Facts about Saturn

 Saturn is the most distant planet that can be seen with the naked eye.

It is the fifth brightest object in the solar system and is also easily studied through binoculars or a small
telescope.

 Saturn was known to the ancients, including the Babylonians and Far Eastern observers.

It is named for the Roman god Saturnus, and was known to the Greeks as Cronus.

 Saturn is the flattest planet.

Its polar diameter is 90% of its equatorial diameter, this is due to its low density and fast rotation. Saturn
turns on its axis once every 10 hours and 34 minutes giving it the second-shortest day of any of the solar
system’s planets.

 Saturn orbits the Sun once every 29.4 Earth years.

Its slow movement against the backdrop of stars earned it the nickname of “Lubadsagush” from the
ancient Assyrians. The name means “oldest of the old”.

 Saturn’s upper atmosphere is divided into bands of clouds.

The top layers are mostly ammonia ice. Below them, the clouds are largely water ice. Below are layers of
cold hydrogen and sulfur ice mixtures.

 Saturn has oval-shaped storms similar to Jupiter’s.

The region around its north pole has a hexagonal-shaped pattern of clouds. Scientists think this may be a
wave pattern in the upper clouds. The planet also has a vortex over its south pole that resembles a
hurricane-like storm.

 Saturn is made mostly of hydrogen.

It exists in layers that get denser farther into the planet. Eventually, deep inside, the hydrogen becomes
metallic. At the core lies a hot interior.

 Saturn has the most extensive rings in the solar system.

The Saturnian rings are made mostly of chunks of ice and small amounts of carbonaceous dust. The rings
stretch out more than 120,700 km from the planet, but are amazingly thin: only about 20 meters thick.

 Saturn has 150 moons and smaller moonlets.

All are frozen worlds. The largest moons are Titan and Rhea. Enceladus appears to have an ocean below
its frozen surface.

 Titan is a moon with complex and dense nitrogen-rich atmosphere.

It is composed mostly of water ice and rock. Its frozen surface has lakes of liquid methane and
landscapes covered with frozen nitrogen. Planetary scientists consider Titan to be a possible harbour for
life, but not Earth-like life.
  Four spacecraft have visited Saturn.

Pioneer 11, Voyager 1 and 2, and the Cassini-Huygens mission have all studied the planet. Cassini
orbited Saturn from July 2004 until September 2017, sending back a wealth of data about the planet, its
moons, and rings.

 Saturn has more moons than any other planet.

20 new moons were discovered in 2019 bring the total to 82, 3 more than Jupiter.

Introduction to Saturn

Saturn is the sixth planet from the sun and the second-largest planet in the solar system. It's the farthest
planet from Earth that's visible to the naked human eye, but the planet's most outstanding features —
its rings — are better viewed through a telescope. Although the other gas giants in the solar system —
Jupiter, Uranus and Neptune — also have rings, Saturn's rings are particularly prominent, earning it the
nickname the "Ringed Planet."

Saturn’s name comes from the Roman god of agriculture, who is equated with the Greek deity Cronus,
one of the Titans and the father of Zeus (the Roman god Jupiter). Saturn occupies almost 60 percent of
Jupiter’s volume but has only about one-third of its mass and the lowest mean density—about 70
percent that of water—of any known object in the solar system. Hypothetically, Saturn would float in an
ocean large enough to hold it. Both Saturn and Jupiter resemble stars in that their bulk chemical
composition is dominated by hydrogen.

Basic astronomical data

Saturn orbits the Sun at a mean distance of 1,427,000,000 km (887 million miles). Its closest distance to
Earth is about 1.2 billion km (746 million miles), and its phase angle—the angle that it makes with the
Sun and Earth—never exceeds about 6°. Saturn seen from the vicinity of Earth thus always appears
nearly fully illuminated. Only deep space probes can provide sidelit and backlit views.

Like Jupiter and most of the other planets, Saturn has a regular orbit—that is, its motion around the Sun
is prograde (in the same direction that the Sun rotates) and has a small eccentricity (noncircularity) and
inclination to the ecliptic, the plane of Earth’s orbit. Unlike Jupiter, however, Saturn’s rotational axis is
tilted substantially—by 26.7°—to its orbital plane. The tilt gives Saturn seasons, as on Earth, but each
season lasts more than seven years.

