Saturn's moon Rhea has an oxygen atmosphere
Saturn's moon Rhea possesses an astonishingly thin oxygen atmosphere, a discovery revealing how radiation can create dynamic atmospheres on icy, airless worlds.
Saturn's second-largest moon, Rhea, surprisingly boasts an incredibly thin atmosphere made mostly of oxygen. Discovered in 2010 by NASA's Cassini spacecraft, this exosphere is about a trillion times less dense than Earth's atmosphere. Scientists believe this oxygen forms when high-energy particles from Saturn bombard Rhea's icy surface, splitting water molecules. The lighter hydrogen escapes, leaving oxygen behind. This process reveals how radiation can create atmospheres on otherwise airless bodies, offering clues about the chemistry of outer solar system moons. Intriguingly, Rhea's atmosphere even changes density depending on its position within Saturn's magnetic field.