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Abstract

Jupiter’s large moon Io is intensely tidally heated and is covered by >100 very active volcanic centers (greater than Kilauea’s average heat flow).  These are high-temperature eruptions that can be monitored remotely, even from Earth-based telescopes.  However, there are multiple key questions that can only be answered by a spacecraft mission dedicated to Io:  Is the magma dominantly mafic or ultramafic in composition?  Are the eruptions sourced directly from the mantle or from shallow magma chambers?  What is the role of sulfur and sulfur compounds in the volcanism?  What is Io’s total heat flow and how does it vary with latitude and longitude?    How does the volcanism relate to the tectonics producing >10 km high mountains?  What is the distribution of melt in Io’s interior?  Is there a magma ocean?  Is the orbital resonance creating the tidal heat in equilibrium or does it vary periodically?  How has Io evolved over time?  A spacecraft mission with at least 10 close flybys of Io can address these questions, provided it carries the right science payload including visible cameras designed to measure liquid lava temperatures as well as map the surface topography and monitor activity, thermal-IR cameras sensitive from 1-50 microns, magnetometer and gravity science experiments to understand interior melt and lithospheric thickness, and a mass spectrometer to measure the composition of erupted gases.  This is the basic concept of the Io Volcano Observer mission concept, which will be expanded for NASA’s New Frontiers mission opportunity, with substantial European collaborations.