IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2023A065 PROGRAM_TITLE First Measurements of Parent Volatiles Composition of Anomalous Comet 96P/Machholz 1. PROGRAM_INV1 Mohammad Saki PROGRAM_INV2 Erika Gibb PROGRAM_INV3 Boncho Bonev PROGRAM_INV4 Michael DiSanti PROGRAM_INV5 Neil Dello Russo PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG We propose to use iSHELL to measure parent composition of coma gases [H2O, HCN, C2H2, NH3, CH4, C2H6, CH3OH, H2CO, CO, and OCS] released from ices in the nucleus of Jupiter-family comet [JFC] 96P/Machholz 1. We emphasize three equally important goals: [1] JFCs as an under-represented group in taxonomic studies of parent volatiles, [2] determine abundances of hypervolatiles CO and CH4, and [3] Determining the primary-fragment relationship. 96P's anomalous composition in fragment species and unusual orbit suggested that it could have formed in compositionally different parts of the protoplanetary disk or have interstellar origins. It does not fit in any taxonomic class based on fragment species, so studies of parent volatiles can potentially have a high impact. 96P's high Doppler shift is sufficient for shifting cometary emissions [particularly for CO and CH4] out of their telluric counterparts, allowing us to detect or put stringent upper limits on both species. We will use three iSHELL settings: Lcustom [~2.8-3.1 um, sampling H2O, HCN, NH3, and C2H2]; Lp1 [~3.2-3.6 um, sampling CH4, C2H6, CH3OH, H2CO, and OH*, a proxy for the production and spatial distribution of its parent, H2O]; and M2 [~4.5-5.2 um, sampling H2O, CO, and OCS]. We will use the 3.46 um filter to guide on 96P with Kyle during the day, as this filter covers generally strong gas emission. Due to the day-time nature of 96P and low sensitivity of previous near-IR spectrographs, the parent volatile composition of comet 96P has never been studied before. The 2023A semester provides a rare [and excellent] opportunity to measure its parent volatile abundances for the first time. Owing to its high resolving power, spectral coverage, flexible daytime scheduling for serial observation, and superior M-band guiding, these studies can only be done with iSHELL at NASA-IRTF. PROGRAM_ABSTRACT_END