Jupiter seen from his satellite Ganymede - Illustration - Ridges, grooves, and craters on Ganymede...

Jupiter seen from his satellite Ganymede - Illustration - Ridges, grooves, and craters on Ganymede - Artist's view of the surface of Ganymede, Jupiter's largest satellite. An impact crater about 15 km in diameter differs from the striated surface of the satellite. In the sky are represented Jupiter, the Europe satellite on the top right, and Io on the left of Jupiter. Jupiter's largest satellite Ganymede has a varying surface, some of which is characterized by rumpled bundles of ridges and grooves that run for hundreds of miles over a frozen surface of water - ice. They probably formed long ago when tectonic forces pulled apart Ganymede's upper crust; similar sets of faults occur in rift zones on Earth, as in eastern Africa. Subsequent meteoritic impacts have peppered - - and broken in places - - the continuity of the running formations. In this image an impact crater about 10 miles in diameter dominates a scene otherwise defined by a dozen long ridges. In the middle of the crater is a central peak, formed when the energy of the impact liquefied the crust long enough for it to rebound upward and solidify once again. Immediately above the horizon, Jupiter is still a majestic spectacle, even at a distance of nearly three times that between the Earth and its moon. Much closer on the upper right is Ganymede's sister satellite Europa. At a distance of 307 thousand miles from this vantage point, Europe is only a quarter again as far as the Earth is from its moon. To the lower left of Jupiter at nearly a million miles is Jupiter's volcanic satellite Io