Issue |
A&A
Volume 686, June 2024
|
|
---|---|---|
Article Number | A39 | |
Number of page(s) | 7 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/202348154 | |
Published online | 28 May 2024 |
Laboratory simulations of ice growth in space: An expected nonuniform ice mantle composition
1
INAF – Osservatorio Astronomico di Palermo,
P.za Parlamento 1,
90134
Palermo, Italy
e-mail: antonio.jimenez@inaf.it
2
Department of Physics, National Central University,
Zhongli Dist.,
Taoyuan City
320317, Taiwan
e-mail: asperchen@phy.ncu.edu.tw
3
Institute of Low Temperature Science, Hokkaido University,
Sapporo,
Hokkaido
060-0819, Japan
4
Centro de Astrobiología (INTA-CSIC),
Ctra. de Ajalvir, km 4,
28850
Torrejón de Ardoz, Madrid, Spain
Received:
4
October
2023
Accepted:
6
March
2024
Context. In dense, cold molecular regions, gas-phase chemical species freeze out onto grain surfaces. These icy condensates become an important reservoir of volatile elements and feedstock for molecular diversity.
Aims. While there is a fairly general agreement on the chemical composition of icy mantles, there are differences in how the various molecular components are perceived to be present. Should the materials composing the ice be mixed or are they segregated into distinct chemical zones?
Methods. To answer such a question, we performed a few exploratory experiments that allowed the adsorbing surface (mimic dust grains) to slowly relax to very low temperatures while gas-phase mixtures of H2O, NH3, and CO embed onto it.
Results. We find that mantles are far from being uniform, and they could evolve into completely mixed ices only if the ambient temperature undergoes a catastrophic collapse.
Conclusions. Under the typical conditions of an interstellar dense cloud, ices present a high degree of molecular segregation, with possible consequences on the ice chemistry and the desorption mechanisms.
Key words: astrochemistry / methods: laboratory: solid state / protoplanetary disks
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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