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.
Size and Distance
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.
A 3D model of Saturn, the ringed gas giant planet. Credit: NASA Visualization
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Orbit and Rotation
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.
Structure
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.
Formation
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.
Surface
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.
Atmosphere
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.
Magnetosphere
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.
Rings
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.
Moons
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.
This Cassini image from 2012 shows Titan and its host planet Saturn. Image Credit:
NASA/JPL-Caltech/SSI
Potential for Life
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.
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