The Galilean Satellites are a fascination collection of moons as each is its own
distinctive world, whose surface geology has been affected by the presence of
Jupiter. As in our Solar System, there is a density gradient in the Galilean
satellite system, with the densest objects (Io, Europa) being closest to Jupiter.
A great deal of good information on this system is now available on Wikipedia so we will just summarize the bulk properties of each of these 4 satellites with links to the rich detail on wikipedia as well as some amazing images captured by the satellite Galileo.
Io:
Io is so close to Jupiter that tidal effects actually melt the mantle/interior
portions of Io. As a result, Io has very active vulcanism and an active surface
geology that keeps its overall surface quite young.
Hi-Resolution image of Io
Volcanoes of Io
Eruption
Evolution of Eruption
Hot Spot Tupan Patera
Europa:
Europa has a very smooth surface which essentially completely
frozen. That surface floats on a subsurface ocean and moves causing some fractures.
The lack of much cratering on the surface shows that its quite young so somehow
the ice is able to regenerate itself
Model of Europa Interior
Surface Feature Collage
Broken Ice
Ice Ridges
Hi Res Ridge
Ganymede: This is
the largest moon in the entire solar system (and in fact is larger than the planet
Mercury). Ganymede is composed of silicate rock and water ice, with an ice crust floating over a warmer ice mantle that may contain a layer of liquid water. An extensive system of ridges
and grooves indicates that tectonic activity has helped to form its surface features.
Features reminiscent of old lava flows have also been observed. Extensive cratering is seen on both types of terrain. The density of cratering indicates an age of 4 billion years for the dark terrain, similar to the highlands of the Moon, and a somewhat younger age for the bright grooved terrain (but how much younger is uncertain.
Callisto: Callisto may
be the most heavily cratered surface in the entire solar system. Most of the impacts
have "punched" through the surface to expose Callisto's icy mantle.
Surface: Broken projectile
Recent Impacts
Surface Features
Fly over movie
Bright Terrain
Dark Terrain
Callisto
Ancient Impact Basin
Asgard Ring Detail
Hi Res Scarp
Comparison of All Surfaces
