Why not Ganymede?
Jupiter’s moon Ganymede - NASA/JPL - Galileo Mission
When most people think of Jupiter’s moons, the one that tends to dominate the imagination is Europa. With its vast subsurface ocean sealed beneath a shell of ice, it has long been considered one of the most intriguing worlds in the solar system. NASA clearly agrees — the Europa Clipper spacecraft is already on its way to study it up close. Scientists estimate that Europa may contain twice as much water as Earth, a fact that alone makes it a prime focus of exploration.
But Jupiter has a moon even larger — Ganymede.
Bigger than every other moon in the solar system (including our own), Ganymede also hides a deep global ocean beneath its surface. And while Europa may hold twice Earth’s water volume, Ganymede is believed to contain six to ten times as much.
You would think that would place Ganymede at the center of attention. Fortunately, it soon will. NASA’s Europa Clipper and ESA’s JUICE mission are both en route to the Jovian system — and together, they will study Europa and Ganymede in unprecedented detail.