New data from the Cassini spacecraft indicates that Saturn's trademark rings have their own atmosphere, separate from the gas around the planet they encircle.
During close fly-bys of the rings, instruments on Cassini detected that the environment around the rings is atmosphere-like. More interestingly, though, is that the ring atmosphere is made up of molecular oxygen - two atoms of oxygen bonded together - like that found in Earth's atmosphere.
The ice that makes up Saturn's rings is also the source of the oxygen that makes up this atmosphere.
"As water comes off the rings, it is split by sunlight; the resulting hydrogen and atomic oxygen are then lost, leaving molecular oxygen," said Cassini investigator Andrew Coates of the Mullard Space Science Laboratory at University College London.
Saturn's rings are made up mostly of water ice along with small amounts of dust and rocky bits. Ultraviolet rays from the Sun pry the water molecules loose from the rings and split them into their building blocks - hydrogen and the two forms of oxygen - by a process called photodissociation.
The ring atmosphere is probably kept in place by gravitational forces, Coates says. The check-and-balance between the loss of material from the ring system and a re-supply from the ring particles also helps.
