# # Program information file # PROGRAM_ID 2024A034 PROGRAM_TITLE Comet 12P/Pons-Brooks: Opportunity for an in-depth study of a Halley-type comet PROGRAM_INV1 Erika Gibb PROGRAM_INV2 Mohi Saki PROGRAM_INV3 Bebi Rai PROGRAM_INV4 Nathan Roth PROGRAM_INV5 Boncho Bonev PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG We propose to use iSHELL at NASA-IRTF to study the volatile composition of Halley-type comet 12P/Pons-Brooks. Comets are believed to be relatively pristine and their composition can provide insights into the early solar system. However, several comets have exhibited changes in volatile composition when observed repeatedly, motivating more extensive observing strategies. Compositional variations may be due to seasonal variations, rotational/diurnal effects, evolutionary [thermal processing] processes, or heliocentric distance effects. The 2024A semester provides an excellent opportunity to observe a dynamical class of comets that is severely underrepresented in comet studies: Halley-type. These comets have an Oort cloud origin and hence formed in a similar region to other Oort cloud comets, but have been exposed to thermal processing, allowing for a more direct way to distinguish between natal heritage and thermal processing among comets. 12P is continuously available and sufficiently bright to measure volatile emissions for nearly four months, also allowing for an investigation of heliocentric and seasonal effects on composition. 12P is also known for exhibiting dramatic outbursts during its apparitions, allowing for the potential to measure freshly excavated subsurface material in a comet. We propose to monitor 12P from late-February through early-June 2024 in order to measure ten volatiles using three iSHELL settings: Lp1 will sample CH4, C2H6, CH3OH, and H2CO, M2 will sample H2O, OCS, and CO, and a custom L setting [covering roughly 2.80-3.10 microns] will sample H2O, C2H2, NH3, and HCN. Owing to its cross-dispersed capability, excellent sensitivity, superior guiding while obtaining spectra in M-band, and daytime observing capability, iSHELL at NASA-IRTF is the only suitable instrument/facility combination for this study. PROGRAM_ABSTRACT_END