Saturn’s rotation period was very difficult to determine. Cloud motions in its massive upper atmosphere
trace out a variety of periods, which are as short as about 10 hours 10 minutes near the equator and
increase with some oscillation to about 30 minutes longer at latitudes higher than 40°. Scientists
attempted to determine the rotation period of Saturn’s deep interior from that of its magnetic field,
which is presumed to be rooted in the planet’s metallic-hydrogen outer core. However, direct
measurement of the field’s rotation was difficult because the field is highly symmetrical around the
rotational axis.

Saturn’s Atmosphere

Saturn’s atmosphere is composed primarily of hydrogen (96%) and helium (3%) with traces of other
substances like methane, ammonia, acetylene, ethane, propane and phosphine. Winds in the upper
atmosphere can reach speeds of 500 metres a second, these combined with heat rising from within the
planet’s interior cause yellow and gold bands. The yellow and gold bands seen in Saturn's atmosphere
are the result of superfast winds in the upper atmosphere, which can reach up to 1,100 mph (1,800
km/h) around its equator, combined with heat rising from the planet's interior. Saturn rotates about
once every 10.5 hours. The planet's high-speed spin causes Saturn to bulge at its equator and flatten at
its poles. The planet is around 75,000 miles (120,000 kilometers) across at its equator, and 68,000 miles
(109,000 km) from pole to pole.

Other major molecules observed in Saturn’s atmosphere are methane and ammonia, which are two to
seven times more abundant relative to hydrogen than in the Sun. Hydrogen sulfide and water are also
suspected to be present in the deeper atmosphere but have not yet been detected. Minor molecules
that have been detected spectroscopically from Earth include phosphine, carbon monoxide, and
germane. Such molecules would not be present in detectable amounts in a hydrogen-rich atmosphere in
chemical equilibrium. They may be products of reactions at high pressure and temperature in Saturn’s
deep atmosphere, well below the observable clouds, that have been transported to visible atmospheric
regions by convective motions. A number of other nonequilibrium hydrocarbons are observed in
Saturn’s stratosphere: acetylene, ethane, and, possibly, propane and methyl acetylene.

Saturn’s visible layer of clouds is formed from molecules of minor compounds that condense in the
hydrogen-rich atmosphere. Although particles formed from photochemical reactions are seen
suspended high in the atmosphere at levels corresponding to pressures of 20–70 millibars, the main
clouds commence at a level where the pressure exceeds 400 millibars, with the highest cloud deck
thought to be formed of solid ammonia crystals. The base of the ammonia cloud deck is predicted to
occur at a depth corresponding to about 1.7 bars, where the ammonia crystals dissolve into the
hydrogen gas and disappear abruptly.

The magnetic field and magnetosphere

Saturn’s magnetic field resembles that of a simple dipole, or bar magnet, its north-south axis aligned to
within 1° of Saturn’s rotation axis with the centre of the magnetic dipole at the centre of the planet. The
polarity of the field, like Jupiter’s, is opposite that of Earth’s present field—i.e., the field lines emerge in
Saturn’s northern hemisphere and reenter the planet in the southern hemisphere (see Earth: The
geomagnetic field and magnetosphere). On Saturn a common magnetic compass would point south.
Saturn’s field deviates measurably from a simple dipole field; this manifests itself both in a north-south
asymmetry and in a slightly higher polar surface field than is predicted by a pure dipole model. At
Saturn’s one-bar “surface” level, the maximum polar field is 0.8 gauss (north) and 0.7 gauss (south), very
similar to Earth’s polar surface field, while the equatorial field is 0.2 gauss, compared with 0.3 gauss at
Earth’s surface. Jupiter’s equatorial field, at 4.3 gauss, is more than 20 times stronger than Saturn’s.

Saturn’s magnetic field is generated by the fluid motions in the electrically conducting portion of the
interior of the planet. This region, in which hydrogen exists in a fluid metallic state around a central
rocky core, comprises the inner half of the planet. Compared with Jupiter, less of Saturn’s mass and
volume consists of this conducting metallic fluid, which may partly explain why Saturn’s magnetic field is
much weaker. Jupiter’s interior is also hotter, so the fluid motions in its interior may be more vigorous,
possibly contributing even further to the differences in the field strengths.

