In our solar system there are approximately 140 known moons of which Jupiter has the lion's share at sixty two, four of which are the largest around any planet.
- Callisto: The outermost of the four and the most heavily cratered. It is thought to hold a body of water.
- Io: The innermost moon and the most sulphurous and volcanic, with hundreds of eruptions at any one time. It also appears to have an atmosphere.
- Europa: This has an icy surface which may cover liquid water.
- Ganymede: The largest moon in the solar system being larger in diameter than Mercury and has its own magnetic field.
Mrs Darley's Moon Mysteries will provide more detail on the planets and their fascinating moons.