![Observed spectra compared to laboratory data for CO (left), 13CO2 (middle), and H2O (right) ices on carbonaceous dust analogs. -- [astro-ph.GA]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/Molecule-specific.png?fit=1200%2C570&ssl=1)
[astro-ph.GA] Interstellar ices form on dust grains in the coldest regions of molecular clouds and preserve key volatile reservoirs that could be incorporated into protoplanetary disks during star and planet formation.
Thermal evolution of CO (top row: a, CaF2; b, carbonaceous dust), CO2 (middle row: c, CaF2; d, carbonaceous dust), and H2O (bottom row: e, CaF2; f, carbonaceous dust) ices. The color scale reflects the relative optical depth of the spectra acquired during thermal processing — [astro-ph.GA]
However, the effect of the dust surface composition on the ice structure and spectroscopic behavior remains poorly constrained. We present a comparative laboratory study of astrophysically relevant ices (CO, CO2, and H2O) deposited on inert calcium fluoride (CaF2) substrate and carbonaceous dust analogs under interstellar conditions.
Infrared spectroscopy and temperature-programmed desorption reveal pronounced molecule-specific infrared spectral responses to the amorphous carbonaceous surface. CO and CO2 both exhibit broadened absorption bands, redshifted band positions, and delayed desorption, arising from thermally activated diffusion into the porous dust matrix and indicating strong molecule-surface interactions.
By contrast, H2O varies only very little spectrally and thermally, indicating weak wetting and limited coupling to the substrate. These results provide direct laboratory evidence that dust-ice interfaces can affect the ice structure and desorption kinetics of interstellar ices even in thick ice layers.
These findings offer new constraints for interpreting infrared absorption bands in astronomical observations and highlight the importance of surface effects in models of interstellar ice chemistry.
Yi-Hsuan Chiu, Tushar Suhasaria, Cornelia Jäger, Chun-Yi Lee, Ko-Ju Chuang, Thomas Henning, Yu-Jung Chen
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2608.11729 [astro-ph.GA] (or arXiv:2608.11729v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2608.11729
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Related DOI:
https://doi.org/10.1051/0004-6361/202661379
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Submission history
From: Yi-Hsuan Chiu
[v1] Wed, 12 Aug 2026 07:08:43 UTC (16,659 KB)
https://arxiv.org/abs/2608.11729
Astrobiology, Astrochemistry, Astronomy, interstellar,
