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C. B. Phillips, A. S. McEwen, E. P. Turtle, L. P. Keszthelyi, P. E. Geissler (LPL), D. P. Simonelli (Cornell), Galileo Imaging Team
Sporadic images of Jupiter's satellite Io have been taken by the Galileo spacecraft since 1996. This dataset has allowed us to track the appearance, modification, and fading of various surface deposits associated with Io's active volcanic centers. Io monitoring by terrestrial observers and detections of new hot spots have been used to help prioritize locations to search for new surface features.
We reprocessed the entire Galileo Io dataset to date, and sorted the images by resolution, phase angle, and longitude. We then used an iterative coregistration and ratioing technique to compare images taken at similar lighting and viewing geometries, over time spans of months to years. This dataset allows us to begin to understand the effects of phase and limb-darkening behaviors on the complicated photometric functions of different features and terrain types on Io. We can then distinguish phase function effects from changes in the shape and color of surface features on Io due to volcanic activity.
Ratio images highlight the locations and types of changes due to Io's active volcanoes, and reveal new details about the plume deposits and surface flows. Multi-band ratio images allow us to track changes in different spectral units on the surface as well, from bright SO2 frost deposits, to red deposits linked to recent eruptions, to dark lava flows.
We will report on new results from Galileo orbits C21 and C22, which take place this summer, as compared to our dataset from previous orbits. This fall we will acquire even higher resolution images of Io on three orbits, beginning during the meeting.
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The author(s) of this abstract have provided an email address for comments about the abstract: phillips@lpl.arizona.edu