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[30.07] Are Prometheus-Type Plumes on Io Produced by Lava-SO2 Interactions at the Flow Fronts?

M. P. Milazzo, L. P. Keszthelyi, A. S. McEwen (University of Arizona), Galileo SSI Team

We have investigated how lava-SO₂ interactions could produce Prometheus-type plumes on Io. While most models assume a single source vent for the gas and entrained particles, the evidence at Prometheus suggests that the plume is created from multiple sources. No central plume vent is apparent in the high-resolution and color images acquired by Galileo in February, 2000. Instead, the images reveal a compound flow field with many active flow lobes, often associated with bright and dark streaks. The medium-resolution color image shows diffuse and relatively blue-colored regions suggestive of SO₂ gas spread over the flow field. We propose that the plume may originate from multiple flow lobes advancing over SO₂-rich ground. The plume is remarkably stable in size, shape and optical properties, seemingly inconsistent with the sporadic behavior expected from individual flow lobes, but there are tens of active lobes so the cumulative effect could appear constant at large scales. We have modeled the interaction between basaltic pahoehoe lava and SO₂ snow on Io during the initial emplacement of a new flow lobe. Using an estimated 5 m² s^-1 lava coverage rate at Prometheus, we show that the gas production rate of SO₂ at the flow fronts is enough to produce the deposit annulus with a resurfacing rate of ~0.24 cm yr^-1.