A prime target in the search for extraterrestrial life is Europa, a moon of Jupiter that’s covered with a sheet of salty ice. But what kind of salt is there? Researchers say they’ve created a new kind of salt crystal that could fill the bill, and perhaps raise hopes for finding life under the ice.
This salt crystal is both exotic and common: It’s actually table salt — also known as sodium chloride, with the chemical formula NaCl — but bound up with water molecules to form a hydrate that doesn’t exist naturally on Earth.
Earthly sodium chloride hydrates are composed of one salt molecule linked by hydrogen bonds with two water molecules. In contrast, the hydrates created in the lab consist of two NaCl molecules to 17 water molecules, or one NaCl molecule to 13 water molecules. (The structure for a third type of “hyperhydrated hydrate” couldn’t be determined.)
That’s promising news for scientists who study Europa and other ice-covered worlds — including two other Jovian moons, Callisto and Ganymede; and the Saturnian moons Enceladus and Titan. Spectral observations indicate that Europa’s surface ice contains salts, including sodium chloride, but the observed levels of concentration don’t match up well with Earth’s run-of-the-mill NaCl hydrates.