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Saturn from Cassini Astronomy 161:
An Introduction to Solar System Astronomy
Prof. Richard Pogge, MTWThF 9:30

Lecture 40:
The Saturn System

Family of Saturn
[Saturn System - Voyager 2 image montage, NASA/JPL]

Key Ideas:

Saturn has Bright Rings and 60 known moons



Rings of Saturn

The Moons of Saturn

To date, 60 moons have been found orbiting Saturn

59 smaller moons:

The composition of the smaller moons is mostly ices: All are heavily cratered, but Enceladus stands out for also having very young terrain.

I've chosen two moons for closer scrutiny here: Enceladus and Titan.

For the current census of the Saturnian Moon System, see Scott Sheppard's Saturn Satellite Page.


Enceladus has the brightest (shiniest) surface of any body the solar system. The fresh ice comes from the interior of Enceladus, fed by water-vapor fountains spraying out of cracks in the surface.


The water fountains on Enceladus are an example of Cryovolcanism, or ice volcanos.

Source of heat for the cryovolcanism on Enceladus is Tidal Heating

Ices from the fountains of Enceladus are responsible for building up the faint E-ring around Saturn.


Saturn's only giant moon:

Titan has a heavy atmosphere:

Titan's Atmosphere


Cold, dense atmosphere:

Hazy clouds of methane, nitrogen, & suspended aerosols hide the surface at visible wavelengths.

Methane is Titan's water

Methane appears to play the same role on Titan that water does on the Earth: High pressures allows Methane to condense into clouds that could rain liquid methane? The most spectactular evidence is the recent (early 2006) discovery of lakes on Titan revealed by the Cassini radar mapping experiment. These could be lakes of liquid methane.

The Surface of Titan

Mostly covered by clouds, but we can peer through at infrared wavelengths and with radar: Young surface with few impact craters.

Varied terrain:

Cassini will make many passes by Titan during its multi-year mission, using a combination of visible and IR cameras and radar imaging. Over the next few years, a more complete picture of this strange world should begin to appear from behind its clouds.

The Rings of Saturn

Saturn's rings are not solid, but instead are composed of billions of tiny chunks of ice and rock:

We will study planetary rings in more detail in a separate lecture.

Supplement: Cassini & Huygens

Cassini spacecraft was launched in Oct 1997 on ambitious mission to orbit and study Saturn, its rings, and its moons, specifically the moon Titan:

Huygens Titan probe (January 2005):

The Cassini/Huygens mission is a joint US/European effort. Cassini was built by NASA (JPL), and Huygens by ESA (European Space Agency). You can learn more about Cassini at the Cassini-Huygens Mission to Saturn & Titan web page at JPL. Information on the Huygens probe is on the Huygens page at ESA.

Readings in Universe: Chapter 14 sections on Saturn, and Chapter 15-8 and 15-10
Return to [ Unit 6 Index | Astronomy 161 Main Page ]
Updated: 2006 November 19
Copyright Richard W. Pogge, All Rights Reserved.