Rhea’s Atmosphere holds surprise oxygen
14 Jan 2011 by Evoluted New Media
A fragile atmosphere of carbon dioxide and oxygen has been discovered around Rhea, Saturn’s second-largest moon, by the Cassini-Huygens mission.
A fragile atmosphere of carbon dioxide and oxygen has been discovered around Rhea, Saturn’s second-largest moon, by the Cassini-Huygens mission.
|
Scientists detect carbon dioxide and oxygen in Rhea’s atmosphere |
It is the first time any spacecraft has detected direct evidence of an oxygen atmosphere anywhere other than Earth. The atmosphere is extremely thin, and is sustained by high energy particles bombarding its icy surface and kicking up atoms, molecules and ions into the atmosphere.
“The new results suggest that the active, complex chemistry involving oxygen may be quite common throughout the solar system and even our universe,” said Dr Ben Teolis, lead author and Cassini scientist. “Such chemistry could be a pre-requisite for life. All evidence from Cassini indicates Rhea is too cold and devoid of the liquid water necessary for life as we know it.”
Rhea’s atmosphere makes it unique in the Saturn system – Titan, the largest moon has a very thick nitrogen-methane atmosphere with very little carbon dioxide and oxygen.
“The discovery of this tenuous atmosphere provides key information on how radiation can drive chemistry on icy surfaces throughout the universe,” said Dr Geraint Jones from the UCL Mullard Space Science Laboratory (MSSL).
MSSL – supported by the Science and Technology Facilities Council – led the design and building of an electron spectrometer of the Cassini plasma spectrometer, which detected negative ions streaming off Rhea’s surface. An ion and neutral mass spectrometer detected neutral particles and completed the picture of Rhea’s atmosphere.
The plasma spectrometer saw clear signatures of flowing streams of positive and negative ions, with masses that correspond to ions of oxygen and carbon dioxide. The mass spectrometer detected peak densities of oxygen at around 50 billion molecules per cubic metre – 5 trillion times less dense than the Earth’s atmosphere. It appears to come from water ice on the surface of the moon that is bombarded by energetic particles from Saturn’s magnetic field. Carbon dioxide was detected at 20 billion molecules per cubic metre and possibly comes from dry ice.
