Space probe "Cassini" discovered oxygen in the atmosphere of Rhea - the first time that gas was found somewhere other than Earth.
The spacecraft took the first samples of the atmosphere of another celestial body, flying quite low over the icy satellites of Saturn - Rhea.
Samples were taken in March this year, when Cassini flew at an altitude of 97 km above the surface of the satellite.
Prior to this, the presence of oxygen on the planets and their satellites were determined indirectly, through such means of space exploration, as the Hubble telescope.
Equipment Cassini allowed to open an extremely thin layer of atmosphere consisting of oxygen and carbon dioxide, which is supported by high-energy particles impinging on the surface of the satellite, and raising the atoms, molecules and ions.
Astronomers have counted 62 satellites of Saturn. Average diameter is 1500 km Rhea, making it the second largest. It is believed that it is composed almost entirely of ice.
"We first discovered oxygen in the atmosphere of another celestial body," - said Andrew Coates, from the Scientific Mullard Space Laboratory, co-author of a study published in the journal Science.
"Active complex chemistry involving oxygen may be quite common in our solar system and even our universe," - said the team leader Ben Teolis of the Southwest Research Institute in San Antonio, Texas. "This kind of chemistry is a prerequisite for the emergence of life. All data obtained from Cassini show that Rhea is too cold and devoid of the liquid water necessary to sustain life in the form as we know it on Earth."
Rhea’s atmosphere, making it unique in the Saturn system. Only Rhea and Titan, the largest moon of Saturn, have a mass sufficient to keep the atmosphere by means of gravity. However, titanium has a very thick atmosphere of nitrogen and methane with a very low content of carbon dioxide and oxygen.
Astronomers have previously used telescopes to find signs of the presence of oxygen in the atmospheres of Jupiter’s moons - Europa and Ganymede, but this technique is not justified in the case of Rhea, since the concentration of this gas was too small.
According to the testimony of instruments on board Cassini, in each cubic meter of Rhea’s atmosphere contains about 50 billion molecules of oxygen and 20 billion molecules of carbon dioxide.
Carbon dioxide may come from dry ice traps in the surface of the moon, or be a product of the interaction of high-energy particles from the ice on Rhea. Another source could serve as a carbon-rich materials, listed in small meteors that bombarded Rhea’s surface. Just tell us interesting news in detail.