Europe could be covered in salty ice

Image Credit:NASA/JPL-Caltech/SETI Institute

Jupiter’s second Galilean moon Europa is one of the most fascinating planetary objects in our solar system with its vast underground ocean believed to contain nearly three times the volume of water as the entire Earth, opening up the possibility that There is potentially life on this small moon. But while Europa’s inland ocean could be potentially habitable for life, its unique surface features are also catching scientists’ intrigue, especially the large crisscrossing red streaks on its fissured surface.

Although these red streaks are one of Europa’s most striking features, scientists have been unable to identify their chemical signature because no substance on Earth has a complementary signature of its own. They previously made their own assumptions about their origins, with a 2015 study suggesting that the red streaks may come from sea salt in Europa’s interior ocean that was destroyed by radiation at the surface.

It is these red veins, and more precisely their chemical origin, that an international team of researchers led by the University of Washington (UW) has investigated in a recent study with the discovery of a new type of solid crystal that could help explain the scientific processes responsible for the existence of red stripes in Europe. While this new crystal was created in the laboratory, scientists speculate that it could also form at the bottom of the deep oceans on worlds like Europa. The newly discovered solid crystal is made up of water and table salt (sodium chloride), which are two of the most common substances found on Earth.

“It’s rare these days to have fundamental discoveries in science,” said Dr. Baptiste Revistas, who is an interim assistant professor in the Department of Earth and Space Sciences at UW and lead author of the study. “Salt and water are very familiar to Earth conditions. But beyond that, we are totally in the dark. And now we have these planetary objects that probably have very familiar compounds, but in very exotic conditions. We have to redo all the basic mineralogical science that people were doing in the 19th century, but at high pressure and low temperature. It’s an exciting time.”

For the study, the researchers studied what is called a hydrate, which is an icy network formed at cold-water temperatures from the combination of salts and water. Until now, only one hydrate of sodium chloride was known, known as hydrohalite, which consists of one molecule of salt for two molecules of water.

Using transparent diamonds and cold temperatures, the team compressed a small amount of salty water to almost 25,000 times Earth’s atmospheric pressure, where they observed two new crystalline structures of hydrated sodium chloride. The first structure contains two sodium chloride molecules for 17 water molecules, and the other contains one sodium chloride molecule for 13 water molecules. It was also found that the structure containing 17 water molecules remained stable even near vacuum pressure, which is equivalent to the surface of the Moon, while the structure containing 13 water molecules only remained stable at high pressure. . It is speculated that these unique crystalline structures could help explain the “watery” signatures of Jupiter’s moons.

“We were trying to measure how adding salt would change the amount of ice we could get, because salt acts like antifreeze,” Dr. Journaux said. “Surprisingly, when we pushed, what we saw was that these crystals that we weren’t expecting started to grow. It was a very fortuitous discovery. »

These same cold, high-pressure environments likely exist on Europa, as scientists postulate that its inner ocean could be hundreds of kilometers deep under some 5-10 kilometers of ice, with denser ice structures possibly existing on Europa. the bottom of the ocean. where temperatures and pressures would be even colder and more extreme.

For the next steps, the researchers want to create or collect a larger sample for further investigation to determine if the signatures of icy moons, such as the red streaks found on Europa, complement the two recently discovered hydrates.

NASA and the European Space Agency (ESA) currently have a few planetary missions planned to visit Europa and Titan to explore their potential habitability. These include the ESA Jupiter Icy Moons Explorer, also known as JUICE, which is expected to launch in April this year and arrive in the Jupiter system in July 2031; NASA’s European Clipper mission, which is expected to launch in October 2024 and reach the Jupiter system in 2030; and NASA’s Dragonfly mission to Titan, which is scheduled to launch in 2027 and arrive at Titan in 2034. All of these missions will attempt to learn more about the chemical compositions of these mysterious and intriguing worlds, helping scientists determine the best ways to look for life