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R. Lopes-Gautier (JPL,Caltech), A. S. McEwen (LPL, University of Arizona), W. D. Smythe (JPL,Caltech), P. E. Geissler (LPL, University of Arizona), L. Kamp, A. G. Davies (JPL,Caltech), J. R. Spencer (Lowell Observatory), R. W. Carlson (JPL,Caltech), L. P. Keszthelyi (LPL, University of Arizona), L. A. Soderblom (USGS Flagstaff), NIMS Team, SSI Team
Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the Near-Infrared Mapping Spectrometer (NIMS) for Galileo and the first 3 orbits of the Galileo Europa Mission. We correlate these results with those from Galileo's Solid State System (SSI), from ground-based observations, and from observations made during the two Voyager fly-bys in 1979. A total of 61 active volcanic centers (hot spots and plumes sites) were identified from Galileo, Voyager, and ground-based observations. Of these, 48 are hot spots detected by NIMS and/or SSI. The location of plumes shows a strong equatorial preference, however, the distribution of active volcanic centers does not show any clear correlation with latitude, longitude, Voyager-derived topography, or with heat flow patterns predicted by competing tidal dissipation models. Hot spots are correlated with surface colors, particularly dark and red deposits, and generally anti-correlated with white, SO2-rich areas. Volcanic features on the surface, such as calderas and flows, were identified in the Galileo and Voyager images at all of the hot spot locations. Hot spot temperatures obtained from both NIMS and SSI are consistent with silicate volcanism, which appears to be widespread on Io. The activity of hot spots has been monitored by Galileo since 1996 and results indicate that two types of activity are present: persistent-type, lasting from months to years, and sporadic events, which may represent intermittent activity or activity that often falls to levels below the detection limits of the instruments. Sporadic events are not often detected, but may make an important contribution to Io's heat flow and resurfacing.
The author(s) of this abstract have provided an email address for comments about the abstract: rlopes@issac.jpl.nasa.gov