A groundbreaking study by an international team of scientists has revealed unprecedented insights into the nature of the asteroid Ryugu and sheds light on the composition of the small water- and carbon-rich body in the solar system. Asteroids like Ryugu are remnants of planetary embryos that never reached larger sizes, making them valuable windows into the material that formed the early solar system.

Recent studies of samples from the asteroid Ryugu brought back by Hayabusa2 have provided new insights into materials in the early solar system and challenged previous views on the composition of asteroids and the impact of Earth's atmosphere on meteorites. (Japan's Hayabusa2 mission to the asteroid "Ryuugu") Image source: JAXA

The study centers on laboratory measurements of samples brought back to Earth by the Hayabusa2 spacecraft in 2020. Led by the Japan Aerospace Exploration Agency (JAXA), Hayabusa2 aims to reveal what Ryugu is really like and explore how astrologers can use knowledge of meteorites to explain telescopic observations of other water-bearing asteroids.

Unlike meteorites from similar water-bearing asteroids, the Ryugu samples avoided Earth-altering interactions with oxygen and water in Earth's atmosphere.

Optical images of Ryugu samples (left) and carbonaceous chondrites (Cl) (right). Source: JAXA and KanaAmano et al.

Reflectance spectroscopy, a major technique linking laboratory analysis of meteorites to asteroid observations, was used to compare fresh Ryugu samples to meteorites that had been altered in terrestrial environments. The research team successfully developed an analysis procedure that avoided exposure of the samples to the Earth's atmosphere and ensured the preservation of the samples in their original state.

Previous studies have shown that the mineralogy of Ryugu's samples is similar to the chemical composition of the most primitive meteorites: carbonaceous chondrites. However, other studies have revealed significant differences in reflectance spectra between Ryugu samples and CI meteorites, overturning this view. Further investigation in the new study showed that heating the CI sample under reducing conditions at 300°C reproduced the mineralogy of the Ryugu sample well, resulting in a spectrum that closely matched the Ryugu sample.

Reflection spectra of the Ryugu sample (blue line), the unheated CI sample (black dashed line), and the CI sample heated at 300°C. Modified from Figure 5A of Amano et al. (2023). Source: KanaAmanoeta.

These findings challenge previous assumptions about the parent body of CI meteorites and highlight the susceptibility of primitive meteorite spectra to terrestrial weathering. The study shows that the actual CI nephrite matrix is ​​likely darker and has a flatter reflection spectrum than previously thought.

This research opens up new ways to understand the composition and evolution of small bodies in the solar system. By considering the effects of terrestrial weathering on meteorites, we can refine our interpretation of asteroid composition and advance our understanding of the early history of the solar system.

On December 6, 2023, the magazine Science Advances published the detailed research results of Kana and colleagues.

Compiled source: ScitechDaily