Scientists say they have discovered a faint oxygen atmosphere around Saturn’s icy moon Dione which is 5 trillion times less dense than the air at Earth’s surface.
Dione’s atmosphere was detected by NASA’s Cassini spacecraft, which has been orbiting Saturn since its arrival at the ringed planet in 2004.
The spotted atmosphere contains a very thin layer of oxygen ions equivalent to conditions 480 kilometers above Earth.
According to the study published in the journal Geophysical Research Letters, there is one oxygen ion for every 11 cubic centimeters of space in Dione’s atmosphere.
“We now know that Dione, in addition to Saturn’s rings and the moon Rhea, is a source of oxygen molecules,” said lead author Robert Tokar.
“This shows that molecular oxygen is actually common in the Saturn system and reinforces that it can come from a process that doesn’t involve life.”
Scientists say Dione’s oxygen is likely to have been derived from either solar photons or energetic particles from space bombarding the moon’s water ice surface and liberating oxygen molecules.
The Cassini team scientists detected a similar thin atmosphere around another Saturn moon named Rhea in 2010.
NASA launched the Cassini spacecraft in 1997 and its mission has been extended several times, most recently until 2017.
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