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A. McEwen (LPL, University of Arizona), C. Phillips, E. Turtle, P. Geissler (LPL), D. Simonelli (Cornell U.), Galileo SSI Team
Galileo successfully completed the C21 encounter in early July, and has acquired Galileo's highest-resolution images of Io, 1.25 km/pixel. Playback was ~50 of writing this abstract. We expect to complete a 3-color mosaic at 4 deg. phase angle covering the entire hemisphere centered at longitude 135 (opposite to the hemisphere best seen by Voyager). This mosaic will provide the large-scale context for most of the high-resolution observations planned for the close Io flybys (I24, I25, and I27). Many new details can be seen such as lobate flows and unique spectral units, and a plume was detected over Masubi (~44 S, 54 W). There appear to be changes (compared with previous Galileo images) around several active volcanic centers (Phillips et al., this conference). The dark deposits around Pillan Patera have brightened, and there is a new plume deposit to the northeast. A C21 eclipse image reveals the intense Pele hot spot and an even more intense feature at 10 S, 14 W, first seen from the ground by J. Spencer. The Kanehekili and Marduk plumes are seen in eclipse, although Marduk may have moved north of its previous position. Acala, Pillan, and Prometheus remain active. A near-global plume inventory sequence is expected from orbits C21 and C22 to characterize the activity prior to the in-situ measurements in the close flybys later this year. In C21 we have also acquired a sequence designed to provide regional stereo coverage along with companion images planned for orbit I24. Image noise due to energetic particles has been less than expected in C21, which increases our optimism for data quality during the close flybys.