Jupiter, the planet with a planetary system of its own (2025)

Highlights

• Jupiter, the fifth planet from the Sun, is twice as massive as every other object in our Solar System combined (except the Sun).
• Jupiter's four planet-like moons have features like volcanoes and subsurface oceans, making Jupiter aminiature planetary system of its own.
• By studying Jupiter we learn more about how planetary systems evolve.

Why we studyJupiter

Named after the king of the gods in Roman mythology, Jupiter is a stunning sight to behold. Its red, orange, and yellow swirls, spots, and bands are visible even from small backyard telescopes. Astronomers have observed the planet’s Great Red Spot, a raging storm larger than Earth, for at least 200 years.

Jupiter was the first planet in our Solar System to form. It was probably born much closer to the Sun before migrating to its currentposition about four billion years ago, scattering asteroids and comets with its gravity in the process. Some of those asteroids and comets slammed into early Earth, possibly bringing water here in the process — the key ingredient for life as we know it.

Many of the exoplanets— planets in other star systems — that we have discovered are Jupiter-like worlds closeto their stars, reinforcing the idea that our own Solar System’s large planets have moved from their original positions. By studying Jupiterand comparing it to similar exoplanets, we learn how planetary systems evolve and the possibilities for life elsewhere.

Jupiter has a faint ring system and at least 79 moons, four of which are active, planet-like worlds ranging in size from just smaller than Earth’s Moon to larger than Mercury. Three of those four likely have liquid-water oceans under their surfaces, making them possible havens for life. Europa’s ocean in particular may be one ofthe most biologically promising environments beyond Earth for life. Jupiter challenges our perceptions about where life can exist in the Universe.

Meet the Moons

Io is the Solar System’s most volcanically active world. Because of friction caused by the gravity of Jupiter on one side and Europa and Ganymede on the other, it is molten nearly all the waythrough and continuously erupts in at least a dozen locations.

Ganymede is the largest moon in the Solar System and the only moon with a magnetic field, likely produced by its churning liquid-iron core. It too is geologically active due to gravitational tugs, which gives it a subsurface ocean. More study of this moon is needed to determine whether its ocean is likely to be habitable to life.

Callisto, the outermost of Jupiter’s large moons, does not experience enough gravitational pushing and pulling to heat itsinterior like the other moons. Yet there is evidence of a subsurface liquid-water ocean, likely due to high pressure from its thick ice shell above andimpurities in the ocean that keep the water liquified at cool temperatures.

Jupiter and its moons are essentially a miniature planetary systemunto themselves and can together teach us a lot. Every branch of planetary science has questions that can be answered here: atmospheric scientists can study storm dynamics on Jupiter, geologists can examinediverse terrains on moons with active volcanoes and geysers, and astrobiologists can search for life.

Jupiter Facts

Average temperature: -108°C (-162°F) where atmospheric pressure equals sea level on Earth
Average distance from Sun: 779 million kilometers (484 million miles), or 5.2 times farther from the Sun than Earth
Diameter: 142,984 kilometers (88,846 miles), Jupiter is 11.2 times wider than Earth
Volume: 1,431 trillion km3 (343 trillion mi3), Earth could fit inside Jupiter 1,431 times
Gravity: 23.1 m/s², or 2.4 times that of Earth’s
Solar day: 10 Earth hours
Solar year: 4,333 Earth days
Atmosphere: 90% hydrogen, 10% helium, less than 1% other gases

How we study Jupiter

Jupiter has long been studied from Earth-based telescopes. GalileoGalilei’s observations of Jupiter’s moons in the early 1600srevolutionized humanity’s understanding of the Universe by showing thatnot every celestial object orbits the Earth, which was the leadingtheory at the time.

NASA’s Pioneer 10 spacecraft made the first Jupiter flyby in 1973,returning the first close-up images of Jupiter and discovering the planet’s huge magnetic field that traps charged particles from the Sun,creating a deadly radiation field. Spacecraft exploring Jupiter must carry radiation shielding to survive.

NASA’s legendary Voyager 1 and 2 spacecraft flew past Jupiter in1979, capturing up-close views of the Galilean moons that revealed they were complex worlds unto themselves, with volcanoes, oceans, and other significant features. The probes also saw Jupiter’s faint ring system.The planet finally received its own, dedicated mission when NASA’sGalileo spacecraft arrived in 1995 and orbited Jupiter until 2003.Galileo dropped a probe into Jupiter’s atmosphere to measure its composition and discovered evidence of Europa’s saltwater ocean.

What’s under Jupiter’s beautiful clouds? When Jupiter formed, it likely had a large, rock-and-metal core. But as the planet gobbled up leftover gases from the Solar System’s formation, intense pressures may have dissolved the core into an exotic substance called metallic hydrogen. The most recent data from NASA’s Juno spacecraft suggests there is no distinct core.

Though Jupiter’s immense gravitational field wreaked havoc during the Solar System’s early days, today it shepherds the orbits of asteroids and helps protect the inner planets from impacts. Comet Shoemaker-Levy 9 impacted Jupiter in 1994, just as the Galileo spacecraft was approaching the planet. Galileo teamed up with Earth-based telescopes to watch the impact, and the observations taught us valuable lessons about the importance of defending our own planet from asteroids and comets.

In 2016, NASA’s Juno spacecraft entered orbit around Jupiter to findout what's at the giant planet’s core, map its magnetic field, andmeasure how much water and ammonia are present in the deeper levels ofits atmosphere. These measurements are helping us learn more aboutJupiter's formation and evolution.

The European Space Agency's Juice (Jupiter Icy Moons Explorer) mission will arrive at the Jupiter system in 2031to explore Jupiter's Galilean moons. Juice will enter intoorbit around Ganymede after flybys of Europa andCallisto, aiming to figure out whether the moons’ subsurface oceans could support life. NASA's Europa Clipper mission will launch in themid-2020s to try and answer the same question at Europa by performing adetailed survey of the moon.

The Planetary Society andJupiter exploration

Space missions to worlds like Jupiter don’t just happen; they require persistent, organized support from both scientists and the publicalike. In the U.S., the scientific community has a formal process to setNASA’s exploration priorities called the decadal survey. Thisonce-a-decade effort represents a consensus opinion of top scientificgoals in the Solar System, and, once released, requires support from thepublic and organizations like The Planetary Society to ensure thosepriorities are funded. Europa Clipper was a top recommendation of a prior decadal survey, yet required years of steady advocacy to become reality.

Learn more

• The best Jupiter pictures from NASA's Juno mission
• Why lightning on Jupiter is a planetary unsolved mystery
• Jupiter's clouds: a primer