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R. Lopes-Gautier, W. Smythe, L.W. Kamp (JPL/Caltech), S. Doute' (UCLA), R. Carlson, A. Davies (JPL/Caltech), A. McEwen, P. Geissler (LPL, University of Arizona), S. Kieffer (Kieffer Science Consulting), F. Leader, R. Mehlman (UCLA), Galileo NIMS Team
The Near-Infrared Mapping Spectrometer (NIMS) on Galileo observed Io during the spacecraft's three close fly-bys in October and November 1999, and February 2000. The spectral range of NIMS (0.7 to 5.2 microns) allows the instrument to map the thermal emission from Io's many volcanic regions, as well as absorption bands seen in reflected sunlight. NIMS data obtained during the fly-bys were used to make detailed maps of the temperature distribution within volcanic centers, maps of the SO2 distribution on the surface, and of an yet-unidentified absorption band detected at 1 micron. The distribution of SO2 on the surface will be discussed by Doute' et al. (this volume). This paper will present the results of our thermal mapping of different hot spots, and of the relationship between the absorption near 1 micron and surface color, albedo, and proximity to hot spots. We find that hot spots such as Pele and Tvashtar have high temperatures that may be consistent with ultramafic magmas, while the temperatures are Loki are significantly lower, consistent with large expanses of cooling lavas erupted perhaps a few months earlier. Prometheus and Amirani have long lava flows, probably tube-fed and, at least in the case of Prometheus, responsible for the generation of a plume as the lava interacts with SO2 frost. These volcanic regions are different from each other and provide examples of the variety of volcanic processes taking place on Io. Portions of this work were performed at JPL under contract with NASA.
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