Jupiter’s moon Io has long been famous for its sky-splitting volcanic eruptions, powered by Jupiter’s tidal gravity. But strange ridge-like features in regions adjacent to the volcanoes have raised questions since their discovery — What are they? How are they formed? Are they somehow related to the volcanoes? A recent study has argued that, even under Io’s whisper-thin atmosphere, these ridges are probably vast dune fields. This new discovery adds yet another world to our growing trove of worlds where aeolian processes operate.