Jupiter’s moons Io and Europa were born with starkly different fates

Jupiter’s moons Io and Europa have always stood out for their stark differences. One is bone-dry, while the other may harbour a vast hidden ocean. New findings suggest these contrasts were set in place when the moons first formed.

Scientists have long puzzled over why Io and Europa differ so dramatically. Io is completely dry, lacking even traces of water ice. Europa, by contrast, appears to have a thick icy shell covering a global liquid ocean.

Research now points to their origins as the key. Both moons took shape under different conditions in Jupiter’s early system. Io formed in a dry environment, while Europa emerged with abundant water. These differences were locked in from the start, rather than evolving later through geological or planetary changes.

The discovery challenges earlier ideas that the moons’ current states resulted from later processes. Instead, their contrasting compositions were determined at birth, shaped by the unique circumstances of their formation around Jupiter.

The findings confirm that Io’s arid surface and Europa’s potential subsurface ocean were not accidental. Their distinct natures were established when Jupiter’s moons first came into being. This insight reshapes our understanding of how planetary bodies form and evolve in a system.