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Spatial distribution of organics in the inner coma of 103P/Hartley 2

Presentation #208.02 in the session “Observations of Short Period Comets”.

Published onOct 03, 2021
Spatial distribution of organics in the inner coma of 103P/Hartley 2

Contemporaneous high spatial (spacecraft) and high spectral (ground-based) resolution infrared data were acquired of comet 103P/Hartley 2 in 2010 near its perihelion passage (1.05 AU). Spatially heterogeneous signatures of gaseous bands of H2O, CO2, and a spectral blend of organics, along with water ice, were detected in Hartley 2’s coma with the Deep Impact High Resolution Instrument Infrared spectrometer (DI HRI-IR, λ/δλ ~ 250) [1]. Similarly, the Keck NIRSPEC instrument (λ/δλ ~ 25,000) detected and resolved individual lines of H2O, OH, and several organic molecules displaying asymmetric radial profiles [2]. In addition, the near-nucleus observations of Hartley 2 revealed multiple sources of H2O, i.e., the sunlit nucleus, illuminated fallback material on the waist of the bilobed nucleus, and a tailward population of icy particles dragged from the subsurface primarily by CO2 sublimation jets emanating from the small lobe [3,4]. Here we apply established fluorescence models of CH4, C2H6, and OH with an extended molecular emission model of CH3OH, empirically derived from Keck data of comets Hartley 2 and C/1999 H1 (Lee) where gaps in the fluorescence model existed, to the DI HRI-IR spectra extracted from two regions of interest in Hartley 2’s innermost coma. Specifically, we will independently examine the organics found in the tailward source of H2O and those in the CO2 jet by fitting the spectral shape of the bulk organic feature in the DI data with the improved fluorescence model, comparing the inferred organic components, and identifying any spatial correlations among the organics and other volatiles. These results will aid in our understanding of Hartley 2’s source regions, formation, and processes at work during volatile release.

This research is supported by NASA DDAP Awards 80NSSC18K1041 and 80NSSC18K1280.

[1] A’Hearn, M.F., et al., 2011, Science, 332, 1396.

[2] Dello Russo, N., et al., 2013, Icarus, 222, 707.

[2] Sunshine, J.M., & Feaga, L.M., 2021, PSJ, 2, 92.

[4] Bonev, B.P., et al., 2013, Icarus, 222, 740.

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