Observations and initial modeling of lava-SO2 interactions at Prometheus, Io

We present observations and initial modeling of the lava-SO₂ interactions at the flow fronts in the Prometheus region of Io. Recent high-resolution observations of Prometheus reveal a compound flow field with many active flow lobes. Many of the flow lobes are associated with bright streaks of what is interpreted to be volatilized and recondensed SO₂ radiating away from the hot lava. Lower-resolution color data show diffuse blue to violet areas, also near the active flow front, perhaps from active venting of SO₂. Not clearly visible in any of the images is a single source vent for the active plume. While the size of the proposed vent is probably near the limit of the resolution, we expected to see radial or concentric albedo patterns or other evidence for gas and entrained particles above the flow field. The lack of an obvious plume vent, earlier suggestions that the Prometheus-type plumes may originate from the advancing flow lobes, and the high-resolution images showing evidence for large-scale volatilization of the SO₂-rich substrate at Prometheus encouraged us to develop a model to quantify the heat transfer between a basaltic lava flow and a substrate of SO₂ snow. We calculate that the vaporization rate of SO₂ snow is 2.5×10^-6ms^-1 per unit area. Using an estimated 5 m²s^-1 lava coverage rate (from change detection images), we show that the gas production rate of SO₂ at the flow fronts is enough to produce a resurfacing rate of ~0.24 cm yr^-1 at the annulus of Prometheus. This is much less than other estimates of resurfacing by the Prometheus plume. While not easily explaining the main Prometheus plume, our model readily accounts for the bright streaks.