Adorned with a dazzling, complex system of icy rings, Saturn is unique in our solar system. The other giant planets have rings, but none are as spectacular as Saturn's.
Saturn is the sixth planet from the Sun and the second largest planet in our solar system. Adorned with a
dazzling system of icy rings, Saturn is unique among the planets. It is not the only planet to have
rings, but none are as spectacular or as complex as Saturn's. Like fellow gas giant Jupiter, Saturn is a
massive ball made mostly of hydrogen and helium.
Surrounded by more than 60 known moons, Saturn is home to some of the most fascinating landscapes in our
solar system. From the jets of water that spray from Enceladus to the methane lakes on smoggy Titan, the
Saturn system is a rich source of scientific discovery and still holds many mysteries.
The farthest planet from Earth discovered by the unaided human eye, Saturn has been known since ancient
times. The planet is named for the Roman god of agriculture and wealth, who was also the father of
Jupiter.
Cassini: Cassini was one of the most ambitious efforts ever mounted in planetary exploration. A
joint endeavor of NASA, ESA (the European Space Agency) and the Italian space agency (ASI), Cassini was
a sophisticated robotic spacecraft sent to study Saturn and its complex system of rings and moons in
unprecedented detail.
Cassini carried a probe called Huygens to the
Saturn system. The probe, which was built by ESA, parachuted to the surface of Saturn’s largest moon,
Titan, in January 2005—the most distant landing to date in our solar system. Huygens returned
spectacular images and other science results during a two-and-a-half-hour descent through Titan’s hazy
atmosphere, before coming to rest amid rounded cobbles of ice on a floodplain damp with liquid methane.
Cassini completed its initial four-year mission in June 2008 and earned two mission extensions that
enabled the team to delve even deeper into Saturn’s mysteries. Key discoveries during its 13 years at
Saturn included a global ocean with strong indications of hydrothermal activity within Enceladus, and
liquid methane seas on Titan. The mission ended on Sept. 15, 2017.
With a radius of 36,183.7 miles (58,232 kilometers), Saturn is 9 times wider than Earth. If Earth were
the size of a nickel, Saturn would be about as big as a volleyball.
From an average distance of 886 million miles (1.4 billion kilometers), Saturn is 9.5 astronomical units
away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth.
From this distance, it takes sunlight 80 minutes to travel from the Sun to Saturn.
Saturn has the second-shortest day in the solar system. One day on Saturn takes only 10.7 hours (the time
it takes for Saturn to rotate or spin around once), and Saturn makes a complete orbit around the Sun (a
year in Saturnian time) in about 29.4 Earth years (10,756 Earth days).
Its axis is tilted by 26.73 degrees with respect to its orbit around the Sun, which is similar to
Earth's 23.5-degree tilt. This means that, like Earth, Saturn experiences seasons.
Saturn took shape when the rest of the solar system formed about 4.5 billion years ago, when gravity pulled swirling gas and dust in to become this gas giant. About 4 billion years ago, Saturn settled into its current position in the outer solar system, where it is the sixth planet from the Sun. Like Jupiter, Saturn is mostly made of hydrogen and helium, the same two main components that make up the Sun.
Like Jupiter, Saturn is made mostly of hydrogen and helium. At Saturn's center is a dense core of metals
like iron and nickel surrounded by rocky material and other compounds solidified by the intense pressure
and heat. It is enveloped by liquid metallic hydrogen inside a layer of liquid hydrogen—similar to
Jupiter's core but considerably smaller.
It's hard to imagine, but Saturn is the only planet in our solar system whose average density is less
than water. The giant gas planet could float in a bathtub if such a colossal thing existed.
As a gas giant, Saturn doesn’t have a true surface. The planet is mostly swirling gases and liquids deeper down. While a spacecraft would have nowhere to land on Saturn, it wouldn’t be able to fly through unscathed either. The extreme pressures and temperatures deep inside the planet crush, melt and vaporize spacecraft trying to fly into the planet.
Saturn is blanketed with clouds that appear as faint stripes, jet streams and storms. The planet is many
different shades of yellow, brown and grey.
Winds in the upper atmosphere reach 1,600 feet per second (500 meters per second) in the equatorial
region. In contrast, the strongest hurricane-force winds on Earth top out at about 360 feet per second
(110 meters per second). And the pressure—the same kind you feel when you dive deep underwater—is so
powerful it squeezes gas into liquid.
Saturn's north pole has an interesting atmospheric feature—a six-sided jet stream. This hexagon-shaped
pattern was first noticed in images from the Voyager I spacecraft and has been more closely observed by
the Cassini spacecraft since. Spanning about 20,000 miles (30,000 kilometers) across, the hexagon is a
wavy jet stream of 200-mile-per-hour winds (about 322 kilometers per hour) with a massive, rotating
storm at the center. There is no weather feature like it anywhere else in the solar system.
Saturn's environment is not conducive to life as we know it. The temperatures, pressures and materials
that characterize this planet are most likely too extreme and volatile for organisms to adapt to.
While planet Saturn is an unlikely place for living things to take hold, the same is not true of some of
its many moons. Satellites like Enceladus and Titan, home to internal oceans, could possibly support
life.
Saturn is home to a vast array of intriguing and unique worlds. From the haze-shrouded surface of Titan to crater-riddled Phoebe, each of Saturn's moons tells another piece of the story surrounding the Saturn system. Currently Saturn has 53 confirmed moons with 29 additional provisional moons awaiting confirmation.
Saturn's rings are thought to be pieces of comets, asteroids or shattered moons that broke up before they
reached the planet, torn apart by Saturn's powerful gravity. They are made of billions of small chunks
of ice and rock coated with another material such as dust. The ring particles mostly range from tiny,
dust-sized icy grains to chunks as big as a house. A few particles are as large as mountains. The rings
would look mostly white if you looked at them from the cloud tops of Saturn, and interestingly, each
ring orbits at a different speed around the planet.
Saturn's ring system extends up to 175,000 miles (282,000 kilometers) from the planet, yet the vertical
height is typically about 30 feet (10 meters) in the main rings. Named alphabetically in the order they
were discovered, the rings are relatively close to each other, with the exception of a gap measuring
2,920 miles (4,700 kilometers) wide called the Cassini Division that separates Rings A and B. The main
rings are A, B and C. Rings D, E, F and G are fainter and more recently discovered.
Starting at Saturn and moving outward, there is the D ring, C ring, B ring, Cassini Division, A ring, F
ring, G ring, and finally, the E ring. Much farther out, there is the very faint Phoebe ring in the
orbit of Saturn's moon Phoebe.
Saturn's magnetic field is smaller than Jupiter's but still 578 times as powerful as Earth's. Saturn, the
rings, and many of the satellites lie totally within Saturn's enormous magnetosphere, the region of
space in which the behavior of electrically charged particles is influenced more by Saturn's magnetic
field than by the solar wind.
Aurorae occur when charged particles spiral into a planet's atmosphere along magnetic field lines. On
Earth, these charged particles come from the solar wind. Cassini showed that at least some of Saturn's
aurorae are like Jupiter's and are largely unaffected by the solar wind. Instead, these aurorae are
caused by a combination of particles ejected from Saturn's moons and Saturn's magnetic field's rapid
rotation rate. But these "non-solar-originating" aurorae are not completely understood yet.