The ring’s origin was to begin with associated with the missing moon Dia, but Dia’s recovery in 2010 disproved this relationship. Rhea is the 2nd biggest moon of Saturn. Rhea has a thin environment―named an exosphere―which is the initial location a spacecraft foundtraces of oxygen in an environment past Earth. https://moons49370.therainblog.com/33646557/bestmoons-no-further-a-mystery