No. 22: Jul-Aug 1982
When Jupiter's satellite Io ducks into Jupiter's shadow, something mysterious happens. Some of the time, but not always, Io emerges from the shadow about 10% brighter than when it entered. In 10-20 minutes, its brightness decays to normal levels. One suspicion is that SO2 in Io's atmosphere condenses on the planet's surface when it is in the cold shadow, thus coating some dark areas with a bright sulfurous 'frost.' However, a recent measure of Io's post-eclipse brightness detected no brightness change whatsoever. Apparently we have a real but rather unreliable phenomenon.
(Morrison, Nancy D., and Morrison, David; "Io; Post-Eclipse Brightening Still Mysterious," Mercury, 11:27, 1982.)
Reference. Io's post-eclipse brightening is cataloged at AJX6 in The Moon and the Planets. To order this book, visit: here.