New analysis of Cassini data finds salt-rich ice grains from Enceladus's plume are far more varied than thought, because ocean spray freezes slowly and shatters on its way out
Ice grains blasted into space from Saturn's moon Enceladus are far more chemically varied than scientists realized, and the reason may make the hunt for life there easier, according to a study published September 25 in Science Advances.
Enceladus hides a salty ocean beneath its icy crust, which sprays into space through cracks near the moon's south pole. NASA's Cassini spacecraft, which arrived at Saturn in 2004, flew through this plume repeatedly, sampling ocean material without landing or drilling.
The research team, led by Frank Postberg of Freie Universität Berlin, examined 961 salt-rich ice grains recorded by Cassini's Cosmic Dust Analyzer. Instead of a uniform salty composition, they found at least five distinct chemical subtypes, dominated variously by sodium chloride, sodium carbonate and bicarbonate, sodium phosphate and other compounds.
The researchers propose that droplets of ocean spray freeze slowly as they rise through cracks in the ice, causing different salts to crystallize separately before the droplets shatter into tiny grains. The result is a natural chemical separation of the ocean's ingredients into different particles.
"Enceladus actually does a lot of the work for us in preparing samples for analysis that usually take a lot of effort in chemical labs on Earth," Postberg said.
The finding means a single grain may not represent the ocean's average composition, and future missions should analyze individual grains rather than bulk plume material. "While that doesn't mean that there is life on Saturn's moon," Postberg said, if there is, "future space missions might have a good chance of finding traces."
