Oxygen ions detected in the upper atmosphere of Dione

Comparison of Earth, our moon and Dione.

Dione is an icy moon orbiting Saturn.  The Cassini spacecraft that is currently investigating Saturn and its moons has found molecular oxygen ions (O₂⁺) in the upper atmosphere of Dione.  What this does not mean: there could be life on Dione.  I’m not saying there can’t be life on Dione, just that this new information doesn’t sway the balance one way or the other.  What it does mean: life is not required to create abundant amounts of atmospheric oxygen above icy moons.

Robert Tokar and Michelle Thomsen from Los Alamos National Laboratory and their colleagues from six other institutions in the U.S. and U.K used the Cassini Plasma Spectrometer to identify molecules present in Dione’s atmosphere and to determine where those molecules came from. In effect, the cosmologists have identified a way to create O₂⁺ and other forms of oxygen without resorting to photosynthetic organisms. Here’s how it works.

Dione is covered with water ice (H₂O). Like all of Saturn’s moons, Dione is subject to a constant storm of charged particles spewing out from Saturn’s magnetosphere. These high-energy particles slam into Dione’s surface and throw a cascade of oxygen molecules high up into the atmosphere.  This phenomenon, called ‘sputtering’, is surprisingly effective. In fact, the concentration of oxygen ions in Dione’s upper atmosphere is similar to the amount found high above the Earth, though obviously our oxygen has a different origin. 

If you are a regular reader of this blog, you’ll know that I include a relevant video with some frequency.  This article is no exception, and the video below is from astronomy fan, isaworld2012.  I admire her enthusiasm, although the symbol for oxygen is not zero.