The composition of comets has remained largely unchanged compared with other planetary bodies in our Solar System since their formation in the protoplanetary disk. Studying their compositions can therefore provide insights into the chemical and physical processes that occurred during planet formation. Carbon dioxide (CO2) is an abundant volatile in comets and can be an important driver of cometary activity. Thus, CO2 abundances are a key aspect of cometary chemical composition. However, direct ground-based observations of CO2 are not possible owing to complete telluric absorption. While CO2 is observable from space-borne facilities, available observing time on these facilities is limited. Proxy observations that can be obtained from the ground are needed to overcome these barriers. Forbidden oxygen ([OI]) lines have been proposed as a candidate for such a proxy (specifically the flux ratio of the [OI]5577 Å line to the sum of the [OI]6300 Å and [OI]6364 Å lines, hereafter referred to as the oxygen line ratio). However, our understanding of the photochemistry responsible for the release of OI into the coma is still incomplete. We present analysis of narrowband OH imaging and high-resolution optical spectroscopy (acquired using facilities at McDonald Observatory) and IR imaging (obtained using the Spitzer Space Telescope and from the NEOWISE mission) of comet C/2013 X1 (PanSTARRS) to test [OI] as a proxy for the CO2 abundance. We utilize our OH observations as a proxy for the H2O production, while the spectroscopic observations sample [OI] emission and the Spitzer and NEOWISE observations are sensitive to CO2 emission. By comparing the inferred CO2 abundances from our oxygen line ratios to measured values based on the narrowband OH and Spitzer/NEOWISE imaging, we will test and calibrate the use of ground-based [OI] observations as a proxy for CO2 observations.
This work was supported by NASA’s Summer Undergraduate Program for Planetary Research and the NASA Solar System Workings Program through grant 80NSSC20K0140.