Ionian Plumes: High-Value Targets for a Sample Return Mission

Io, the most volcanically active body in the Solar System, features hundreds of active volcanoes that produce towering plumes exceeding 100 km in height and width. These plumes contain sulfur dioxide (SO2), various sulfur species, and pyroclastic dust grains. Voyager 1's 1979 flyby revealed a startingly dynamic world, replacing expectations of a cratered, ancient surface with images of smooth plains, towering mountains, volcanic calderas, and extensive lava flows and plumes of gas and dust grains. This discovery challenged existing assumptions about planetary geology and positioned Io as a critical target for understanding the effects of intense internal processes.

Subsequent spacecraft missions, including Galileo, New Horizons, and Juno, and ground-based observations, have deepened our understanding of Io's geology, atmosphere, and interactions within the Jovian system. However, many fundamental questions remain unanswered, particularly regarding Io's formation, volatile history, and internal structure. These mysteries make Io a prime candidate for a sample return mission to address key scientific questions. Io sample return was recently studied as part of the keck Institute for Space Studies workshop "Sample Return from All Across the Solar System."