Thanks to the James Webb Space Telescope (JWST), a team of astronomers has identified the presence of carbon dioxide and hydrogen peroxide on the icy surface of Charon, the largest moon of Pluto.
These discoveries could provide new insights into the origin of Charon and other icy bodies in the Kuiper Belt, the region at the edge of the solar system. Charon, discovered in 1978, has been extensively studied over the years, but previous research was limited by the available technology and the range of wavelengths that could be explored.
Before the use of the JWST, traces of water ice, ammonia, and organic compounds had been detected, but carbon dioxide and hydrogen peroxide had not been identified. The research team, led by Silvia Protopapa of the Southwest Research Institute, used the Near-Infrared Spectrograph (NIRSpec) instrument on the JWST to fill these gaps. “Our investigation shows that the surface of Charon retains traces of its formation through the presence of carbon dioxide, and indicates irradiation processes through hydrogen peroxide,” said the researcher. Charon, with a diameter of about 1,207 kilometers, is a medium-sized body within the Kuiper Belt, but unlike the larger objects in this region, its surface is not covered by volatile ices like methane.
This makes Charon a valuable object for studying the effects of solar exposure and cratering on distant icy bodies. The JWST observations also rely on detailed geological maps provided by NASA’s New Horizons probe during its exploration mission of the Pluto-Charon system in 2015.
The mission’s images revealed a surface rich in craters and ejecta blankets, suggesting that materials from the subsurface have been exposed by meteoric impacts. The spectroscopic analysis performed with the JWST allowed the team to compare the observations with laboratory models, concluding that the carbon dioxide on Charon primarily deposits as an outer layer over a substrate of water ice. An additional surprise for the researchers was the detection of hydrogen peroxide.
This chemical compound indicates that the surface of Charon undergoes active modifications due to exposure to solar ultraviolet light, energetic particles from the solar wind, and galactic cosmic rays. Protopapa’s team will continue to use the JWST to further study Charon and other icy trans-Neptunian objects, expanding our understanding of the geological and chemical dynamics of these remote celestial bodies.
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