# # Program information file # PROGRAM_ID 2023B081 PROGRAM_TITLE Investigating Changes in Volatile Production and Mixing Ratios of Comet 103P/Hartley 2: A Multi-Epoch Analysis with iSHELL. PROGRAM_INV1 Mohammad Saki PROGRAM_INV2 Bebi Muskan Rai PROGRAM_INV3 Erika Gibb PROGRAM_INV4 Neil Dello Russo PROGRAM_INV5 Michael DiSanti PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG We propose to use iSHELL to measure the coma composition of parent volatiles of the Jupiter-family comet 103P/Hartley 2. 103P/Hartley 2 was the flyby target of NASA's EPOXI mission in November 2010, and our study provides the first opportunity since then to measure its coma composition and outgassing activity near its perihelion. We aim to achieve three scientific goals: quantify possible changes between the two apparitions, test the role of seasons and rotation on a heterogeneous nucleus, and test hyperactivity and volatile outgassing patterns. To achieve these goals, we request observations of 103P during three epochs, each spanning pre-, near-, and post-perihelion dates. We require two iSHELL settings, Lp1 and a custom L-band setting, to measure the chemistry and spatial distributions of species in the coma. Lp1 samples C2H6, CH3OH, and OH prompt emission, which traces the production and spatial distribution of its parent [H2O]. The custom L-band setting spans ~2.83--3.1 micron and samples H2O, NH3, and HCN. By measuring and comparing parent volatile production rates and mixing ratios for 103P in 2023 with measurements from 2010, our study aims to quantify possible changes between the two apparitions and search for evolutionary changes in a comet mission target across multiple perihelion passages for multiple species. We will investigate the role of diurnal/rotational effects on production rates and mixing ratios of volatiles and finally search for outgassing patterns of polar and apolar molecules sublimating into the coma. PROGRAM_ABSTRACT_END