New simulations suggest Jupiter's strong early magnetic field created a safe zone that allowed several giant moons to survive, while Saturn's weaker field left it with only Titan.
Researchers from Kyoto University and partner institutions in China modeled the young gas giants and their circumplanetary disks. The work shows that Jupiter formed a magnetospheric cavity that trapped and preserved Io, Europa, and Ganymede as they migrated inward.
Saturn lacked a comparable cavity because its magnetic field was weaker. Moons migrating through its disk were lost, leaving Titan as the sole large survivor.
The team used numerical simulations of planetary interiors, thermal evolution, and N-body orbital dynamics. First author Yuri I. Fujii noted that multiple satellite systems near us provide detailed data for testing formation theories.
The findings, published in Nature Astronomy, predict that gas giants the size of Jupiter or larger should commonly host compact multi-moon systems, while Saturn-sized worlds typically retain one or two.