SwRI team detects carbon dioxide and hydrogen peroxide on Pluto's moon Charon

"Charon is the only midsized Kuiper Belt object, between 300 and 1,000 miles in diameter, that has been geologically mapped, thanks to the SwRI-led New Horizons mission, which flew by the Pluto system in 2015," said Dr. Silvia Protopapa of SwRI, lead author of a paper in 'Nature Communications' and a co-investigator on the New Horizons mission. "Unlike larger Kuiper Belt objects, Charon's surface isn't covered by volatile ices like methane, giving us key insights into how processes like sunlight and impacts shape these distant bodies."

The Webb telescope's advanced capabilities allow detailed exploration of objects in the outer solar system. Using Webb's Near-Infrared Spectrograph, the team conducted four observations of Charon in 2022 and 2023, covering its northern hemisphere.

"The advanced observational capabilities of Webb enabled our team to explore the light scattered from Charon's surface at longer wavelengths than what was previously possible, expanding our understanding of the complexity of this fascinating object," added Dr. Ian Wong, a co-author and staff scientist at the Space Telescope Science Institute.

Charon's new observations revealed carbon dioxide on the surface, which the team believes is a thin layer on top of a water ice-rich interior. "Our preferred interpretation is that the upper layer of carbon dioxide originates from the interior and has been exposed to the surface through cratering events," said Protopapa. Carbon dioxide is thought to have been present in the protoplanetary disk from which Pluto and its moons formed.

The detection of hydrogen peroxide on Charon's surface points to changes caused by solar ultraviolet light and particles from the solar wind. Hydrogen peroxide forms when water ice is broken down by incoming ions and particles.

"Laboratory experiments at SwRI's CLASSE facility showed that hydrogen peroxide can form in mixtures of carbon dioxide and water ice under conditions similar to those on Charon," said Dr. Ujjwal Raut of SwRI, who leads the CLASSE lab and is the second author of the paper.

These discoveries highlight Webb's exceptional ability to reveal complex surface features shaped by impacts and irradiation, offering new insights that may apply to other Kuiper Belt objects. "The new insights were made possible by the synergy between Webb observations, spectral modeling, and laboratory experiments," added Protopapa.

Research Report:Detection of carbon dioxide and hydrogen peroxide on the stratified surface of Charon with JWST