Detection of Carbon Dioxide and Hydrogen Peroxide on the Layered Surface of Charon Using the James Webb Space Telescope

We report the first detection of carbon dioxide (CO2) and hydrogen peroxide (H2O2) on Charon's frozen surface as revealed by JWST NIRSpec instrument. With the extended spectral range of NIRSpec, we have expanded Charon's compositional inventory to include these two new species. Previously, the inventory primarily consisted of water ice (mostly in crystalline form), ammoniated species, and a tholin-like darkening constituent. The synergy of laboratory measurements and modeling analysis reveals a stratified surface rich in crystalline water ice with ammonia diluted in water ice at penetration depths of approximately ~100 micron. Additionally, a layer of pure crystalline CO2 is evident at shallower penetration depths of about ~1 micron. This feature is likely attributable to an endogenous source, unearthed by external impacts. This layering configuration is believed to cause a scattering effect, which may account for the peculiarly strong CO2 absorption band at longer wavelengths. Moreover, the surface is undergoing continuous alteration by photolysis and radiolysis, which are responsible for the presence of H2O2 and amorphous water ice.