Juno Mission: The Solar-Powered Explorer of the Gas Giant Jupiter
As of early 2026, NASA’s Juno spacecraft stands as one of the most resilient explorers in the history of spaceflight. Originally scheduled to end its mission years ago, this solar-powered endurance runner is still operating in the harsh environment of Jupiter, rewriting our textbooks on planetary science. While the newly launched Europa Clipper is currently making its long journey to the Jupiter system, Juno is already there, acting as our eyes and ears in the realm of the giants.
The Juno Mission
Launched in 2011 and arriving at Jupiter in July 2016, Juno faced a unique challenge. Jupiter possesses the strongest magnetic field of any planet, trapping charged particles that create radiation belts millions of times more intense than Earth’s. To survive, Juno does not orbit the planet’s equator like previous missions. Instead, it performs highly elliptical polar orbits.
The spacecraft dives from the north pole to the south pole, skimming just a few thousand kilometers above the cloud top – closer than any spacecraft before it – before swinging far out into space to avoid the worst of the radiation. Even with this clever trajectory, the sensitive electronics are housed in a “Radiation Vault,” a 180-kilogram titanium box that acts as a shield.
Redefining Jupiter
Before Juno, scientists believed Jupiter had a small, dense, rocky core. Juno’s gravity measurements shattered this theory. The data suggests Jupiter has a “dilute” or “fuzzy” core, where heavy elements and rocks are dissolved into the metallic hydrogen mantle, extending out for nearly half the planet’s radius. This implies a violent formation history, possibly involving a massive collision with a protoplanet early in the solar system’s life.
In the atmosphere, Juno discovered a weird weather phenomenon: “Mushballs.” High in the clouds, ammonia gas melts water ice crystals, creating a slushy hail. These ammonia-water hailstones fall deep into the atmosphere, sequestering ammonia and creating “dry spots” in the cloud layers. This process also drives “shallow lightning,” electrical storms that occur much higher in the atmosphere than previously thought possible.
The Extended Juno Mission: A Tour of the Moons
Since completing its primary mission, Juno has transitioned into an “Extended Mission” phase, effectively becoming a moon explorer. By adjusting its orbit, the spacecraft has performed daring flybys of Jupiter’s three largest moons:
- Ganymede: Juno gave us the first close-up infrared maps of the solar system’s largest moon and measured its unique magnetic field.
- Europa: In January 2026, scientists published new findings based on Juno’s earlier flybys, revealing that Europa’s ice shell is approximately 29 kilometers (18 miles) thick in certain regions. This data is critical for the Europa Clipper mission, helping it identify where the ice might be thinnest and most accessible.
- Io: Throughout late 2023 and 2024, Juno performed ultra-close flybys of Io, the volcanic moon. It captured the highest-resolution images of lava lakes and volcanic plumes ever seen, revealing a surface constantly resurfaced by molten sulfur and silicate rock.
What’s Next?
As of 2026, Juno remains operational. Mission planners are currently evaluating a Second Extended Mission that would send the probe into the inner sanctum of the Jovian system to explore the faint ring system and the small inner moons like Amalthea. Eventually, however, Juno will meet a dramatic end. To strictly adhere to “planetary protection” protocols, the spacecraft will perform a controlled deorbit, burning up in Jupiter’s atmosphere to ensure it never accidentally crashes into—and contaminates—the potentially habitable ocean of Europa.
Until that final dive, Juno continues to be humanity’s active sentinel at the King of Planets.