On the prospective detection of polyoxymethylene in comet 67P/Churyumov-Gerasimenko with the COSIMA instrument onboard Rosetta

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• 作者：L&eacute ; na Le Roy^a ; ^b ; Giacomo Briani^b ; ¹ ; Christelle Briois^a ; Herv&eacute ; Cottin^b ; ^{Herve.Cottin@lisa.u-pec.fr} ; Nicolas Fray^b ; Laurent Thirkell^a ; Gilles Poulet^a ; Martin Hilchenbach^c
• 关键词：Polyoxymethylene ; Cometary grains ; COSIMA ; Rosetta ; TOF SIMS
• 刊名：Planetary and Space Science
• 出版年：2012
• 期刊代码：60_00320633
• 类别：ph
• 出版时间：May, 2012
• 卷：65
• 期：1
• 页码：83-92
• 文件大小：851 K

摘要

The presence of polyoxymethylene (POM) in cometary grains has been debated years ago. Although never proven, its presence can not be excluded. Rosetta, the ESA mission to comet 67P/Churyumov-Gerasimenko, may answer this question. On board the spacecraft, COSIMA (COmetary Secondary Ion Mass Analyzer) will analyze the grains ejected from the nucleus using a Time Of Flight Secondary Ion Mass Spectrometer (TOF-SIMS). In this paper we report the extent to which COSIMA will be able to detect POM if this compound is present on cometary grains. We have analyzed two kinds of POM polymers with a laboratory model of COSIMA. Positive mass spectra display alternating sequence of peaks with a separation of 30.011 Da between 1 and 600 Da related to formaldehyde and its oligomers but also to the fragmentation of these oligomers. The separation of 30.011 Da of numbers peaks, corresponding to the fragmentation into H₂CO is characteristic of POM and we show that it could be highlight by mathematical treatment. POM lifetime on COSIMA targets have also been studied as POM is thermally instable. It can be concluded that the cometary grains analysis have to be planned not too long after their collection in order to maximize the chances to detect POM. This work was supported by the Centre National d'Etudes Spatiales (CNES).