This is a composite image of three of the Galilean satillites.
Click on image for full size
Evolution of Icy Moons
The three moons to the left illustrate three possible stages in the history
of an icy satellite. The satellite can be cold and so have no internal activity
. In that case, the surface is unchanged, old, and heavily cratered. This case may be illustrated by Callisto
, the top moon in the picture. The craters are left over from the formation of the moon itself, 4 billion years ago. Nothing has happened to this moon to ever change its surface appearance.
If there was some internal heating, then the surface may show some changes and will not be as heavily cratered. This case may be illustrated by Ganymede, the moon in the middle of the picture. Ganymede has many craters but also trenches and grooves which indicate that the surface flowed at some point in time.
If the heating took place over a long time, then the surface may show many changes, and in fact may still be evolving. This case may be illustrated by Europa, the third moon in the picture. The surface of Europa is lightly cratered with evidence of cracks and fractures.
Many moons in the solar system exhibit features of evolution somewhere between those of Ganymede and those of Europa. Examples of these moons include Dione, Rhea, Enceladus, Tethys, Ariel, Umbriel, Miranda, Titania, Oberon, and Triton.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
This is a picture of ice flowing at the south pole, or the Antarctic region of the Earth. Ice flows very easily, but very slowly. Glaciers are perfect examples of the fact that ice can move. Glaciers flow...more
The surface of Dione does not have many craters. Instead it has wispy white streaks similar to those found on Rhea extending for many kilometers over the entire surface. These two things indicate that...more
The surface of Rhea is typical of an icy moon. Rhea is as heavily cratered (despite the appearance of this picture) as Saturn's "death star" moon Mimas on its leading side. Its trailing side has unusual...more
The surface of Enceladus does not have many craters. Instead it has grooves similar to those found on Ganymede. These grooves extend for many kilometers over the surface. The presence of grooves indicates...more
The surface of Tethys is heavily cratered, which means that the surface is very old and hasn't been changed. Tethys is more lightly cratered in one region, however. This may be a sign of some internal...more
The surface of Umbriel seems to be like many icy moons. It appears to have many craters, but is not as heavily cratered as Callisto. ...more
The surface of Miranda is very unusual. It is not like any other moon in the solar system. Miranda has many craters but also very big grooves. These indicate that there has been activity inside Miranda...more
The surface of Titania is like many icy moons. It appears to be changed for it does not have many craters. Instead it has grooves and ridges similar to those found on Ganymede. These grooves e xtend for...more