November 26, 2010

Oxygen Found In Atmosphere Of Saturn Moon

A NASA probe has discovered oxygen in the atmosphere of one of Saturn's moons, discovering the element alongside carbon dioxide in the thing exosphere of the icy satellite known as Rhea.

According to the UK newspaper The Guardian, instruments onboard the Cassini probe were able to acquire samples of both elements in March, when it passed within 100km of Saturn's second largest moon.

The results reveal that there is an extremely thin layer of oxygen and carbon dioxide in Rhea's atmosphere, and that high-energy particles sustain the exosphere by making impact with the planet's surface.

"As the magnetic field rotates around Saturn, particles carried in the field slam into the hemisphere of Rhea that's facing their flow," Dr Ben Teolis, project leader and a member of the Southwest Research Institute (SwRI) in San Antonio, Texas, told BBC News Science Correspondent Jonathan Amos on Thursday.

"They hit that hemisphere and break water molecules on the surface. The atoms are then rearranging themselves to make O2 molecules, which are sputtered from the surface by additional impacting particles," he added.

More than 60 moons have been discovered orbiting Saturn, but Cassini's discovery makes Rhea stand out from the bunch, and marks a significant achievement in the study of our solar system.

"This really is the first time that we've seen oxygen directly in the atmosphere of another world," Andrew Coates, the Head of the University College London (UCL) MSSL Planetary Science Group, told Guardian Science Correspondent Ian Sample on Thursday.

"What we've been able to do now with Cassini is actually fly through this atmosphere and measure it in situ--to 'sniff' and 'taste' it, and find out what it's made of," Coates, who is also the co-author of a paper describing the findings, which appears in the latest edition of the journal Science, added in a separate interview with Amos.

The Cassini Solstice Mission, which is an international effort to probe Saturn and its moons, is currently set to last until September 2017. The probe originally launched in October 1997, and has already completed two previous missions around the planet, successfully landing on Titan, Saturn's largest satellite, in the process. It will also analyze Saturn's rings prior to the completion of its latest mission.


Image Caption: The cratered plains of Saturn's moon Rhea are visible in this image obtained by NASA's Cassini spacecraft on Nov. 21, 2009. Image credit: NASA/JPL/Space Science Institute


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