Laboratory-based Sticking Coefficients For Ices On A Variety Of Small Grains Analogs

Abundances and partitioning of ices and gases produced by gas-grain chemistry are governed by adsorption and desorption on grains. Understanding astrophysical observations rely on laboratory measurements of adsorption and desorption rates on dust grains analogs.

On flat surfaces, gas adsorption probabilities (or sticking coefficients) have been found close to unity for most gases. Here we report a strong decrease of the sticking coefficients of H2O and CO2 on substrates more akin to cosmic dust, such as submicrometer-sized particles of carbon and olivine, bare or covered with ice. This effect results from the local curvature of the grains, and then extends to larger grains made of aggregated small particles, such as fluffy or porous dust in more evolved media (e.g. circumstellar disks). The main astrophysical implication is that accretion rates of gases are reduced accordingly, slowing the growth of cosmic ices.

Furthermore, volatile species that are not adsorbed on a grain at their freeze-out temperature will pertain in the gas phase, which will impact gas-ice partitions. We also found that thermal desorption of H2O is not modified by grains size, and thus the snowlines temperature should be independent on the dust size distribution.

Carine Laffon, Daniel Ferry, Olivier Grauby, Philippe Parent

Comments: Manuscript : 20 pages, 3 figures, 1 table; Supplementary informations : 9 pages, 5 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)
DOI: 10.1038/s41550-020-01288-7
Cite as: arXiv:2102.09862 [astro-ph.GA] (or arXiv:2102.09862v1 [astro-ph.GA] for this version)
Submission history
From: Philippe Parent Dr
[v1] Fri, 19 Feb 2021 11:00:19 UTC (1,627 KB)
https://arxiv.org/abs/2102.09862

Astrobiology, Astrochemistry,