Sunday, 4 March 2012

Oxygen discovered on Saturn's moon, Dione


Since the space probes, Galileo and Cassini, began sending ever more precise data from the farther reaches of the solar system, the Saturnian moon system has provided astronomers with a more-or-less constant stream of incredible information.

The latest discovery is that Saturn's moon, Dione, has an oxygen atmosphere.

Los Alamos National Laboratory announced this week that their scientists have detected molecular oxygen ions (O2+) in the upper atmosphere of the moon.

A sensor aboard the Cassini spacecraft called the Cassini Plasma Spectrometer (CAPS) detected the oxygen ions in Dione's wake during a flyby of the moon two years ago. Researchers Robert Tokar and Michelle Thomsen noticed the presence of the oxygen ions, and published their results in Geophysical Research Letters.

Robert Tokar notes:
"The concentration of oxygen in Dione's atmosphere is roughly similar to what you would find in Earth's atmosphere at an altitude of about 300 miles. It's not enough to sustain life, but, together with similar observations of other moons around Saturn and Jupiter, these are definitive examples of a process by which a lot of oxygen can be produced in icy celestial bodies that are bombarded by charged particles or photons from the Sun or whatever light source happens to be nearby."

The discovery is already generating interest within the astrobiology community. If oxygen exists on Dione, then why not also on some of the solar system's other moons? If oxygen is present on a moon within our solar system which is known to have sub-surface water - such as the Jovian moon, Europa - that oxygen could combine with carbon in subsurface lakes to form the building blocks of life.

Astronomy journalist, Jason Major notes:

"On Dione the energy source is Saturn's powerful magnetic field. As the moon orbits the giant planet, charged ions in Saturn's magnetosphere slam into the surface of Dione, stripping oxygen from the ice on its surface and crust. This molecular oxygen flows into Dione's exosphere, where it is then steadily blown into space by - once again - Saturn's magnetic field.

[...] Molecular oxygen, if present on other moons as well could potentially bond with carbon in subsurface water to form the building blocks of life. Since there's lots of water ice on moons in the outer solar system, as well as some very powerful magnetic fields emanating from planets like Jupiter and Saturn, there's no reason to think there isn't more oxygen to be found? in our solar system or elsewhere."

Dione was discovered by renown Italian-French astronomer, Giovanni Cassini (who the Cassini spaceprobe is named after) in 1684. It is one of 62 known moons which orbit Saturn, and is is the 15th largest. It is composed primarily of water ice and shared many physical features with it's neighbour, Rhea.

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