Jupiter

Planet · Gas giant · orbits Sun

Jupiter is more massive than all the other planets combined - a giant ball of hydrogen and helium with no solid surface to stand on. Its Great Red Spot is a storm wider than Earth that has raged for at least 190 years.

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Quick facts

1,300 Earths would fit inside it.
It spins fastest of all planets: one day lasts under 10 hours.
Its four largest moons were discovered by Galileo in 1610.

Gas giants have no ground

Descend into Jupiter and the air just gets thicker and hotter until it becomes liquid metallic hydrogen. There is no surface - “diameter” here means the level where the pressure matches Earth’s at sea level.

Physical characteristics

Diameter	142,984 km
Mass	1.898e+27 kg
Surface gravity	23.1 m/s²
Density	1.33 g/cm³
Rotation period	9.93 h
Axial tilt	3.1°
Mean temperature	-110 °C
Geometric albedo	0.54
Known moons	95

Atmosphere and composition

Atmosphere	About 90% H₂ and 10% He with traces of methane, ammonia and water; ammonia clouds paint its banded belts and zones.
Composition	Hydrogen and helium compressed into a vast shell of liquid metallic hydrogen around a dense, possibly diffuse core.

Interior structure

Dilute core modelled

Not a solid ball: heavy elements smeared through hydrogen - a "fuzzy" core.

Metallic hydrogen modelled

Hydrogen crushed until it conducts like a metal; source of the giant magnetic field.

Molecular hydrogen envelope modelled

The visible clouds are just the top of this bottomless atmosphere.

How we know: Juno’s precise gravity measurements reshaped this model - the dilute core was a surprise. No probe can survive below the outer atmosphere.

Missions

Pioneer 10 NASA · Flyby probe · 1972–2003 · completed

The trailblazer of the outer Solar System: first spacecraft through the asteroid belt and first to fly past Jupiter, in December 1973. Its last faint signal was heard in January 2003, from roughly 12 billion km away.

Voyager 2 NASA · Flyby probe · 1977 · active

Launched 16 days before its twin, Voyager 2 is the only spacecraft ever to visit all four giant planets - Jupiter, Saturn, Uranus and Neptune. It entered interstellar space in 2018 and is still returning data.

Voyager 1 NASA · Flyby probe · 1977 · active

The most distant human-made object, now roughly 25 billion km from the Sun. After historic flybys of Jupiter, Saturn and Titan, Voyager 1 became the first spacecraft to enter interstellar space in 2012.

Galileo NASA · Orbiter · 1989–2003 · completed

The first spacecraft to orbit an outer planet, Galileo circled Jupiter from 1995 to 2003 and dropped a probe into its atmosphere. In 2003 it was deliberately flown into Jupiter so it could never crash into - and contaminate - Europa’s possible ocean.

New Horizons NASA · Flyby probe · 2006 · active

New Horizons gave humanity its first close look at Pluto in July 2015, revealing nitrogen-ice glaciers and towering water-ice mountains. It then flew past the Kuiper belt object Arrokoth in 2019 - the most distant world ever explored - and continues outward on an extended Kuiper belt mission.

Juno NASA · Orbiter · 2011–2025 · completed

Juno looped over Jupiter’s poles from 2016 to 2025, peering beneath the clouds to map the planet’s interior, gravity and magnetic field. Its extended mission added daring close flybys of Ganymede, Europa and volcanic Io.

James Webb Space Telescope NASA/ESA/CSA · Space telescope · 2021 · active

The most powerful space telescope ever built, JWST observes the infrared universe with a 6.5 m gold-coated mirror from a point 1.5 million km beyond Earth. Alongside the distant cosmos it studies Solar System targets, from Jupiter’s auroras to the surfaces of Kuiper belt worlds.

Europa Clipper NASA · Orbiter · 2024 · en route

The largest spacecraft NASA has ever built for a planetary mission is on its way to Jupiter, arriving in 2030. From Jupiter orbit it will make dozens of close Europa flybys, using ice-penetrating radar to probe the ocean hiding beneath the moon’s frozen shell.