Oxygen discovered at Saturn's moon Dione

Mar 02, 2012
A southerly view of Dione shows enormous canyons extending from mid-latitudes on the trailing hemisphere, at right, to the moon's south polar region. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 8, 2008. Credit: NASA/JPL/Space Science Institute

(PhysOrg.com) -- Dione, one of Saturn’s icy moons, has a weak exosphere which includes molecules of oxygen, according to new findings from the Cassini-Huygens mission.

The international mission made the discovery using combined data from one of Cassini’s instruments, called CAPS (Cassini Plasma Spectrometer), which includes a sensor designed and built at UCL’s Mullard Space Science Laboratory.

joins Rhea and the main rings in Saturn's system in having an rich exosphere, as well as Jupiter’s moons Ganymede, Europa and Callisto - the target for ESA's proposed JUICE (JUpiter ICy moons Explorer) mission for launch in 2022.

Professor Andrew Coates (UCL Mullard Space Science Laboratory), one of the authors of the study said: “It now looks like oxygen production is a universal process wherever an icy is bathed in a strong trapped radiation and plasma environment.

“Energetic particles hit the icy surface, the hydrogen is lost and molecular oxygen remains as an exosphere. We now know that this happens at Saturn's moons as well as Jupiter's - and it may well occur in extrasolar planetary systems too.”

Cassini flew by Dione on 7 April 2010. During that flyby, CAPS detected molecular oxygen ions near the moon's icy surface, due to bombardment by particles trapped in Saturn's strong magnetic field. The research is published online in the journal Geophysical Research Letters.

A team of scientists, led by Robert Tokar at the Los Alamos National Laboratory in the US, used the measurements to estimate the density of the molecular oxygen ions to be in the range of 0.01 to 0.09 ions per cubic centimetre. These molecular oxygen ions are produced when neutral molecules are ionized; the measurements confirm that a neutral exosphere surrounds Dione.

Electron measurements from UCL's electron spectrometer (ELS), part of CAPS, played a key role in reaching the conclusion of an exosphere, data from ELS showed the plasma wake due to Dione and characterized the changes in Saturn's magnetosphere during the flyby. 

Dr. Geraint Jones (UCL Mullard Space Science Laboratory), also an author of the paper, said: “Dione's exosphere is very thin - compared to Earth's atmosphere the density is about a million billionth. The exciting thing is that there is oxygen - and the oxygen may be being recycled via the surface.”

Explore further: Cassini sees sunny seas on Titan

More information: The research can be found at: www.agu.org/journals/gl/gl1203/2011GL050452/

Related Stories

Beams of electrons link Saturn with its moon Enceladus

Apr 20, 2011

(PhysOrg.com) -- Data from NASA's Cassini spacecraft have revealed that Enceladus, one of Saturn's diminutive moons, is linked to Saturn by powerful electrical currents - beams of electrons that flow back ...

Portraits of moons captured by Cassini

Dec 13, 2011

(PhysOrg.com) -- NASA's Cassini spacecraft successfully completed its closest-ever pass over Saturn's moon Dione on Monday, Dec. 12, slaloming its way through the Saturn system on its way to tomorrow's close ...

Cassini's Photo Album From a Season of Icy Moons

Dec 07, 2005

Wrapping up a phenomenally successful year of observing Saturn's icy moons, the Cassini mission is releasing a flood of new views of the moons Enceladus, Dione, Rhea, Hyperion and Iapetus.

Cassini Finishes Saturnian Doubleheader

Apr 12, 2010

(PhysOrg.com) -- NASA's Cassini spacecraft completed its double flyby this week, swinging by Saturn's moons Titan and Dione with no maneuver in between. The spacecraft has beamed back stunning raw images of ...

NASA's Cassini Spacecraft Continues Making New Discoveries

Feb 24, 2005

NASA's Cassini spacecraft continues making new and exciting discoveries. New findings include wandering and rubble-pile moons; new and clumpy Saturn rings; splintering storms and a dynamic magnetosphere. "For the ...

Recommended for you

Cassini sees sunny seas on Titan

21 hours ago

(Phys.org) —As it soared past Saturn's large moon Titan recently, NASA's Cassini spacecraft caught a glimpse of bright sunlight reflecting off hydrocarbon seas.

Is space tourism safe or do civilians risk health effects?

Oct 30, 2014

Several companies are developing spacecraft designed to take ordinary citizens, not astronauts, on short trips into space. "Space tourism" and short periods of weightlessness appear to be safe for most individuals ...

An unmanned rocket exploded. So what?

Oct 30, 2014

Sputnik was launched more than 50 years ago. Since then we have seen missions launched to Mercury, Mars and to all the planets within the solar system. We have sent a dozen men to the moon and many more to ...

NASA image: Sunrise from the International Space Station

Oct 30, 2014

NASA astronaut Reid Wiseman posted this image of a sunrise, captured from the International Space Station, to social media on Oct. 29, 2014. Wiseman wrote, "Not every day is easy. Yesterday was a tough one. ...

Copernicus operations secured until 2021

Oct 30, 2014

In a landmark agreement for Europe's Copernicus programme, the European Commission and ESA have signed an Agreement of over €3 billion to manage and implement the Copernicus 'space component' between 2014 ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

jibbles
not rated yet Mar 03, 2012
2 questions: might enceladus have magnetoshere with a strong enough flux near the tiger stripes that the resulting auroral sputtering energy would significantly contribute to (or perhaps even be the main cause of) the heating there? i ask because -- haven't they figured tidal friction plus isotopic decay alone insufficient?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.