Japanese researchers discover salt crystals in Ryugu asteroid samples

TOKYO — Japanese researchers have identified sodium carbonates, or salt crystals, in samples from the Ryugu asteroid brought back to Earth by the Hayabusa2 space probe.

The findings, published in the online journal “Nature Astronomy” by a team from Kyoto University, Tohoku University and other institutions, are considered significant for understanding the evolution of organic materials in relation to water and other substances in celestial bodies.

Using electron microscopy and other techniques, researchers observed four crystals in the samples. These were up to around 500 micrometers long, 20 micrometers wide, and 1 micrometer thick. (One micrometer is 0.001 millimeters.) The crystals consisted of rock salt, sodium carbonate and sodium sulfate. To prevent the salts from degrading under electron beams, the team used reduced beam intensity during the analysis.

Scientists believe the Ryugu asteroid’s parent body contained large amounts of salt water some 4.6 billion years ago, but the fate of that water remains unclear. Salt crystals typically form when salt water’s saline concentration is high, suggesting the water may have disappeared through evaporation or freezing.

The crystal structures resemble salts found in subsurface oceans on Ceres, a dwarf planet located between Mars and Jupiter, and Enceladus, one of Saturn’s moons. Toru Matsumoto, a program-specific assistant professor at Kyoto University’s Hakubi Project, commented, “This is an important step in understanding the evolution of organic matter in environments similar to oceans within our solar system.”

(Japanese original by Yurika Tarumi, Lifestyle, Science & Environment News Department)