Volatiles in Jupiter-family Comets: Synergy Between Infrared Observations and Protoplanetary Disk Chemistry Models

Jupiter-family comets (JFCs) are dynamically-sourced in the scattered Kuiper disk, and are generally less productive than Oort Cloud comets (OCCs). For this reason, JFCs have been underrepresented in ground-based observations of volatiles, such as C₂H₂, C₂H₆, CH₃OH, HCN, H₂O, NH₃, H₂CO, and especially CO and CH₄, for which large Doppler shifts are needed to offset cometary lines from their telluric counterpart absorptions.

The period since 2017 has encompassed some of the best apparitions of JFCs in modern history. These have benefitted from the availability of significantly improved instrumentation for near-IR spectroscopy, and have also coincided with increased synergy between studies of cometary volatiles and model simulations of protoplanetary disk (PPD) chemistry. This presentation will connect findings stemming from near-IR observations of JFCs and OCCs with predictions of PPD midplane ices produced by chemical models for the early solar nebula [Willacy et al. 2022; Astrophysical Journal, 931:164]. Open questions will be discussed in the context of better disentangling natal heritage in cometary volatiles from signatures of post-formative processing, as is needed to understand the comet – early solar system link.

Acknowledgments: Team members gratefully acknowledge support from the following US funding programs: NSF/AAG, NASA/SSO, and NASA/EW. This work benefited from discussions at the International Space Science Institute in Bern during meetings of International Team 361, “From Qualitative to Quantitative: Exploring the Early Solar System by Connecting Comet Composition and Protoplanetary Disk Models.”