Moons

Definition

A moon is a natural satellite that orbits a planet. Moons can vary in size, composition, and geological activity.

5 Must Know Facts For Your Next Test

1. The Galilean moons of Jupiter are Io, Europa, Ganymede, and Callisto.
2. Ganymede is the largest moon in the solar system and even larger than the planet Mercury.
3. Europa has a subsurface ocean beneath its icy crust, making it a candidate for extraterrestrial life.
4. Io is the most volcanically active body in the solar system due to tidal heating from Jupiter's gravity.
5. Callisto has an ancient, heavily cratered surface indicating minimal geological activity.

Review Questions

• What are the names of the four Galilean moons of Jupiter?
• Which moon is known for having a subsurface ocean?
• Why is Io considered the most volcanically active body in the solar system?

Related terms

planet: A celestial body orbiting a star, typically with sufficient mass to be rounded by its gravity but not massive enough to cause thermonuclear fusion.

ring system: Collections of dust, rock particles, and ice orbiting around planets like Saturn.

tidal heating: A process where gravitational forces from a larger body cause internal friction and heat within a smaller body.