Saturn’s magnetosphere is the teardrop-shaped region of space around the planet where the behaviour
of charged particles, which come mostly from the Sun, is dominated by the planet’s magnetic field
rather than by interplanetary magnetic fields. The rounded side of the teardrop extends sunward,
forming a boundary, or magnetopause, with the outflowing solar wind at a distance of about 20 Saturn
radii (1,200,000 km [750,000 miles]) from the centre of the planet but with substantial fluctuation due
to variations in the pressure from the solar wind.

Saturn’s inner magnetosphere, like the magnetospheres of Earth and Jupiter, traps a stable population
of highly energetic charged particles, mostly protons, traveling in spiral paths along magnetic field lines.
These particles form belts around Saturn similar to the Van Allen belts of Earth. Unlike the cases of Earth
and Jupiter, Saturn’s charged-particle population is substantially depleted by absorption of the particles
onto the surfaces of solid bodies that orbit within the field lines. Voyager data showed that “holes” exist
in the particle populations on field lines that intersect the rings and the orbits of moons within the
magnetosphere.

Saturn’s moons Titan and Hyperion orbit at distances close to the magnetosphere’s minimum
dimensions, and they occasionally cross the magnetopause and travel outside Saturn’s magnetosphere.
Energetic charged particles trapped in Saturn’s outer magnetosphere collide with neutral atoms in
Titan’s upper atmosphere and energize them, causing erosion of the atmosphere. A halo of such
energetic atoms was observed by the Cassini orbiter.

Saturn possesses ultraviolet auroras produced by the impact of energetic particles from the
magnetosphere onto atomic and molecular hydrogen in Saturn’s polar atmosphere.

The interior of Saturn

Saturn’s low mean density is direct evidence that its bulk composition is mostly hydrogen. Under the
conditions found within the planet, hydrogen behaves as a liquid rather than a gas at pressures above
about one kilobar, corresponding to a depth of 1,000 km (600 miles) below the clouds; there the
temperature is roughly 1,000 K (1,340 °F, 730 °C). Even as a liquid, molecular hydrogen is a highly
compressible material, and to achieve Saturn’s mean density of 0.69 gram per cubic cm requires
pressures above one megabar. This occurs at a depth of 20,000 km (12,500 miles) below the clouds, or
about one-third of the distance to the planet’s centre.
Information about the interior structure of Saturn is obtained from studying its gravitational field, which
is not spherically symmetrical. The rapid rotation and low mean density that lead to distortion of the
planet’s physical shape also distort the shape of its gravitational field.

Analysis of the distortion shows that Saturn is substantially more centrally condensed than Jupiter and
therefore contains a significantly larger amount of material denser than hydrogen near its centre.
Saturn’s central regions contain about 50 percent hydrogen by mass, while Jupiter’s contain
approximately 67 percent hydrogen.

At a pressure of roughly two megabars and a temperature of about 6,000 K (10,300 °F, 5,730 °C), the
fluid molecular hydrogen is predicted to undergo a major phase transition to a fluid metallic state, which
resembles a molten alkali metal such as lithium.

The calculated electrical conductivity of Saturn’s outer core of fluid metallic hydrogen is such that if slow
circulation currents are present—as would be expected with the flow of heat to the surface
accompanied by gravitational settling of denser components—there is sufficient dynamo action to
generate the planet’s observed magnetic field.

On average, Saturn radiates about twice as much energy into space than it receives from the Sun,
primarily at infrared wavelengths between 20 and 100 micrometres. This difference indicates that
Saturn, like Jupiter, possesses a source of internal heat. Kilogram for kilogram of mass, Saturn’s internal
energy output at present is similar to Jupiter’s. But Saturn is less massive than Jupiter and so had less
total energy content at the time both planets were formed.

Saturn’s rings and moons

Although Saturn’s rings and moons may seem to constitute two groups of quite different entities, they
form a single complex system of objects whose structures, dynamics, and evolution are intimately
linked. The orbits of the innermost known moons fall within or between the outermost rings, and new
moons continue to be found embedded in the ring structure. Indeed, the ring system itself can be
considered to consist of myriad tiny moons—ranging from mere dust specks to car- and house-sized
pieces—in their own individual orbits around Saturn. Because of the difficulty in distinguishing between
the largest ring particles and the smallest moons, determining a precise number of moons for Saturn
may not be possible.

