Geophysical Research Letters reports that scientists have confirmed the presence of oxygen in the upper atmosphere of Dione, one of Saturn’s many moons. The international team responsible for the announcement reported that it noticed the trace amounts of the element from data collected by NASA’s Cassini spacecraft.
A sensor on the Cassini spacecraft, named the Cassini Plasma Spectrometer, picked up signals that indicated oxygen ions were present in an area of space where Dione had just been during a pass by the moon in 2010. After another recent run, the team was able to verify that oxygen does in fact exist in Saturn’s moon, although not in large amounts.
According to Team Leader Robert Toker: “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 amount of oxygen present in Dione is roughly the equivalent of what is present in the Earth’s atmosphere at an altitude of 300 miles. Dione was discovered in 1684 by the astronomer Giovanni Cassini, who lends his name to the aforementioned spacecraft. Dione is one of 62 known moons that orbit Saturn. It is small, clocking in at only 700 miles wide. Its surface exists only as a thick layer of watery ice that bears marks and scars from an innumerable number of asteroid collisions, inside of which lies a hard, solid core.
Although Dione and the Earth’s moon both orbit their respective planet at around the same distance, Dione completes its orbit in roughly a tenth of the amount of time Earth’s moon does, coming full circle in about 2.7 days.
As it circles Saturn, Dione is assailed by ions, or charged particles, from Saturn’s magnetosphere. These hit Dione’s icy surface with enough strength to violently throw up molecular oxygen ions into the moon’s small atmosphere, in a process that is known as sputtering. The oxygen particles are then pulled away from Dione by Saturn’s magnetosphere.
Although the announcement has disproven the idea of life existing on Dione, showing its oxygen levels are much too low, it has opened the door for different possibilities. Other icy worlds and moons not thought to have oxygen could now be shown to harbor the element within their atmospheres, and with such discoveries comes the tantalizing idea of oxygen-based life forms. Hopefully more research can shed light on the subject.