The Last Generation: Why Europa Might Be Jupiter's Final Attempt at Making Moons

There’s something hauntingly poetic about the idea that Europa and her Galilean siblings might be the survivors of a cosmic graveyard. According to an interesting paper by Robin Canup and William Ward, the four large moons we see today orbiting Jupiter could be the “last generation” of satellites, the sole survivors of multiple attempts at moon-making during Jupiter’s younger days.

This would also change how we think about Europa’s story as well as its potential for harboring life.

The traditional view of moon formation around giant planets has been relatively straightforward: gas and dust swirl around the forming planet, gradually coalescing into satellites. But Canup and Ward’s work paints a much more dramatic picture. They suggest that Jupiter went through multiple cycles of satellite formation and destruction, with earlier generations of moons spiraling inward to their doom as gravitational interactions with the gas disk dragged them to fiery ends.

So Europa might not be Jupiter’s first attempt at creating an ice-covered ocean world. There could have been predecessors, entire satellite systems that formed, evolved, and were ultimately consumed by their parent planet. It’s like discovering that your neighborhood wasn’t the first town built there, but rather sits atop the ruins of several previous settlements.

What makes this particularly intriguing for astrobiology is the timing. The Galilean satellites formed slowly, over hundreds of thousands of years, in what the authors describe as a “low pressure, low gas density environment.” This extended formation period in relatively gentle conditions could have been crucial for establishing Europa’s subsurface ocean and the complex chemistry that might support life.

If Jupiter did indeed go through multiple generations of satellites, each earlier system would have formed under slightly different conditions, as the planet continued to accrete mass and change. Some of these lost Moon worlds might have been even more conducive to life than Europa. Others might have been sterile ice balls or rocky chunks.

This has broader implications for exomoon hunting. As we start detecting moons around planets in other star systems (exomoons!) we need to remember that we’re probably seeing the end products of similarly violent and selective processes. The absence of large moons around some giant exoplanets might not mean they never had them, but rather that they lost them during formation.

For Europa specifically, being part of this “last generation” might actually be good news for astrobiology. The satellite system that survived would likely be the most stable configuration, the one best suited to maintain long-term orbital relationships and, crucially, the tidal heating that keeps Europa’s ocean liquid.

Read the full paper: Origin of Europa and the Galilean Satellites