Jupiter has 95 confirmed moons — the most of any planet. The four largest were discovered by Galileo in 1610.
Io
Most volcanically active body in the solar system
🌋 400+ active volcanoes
📏 Diameter: 3,643 km
⏱ Orbital period: 1.77 days
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Europa
Best candidate for extraterrestrial life
🌊 Subsurface ocean ~100 km deep
📏 Diameter: 3,122 km
⏱ Orbital period: 3.55 days
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Ganymede
Largest moon in the solar system
🏆 Bigger than Mercury
📏 Diameter: 5,268 km
🧲 Has its own magnetic field
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Callisto
Most heavily cratered object known
💥 Ancient, geologically dead surface
📏 Diameter: 4,821 km
⏱ Orbital period: 16.7 days
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+ 91 more smaller moons including Amalthea, Himalia, and the recently discovered irregular moons
Jupiter has been visited by 9 spacecraft — flybys, orbiters, and even an atmospheric probe.
Pioneer 10 & 11 (1973–74)
First spacecraft to fly through the asteroid belt and reach Jupiter. Sent back the first close-up images.
Voyager 1 & 2 (1979)
Discovered Jupiter's rings, active volcanoes on Io, and the complex moon system. Sent stunning high-res imagery.
Ulysses (1992)
Used Jupiter's gravity for a slingshot to study the Sun's poles. Studied Jupiter's magnetic environment.
Galileo (1995–2003)
First spacecraft to orbit Jupiter. Deployed an atmospheric probe. Discovered evidence of subsurface oceans on Europa, Ganymede & Callisto.
Cassini & New Horizons (2000, 2007)
Both used Jupiter flybys for gravity assists en route to Saturn and Pluto respectively, gathering bonus science.
Juno (2016–present) 🔴 ACTIVE
Currently orbiting Jupiter! Studies the planet's atmosphere, magnetic field, and interior. Extended to study Ganymede, Europa & Io up close.
Europa Clipper (Launched Oct 2024) 🚀 EN ROUTE
NASA's mission to perform 49 flybys of Europa to assess its habitability. Arrives at Jupiter in 2030.
Visual scale comparison — all circles are proportional to planet diameter.
Jupiter: 139,820 km diameter
2.5× the mass of all other planets combined
Earth: 12,742 km diameter
You could fit 1,321 Earths inside Jupiter
Moon: 3,475 km diameter
Ganymede (Jupiter's moon) is actually larger than Mercury!