Science Daily 2/20/2023
Source: University of Washington
Summary: An international team has found two new crystal structures for salty ice, or solid hydrate made from water and sodium chloride. The newly discovered material's properties match those of the substance seen on the surface of icy moons, like Europa and Ganymede, and may offer clues to their icy oceans.
The red streaks crisscrossing the surface of Europa, one of Jupiter's moons, are striking. Scientists suspect it is a frozen mixture of water and salts, but its chemical signature is mysterious because it matches no known substance on Earth.
A team led by the University of Washington may have solved the puzzle with the discovery of a new type of solid crystal that forms when water and table salt combine in cold and high-pressure conditions. Researchers believe the new substance created in a lab on Earth could form at the surface and bottom of these worlds' deep oceans.
The study, published Feb. 20 in the Proceedings of the National Academy of Sciences, announces a new combination for two of Earth's most common substances: water and sodium chloride, or table salt.
"It's rare nowadays to have fundamental discoveries in science," said lead author Baptiste Journaux, a UW acting assistant professor of Earth and space sciences. "Salt and water are very well known at Earth conditions. But beyond that, we're totally in the dark. And now we have these planetary objects that probably have compounds that are very familiar to us, but in at very exotic conditions. We have to redo all the fundamental mineralogical science that people did in the 1800s, but at high pressure and low temperature. It is an exciting time."
At cold temperatures water and salts combine to form a rigid salted icy lattice, known as a hydrate, held in place by hydrogen bonds. The only previously known hydrate for sodium chloride was a simple structure with one salt molecule for every two water molecules.
But the two new hydrates, found at moderate pressures and low temperatures, are strikingly different. One has two sodium chlorides for every 17 water molecules; the other has one sodium chloride for every 13 water molecules. This would explain why the signatures from the surface of Jupiter's moons are more "watery" than expected.
More:
https://www.sciencedaily.com/releases/2023/02/230220162942.htm
