What are the gases in Callisto atmosphere?

Callisto, one of Jupiter's moons, has a thin atmosphere primarily composed of carbon dioxide (CO2) and small amounts of oxygen (O2). The atmospheric pressure is extremely low, about 1/100,000th that of Earth's atmosphere. Additionally, trace amounts of other gases, such as methane (CH4) and possibly noble gases, have been detected. Overall, Callisto's atmosphere is tenuous and not conducive to supporting life as we know it.