It will take the robotic explorer, dubbed Juice, eight years to reach Jupiter, where it will scope out not only the solar system’s biggest planet but also Europa, Callisto and Ganymede.
Even more enticing, it’s thought to have an underground ocean holding more water than Earth.
“These things take time — and they change our world,” said the Planetary Society’s chief executive, Bill Nye.
Juice — short for Jupiter Icy Moons Explorer — will spend three years buzzing Callisto, Europa and Ganymede.
Europa is especially attractive to scientists hunting for signs of life beyond Earth.
Late next year, NASA will send an even more heavily shielded spacecraft to Jupiter, the long-awaited Europa Clipper, which will beat Juice to Jupiter by more than a year because it will launch on SpaceX’s mightier rocket.
NASA has long dominated exploration at Jupiter, beginning with flybys in the 1970s by the twin Pioneers and then Voyagers.