Which planet's gravity induces tidal forces causing volcanism on its moons, including Io?

• A. Earth
• B. Jupiter
• C. Mars
• D. Saturn

Answer: (B)

Tidal heating happens when a moon is pulled unevenly by the gravity of the planet it orbits. If the orbit isn’t perfectly circular, the varying gravitational tug flexes the moon as it moves, and that flexing generates internal heat through friction. Io shows this most dramatically because its orbit around Jupiter is affected by resonances with Europa and Ganymede, keeping the pull irregular and strong. The continual squeezing heats Io’s interior, melting rock and fueling intense volcanic activity. So the planet whose gravity drives this tidal heating for Io is Jupiter. Other planets can influence tides on their moons, but Io’s famous volcanism is a direct consequence of Jupiter’s immense gravity.