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. The near-infrared spectrometer onboard JWST has detected CO2 and CO ices on 56 and 29 trans-Neptunian objects, respectively, indicating two dominant compositional types among them. These compositional differences suggest varied formation regions in the protoplanetary disk.