Loki, a faraway volcanic feature on Jupiter’s moon Io, is acting up and planetary scientists want to know why.

Loki has always been a troublemaker.

This particular Loki is a bowl of magma on Jupiter’s moon Io. For a while, Loki brightened and faded with surprising regularity, but then it started misbehaving — Loki completely stopped its regular behavior for a decade, then seems to have restarted on a different timescale. Now, planetary scientists are trying to make sense of what’s happening on this faraway volcanic world.