One of Jupiter’s many moons, Callisto, may contain much more oxygen than scientists expected, recent research shows. This discovery raises many questions and could change our understanding of this mysterious moon of Jupiter.
Callisto, despite its status as the second largest moon of Jupiter and the third largest in the solar system, has always remained hidden in the shadows of its neighbors such as Europa and Ganymede, which have attracted the attention of scientists with their mysterious subsurface oceans and gigantic water jets.
Callisto is distinguished by its ancient surface, believed to be the oldest in the solar system, and many researchers suggest an ocean may lie beneath its thick crust. For a long time, however, it did not attract much scientific interest, and NASA missions mostly avoided it.
However, recent studies have shown that this moon contains much more oxygen than expected.
The researchers decided to study the effect of intense plasma in Jupiter’s magnetosphere on its icy moons, including Callisto. They conducted experiments measuring the release of water molecules from low-temperature ice caused by falling charged particles, a process called sputtering.
“The results showed that water ice sputtering is dominated by electronic excitations and ionizations occurring in the ice (electron sputtering) rather than by detonation collisions of ions with water molecules (nuclear sputtering), a sputtering process that has been widely studied until now,” the researchers said.
Further experiments led to a surprising discovery: the bonds in water ice molecules can be dissociated by the electron energy released by falling charged particles, and the fragmented molecules can recombine to form new species, such as H2 and O2.
Most surprising, the amount of oxygen detected on Callisto was much greater than expected. This caused confusion among scientists, as existing models could not explain such high oxygen levels on Jupiter’s moon.
Lead study author Shane Carberry Maughan said: “There is a huge discrepancy. We are about two or even three orders of magnitude behind.”
Even if Callisto were completely covered in ice, and not just 10 percent as the team had assumed, this still wouldn’t explain the amount of oxygen. Scientists have proposed several hypotheses, but none offers a satisfactory explanation.
This discovery challenges our understanding of the origin and composition of Jupiter’s moons. Perhaps answers to these questions will be found during the upcoming JUICE (JUpiter ICy moons Explorer) mission, which will fly around Jupiter’s icy moons.
Scientists hope this mission will be able to provide “multipoint parallel measurements of the moon’s charged and neutral particle environment,” which could help solve the mystery of the presence of vast amounts of oxygen on Callisto.
