A Hubble Space Telescope Study of Posteclipse Brightening and Albedo Changes on Io

Images of Io taken by the Hubble Space Telescope Planetary Camera using filters at 7120 and 3577 Å in April and May 1992 shortly after Io emerged from Jupiter's shadow have been analyzed for the effect of posteclipse brightening first reported by Binder and Cruikshank (1964, Icarus 3,299-305). The classic effect displays a 10% increase in brightening lasting for 10 to 15 min. This was not seen in any of the eclipses that were studied.

A comparison of the 3577-Å images with UV maps produced from images taken with Voyager 1 (McEwen 1988,Icarus 73, 385-426) showed little change in 13 years. The striking, detailed similarity of the two demonstrate that the Hubble Space Telescope Planetary Camera has the capability to monitor temporal changes on Io's surface.