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

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, C₂, CH, NH₂, 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/H₂O and C₂/CN ratios, which has not been previously reported for any comet. There may also be variability in the NH₂/H₂O ratio with rotational phase, but this trend is not as clear as for CN/H₂O. We interpret the changing mixing ratios as due to H₂O and C₂ 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 NH₂ abundances are consistent with HCN and NH₃ being the dominant parent molecules for these species. The C₂ and CH abundances are higher than those of candidate parent molecules (C₂H₂ and CH₄ respectively), so there must be another source for these molecules in 103P's coma. Carbonaceous dust grains could serve as this source.