Here are a few of my favorite images of the moons of the gas giant planets, all taken by the various probes that have gone through the outer solar system in the past thirty years:
Io, the innermost of Jupiter’s four large moons, and the body in the solar system that is the most volcanically active. The dark spots are each an active volcano.
Two volcanic eruptions occuring on Io; one on the upper horizon, and one just below the day/night terminator line (the faint spot bottom center). Material can be ejected several hundred kilometers above the surface.
Europa is one of the four large moons of Jupiter discovered by Galileo in 1610. Its surface is made predominantly of water ice.
More detailed image of the surface of Europa, showing large flat blocks of ice frozen in place.
Ganymede, one of the moons of Jupiter, and the largest moon in the solar system.
Callisto, one of the four large moons of Jupiter.
Enceladus orbits Saturn
Miranda is one of the five medium-sized moons of Uranus. Many of the moons of Uranus are named after characters in plays by William Shakespeare.
Triton, the one large moon of Neptune. It has geysers on its surface which erupt either liquid nitrogen or liquid methane.
Grace and Peace