Jupiter, also known as the Giant Among Giants for its massive size, is the fourth outermost planet in our Solar System. It joins Neptune, Uranus, and Saturn as one of the giant planets. Giant planets are unimaginably huge, stunningly beautiful, and sometimes a little weird. They are made mostly of gases instead of solid materials.
Characteristics of Jupiter
The largest planets in our solar system, Saturn and Jupiter are made up mostly of hydrogen and helium. They rotate fast and have strong winds and storms. Because they are so massive, temperatures and pressures deep within them increase to extraordinary levels. Hydrogen takes on a liquid metallic form. The nature of their rocky cores remains a mystery.
Jupiter is wider than 11 Earths. It has more mass than all the other seven planets of our solar system combined.
Jupiter’s Great Red Spot is a gigantic storm that has been observed for over three centuries. More than 10,000 miles (16,000 kilometers) across, it rotates counterclockwise.
Jupiter’s colorful cloud bands spin around the planet at different speeds. The dark dot on the bottom left of this image is the shadow of the moon Europa on Jupiter’s ammonia clouds.
All four giant planets have rings. Jupiter, Uranus, and Neptune have only a few faint, narrow rings that are difficult to observe.
Voyager 2 was the spacecraft that made the surprising discovery that Jupiter had rings. They are so thin and faint that they had never been seen from Earth.
The innermost ring, known as the halo, consists of dust particles that rise above and below the ring plane. The main ring is flat. Two thin structures called the gossamer rings lie outside.
Jupiter has 79 moons. The Voyager spacecraft revealed the moons of the giant planets to be surprisingly diverse worlds in their own right. Further exploration has unveiled intricate surfaces both young and old, volcanoes and impact features, huge plumes and geysers, deep canyons, subsurface oceans, and even clues to possible environments that might be friendly to simple forms of life.
The moons of Jupiter and Saturn are not dead, unchanging worlds. Several show evidence of geologic activity throughout their history. Complex patterns, faulting, cliffs, and deep canyons tell stories of stresses and resurfacing that have shaped and reshaped the terrain. Explore some of Jupiter's moons in the gallery below.
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Ganymede
Jupiter’s moon Ganymede is the largest moon in our solar system, even larger than the planet Mercury. Its surface is an icy layer overlying a rocky mantle and iron core. Salty water might exist within the outer crust as well. Ganymede has two broad types of terrain: dark cratered regions and brighter-colored deeply grooved areas.
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Europa
Scientists using the Hubble Space Telescope reported evidence of water vapor plumes (lower-left edge) erupting from the south pole of Jupiter’s moon Europa. These plumes could provide a sample of the deep ocean beneath the icy crust—an exciting target in the search for life. Planned to arrive at Jupiter in the 2020s, the Europa Clipper spacecraft will perform a series of flybys of the icy moon to explore its surface, subsurface, and plumes, in order to assess its potential to harbor life.
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Callisto
Jupiter’s moon Callisto has one of the most heavily cratered surfaces in our solar system. This ancient terrain preserves a record of intense bombardment early in the moon’s history. Large impact basins often exhibit a few concentric rings. But scientists were amazed when Voyager 1 revealed this “bulls-eye” of countless rings of Callisto’s huge Valhalla Basin. The basin is 2,500 miles (4,000 kilometers) across.
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Io
Some scientists predicted that Jupiter’s moon Io would show signs of volcanism. But few expected the colorful beauty and ongoing volcanic activity revealed by the Voyager spacecraft in 1979.Nearly 20 years later, this Galileo spacecraft image showed widespread surface changes due to continuing volcanism.
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Io
Io is the most volcanically active object in our solar system. Three volcanoes were erupting as New Horizons flew by in 2007.The huge plume of a volcano gushes 180 miles (290 kilometers) upward near the north pole. Smaller plumes can be seen on the left horizon and as a bright spot near the south pole.