Io's Sodium Cloud Io has its own cloud. Jupiter's most active moon is visible on the left of the above false-color photograph, with its left side illuminated by sunlight. Here a plume of gas from the active volcano Prometheus also reflects sunlight. Surrounding the moon is a yellow haze originating from gas ejected by Io's volcanos.
Sodium atoms in the gas cloud are particulary efficient at reflecting yellow light.
Several points of light are background stars. All rights reserved.