The Heavyweight Champion

Jupiter is the largest planet in our solar system and is 318 times as massive as the Earth! Gas giants like Jupiter are made mostly of molecular hydrogen (H2). Jupiter’s enormous mass means that the pressures near the core are immense. At about 12,500 miles below Jupiter’s cloud tops the pressure is so large that hydrogen becomes a liquid metal. The quickly rotating currents from metallic hydrogen give Jupiter the strongest magnetic field in the solar system.

An Amazing Atmosphere

Looking at Jupiter through a telescope, you will see the cloud tops in distinctive bands due to their differing chemical compositions. The dark bands (called “belts”) are regions in Jupiter’s atmosphere where the gas is sinking downwards. The lighter bands (called “zones”) are regions where the gas is rising upwards. Jupiter is also known for its iconic, Great Red Spot, a giant storm twice the size of the Earth that has existed for over 360 years. This massive storm contains clouds that spin in a counter-clockwise direction at speeds up to 680 kilometers per hour (425 miles per hour)!

University of Arizona Legacy

Dr. Tom Gehrels, a professor at the University of Arizona's Lunar and Planetary Laboratory, built the imaging photopolarimeter onboard the Pioneer 10 mission that took the first spacecraft images of Jupiter in 1973. As a co-investigator on the Juno mission, Professor William Hubbard used high-precision gravity data to determine the depths of Jupiter’s belts and zones.

Galilean Moons

Jupiter has at least 79 moons, the largest of which—now called the Galilean Moons—were discovered by Galileo Galilei in 1610. Io, the planet's closest Galilean moon, is the most volcanically active body in the solar system due to constant stretching from Jupiter’s mass. Ganymede is the largest moon in the solar system and the only one known to have its own magnetic field. Callisto’s heavily cratered surface appears to be made up of both rock and ice. Europa’s icy surface is actually a thick shell covering a global subsurface ocean, which has the potential to harbor life. Certain organisms live in the sunless depths of Earth’s oceans by living near hydrothermal vents called black smokers, which provide energy and nutrients. Similar geologic features could exist on the floor of Europa’s vast ocean and it is one of the more promising places in the solar system to search for life beyond Earth.


MASS: 1.8x10^27 kg 318 times Earth
DIAMETER: 142,984 km 11 times Earth
SURFACE GRAVITY: 23.1 m/s2 2.5 times Earth
AVG. DISTANCE TO SUN: 778 million km 5.2 au

Jupiter in the background with Io and Ganymede shown in the foreground with cross sections showing their interiors.