Jupiter's mass exceeds that of all other planets in our solar system combined. Its iconic Great Red Spot is a centuries-old storm larger than Earth itself.
As the fifth planet from the Sun, Jupiter is the solar system's undisputed giant, possessing more than
double the mass of all its planetary siblings combined. Its swirling stripes are actually cold, windy
clouds of ammonia and water, drifting in an atmosphere dominated by hydrogen and helium. The Great Red
Spot, a storm larger than Earth, has raged for centuries.
Jupiter commands a vast retinue of moons and possesses a faint ring system, composed mainly of dust
rather than the icy brilliance of Saturn's rings.
Nine spacecraft have ventured to Jupiter. NASA's Juno orbiter currently studies the gas giant. Arriving in July 2016, Juno is peeling back the layers of the planet's cloud-shrouded interior. Observations also continue via the Hubble Space Telescope and ground-based observatories.
Pioneer 10 became the first to fly past Jupiter, followed by Pioneer 11 and the Voyager missions. The Galileo orbiter was the first to circle the planet, dropping a probe into its stormy atmosphere. The Ulysses mission utilized Jupiter's gravity to swing into a polar solar orbit. More recently, Cassini and New Horizons captured data while en route to Saturn and Pluto, respectively.
Two new missions are in the works to make close studies of Jupiter's moons NASA's Europa Clipper and ESA's JUpiter ICy Moons Explorer (JUICE).
Jupiter marks a turning point in astronomy. In 1610, Galileo Galilei used his telescope to discover four moons orbiting the giant planet. This observation shattered the geocentric model, proving that not everything in the universe orbited Earth.
With a radius of 43,440.7 miles (69,911 kilometers), Jupiter is 11 times Earth's width. Imagine Earth as
a nickel; Jupiter would be a basketball.
Orbiting at an average distance of 484 million miles (778 million kilometers), Jupiter resides 5.2
astronomical units (AU) from the Sun. Light takes 43 minutes to traverse this distance.
Jupiter rotates faster than any other planet, completing a day in just 10 hours. A full orbit around the
Sun takes about 12 Earth years (4,333 days).
With an axial tilt of just 3 degrees, Jupiter spins nearly upright, meaning it lacks the extreme
seasonal variations found on other planets.
Jupiter formed alongside the rest of the solar system 4.5 billion years ago, growing from swirling gas
and dust. It claimed the lion's share of the material left over after the Sun's creation, accumulating
twice the mass of all other solar system bodies combined. Despite sharing the Sun's composition, it
never gained enough mass to ignite into a star.
Roughly 4 billion years ago, it settled into its current position as the fifth planet.
Jupiter's composition mirrors the Sun, consisting mainly of hydrogen and helium. Deep within, immense pressure compresses hydrogen into a fluid, creating the largest ocean in the solar system—an ocean of liquid hydrogen. Further down, pressures likely strip electrons from hydrogen atoms, creating a liquid metallic hydrogen that conducts electricity. The rapid rotation within this metallic layer generates Jupiter's massive magnetic field. The core remains a mystery; it may be solid or a dense, super-hot soup of iron and silicates at temperatures reaching 90,000°F (50,000°C).
Lacking a true solid surface, Jupiter is a swirling mass of gases and liquids. Any spacecraft attempting to land would find no purchase; instead, it would be crushed, melted, and vaporized by the crushing pressures and searing temperatures deep within.
Jupiter presents a vibrant tapestry of cloud bands and storms. Its atmosphere likely spans 44 miles (71
kilometers) across three distinct layers: an upper layer of ammonia ice, a middle layer of ammonium
hydrosulfide, and an inner layer of water ice and vapor.
The striking colors arise from sulfur and phosphorus gases rising from the warm interior. The planet's
rapid rotation creates high-speed jet streams that separate clouds into dark belts and bright zones.
Without solid land to break them up, storms persist for decades or centuries. The Great Red Spot, a
storm twice the width of Earth, has been observed for over 300 years. Winds on Jupiter can scream at
speeds up to 335 mph (539 kph).
Life as we understand it is unlikely to exist in Jupiter's volatile environment. However, its moons tell a different story. Europa, with its subsurface ocean beneath an icy crust, is considered one of the most promising places to search for life elsewhere in the solar system.
Jupiter anchors a mini-solar system of 53 confirmed moons and dozens more awaiting confirmation.
The four largest—Io, Europa, Ganymede, and Callisto—were discovered by Galileo in 1610. Io is a volcanic
hellscape, the most active body in the solar system. Ganymede is the largest moon, surpassing even the
planet Mercury in size. Callisto is an ancient, cratered world, while Europa lures scientists with its
hidden liquid ocean.
NASA's Voyager 1 spacecraft unveiled Jupiter's rings in 1979. Unlike Saturn's icy spectacles, these rings are faint and dark, composed of small particles. Data suggests they are formed by dust kicked up when meteoroids strike Jupiter's small inner moons.
Jupiter's magnetosphere is immense, ballooning 1 to 3 million kilometers toward the Sun and stretching a
tail over 1 billion kilometers behind the planet—reaching Saturn's orbit.
Its magnetic field is 16 to 54 times stronger than Earth's. It traps charged particles, accelerating
them to high energies that create intense radiation belts capable of damaging spacecraft. This field
also drives spectacular aurorae at Jupiter's poles.