Adaptive Optics mapping of Io's volcanism in the thermal IR (3.8 mu m)

live opposite hemispheres of Io were observed on October 20 and 21, 1996, t hrough an L' broadband filter, using the high-resolution capability of the Adaptive Optics (AO) system implemented on the ESO 3.6-m telescope at La Si lla, Chile. These observations, performed at thermal wavelengths when Io is in daylight, have been carefully processed to improve the sharpness of the initial, diffraction-limited, images. The myopic deconvolution process use d (idac) achieved an angular resolution estimated to be 0.15 arcsec, corres ponding to a spatial resolution of -570 km on Io's dise at the time of the observations. The final images show a number of bright features which have been compared with the Galileo/NIMS data, the only data set with a comparab le resolution available for the anti-Jovian side of the satellite as well a s its Jupiter-facing side. Our maps of the hot spot distribution are quite consistent with the Galileo data. The Jupiter-facing side is dominated by e mission from Loki, which accounts for similar to 25% of the total hot spot emission from that side land 45% of that we were able to resolve and identi fy), although Loki was in a phase of decreasing activity (but not yet quies cent), as derived from ground-based monitoring observations. A few more hot sources are detected, including Pele-Pillan. The other hemisphere is chara cterized by a large number of moderately bright hot spots which are distrib uted around Bosphorus Regio, These preliminary observations fully demonstra te the capabilities of an AO system coupled with a thermal camera to monito r the volcanic activity of lo, in terms of morphology as well as thermal ou tput. These monitoring capabilities will become especially important when t he Galileo mission ends. (C) 2000 Academic Press.