Rotational variation of daughter species production rates in Comet 103P/Hartley: Implications for the progeny of daughter species and the degree of chemical heterogeneity

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• 作者：Adam J. McKay ; Nancy J. Chanover ; Michael A. DiSanti ; Jeffrey P. Morgenthaler ; Anita L. Cochran ; Walter M. Harris ; Neil Dello Russo
• 关键词：Comets ; Comets ; coma ; Comets ; composition
• 刊名：Icarus
• 出版年：1 March, 2014
• 年：2014
• 卷：231
• 期：Complete
• 页码：193-205
• 全文大小：844 K

文摘

We present analysis of high spectral resolution optical spectra of Comet 103P/Hartley taken during its Fall 2010 apparition. These spectra include transitions belonging to CN, C<sub>2sub>, CH, NH<sub>2sub>, and OI. We measure production rates and mixing ratios from these spectra. We find evidence for large changes in production rates (factors of a few) over the course of a nucleus rotation, in agreement with other measurements. We also measure variability with rotational phase in the CN/H<sub>2sub>O and C<sub>2sub>/CN ratios, which has not been previously reported for any comet. There may also be variability in the NH<sub>2sub>/H<sub>2sub>O ratio with rotational phase, but this trend is not as clear as for CN/H<sub>2sub>O. We interpret the changing mixing ratios as due to H<sub>2sub>O and C<sub>2sub> being released primarily from the icy grain halo, while the CN parent molecule comes directly from the nucleus. There is evidence that the CH/CN ratio is higher pre-perihelion than post-perihelion. We conclude that the observed CN and NH<sub>2sub> abundances are consistent with HCN and NH<sub>3sub> being the dominant parent molecules for these species. The C<sub>2sub> and CH abundances are higher than those of candidate parent molecules (C<sub>2sub>H<sub>2sub> and CH<sub>4sub> respectively), so there must be another source for these molecules in 103P鈥檚 coma. Carbonaceous dust grains could serve as this source.