Want some salt with that

Want some salt with that
by Riko Seibo
Tokyo, Japan (SPX) Feb 18, 2025

Asteroids that pass close to Earth often raise concerns about potential collisions, but they also present valuable opportunities for scientific discovery. One such celestial body, the 900-meter-wide asteroid Ryugu, has recently yielded intriguing evidence that may enhance our understanding of life's building blocks in the Solar System.

Scientists from Kyoto University have detected salt minerals in samples retrieved from Ryugu during the early phase of Japan's Hayabusa2 mission. These deposits, which include sodium carbonate, halite, and sodium sulfates, suggest that Ryugu's parent body once contained liquid saline water.

Prior to examining the samples, researchers hypothesized that the asteroid might contain substances absent in typical meteorites. They suspected these materials could be highly soluble in water, making them difficult to preserve in Earth's humid atmosphere.

"Careful handling allowed us to identify the delicate salt minerals, providing a unique glimpse into Ryugu's chemical history," explained corresponding researcher Toru Matsumoto.

Experts estimate that Ryugu was once part of a much larger celestial body that existed around 4.5 billion years ago, shortly after the Solar System formed. This parent body likely underwent internal heating due to radioactive decay, resulting in the presence of hot water at temperatures below 100 C. Although the asteroid no longer retains moisture, scientists are investigating the mechanisms that led to the loss of liquid water.

"These crystals tell us how liquid water disappeared from Ryugu's parent body," Matsumoto noted. The easy solubility of these salt crystals suggests they could have formed only in highly saline water and in conditions where liquid was scarce.

"We hypothesize that as fractures exposed the saltwater to space or as the parent body cooled, the liquid either evaporated or froze," Matsumoto added. "The salt minerals we've identified are crystallized remnants of that ancient water."

This discovery holds broader implications for the study of water in the outer Solar System. Researchers believe that sodium carbonate and halite are likely present on the surface of the dwarf planet Ceres, within the water plumes of Saturn's moon Enceladus, and on the icy surfaces of Jupiter's moons Europa and Ganymede.

Since salt formation is closely tied to planetary geology and brine chemistry, the identification of sodium salts in Ryugu's samples provides new comparative insights into how water has shaped celestial bodies beyond Earth.

Research Report:Sodium carbonates on Ryugu as evidence of highly saline water in the outer Solar System