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Water–Carbon Dioxide Dichotomy in Comet 22P/Kopff in JWST Spectral Maps

Presentation #400.03 in the session Comets: Coma (Oral Presentation)

Published onOct 23, 2023
Water–Carbon Dioxide Dichotomy in Comet 22P/Kopff in JWST Spectral Maps

Cometary activity is a dynamic process that produces a coma of dust and volatiles. Observations of comets, whether they are from spacecraft, ground-based, or space-based telescopes, have shown that coma asymmetries and heterogeneity are common. Analyses of comae have even demonstrated that individual coma gasses produced by the nucleus are not strictly spatially correlated with each other, indicating that they can have different origins on the surface. Thus, the study of comae may be used to understand the heterogeneity of cometary surfaces and the mass-loss process. The Rosetta mission to comet 67P/Churyumov-Gerasimenko has well-illustrated this point. The surface of comet 67P has two major terrain types correlated with composition: rough, consolidated terrain with a given abundance of H2O, CO2, and CO; and smooth terrain that appears to be a thermally processed version of the rough terrain, i.e., depleted in CO2 and CO (Keller et al. 2017, MNRAS 469, S357). Comet 22P/Kopff is a Jupiter-family comet with a remarkable coma asymmetry (see, e.g., the images and dynamical analysis of Moreno et al. 2012, ApJ 752, 136). Observations of this comet were taken with JWST’s NIRSpec instrument on 2022 August 25, with the comet at a heliocentric distance of 2.18 au. Spectral maps with the NIRSpec Integral Field Unit reveal a heterogenous inner coma: water and dust are highly correlated, but CO2 appears to be independent. Similar findings for 67P were reported by Rinaldi et al. (2016, MNRAS 462, S547) and Tubiana et al. (2019, A&A 630, A23), suggesting the surface dichotomy of 67P may be a good model for comet 22P, although the cause of the dichotomy could be different. We additionally present maps of CH3OH, and report coma abundances for H2O, CO2, 13CO2, CO, CH3OH, C2H6, CH4, and OCS. Finally, we examine how the coma abundances are affected by the water sublimation rate at 2.18 au.

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