It has proved possible to track thermal emission from a number of volcanic centers over several orbits to enable individual eruptions to be observed as they start, build, and wane. This has yielded new information about the magma temperature, eruption style, and evolution of these volcanic centers. We show how, with sufficient temporal and wavelength coverage, it is possible to constrain style of eruption from the evolution of thermal emission spectra at two different hot spots, initially using a two-temperature fit to NIMS data to determine temperatures, areas, and total thermal output. Using a silicate cooling model [Davies, 1996], we show that it is possible to constrain magma temperature from the combined NIMS-SSI data and to determine rates of areal coverage. Finally, the eruption styles are compared with their terrestrial counterparts. 2.Galileo NIMS and SSI Observations of Io

Infrared wavelength observations of Io by the Galileo spacecraft show that at least 12 different vents are erupting lavas that are probably hotter than the highest temperature basaltic eruptions on Earth today. In at least one case, the eruption near Pillan Patera, two independent instruments on Galileo show that the lava temperature must have exceeded 1700 kelvin and may have reached 2000 kelvin. The most likely explanation is that these lavas are ultramafic (magnesium-rich) silicates, and this idea is supported by the tentative identification of magnesium-rich orthopyroxene in lava flows associated with these high-temperature hot spots.