November 2014 • 2014Icar..242..365D
Abstract • Observations obtained with the near-infrared camera NIRC2, coupled to the adaptive optics system on the 10-m W.M. Keck II telescope on Mauna Kea, Hawaii, on 15 August 2013 at ∼15:30 UT revealed two large "Outburst"-class volcanic eruptions on Io. Follow-up observations five days later showed that both eruptions had substantially faded. The most energetic eruption was at Rarog Patera, at a location near 305°W, 42°S; a smaller one occurred further south at ∼310°W and ∼57°S, close to Heno Patera. Total radiant fluxes at Rarog Patera on August 15 were of order ∼500 GW/sr/μm at wavelengths between 2 and 4 μm, and close to 250 GW/sr/μm at 1.6 μm, indicative of an effective temperature of ∼1040 K over an area of ∼120 km2, and a total thermal emission of nearly 8 TW. At Heno Patera the 4-μm flux measured ∼250 GW/sr/μm, and ∼90 GW/sr/μm at 2.2 μm, suggestive of an effective temperature of ∼720 K over an area of more than 300 km2, and a total thermal emission of ∼5-6 TW. Fits of the Davies (Davies, A.G. . Icarus 124(1), 45-61) Io Flow Model indicate that these two eruptions are vigorous and the exposed surfaces are mostly very young, no older than 4-5 min at Rarog Patera and a few hours at Heno Patera. The model fits suggest that in both locations lava fountaining is taking place, a highly-energetic style of volcanism. Using follow-up observations taken between August 20 and September 7 we estimate peak effusion rates between 5 × 104 and 105 m3/s.