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DIONE:
Dione is the twelfth satellite of Saturn. It has an orbital of 377,400
km from Saturn and a diameter of 1120 km. The mass is 1.05e21 kg. This
moon was discovered by Cassini in 1684. Dione is the densest of Saturn's
moons. It is made mostly of water ice and also must have a fraction of
denser material such as silicate rock. Dione is otherwise similar to
Rhea, but smaller. They both have similar compositions, albedos and
terrain. They both rotate synchronously and have dissimilar leading and
trailing hemispheres. On the trailing hemisphere, there is a network of
bright streaks on a dark background and a few visible craters. These
streaks overlay the craters, indicating that they are new. The leading
hemisphere is heavily cratered and uniformly bright. It is believed that
shortly after its formation Dione was active. Some processes resurfaced
Dione, leaving the pattern of streaks, on the whole surface. After the
internal activity and resurfacing ended, a less intense series of
impacts occurred. This was concentrated on the leading hemisphere and
wiped out the streak patterns but left them intact on the trailing
hemisphere. Helene orbits in Dione's leading Lagrange point.
HELENE: RHEA: TITAN: |
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Rhea is the fourteenth moon as well as the second largest. It has an
orbit of 527,040 km from Saturn and a diameter of 1530 km. The mass of
this moon is 2.49e21 kg. In Greek myths, Rhea is the sister and wife of
Cronus (Saturn) and the mother of Demeter, Hades (Pluto), Hera, Hestia,
Poseidon (Neptune), and Zeus (Jupiter). Rhea was discovered by Cassini
in 1672. Rhea is very similar to Dione, just larger. They have similar
compositions, albedos, and terrain. They both rotate synchronously and
have dissimilar leading and trailing hemispheres. Rhea is composed
primarily of water ice with rock making up less than 1/3 of its mass.
The leading hemisphere is heavily cratered and uniformly bright. The
trailing hemisphere has a network of bright swaths on a dark background
and few visible craters.
Titan is the fifteenth of Saturn's satellites and the largest. It has an
orbit of 1,221,830 km from Saturn and a diameter of 5150 km. The mass is
1.35e23 kg. It was discovered by Huygens in 1655. It was long believed
that that Titan was the largest satellite in the solar system, but
recent observations have shown that Titan's atmosphere is so thick that
its solid surface is actually slightly smaller than Ganymede's. Titan is
larger in diameter than Mercury, and even more massive than Pluto. Titan
is surrounded by a thick, opaque atmosphere. The surface cannot be seen
at all in visible light. Titan is similar in 
