CO and CO₂ Production Rates in Comets and Centaurs

CO and CO₂ are abundant molecules in comets and have major roles in driving activity, especially in objects farther than 3 au from the Sun, where water-ice sublimation is inefficient. While CO can be measured from the ground, CO₂ is limited to space-based observations, often providing difficulties in obtaining the relative abundances of the two species. The CO and CO₂ ratios beyond 3 au have been observed in 7 of the comets. The CO and CO₂ mixing ratios provide observational constraints to models of solar system formation and evolution, as well as physical models of comet nuclei. We compiled CO, CO₂, and H₂O production rates for 20 cometary (8 JFCs, 10 OCCs, 1 HTC, and 1 Centaur) objects using published results of spectroscopic and photometric measurements in comets and centaurs over a range of heliocentric distances. We present and discuss aggregate properties of the CO/CO₂ ratio in the sample, as well as evidence for differences among major orbital dynamical groups, and possible heliocentric dependence on the outgassing rates of these volatiles.

O.H.P. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant #1829740, the Brinson Foundation, and the Moore Foundation; her participation in the program has benefited this work. This work was also supported in part by the National Science Foundation undergrant No. AST-1945950. This material is based in part on work done by M.W. while serving at the National Science Foundation.