Prestellar grain-surface origins of deuterated methanol in comet 67P/Churyumov–Gerasimenko

Drozdovskaya, Maria N; Schroeder I, Isaac R. H. G.; Rubin, Martin; Altwegg, Kathrin; van Dishoeck, Ewine F; Kulterer, Beatrice M; De Keyser, Johan; Fuselier, Stephen A; Combi, Michael (2021). Prestellar grain-surface origins of deuterated methanol in comet 67P/Churyumov–Gerasimenko. Monthly notices of the Royal Astronomical Society, 500(4), pp. 4901-4920. Oxford University Press 10.1093/mnras/staa3387

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Deuterated methanol is one of the most robust windows astrochemists have on the individual chemical reactions forming deuterium-bearing molecules and the physicochemical history of the regions where they reside. The first-time detection of mono- and di-deuterated methanol in a cometary coma is presented for comet 67P/Churyumov–Gerasimenko using Rosetta–ROSINA data. D-methanol (CH3OD and CH2DOH combined) and D2-methanol (CH2DOD and CHD2OH combined) have an abundance of 5.5 ± 0.46 and 0.00069 ± 0.00014 per cent relative to normal methanol. The data span a methanol deuteration fraction (D/H ratio) in the 0.71−6.6 per cent range, accounting for statistical corrections for the location of D in the molecule and including statistical error propagation in the ROSINA measurements. It is argued that cometary CH2DOH forms from CO
hydrogenation to CH3OH and subsequent H–D substitution reactions in CH3–R. CHD2OH is likely produced from deuterated formaldehyde. Meanwhile, CH3OD and CH2DOD could form via H–D exchange reactions in OH–R in the presence of deuterated water ice. Methanol formation and deuteration is argued to occur at the same epoch as D2O formation from HDO, with formation of mono-deuterated water, hydrogen sulphide, and ammonia occurring prior to that. The cometary D-methanol/methanol ratio is demonstrated to agree most closely with that in prestellar cores and low-mass protostellar regions. The results suggest that cometary methanol stems from the innate cold (10–20 K) prestellar core that birthed our Solar system. Cometary volatiles individually reflect the evolutionary phases of star formation from cloud to core to protostar.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Other Institutions > Emeriti, Faculty of Science
08 Faculty of Science > Physics Institute

UniBE Contributor:

Drozdovskaya, Maria N; Schroeder I, Isaac Raedwald Hans Garfield; Rubin, Martin; Altwegg, Kathrin and Kulterer, Beatrice Marie

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics

ISSN:

0035-8711

Publisher:

Oxford University Press

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

18 Feb 2021 09:04

Last Modified:

18 Feb 2021 09:04

Publisher DOI:

10.1093/mnras/staa3387

BORIS DOI:

10.48350/152228

URI:

https://boris.unibe.ch/id/eprint/152228

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