Astronomers using the Keck and Gemini telescopes on Maunakea have observed a strange pattern of volcanic activity on Jupiter’s moon Io. This moon, and our Earth, are the only two bodies in our solar system where widespread volcanism is seen. But the source of Io’s inner heat, which in turn powers its volcanoes, is radically different than Earth’s. Io’s interior is heated by the varying pull of Jupiter’s gravity (a process called tidal heating), the same process by which the Earth’s moon causes tides on our planet. While monitoring Io’s most powerful volcano, Loki Patera, researchers found an unexpected pattern: this volcano’s activity varies on a similar timescale to a 500-day variation in the shape of Io’s orbit. The researchers believe these long-timescale orbital changes help to mobilize magma and bring it to the surface of the moon for an eruption. Understanding these dynamics may provide clues to Io’s mysterious interior, as well as the interiors of other bodies in the solar system.