The Icy Satellites

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 The Icy Satellites General Information Definition

Enceladus (Saturn's satellite)
(credit: JPL/NASA)
Definition :
Around the gaseous planets of the Solar System, we can see a number of satellites that, due to their dimensions and compositions, are a distinct group of objects in the system.
These are the Icy Satellites!

More specifically, the Icy Satellites are natural satellites of planets in our Solar System with the following characteristics:
  • A near spherical shape and a maximum diameter of 400 km.
  • A density of less than 2 gr/cm3 (the density of water is 1gr/cm3), which implies that they are made essentially of ice of low density (water, ammoniac, ...).
We find icy satellites around the four gaseous planets of the Solar System:
  • Jupiter
  • Saturn
  • Uranus
  • Neptune
The four biggest satellites around Jupiter are the Galilean Moons. The first Galilean satellite, Io, does not comply with the definition of icy satellites because its density is of 3.5 and it is mostly made of rocks and metals. It is never the less very interesting because it has strong volcanic activity as discovered by the Voyager missions. Europa, the second Galilean satellite, Europa, also has a high density 3.0) and contains only a little water. But all this water, of which only a little is in ice form, covers the entire surface. That's why Europa is included in the Icy Satellites. The other two Galilean satellites, Ganymede and Callisto, have a density that complies with the Icy Satellites' definition (1.9 and 1.8). They are about half ice water.

Almost all the icy satellites of Saturn and Uranus are even less dense (less than 1.7), they therefore contain even more ice. Among these, the more intriguing are Enceladus, Titan and Miranda.

Neptune only has one big spherical satellite: Triton.

The telluric planets, located in the inner solar system, do not have icy satellites due to the fact that, in the formation of the solar system, water became rare there. Furthermore, the masses of the gaseous planets allow them to have more massive satellites.

The first observations of the icy satellites were determined by the probes Voyager 1 and 2. PMore recently the probes Galileo and Cassini-Huygens, each dedicated to Jupiter and Saturn respectively, made it possible to get more information on these distant worlds.

The surfaces of these satellites have more or less varying size characteristics depending on their ages. The age of the surface of a satellites depends on the activity inside it which allows for the "resurfacing" of the satellite induced by different mechanisms(tectonics, cryovolcanique), and therefore the internal structure.

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