received considerable attention in the literature. [25][26][27][28][29][30][31][32][33] Such processes are of particular importance to the ISM with regards to elucidating star-formation, in addition to determining the ice composition and thermal ageing of astrophysical bodies and out-gassing kinetics. 20 Several laboratory studies have demonstrated that the thermal desorption behaviour of molecules deposited on the surface of a H 2 O film, or co-deposited as a mixture, are controlled by the morphology and desorption properties of the H 2 O.…”

Compaction of microporous amorphous solid water by ion irradiation

“…2,3 The microporous structure has a high internal surface area ͑several hundred m 2 /g͒ deduced from the high gas adsorption capacity, which also indicates that most of the pores are accessible to gas molecules from the external environment. [3][4][5] The micropores have an infrared absorption signature, weak narrow bands near 2.7 m due to O-H stretch vibration of dangling bonds of incompletely coordinated molecules on the pore surfaces. 6 The microporosity of ice could play an important role in the chemical evolution of interstellar molecular clouds by enhancing the accretion of gas-phase species that can later react and form new molecules.…”