The Solar System

PART 4 | THE SOLAR SYSTEM

Encke

Gap

Cassini

Division

The C ring

contains

boulder-size

chunks of ice,

whereas most

particles in the A

and B rings are more

like golf balls, down to

dust-size ice crystals.

Further, C ring particles

are less than half as bright

as particles in the A and B

rings. Cassini observations

show that the C ring particles

contain less ice and more minerals.

As in the

case of

Jupiter’s ring,

Saturn’s rings lie

inside the planet’s

Roché limit where

the ring particles

cannot pull themselves

together to form a moon.

Because it is so dark, the C ring

was once called the crepe ring.

An astronaut could swim through the rings.

Although the particles orbit Saturn at high

velocity, all particles at the same distance from

the planet orbit at about the same speed, so they

collide gently at low velocities. If you could visit

the rings, you could push your way from one icy

particle to the next. This artwork is based on a

model of particle sizes in the A ring.

Earth to scale

C ring

A ringA ring

B ringB ring

C ring

Visual-wavelength image

NASA

The brilliant rings of Saturn are made up of billions of ice particles ranging from
microscopic specks to chunks bigger than a house. Each particle orbits Saturn in
its own circular orbit. Much of what astronomers know about the rings was learned when
the Voyager 1 spacecraft flew past Saturn in 1980, followed by the Voyager 2 spacecraft
in 1981. The Cassini Spacecraft reached orbit around Saturn in 2004. From Earth,
astronomers see three rings labeled A, B, and C. Voyager and Cassini images reveal
over a thousand ringlets within the rings.

Saturn’s rings can’t be leftover material from the formation of Saturn. The rings are made
of ice particles, and the planet would have been so hot when it formed that it would have
vaporized and driven away any icy material. Rather, the rings must be debris from
collisions between passing comets, or other objects, and Saturn’s icy moons. Such
impacts should occur every 100 million years or so, and they would scatter ice
throughout Saturn’s system of moons. The ice would quickly settle into the
equatorial plane, and some would become trapped in rings. Although the
ice may waste away due to meteorite impacts and damage from radiation
in Saturn’s magnetosphere, new impacts could replenish the rings with
fresh ice. The bright, beautiful rings you see today may be only a
temporary enhancement caused by an impact that occurred
since the extinction of the dinosaurs.

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