Atmosphere at Dione discovered by NASA spacecraft - "Cassini", which saw the ultra-thin layer of oxygen ions, it was so rare that it can be compared to the conditions at an altitude of 480 kilometers above the Earth. For every 11 cubic centimeters of space satellites there is one oxygen ion, but it's enough to take a layer of the atmosphere, scientists announced the mission "Cassini».
"We now know that Dione, in addition to the rings of Saturn and its moon another Rhea, is a source of oxygen molecules," - said in a statement a member of the team "Cassini" Robert Tokar of the Los Alamos National Laboratory in New Mexico. "This shows that molecular oxygen is actually common in the Saturn system and reinforces the view that it may be the result of a process that is not associated with life».
Dion is one of the smaller moons of Saturn and reaches a width of about 1123 km. One revolution around Saturn, it makes every 2 to 7 days at a distance of approximately 377,400 kilometers - that's about the same distance as between the Earth and its satellite, NASA explained.
It is assumed that the oxygen on Dione could have been formed by the action of solar photons or high-energy particles that bombard the surface of the icy moon of Saturn, and thus raise the oxygen ions, explained Tokar. Another idea is that the atmosphere of the moon could appear as a result of geological processes on Dione, the researchers added.
Dion is not the only space object with the atmosphere in our solar system. Covered with a thick layer of the atmosphere of the planet Earth, Venus and Mars, and Saturn's largest moon - Titan.
The thin atmosphere on Saturn's moon Rhea - similar to Dione - was discovered in 2010. These observations and the discovery of ozone on Dione, with the Hubble Space Telescope, led researchers to suggest that it may be there is a thin atmosphere.
But scientists could not confirm this until the spacecraft "Cassini" not found molecules ionized oxygen on Dione, using a tool called a plasma spectrometer in April 2011, flying at a distance of 503 km from the icy moon. "Noted" spacecraft atmosphere is about 2550 ions of oxygen at 90 000 cubic meters, the researchers said.
"Scientists were not sure Dion is small enough to have the exosphere, but this new study shows that it is even more interesting than we expected," - said Amanda Hendrix, deputy project scientist "Cassini".