This was reported by The Insider with reference to a study published in Science Advances. The authors analyzed data from the Cassini probe, which captured individual particles from Saturn’s E ring and determined their composition.
Hidden beneath Enceladus’s icy crust is a global ocean of salt water, and through cracks near the moon’s south pole it ejects fountains of vapor and ice grains. From more than 7,300 particles, the researchers selected 961 grains with a high salt content and found at least five groups among them: with table salt, soda, phosphates, and potassium compounds.
Different salts were rarely found together. Chlorides and carbonates were detected simultaneously in only 12 out of 858 particles, although about 88 would have been expected with random mixing.
To test the reason, the scientists froze drops of a solution in the lab that was close in composition to Enceladus’s waters. They found that the salts gather into separate clusters if the drop is large enough — more than a dozen micrometers — and cools slowly, at no more than 20 degrees per minute. According to the authors’ calculations, phosphates crystallize first at about minus one degree, then carbonates at minus four degrees, and chlorides at around minus 23 degrees.
On this basis, the researchers proposed a new picture of Enceladus’s plumes: deep in the cracks, gas bubbles burst, splashing droplets of ocean water hundreds of micrometers in size, which rise with the vapor flow and freeze for at least a minute. Closer to the surface, the flow accelerates to hundreds of meters per second, the ice grains collide with the crack walls and break into fragments a few micrometers across. Most such fragments contain only one substance, and the authors believe that organic compounds may separate in the same way.
In their view, future missions to Enceladus that will study the moon’s potential habitability should analyze particles individually. If the entire plume is studied at once, the separated compounds will mix again and their traces may be harder to distinguish.
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