NASA's Cassini spacecraft has detected oxygen around Saturn's icy moon Dione. The oxygen particles discovered are very few and far between, and the ultra thin atmosphere is known as an exosphere.
Dr Lucie Green, a space scientist and solar expert based at the Mullard Space Science Laboratory, explains solar activity and how coronal mass ejections can have a major impact on Earth.
Cassini's exploration of Saturn and its moons, which has been going on since 2004, has been one of the greatest achievements of NASA, in conjunction with European partners. Paul Sutherland looks at the Cassini mission.