Parent Volatile Outgassing Associations in Cometary Nuclei: Synthesizing Rosetta Measurements and Ground-based Observations

Abstract

Comets, as remnants of the solar system’s formation, vary in volatile-refractory content. In situ comet studies, such as the Rosetta mission to 67P/Churyumov–Gerasimenko, provide detailed volatile composition insights, while ground-based studies offer broader comet samples but in fewer species. Comparing 67P’s volatile correlations during the 2 yr Rosetta mission with those from remote sensing gives insights into volatile distribution in the nucleus and factors influencing their release. Our goal is to identify associations between volatiles seen from the ground and those in 67P. Given 67P’s seasonal variations, we segmented the Rosetta mission around 67P into six epochs, reflecting different insolation conditions. It has been suggested that there are at least two different ice matrices, H2O and CO2 ice, in which the minor species are embedded in different relative abundances within them. We employed various methodologies to establish associations among volatiles, such as volatile production rates, spatial distributions, patterns in mixing ratio, and local outgassing source locations. We note that different techniques of grouping molecules with respect to H2O and CO2 may yield different results. Earth’s atmosphere blocks CO2; however, due to observed differences between H2O and C2H6 from the ground and between H2O and CO2 from comet missions, C2H6 is suggested to be a CO2 proxy. Our study delves into cometary coma molecular correlations, highlighting their associations with H2O and CO2 matrices and advancing our understanding of the early solar system comet formation and evolution.