University College London | 26 Nov 2010
Cassini Finds Ethereal Atmosphere at RheaA fragile atmosphere infused with oxygen and carbon-dioxide has been discovered at Saturn's moon Rhea by the Cassini-Huygens mission - the first time a spacecraft has captured direct evidence of an oxygen atmosphere at a world other than Earth.
The NASA-led international mission made the discovery using combined data from Cassini’s instruments, which includes a sensor designed and built at UCL’s (University College London) Mullard Space Science Laboratory.
Published today in Science Express, results from the mission reveal that the atmosphere of Rhea, Saturn’s second largest moon at 1500 km wide, 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 density of oxygen is probably about 5 trillion times less dense than in Earth’s atmosphere. However, the formation of oxygen and carbon dioxide could possibly drive complex chemistry on the surfaces of many icy bodies in the universe.
"The new results suggest that active, complex chemistry involving oxygen may be quite common throughout the solar system and even our universe," said Dr Ben Teolis, a Cassini team scientist based at Southwest Research Institute in San Antonio and lead author. "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."
NASA JPL Cassini | 2010-399 | 26 Nov 2010
Cassini Finds an Oxygen–Carbon Dioxide Atmosphere at Saturn’s Icy Moon Rhea - BD Teolis et alNASA's Cassini spacecraft has detected a very tenuous atmosphere known as an exosphere, infused with oxygen and carbon dioxide around Saturn's icy moon Rhea. This is the first time a spacecraft has directly captured molecules of an oxygen atmosphere – albeit a very thin one -- at a world other than Earth.
The oxygen appears to arise when Saturn's magnetic field rotates over Rhea. Energetic particles trapped in the planet's magnetic field pepper the moon’s water-ice surface. They cause chemical reactions that decompose the surface and release oxygen. The source of the carbon dioxide is less certain.
Oxygen at Rhea's surface is estimated to be about 5 trillion times less dense than what we have at Earth. But the new results show that surface decomposition could contribute abundant molecules of oxygen, leading to surface densities roughly 100 times greater than the exospheres of either Earth's moon or Mercury. The formation of oxygen and carbon dioxide could possibly drive complex chemistry on the surfaces of many icy bodies in the universe.
- Science Express (online 25 Nov 2010) DOI: 10.1126/science.1198366
Space.com | Science News | 25 Nov 2010
Saturn Moon Has Oxygen Atmosphere
National Geographic | Daily News | 25 Nov 2010
Cassini finds oxygen-carbon dioxide atmosphere on Saturn's moon Rhea
PhysOrg | Space Exploration | 26 Nov 2010