Widespread CO₂ and CO ices in the trans-Neptunian population revealed by JWST/DiSCo-TNOs

Carbon dioxide (CO₂) is one of the most abundant ices in the Solar System. It has been detected in giant planet atmospheres and on their moons, on and around comets, and even in regions of Mercury, the Moon and Mars. However, despite formation in the coldest regions of the protoplanetary disk, CO₂ has not previously been detected throughout the trans-Neptunian objects (TNOs). Furthermore, carbon monoxide (CO) was detected to be present on the surface of only the largest TNOs. Out of 59 TNOs and centaurs observed by the James Webb Space Telescope (JWST) and the NIRSpec Integral Field Unit as part of the DiSCo-TNOs project (PID 2418), we report the widespread detection of CO₂ ice in 95% of the sample and CO ice in 47% of the sample. CO is predominantly found in objects where the abundance of CO₂ is higher. The abundance and characteristics of these ices suggest the prevalence of at least two types of TNO surfaces. The differences in compositions between these groups can be attributed to different formation regions in the protoplanetary disk, where the ability to accrete or maintain the CO₂ ice played a major role in the subsequent evolution of TNO surfaces. Although the nature of the CO remains elusive, its correlation with an augmented abundance of CO₂ suggests a potential production mechanism involving the irradiation of carbon-bearing ices.