Detecting oxygen on Saturn satellite

A Saturn satellite has an atmosphere made up of oxygen and carbon dioxide.

US Cassini spacecraft discovered the existence of the atmosphere on Rhea , Saturn's second largest satellite, during a close-up of this celestial body in March, National Geographic reported.

The oxygen-containing atmosphere exists on several satellites in the solar system, but this is the first time humans have confirmed its existence on a Saturn satellite.

" Scientists have discovered oxygen on two moons of Jupiter and now it happens on a Saturn satellite, " said Ben Teolis , an expert at the Southwest Research Institute in the US.

Saturn's Rhea satellite. (Photo: National Geographic).

The US Hubble Space Telescope once discovered thin oxygen layers around Jupiter's and Europa's Ganymede satellites in the 1990s. On both satellites, oxygen escapes from the ice on the surface. The ice is broken down into oxygen and hydrogen is ' bombarded ' by particles that carry electricity from Jupiter.

From the discovery of Jupiter's satellites, scientists from the US Aerospace Agency (NASA) believe that oxygen can exist on Saturn's satellites, because they are sized large and covered with water in the form of ice.

Rhea is a suitable target for the search. Water in ice form accounts for a large proportion of its physical composition. With a diameter of 1,529 km, Rhea has a gravitational force large enough to hold the atmosphere on the surface.

Cassini had been searching for oxygen around Rhea during two passes (2005 and 2007). In those times, Cassini flew by Rhea 501 km and 5,736 km respectively. However, scientists found no evidence of the existence of oxygen around Rhea.

In March, Cassini flew 97 km from the surface of Rhea, much closer than the previous two, Teolis said. With that distance, it actually flies through the atmosphere of this celestial body. Cassini's spectrophotometer confirms the existence of both oxygen and CO2.

Oxygen accounts for about 70% of Rhea's atmosphere, while CO ₂ accounts for 30%. When Cassini sampled, the data it sent showed that Rhea's atmosphere was about 100 times thinner than the atmosphere of Jupiter's Europa and Ganymede. So Cassini cannot detect the existence of the atmosphere around Rhea.

' Rhea's atmosphere is not thick enough for spacecraft to detect from afar. The concentration of oxygen in the earth's atmosphere is at least 5,000 billion times greater than that of Rhea ', Teolis explained.