• Ganymede is the next moon out orbiting at over 660,000 miles. It is the
largest known moon in the Solar System, almost double the size of Earth’s
Moon. It is composed of silicate rocks
(similar to Earth) and water ice. Ganymede has a small ferrous core that
generates a magnetic field about
1% the strength of the Earth’s. The
surface of this moon is old and pockmarked with craters from impacts.
In 2015 the Hubble Space Telescope
found evidence that there may be
a huge underground ocean containing more water than Earth.
• Callisto is the furthest out of the Galilean moons orbiting at about
1.1 million miles. The surface of Callisto is the oldest in the Solar
System, it also has the most cratered
body in the solar system. The implication of this is that there is no volcanic
or teutonic activity on the moon
which renews the surface. The moon
is thought to have a small rocky core
and has been proven to contain water ice, carbon dioxide, silicates and
organic compounds. It is believed that
underneath a 124 mile thick crust lies a
salt water ocean some six miles deep.
The Rings of Jupiter
• Possibly the least known fact about Jupiter is that it has rings.
In fact there are three rings which orbit inside the Galilean
moons. These are known as the halo, the main ring, and two
gossamer rings from inner to outside. It is believed that the
rings are made of small dust particles, not ice. The space
probe Galileo confirmed that the main ring was formed from
deposits from the inner moons Adrastea and Metis, the two
closest moons of Jupiter. The gossamer rings from the small
moons Amalthea and Thebe. The rings were first discovered in
1979 by the Voyager 1 spacecraft. They are so faint that they
can only be seen looking through them towards the Sun.
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