A Chemistry-First Centered Icy Chemical Inventory of Protostellar Sources with JWST

The chemical evolution in star forming regions is driven by the interplay between gas and ice mantles. Identifying the ice compositions at the early stage of star formation thus provides constraints on the chemical processes inaccessible from gas-phase characterizations.

As part of the CORINOS program, spectra from the James Webb Space Telescope (JWST) MIRI MRS were taken toward four Class 0 protostars: IRAS 15398-3359, Ser-emb7, L483, and B335. The spectra were processed with simultaneous fitting of a continuum and silicate absorption to produce optical depth mid-infrared spectra of the ices at 5-28 μm (360-2000 cm⁻¹) toward these four sources.

Simple molecules such as water (H₂O), carbon dioxide (CO₂), methanol (CH₃OH), formic acid/formate (HCOOH/HCOO−), ammonia/ammonium (NH₃/NH₄+), and formaldehyde (H₂CO) are the most abundant features in these ices, while complex organic molecules (COMs) represent a smaller contribution.

Likely COMs include hydroxylamine (NH₂OH), methylamine (CH₃NH₂), and ethanol (CH₃CH₂OH). Absorption features belonging to functional groups such as -CH₃ and -OH suggest that additional COMs are present, but these cannot be unambiguously assigned due to overlapping bands. Formation pathways toward these COMs utilizing radical-radical combination reactions based on laboratory simulation experiments is presented.

By extension, COMs predicted by these reactions, but absent from the spectra, are discussed. The results provide insight into the chemical environment of these ices and also highlight the critical need for caution and sufficient evidence in order to confidently identify COMs in ice.

Reaction scheme demonstrating the formation of complex organic molecules in the JWST spectra via radical-radical recombination reactions starting from simple reactants such as carbon dioxide (CO₂), formaldehyde (H₂CO), methanol (CH₃OH), water (H₂O), ammonia (NH₃), and methane (CH₄). Each of these pathways have been identified identified in laboratory ice analogue experiments. Chemical names in bold were identified in the JWST spectra with greater confidence. — astro-ph.GA

Andrew M. Turner, Yao-Lun Yang, Rachel Gross, Nami Sakai, Ralf I. Kaiser

Comments: Accepted to The Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2602.05383 [astro-ph.GA] (or arXiv:2602.05383v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2602.05383
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Submission history
From: Yao-Lun Yang
[v1] Thu, 5 Feb 2026 07:08:33 UTC (8,710 KB)
https://arxiv.org/abs/2602.05383
Astrobiology, AStrochemistry,