Evidence of a Global Magma Ocean in Io’s Interior

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Science  12 May 2011:
DOI: 10.1126/science.1201425


Extensive volcanism and high-temperature lavas hint at a global magma reservoir in Io, but no direct evidence has been available. We exploited Jupiter's rotating magnetic field as a sounding signal and show that the magnetometer data collected by the Galileo spacecraft near Io provide evidence of electromagnetic induction from a global conducting layer. We demonstrate that a completely solid mantle provides insufficient response to explain the magnetometer observations, but a global subsurface magma layer with a thickness >50 km and a rock melt fraction ≥20% is fully consistent with the observations. We also place a stronger upper limit of ~110 nT-RIo3 on the dynamo dipolar field generated inside Io.