Unexpected Mineral Discovery in Ryugu Asteroid Challenges Solar System Formation Theories

July 3, 2025
Unexpected Mineral Discovery in Ryugu Asteroid Challenges Solar System Formation Theories

On May 28, 2025, a research team from Hiroshima University published findings that may alter our understanding of the early Solar System. The study, published in the journal Meteoritics & Planetary Science, revealed the presence of djerfisherite, a potassium-containing iron-nickel sulfide, in a sample from the asteroid Ryugu, which was brought back to Earth by Japan's Hayabusa2 mission on December 6, 2020. This mineral is typically associated with very reduced environments, such as enstatite chondrites, and its discovery in a CI chondrite like Ryugu is surprising, as conditions for its formation were not believed to exist in such asteroids.

Masaaki Miyahara, an associate professor at the Graduate School of Advanced Science and Engineering at Hiroshima University, led the research team. "Finding djerfisherite in a Ryugu grain is akin to discovering a tropical seed in Arctic ice," Miyahara stated, suggesting this may indicate either unusual local environments during the asteroid's history or long-distance transport of materials in the early solar system.

The Hayabusa2 mission aimed to investigate the origins of organic matter and water in the context of planetary formation. Ryugu, a C-type asteroid, is rich in carbon and is believed to have undergone extensive aqueous alteration. The presence of djerfisherite challenges the long-held notion that Ryugu's composition is uniform and suggests a more complex history.

The research team conducted experiments to assess terrestrial weathering effects on Ryugu grains while employing field-emission transmission electron microscopy (FE-TEM). Their investigation revealed djerfisherite in sample plate C0105-042, raising questions about the formation history and environmental conditions of Ryugu's parent body, which is estimated to have formed between 1.8 to 2.9 million years after the Solar System's inception.

Thermodynamic calculations indicate that djerfisherite in enstatite chondrites forms from high-temperature gas, while hydrothermal synthesis experiments suggest it can also arise from reactions involving potassium-bearing fluids and iron-nickel sulfides at elevated temperatures. The team proposed two hypotheses regarding the presence of djerfisherite in Ryugu: it either arrived from another source or formed intrinsically when Ryugu's temperature exceeded 350°C. Preliminary evidence leans toward the latter hypothesis.

Miyahara emphasized the significance of these findings, stating, "Ultimately, our goal is to reconstruct the early mixing processes and thermal histories that shaped small bodies like Ryugu, thereby improving our understanding of planetary formation and material transport in the early solar system."

This discovery not only enhances scientific knowledge of Ryugu but also prompts further investigations. Future studies will focus on isotopic analyses of Ryugu grains to clarify their origins and the processes that influenced their formation. Such research could have profound implications for understanding the evolution of asteroids and the early Solar System.

The Hayabusa2 mission, launched by the Japan Aerospace Exploration Agency (JAXA), aimed to gather data on primitive asteroids and their role in the origin of life on Earth. The findings from Ryugu may provide crucial insights into the materials that contributed to the formation of terrestrial planets and the prebiotic chemistry necessary for life.

In light of these revelations, the scientific community is now tasked with reevaluating existing models of solar system formation, considering the newfound complexity of materials found in asteroids. As further research unfolds, the discovery of djerfisherite in Ryugu could pave the way for a more nuanced understanding of planetary evolution and the dynamics of our cosmic neighborhood.

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Ryugu asteroiddjerfisheriteHayabusa2 missionHiroshima Universityplanetary formationasteroid researchMasaaki MiyaharaSolar SystemCI chondritesenstatite chondritesmeteorite studiescosmic materialsspace explorationJAXAgeochemical processesplanetary scienceprimitive asteroidsorganic matter originsmaterial transportisotopic analysissolar system evolutionhydrothermal synthesisfield-emission microscopyscientific discoveryearly solar systemspace geologymineralogyvariable environmentscosmic historyasteroid samples

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