Signs of life-of some sort, possibly-may be percolating beneath the surface of Saturn's moon Enceladus.
Using data gained from the Cassini Equinox Mission, scientists have detected sodium salts in ice grains of Saturn's outermost ring. The salty ice indicates that Enceladus, which primarily replenishes the ring with material from geysers or plumes on the moon's surface, could harbor a small saline ocean beneath its surface.
"Our measurements imply that besides table salt, the grains also contain carbonates like soda. Both components are in concentrations that match the predicted composition of an Enceladus ocean," said Frank Postberg, Cassini scientist for the cosmic dust analyzer at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany.
Postberg is the lead author of a study that appears in the June 25 issue of the journal Nature.
"The carbonates also provide a slightly alkaline pH value. If the liquid source is an ocean, it could provide a suitable environment on Enceladus for the formation of life precursors when coupled with the heat measured near the moon's south pole and the organic compounds found within the plumes," Postberg said.
The Cassini Equinox Mission, a cooperative project of NASA, the European Space Agency and the Italian Space Agency, first discovered the water-ice jets on Enceladus in 2005. The plumes expel tiny ice grains and vapor, some escaping Enceladus' gravity and forming Saturn's outermost ring. A cosmic dust analyzer developed by the German Aerospace Center examined the composition of the grains and found salt within them.
The Cassini scientists concluded that liquid water must be present because it is the only way to dissolve the significant amounts of minerals that account for the levels of salt detected.
"We believe that the salty minerals deep inside Enceladus washed out from rock at the bottom of a liquid layer," said Postberg.
Added Linda Spilker, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.: "Potential plume sources on Enceladus are an active area of research with evidence continuing to converge on a possible salt water ocean. Our next opportunity to gather data on Enceladus will come during two flybys in November."
Not everyone, however, agrees with the findings. In another study published in Nature, researchers doing ground-based observations could not detect sodium in the plume vapor and could not see it in the expelled ice grains.
"The original picture of the plumes as violently erupting Yellowstone-like geysers is changing," said Postberg. "They seem more like steady jets of vapor and ice fed by a large water reservoir. However, we cannot decide yet if the water is currently 'trapped' within huge pockets in Enceladus' thick ice crust or still connected to a large ocean in contact with the rocky core."