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A.G. Davies (Jet Propulsion Laboratory-California Institute of Technology), L.P. Keszthelyi (LPL, University of Arizona), D.A. Williams (Dept. Geological Sciences, Arizona State University), A.J.L. Harris (HIGP/SOEST, University of Hawai'i)
Analyses of observations from the Galileo Near Infrared Mapping Spectrometer (NIMS), along with data from the Galileo Solid State Imaging experiment (SSI), Photo-Polarimeter Radiometer (PPR), and other datasets stretching back to the Voyager encounters indicate that the Io volcano Pele is an active lava lake. The evolution of the thermal emission spectrum from Pele, as seen by NIMS, is so far unique of all of the volcanoes on Io, with a consistent preponderance of thermal emission at short IR wavelengths. The lava at Pele is at a temperature of at least 1394 K (1121 C), and may be as high as 1600 K (1327 C), consistent with mafic to ultramafic lavas. The maximum thermal output derived from a two-temperature model fit to NIMS data is 280 GW, from an area of 16.5 km2. The inferred mass eruption rate necessary to produce this thermal output is 644,000 to 889,000 kg/s, greater than that seen at any terrestrial lava lake. However, the flux density, the thermal emission per unit area, is low when compared to flux densities from terrestrial lava lakes, being similar to the lowest observed flux density from Erte 'Ale. This may be due to the comparatively large size of the Pele lake where large, cool areas can form away from the most active portions of the lake. Finally, we consider endogenous growth and recycling of magma at Pele, based on models of terrestrial lava lakes.