Red streaks across the surface of Europa, the smallest of Jupiter’s four large moons.
This image shows red streaks across the surface of Europa, the smallest of Jupiter’s four large moons. The discovery of new types of salty ice could explain the material in these streaks and provide clues on the composition of Europa’s ice-covered ocean.

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.

An international 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 the week of 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 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.”

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