About Saturn Moons :

1] Titan

Titan discovered 1655. The largest of Saturn's satellites at 2575±2 kilometres radius - larger than the planet Mercury, only slightly smaller than Mars. But much less density at 1.88. (The inner planets are all around 5). Titan has a synchronous rotation round Saturn, it rotates once in the same time it takes to orbit Saturn.
Titan is interesting, for not only is it the size of a planet, it has a thick atmosphere, ten times the mass of the Earth's atmosphere, which is mainly nitrogen like the Earth's. There are many chemical reactions going on in the atmosphere of Titan, and the resulting compounds form a layer of orange photochemical smog screening the surface from view.

Cassini is able to see surface features on Titan using radar. The picture shows features seen end October, which look like a cat. Also seen is that the thick atmosphere is in bands parallel to the equator and has changing clouds.

The surface temperature of Titan at -180°C is near the triple point of methane. At a triple point, a substance can be gas, liquid or solid. The atmosphere of Earth early in its history, some four thousand million years ago may have been similar to the present atmosphere on Titan, and study of the chemical processes on taking place on Titan might give clues to the formation of life on Earth.

2] Lapetus 

discovered in 1671, is 718±8 kilometres in radius with a density of 1.21. It is half one colour, half another. Its leading hemisphere is dark red in colour, with an albedo of 0.1. (The albedo is the reflected light, total reflection of light, that is the maximum brightness possible, is 1). The trailing hemisphere of Iapetus is light coloured with an albedo of 0.5. This bright side is heavily cratered. The dark floors of craters near the edge of the pale side indicate the dark red of the other side may be the main colour of the whole body, not a coating collected from space. Information from Cassini shows that Iapetus is divided all around its equator by a mountainous ridge in some places about 13 km high. Further research helped by the Cassini mission has shown that Iapetus is much as it was soon after the formation of the solar system. Its bulging midsection with a ridge of mountains along its equator, and slow spin rate may be caused by heating from long-extinct radioactive elements present when the solar system was born. Names of features on Iapetus are taken from the Mediaeval French epic Chanson de Roland. 

3] Rhea

discovered in 1672 is 764±4 kilometres in radius with a density of 1.33. It is made of rock and ice, with slightly more ice than rock. It has a high albedo of 0.6 so it must have a fairly clean icy surface. At the low temperatures this far from the Sun, ice can be frozen very hard - so that it can be frozen into a state when it behaves more like a kind of rock. The icy surface of Rhea is heavily pocked with impact craters. This indicates that there has been little geological activity in recent times in Rhea's history. Early in Rhea's history, there was geological activity resulting in large troughs, faults or chasms, like the Kun Lun Chasma. The names of features on Rhea's surface are all taken from the world's creation myths.

4] Dione :

was discovered in 1684. Its radius is 559±5 kilometres, and density 1.44. It has a bright icy surface, albedo 0.5. Its leading hemisphere is brighter than its trailing hemisphere. There are three main types of terrain - heavily cratered, lightly cratered plains, and smooth plains with few craters. As geological activity obliterates earlier features such as craters, a heavily cratered surface indicates an older surface and the comparative age of other features can be ascertained by the partial obliteration of earlier features. Dione had active volcanism up to about two and a half thousand million years ago, and changes have continued to occur on its surface. There are active tectonic faults, which look like long pale wispy streaks in the Voyager 2 pictures. From Cassini in December 2004 these are seen to be bright ice cliffs created by tectonic fractures. The names of Dione's features are taken from Virgil's Aeneid.

5]  Tethys :

was discovered in 1684. It is 524±5 kilometres in radius, with a density of 1.26. It has two very impressive surface features. It is encircled by a mighty chasm, the Ithaca Chasma, which is 2.500 kilometres long and up to 100 kilometres wide, and about 3 kilometres deep. In the centre of this is its possible cause, the remains of the giant Odysseus crater, which has long since settled (relaxed) into the surface terrain. The body causing this massive crater landed a long time ago, and nothing much has happened to Tethys since .

6] Polydeuces
A tiny moon, about 5 kilometers across discovered by Professor Carl Murray at Queen Mary, University of London, in October 2004. Polydeuces is a companion, or Trojan, moon of Dione. Trojan moons are found near gravitationally stable points ahead or behind a larger moon. Saturn is the only planet known to have moons with companion Trojan moons.

7]  Enceladus :

Enceladus was discovered in 1789. It has a radius of 251±5 kilometres and density of 1.24. It is in 2:1 resonance with Dione, so they have a tidal effect on each other.Enceladus has a very mixed terrain, at least five different types of scenery. Cratered material is divided and covered by great curved grooves and flows of material which may have erupted from them. Straight grooves at angles to each other by these sites, may be fracture faults. In July 2005, Cassini skimmed just 175 km above the surface and saw white boulders scattered on the surface about 10m.-20m. across. (see picture). They do not fill the cracks so they appear to have formed earlier. The surface is very bright - nearly 1, so it must be covered by recent icy frost and other indications have been found recently by Cassini that Enceladus is geologically active with hot eruptions still occuring under its icy surface which are caused by tidal heating. There is a water vapour atmosphere.

8] Mimas :

was discovered in 1789. It is 197±3 kilometres in radius, with a density of 1.17. It is heavily cratered. One crater, called Herschel after William Herschel who discovered Mimas, is absolutely huge in comparison with the size of the planetary body - 130 kilometres in diameter The impact of an object large enough to cause a crater that size must have come near to breaking up the planet, giant cracks cross the surface. Apart from Herschel, other features are named from Mallory's L'Morte d'Arthur .

9] Hyperion :

Hyperion was discovered in 1848. It is a dark reddish colour, and battered by so many craters it looks spongy. 

Recent fly-pasts have shown that Hyperion is indeed spongy with a density only half that of water.Its surface has water ice mixed with frozen carbon-dioxide, and more complex hydro-carbons.

10] Prometheus : 

discovered 1980 by Voyager 1. Prometheus seems to be connected to the F-ring by a stream of material.

11] Pandora :

Pandora also discovered in 1980 are are each side of the F-ring as "shepherds". Pandora is about 84 km in diameter and is covered with craters filmed by icy dust. Its two largest craters are about 30km across.

12]  Jenus :

Both found by Voyager in 1980, have ancient craters, and are in the same orbit, but when they catch up with each other, they do not collide as their gravitational fields cause them to bounce off each other without touching, and they swap orbits about every four years. They are responsible for a wavy pattern in Saturn's rings. They are mostly water ice and rubble. At 116 kilometres across, Epimetheus is slightly smaller than Janus at 181 kilometres across.

13] Pan :

Pan 20 km across, orbits Saturn in the Encke gap of the A ring and was discovered in 1990 - it maintains the Encke gap.

14] Phoebe :

Phobe was discovered in 1898. It is the farthest out from Saturn of all its orbiting satellites and goes round it the wrong way to the others. Closer investigation on the Cassini mission confirmed as suspected that Phoebe is probably a captured Kuiper belt object, and is very cold (minus 163 degrees Celsius) with a much battered, dirty icy surface. Phoebe has a density consistent with that of the only Kuiper Belt objects for which densities are known. Phoebe's mass, combined with an accurate volume estimate from images, yields a density of about 1.6 grams per cubic centimeter (100 pounds per cubic foot), much lighter than most rocks but heavier than pure ice, which is about 0.93 grams per cubic centimeter (58 pounds per cubic foot). This suggests a composition of ice and rock similar to that of Neptune's moon Triton and Kuiper belt objects.