NASA’s Juno orbiter normally focuses on Jupiter’s turbulent atmosphere as it swings around the giant planet, but in this mesmerising view the spacecraft caught the tortured moon Io, the most volcanically active body in the solar system, rising above the planet’s vast horizon. Slightly larger than Earth Moon, Io is dwarfed by Jupiter’s titanic disc. This colour-enhanced image was captured by the JunoCam instrument on 29 October as June flew through its 16th close encounter with Jupiter, passing about 18,400 kilometres (11.400 miles) above the planet’s cloud tops. The image was processed by citizen scientists Gerald Eichstädt and Justin Cowart.
A team of scientists has documented atmospheric changes on Io, Jupiter’s volcanically active satellite, as the giant planet casts its shadow over the moon during daily eclipses. Io’s thin atmosphere collapses as the sulfur dioxide gas emitted from volcanoes freezes when shaded by Jupiter. The atmosphere reforms when Io moves out of eclipse and the ice sublimates.
NASA’s Cassini spacecraft has observed geysers erupting on Saturn’s icy moon Enceladus since 2005, but the process that drives and sustains these eruptions has remained a mystery. Now, scientists have pinpointed a mechanism by which cyclical tidal stresses exerted by Saturn can drive Enceladus’s long-lived eruptions.