With its sensitive infrared cameras and high-resolution spectrometer, the James Webb Space Telescope (JWST) is revealing new secrets of Jupiter’s Galilean satellites, in particular Ganymede, the largest moon, and Io, the most volcanically active.
In two separate publications, astronomers who are part of JWST’s Early Release Science program report the first detection of hydrogen peroxide on Ganymede and sulfurous fumes on Io, both the result of Jupiter’s domineering influence.
“This shows that we can do incredible science with the James Webb Space Telescope on solar system objects, even if the object is really very bright, like Jupiter, but also when you look at very faint things next to Jupiter,” said Imke de Pater, professor emerita of astronomy and earth and planetary science at the University of California, Berkeley. De Pater and Thierry Fouchet from the Paris Observatory are co-principal investigators for the Early Release Science solar system observation team, one of 13 teams given early access to the telescope.
Samantha Trumbo, a 51 Pegasi b postdoctoral fellow at Cornell University, led the study of Ganymede, which was published July 21 in the journal Science Advances. Using measurements captured by the near infrared spectrometer (NIRSpec) on JWST, the team detected the absorption of light by hydrogen peroxide — H2O2 — around the north and south poles of the moon, a result of charged particles around Jupiter and Ganymede impacting the ice that blankets the moon.
“JWST revealing the presence of hydrogen peroxide at Ganymede’s poles shows for the first time that charged particles funneled along Ganymede’s magnetic field are preferentially altering the surface chemistry of its polar caps,” Trumbo said.
The astronomers argue that the peroxide is produced by charged particles hitting the frozen water ice around the poles and breaking the water molecules into fragments — a process called radiolysis — which then recombine to form H2O2. They suspected that…