Carbon chains reservoir as a source for solid-state formation of COMs under cold dark cloud conditions
Abstract
Formation of stellar systems similar to our Solar System begins from gravitational collapse of an interstellar cloud comprised of gas and dust. In the densest regions of such clouds the temperature drops to as low as 10 K, while the lifetime of the cloud is long enough to accrete most of the gas-phase material (with exception of He and H _{2}) onto dust grain surfaces [1]. The depletion of gas-phase species on a grain surface results in a rich chemistry triggered by atom- and radical-addition reactions between accreting species. Hydrogenation of CO molecules under such conditions results in the formation of organic molecules as complex as a three-carbon bearing sugar alcohol glycerol - a backbone glycerides - a necessary component for the formation of micelles and cell membranes in aqueous solutions [2]. However, this "bottom-up" approach meets increasing difficulties in production of long amphiphilic molecules such as fatty alcohols and fatty acids, another missing component in the formation of such glycerides. We present the results of a laboratory based research aiming to investigate formation of COMs starting from carbon chains, at the earliest stages of star formation. We show that two simplest representatives of carbon chains, HCCH and HCCCH _{3}, can efficiently participate in hydroxylation reactions resulting in formation of various alcohols and aldehydes upon reaction of OH radicals with unsaturated carbon-carbon bonds [3,4]. The proposed reaction mechanism holds much potential to form larger COMs starting from various -(C≡C) _{n}- containing carbon chains observed in star-forming regions. Such COMs can either themselves participate in the formation of micelles in warm aqueous solutions, or form ether bonds with glycerol. Thus, the presence of simplest lipid precursors on young planets may be plausable under the assumption that at least a fraction of the original icy-dust material survives upon transfer to an early planet surface. [1] P. Caselli and C. Ceccarelli, 2012, A&ARv 20, p. 56 [2] G. Fedoseev et al., 2017, ApJ 842, p. 52 [3] D. Qasim et al., 2019, ACS Earth Space Chem 3, p. 986 [4] K.-J. Chuang et al., 2020, A&A, 635, A199
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.2740F