A group of scientists from various U.S. institutions recently conducted an investigation aimed at elucidating the oxygen levels within Callisto’s atmosphere, one of Jupiter’s moons, and their findings have revealed a significant deficit. Their research, detailed in a paper published in the Journal of Geophysical Research: Planets, outlines their methodology for testing this theory and exploring alternative research avenues.
Callisto, Jupiter’s second-largest moon, possesses a notably high concentration of oxygen in its atmosphere, a phenomenon that has garnered increased attention in recent times. Previous studies have posited that beneath Callisto’s surface lies a substantial crust concealing a potential ocean, but the precise composition of this subsurface layer remains uncertain, with possibilities ranging from a mixture of crust and ice to predominantly icy material. What has remained an enigma is the origin and persistence of the substantial oxygen content in Callisto’s atmosphere.
One prevailing theory posits that Jupiter’s formidable magnetosphere may be responsible for dislodging molecules of hydrogen, water, and oxygen from the surface ice of Callisto. In their latest endeavor, the researchers rigorously assessed this hypothesis. Their methodology encompassed the simulation of the thermal and energetic elements of Jupiter’s magnetosphere, specifically focusing on its plasma, while estimating the energy that reaches Callisto’s atmosphere and surface. Subsequently, they calculated the anticipated quantity of released oxygen based on this level of exposure. Upon comparing their calculated oxygen levels with the observed atmospheric oxygen content on Callisto, they uncovered a staggering incongruity. The actual oxygen levels in the atmosphere surpassed what could be attributed to Jupiter’s magnetosphere by two to three orders of magnitude.
This inconclusive outcome leaves the origin of the surplus oxygen shrouded in mystery. The research team posits that forthcoming missions, such as the European Space Agency’s JUpiter ICy moons Explorer (JUICE) and NASA’s Europa Clipper, may yield additional insights into this perplexing phenomenon.