# # Program information file # PROGRAM_ID 2022A046 PROGRAM_TITLE Study of the composition and outgassing behavior of comet C/2021 O3 [PanSTARRS] at small heliocentric distances PROGRAM_INV1 Younas Khan PROGRAM_INV2 Erika Gibb PROGRAM_INV3 Nathan Roth PROGRAM_INV4 Neil Dello Russo PROGRAM_INV5 Michael DiSanti PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG We propose to use iSHELL to measure the primary volatile composition of the bright, long-period comet C/2021 O3 [PanSTARRS] on multiple dates in May 2022 just after its perihelion. There is a paucity of measurements of comets at heliocentric distances [Rh] between ~ 0.5 - 0.8 au, a critical range where many comets have shown enhancements in the mixing ratios [production rates with respect to H2O] of multiple molecules [notably NH3, H2CO and C2H2] compared to when they are observed at larger heliocentric distances. These enhancements are possibly due to activation of extended sources from the breakdown of less volatile material [perhaps refractory organics] in the coma. The 2022 apparition of comet C/2021 O3 will allow sampling of these molecules at Rh ranging between ~ 0.45 - 0.8 au, which will enable us to better understand the effect of heliocentric distance on coma composition and to test for possible extended sources of outgassing in the coma. Measuring the hypervolatiles [C2H6, CH4 and CO] is vital for disentangling the natal vs. post-formation processing effects in comets; however, CH4 and CO require sufficiently-large D-dot in order to shift the cometary emissions away from their opaque telluric counterparts. C/2021 O3 has favorable geocentric velocity [D-dot] on multiple proposed dates during its 2022 apparition, that will enable us to measure these hypervolatiles. The extremely favorable 2022 apparition of C/2021 O3 provides an opportunity to measure a large suite of primary volatiles [H2O, HCN, C2H2, NH3, CH3OH, H2CO, C2H6, CH4, CO, and OCS] on multiple dates and with high signal-to-noise ratio. These measurements will provide a valuable contribution to the development of a taxonomic scheme of comets based on their primary volatiles, which are directly sublimated into the coma and therefore are representative of the composition of cometary nuclei. PROGRAM_ABSTRACT_END