NASA's Cassini spacecraft finds oxygen ions near Saturn

New data from the Cassini spacecraft has showed oxygen ions in the atmosphere around Saturn's rings, scientists at US National Aeronautics and Space Administration (NASA) and universities reported Thursday.

This suggests once again that molecular oxygen alone isn't a reliable indicator of whether a planet can support life, the researchers said.

Their findings are outlined in two papers, which were co-authored by scientists at the University of Michigan and the University of Kansas, in the Feb. 25 issue of the journal Science.

Molecular oxygen forms when two oxygen atoms bond together and is known in chemical shorthand as O2. On Earth, it is a continual byproduct of plant respiration, and animals need this oxygen for life.

But in Saturn's atmosphere, molecular oxygen was created without life present, through a chemical reaction with the sun's radiation and icy particles that comprise Saturn's rings.

"That means you don't need biology to produce an O2 atmosphere," said Hunter Waite, co-author of one paper. "If we want indicators to use in the search for life on other planets, we need to know what to look for. But oxygen alone isn't it."

Because Saturn's rings are made of water ice, one would expect to find atoms derived from water, such as atomic oxygen rather than O2, the researchers said.

However, the paper suggests the formation of molecular oxygen atmospheres happens more often in the outer solar system than expected. There is earlier evidence of molecular oxygen atmospheres elsewhere in the solar system.

Other new findings include wandering and rubble-pile moons; new and clumpy Saturn rings; splintering storms and a dynamic magnetosphere, NASA said.

Weak, linear density waves caused in Saturn's rings by the small moons Atlas and Pan have yielded more reliable calculations of their masses. The masses imply the moons are very porous, perhaps constructed like rubble piles. They are similar to the moons that shepherd Saturn's F ring, Prometheus and Pandora.

Another discovery was a tiny moon, about 5 km across, recently named Polydeuces. Polydeuces is a companion, or "Trojan" moon of Dione. Trojan moons are found near gravitationally stable points ahead or behind a larger moon. Saturn is the only planet known to have moons with companion Trojan moons.

Several faint Saturn rings have been discovered in Cassini images. Some lie in various gaps in the rings and may indicate the presence of tiny embedded moons acting as shepherds. Several of the rings are kinked, likely evidence of nearby moons.

Scientists also found Saturn's winds change with altitude, and small storms emerge out of large ones. For the first time, Cassini images captured possible evidence of processes that may maintain the winds on Saturn.

Other results improve the understanding of Saturn's complex magnetic environment, according to NASA's Jet Propulsion Laboratory (JPL) that operates the Cassini project.

Saturn's magnetosphere is truly unique. It's dynamically similar to Jupiter's, but in places it chemically resembles water-based plasmas surrounding comets, said the JPL.