Jupiter already has an abundance of moons, but from 1949 to 1961 it had another, temporary satellite in the form of a comet trapped in the gas giant's gravitational grip.
Comet 147P/Kushida-Muramatsu was captured as a temporary moon of Jupiter in the mid-20th century and remained trapped in an irregular orbit for about twelve years, astronomers announced today.
There are only a handful of known comets where this phenomenon of temporary satellite capture has occurred and the capture duration in the case of Kushida-Muramatsu is the third longest.
More: http://news.yahoo.com/s/space/20090914/sc_space/gotchajupiterturnedcometintoamoon (http://news.yahoo.com/s/space/20090914/sc_space/gotchajupiterturnedcometintoamoon)