On March 4, 1979, Voyager 1 snapped an exquisite mosaic of Io as it completed a transit above the Jovian cloud tops. Unfortunately, the apparent motion of Io was so great with respect to Jupiter that it is very difficult to assemble. I still plan to do further tweaking, so this is somewhat of a work in progress. The bit of Jupiter visible is simply the last bit of haze that caught sunlight at the edge of the day side, so there isn't much detail to be seen. The view of Io is quite sharp.
Processed Image Copyright Ted Stryk, Raw Data Courtesy NASA/JPL