SATURN'S RINGS

Galileo Galilei was the first to see Saturn's rings in 1610, although from his telescope the rings looked
more like handles or arms. Forty five years later, in 1655, Dutch astronomer Christiaan Huygens, who
had a more powerful telescope, later proposed that Saturn had a thin, flat ring. Saturn actually has many
rings made of billions of particles of ice and rock, ranging in size from a grain of sugar to the size of a
house. The particles are believed to be debris left over from comets, asteroids or shattered moons. A
2016 study also suggested the rings may be the carcasses of dwarf planets.
The largest ring spans 7,000 times the diameter of the planet. The main rings are typically only about 30
feet (9 meters) thick, but the Cassini-Huygens spacecraft revealed vertical formations in some of the
rings, with particles piling up in bumps and ridges more than 2 miles (3 km) high.

The rings are named alphabetically in the order they were discovered. The main rings, working out from
the planet, are known as C, B and A. The innermost is the extremely faint D ring, while the outermost to
date, revealed in 2009, is so big that it could fit a billion Earths within it. The Cassini Division, a gap some
2,920 miles (4,700 km) wide, separates rings B and A.

Late in its mission, the Cassini spacecraft traveled closer to the rings than any other spacecraft. The
probe collected data that is still being analyzed, but it has already provided insights about the colors of
some of Saturn's moons. In the gaps between the rings, the probe found unusually complex chemicals in
the "ring rain" of debris falling from the rings into the atmosphere, and made new measurements of the
planet's magnetic field, which produces a powerful electron current.

SATURN'S MOONS

Saturn has at least 62 moons. The largest, Titan, is slightly larger than Mercury, and is the second-largest
moon in the solar system behind Jupiter's moon Ganymede (Earth's moon is the fifth largest).

Some of the moons have extreme features. Pan and Atlas are shaped like flying saucers; Iapetus has one
side as bright as snow and one side as dark as coal. Enceladus shows evidence of "ice volcanism": a
hidden ocean spews out water and other chemicals from the 101 geysers spotted at the moon's
southern pole. A number of these satellites, such as Prometheus and Pandora, are referred to as
shepherd moons because they interact with ring material and keep the rings in their orbits.

Though scientists have identified many moons, Saturn has other small moons constantly being created
and destroyed.

SATURN'S IMPACT ON THE SOLAR SYSTEM

As the most massive planet in the solar system after Jupiter, the pull of Saturn's gravity has helped
shape the fate of our solar system. It may have helped violently hurl Neptune and Uranus outward.
Along with Jupiter, it might also have slung a barrage of debris toward the inner planets early in the
system's history.

Scientists are still learning about how gas giants form, and run models on early solar system formation
to understand the role that Jupiter, Saturn and other planets play in our solar system. A 2017 study
suggests that Saturn, more so than Jupiter, steers dangerous asteroids away from Earth.

RESEARCH & EXPLORATION

The Cassini spacecraft, a Saturn orbiter, was the largest interplanetary spacecraft ever built. The two-
story-tall probe weighed 6 tons (5.4 metric tons). It helped identify plumes on the icy moon Enceladus,
and carried the Huygens probe, which plunged through Titan's atmosphere to successfully land on its
surface.

After a decade of observation, Cassini returned incredible data about the Ringed Planet and its moons,
as well as a photo re-creating the original "Pale Blue Dot" image, which captures Earth from behind
Saturn, in 2013. The mission concluded in September 2017 when Cassini, low on fuel, was deliberately
crashed into Saturn to avoid the slight chance of the craft crashing into and contaminating a habitable
moon.

While there are no future missions planned for Saturn, scientists have proposed missions to probe the
icy moon Enceladus or Titan. In 2019, NASA announced there plans to launch their rotorcraft-lander
Dragonfly in 2026 and which will arrive on Titan in 2034. Dragonfly will search for the chemical building
block for life on Titan using its many onboard instruments, including a mass spectrometer.