Salty (2/23/23)

Good afternoon, and happy Thursday. It's been an exciting week of space science, so let's get right into it.

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Salt off the Earth

Forget what you know about salt.

On Earth, salts are abundant and well-understood. They fill our oceans, our bodies, and are necessary to sustaining life as we know it.

Elsewhere in the solar system, salts are more mysterious. Images taken of Jupiter’s moon Europa by NASA’s Galileo probe in 2001, for example, show a crisscrossing lattice of red streaks which has a chemical signature indicating it’s made up of salt and water—but somehow different from networks of salt and water we know on Earth.

“Salt and water are very well known at Earth conditions,” said Baptiste Journaux, a UW acting assistant professor of Earth and space sciences and lead author of the study. “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…very exotic conditions.”

Salty secrets: Findings published on Monday in the Proceedings of the National Academy of Sciences explored various temperature and pressure conditions to simulate two previously unknown types of watery salt that match the chemical properties of the salts found on Europa.

These two new salt structures are called “hyper-hydrates,” and they’re the first new type of hydrate discovered since 1847, when the first and (to now) only known hydrate, hydrohalite, was discovered. Hydrohalite, though, is much less watery, containing two water molecules per salt molecule in a lattice formation held together by hydrogen bonds. The two structures identified in this study contain 13 and 17 water molecules per salt molecule.

The methodology: To understand what was happening on the surface of Europa, the researchers had to create extreme pressure conditions. To do this, they put a drop of salty water between two tiny diamonds, then pressed the diamonds together to simulate a pressure 25,000 times that of Earth’s atmosphere. They then peered through the diamonds using a microscope to watch how the salty mixture reacted.

“We were trying to measure how adding salt would change the amount of ice we could get, since salt acts as an antifreeze,” Journeaux said. “Surprisingly, when we put the pressure on, what we saw is that these crystals that we were not expecting started growing. It was a very serendipitous discovery.”

The hunt for life: Europa is believed to have a salty ocean beneath a thick outer layer of ice. That ocean is one of the most promising locations in our solar system—or anywhere besides Earth right now—in the hunt for extraterrestrial life.

“These are the only planetary bodies, other than Earth, where liquid water is stable at geological timescales, which is crucial for the emergence and development of life,” Journaux said.

In the coming years, a few dedicated missions will continue to study Europa’s surface and attempt to peer into its depths in the hunt for life off Earth. The JUICE (JUpiter ICy moons Explorer) mission is slated for launch this April, and NASA is planning to launch its Europa Clipper mission—the first specifically dedicated to studying Europa—next year.

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Other News from the Cosmos

• NASA’s Lucy asteroid probe will target a tiny rock, newly named Dinkinesh, as its first destination in the Trojan group.

• Saturn’s rings have “spokes,” or small dark spots that seem to move along the rings in a phenomenon that scientists haven’t yet explained.

• Six potential galaxies, so old and huge that current cosmological theories suggest they shouldn’t exist, have been captured by JWST.

• A simulation of black holes colliding shows how the “violent” event could send gravitational waves rippling through the cosmos.

• Rangelands in East Africa maintain the ability to recover from drought and environmental degradation, according to a study based on Landsat imagery from the last two decades.

• A new class of water-rich asteroids has been identified using infrared spectroscopy.

• The California Science Center reopened the space shuttle Endeavour’s payload bay.

• Science published a full chemical analysis of samples from the asteroid Ryugu.

• Enceladus, a moon of Saturn, is known for spewing tiny particles of silica from beneath its surface. A new study finds that tidal heating in the moon’s core is the root cause.

Rachael's Recs

💡 Back to the dark side: In last week’s edition of Parallax, I covered a study that, for the first time, used observational evidence to propose that black holes could be the origin of dark energy, a mysterious force comprising ~68% of the universe and accelerating its expansion. In a deep dive for Big Think, astrophysicist Ethan Siegel breaks down that study and scrutinizes whether it could be a watershed moment in astronomy—or whether we should chalk up the findings to wishful thinking.

💥 The end of the universe: While we’re thinking about the ultimate destiny of the universe, it helps to understand all the ways that everything could potentially end. For Quanta Magazine’s The Joy of Why podcast, host Steve Strogatz interviews theoretical cosmologist Katie Mack about the five ways the universe could meet its ultimate demise.

The View from Space

NASA and ESA’s Solar Orbiter captured a rare, hard-to-spot sight: Mercury transiting the Sun. Here, the planet appears silhouetted against swirls of gas in the solar atmosphere.