THE ice plumes that bloom above Saturn鈥檚 icy moon Enceladus are almost certainly rooted in a subsurface sea of liquid water.
The Cassini spacecraft flew through a plume on 9 October 2008 and measured the molecular weight of chemicals in the ice. Frank Postberg of the in Heidelberg, Germany, and colleagues, found traces of sodium in the form of salt and sodium bicarbonate. The chemicals would have originated in the rocky core of Enceladus, so to reach a plume they must have leached from the core via liquid water. Observations from Earth in 2007 spotted no sign of sodium, casting doubt on such a subsurface sea.
Although the salt could have been leached out by an ancient ocean which since froze solid, that freezing process would concentrate most of the salt very far from the surface of the moon鈥檚 ice, says Julie Castillo of NASA鈥檚 in Pasadena, California. 鈥淚t is easier to imagine that the salts are present in a liquid ocean below the surface,鈥� she says. 鈥淭hat鈥檚 why this detection, if confirmed, is very important.鈥�
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The new results were due to be presented at the this week.
