Voyager 1 captured this mosaic on Io on March 4, 1979, as a nearly full-phase Io appeared to travel across Jupiter’s terminator. Viewed near the edge of its disk and at local dusk, only the uppermost blue hazes of Jupiter’s atmosphere are visible.
Io and Jupiter from Voyager 1
The mosaic, which consists of four clear-filter images followed by violet, blue, orange, and green frames, is a great challenge to assemble because in the 11 minutes it took Voyager to record and transmit the 6 images (from 22:36:35 to 22:47:48) Io completely transited the terminator, and because the color frames are not complete, with pieces of Io cut off. Source images can be downloaded here.
Credit: NASA / JPL / Ted Stryk