Recent analysis of pristine samples from the asteroid Ryugu has yielded a groundbreaking discovery that could reshape our understanding of primitive asteroids and their formation in the Solar System. The Japan Aerospace Exploration Agency’s (JAXA) Hayabusa2 mission returned these intriguing samples on December 6, 2020. Notably, the C-type asteroid Ryugu exhibits traits comparable to certain meteorites classified as CI chondrites, known for their rich carbon content and complex history of aqueous alteration. Surprisingly, within one of these samples, researchers from Hiroshima University have identified an unexpected mineral: djerfisherite.
Djerfisherite, a potassium-bearing iron-nickel sulfide, is a mineral typically found in environments characterized by extreme reduction, conditions not generally associated with the typical geological processes expected on Ryugu. This serendipitous finding was published in the journal "Meteoritics & Planetary Science" on May 28, 2025, marking a significant milestone in planetary science. The presence of djerfisherite suggests that Ryugu may possess a more diverse and heterogeneous chemical background than previously understood, warranting a reevaluation of the asteroid’s geological history.
The research team, spearheaded by Masaaki Miyahara, associate professor at Hiroshima University’s Graduate School of Advanced Science and Engineering, describes the discovery of djerfisherite as akin to finding a tropical seed embedded in Arctic ice. This striking analogy underscores the potential implications of localized environments or material transport occurring during the early epochs of the Solar System’s evolution. Djerfisherite has not been reported in CI chondrites or in other Ryugu grains, raising important questions about the geological processes that could lead to its formation in such a context.
While investigating the effects of terrestrial weathering on Ryugu grains through field-emission transmission electron microscopy (FE-TEM), the researchers identified the mineral in grain number 15 from sample plate C0105-042. This serendipitous finding led the team to delve deeper into the mineral’s origins and the conditions required for its formation. The mineral’s presence challenges the previous paradigm that envisioned Ryugu as a uniform body and highlights the complexity of primitive asteroids, which may harbor diverse histories and compositions.
The astrobiological implications of these findings are significant. Ryugu originates from a larger parent body formed between 1.8 to 2.9 million years following the dawn of the Solar System. The prevailing hypothesis suggests that this parent body was established in the outer solar system, an area where water and carbon dioxide were present primarily in the icy state. The melting of this ice, prompted by heat from the decay of radioactive elements, occurred approximately 3 million years after formation, with temperatures staying below approximately 50°C.
In stark contrast, the parent bodies of enstatite chondrites, known to contain djerfisherite, formed in the inner solar system, far hotter and chemically distinct than those of Ryugu. Thermodynamic calculations indicate that the djerfisherite found in enstatite chondrites likely formed from high-temperature gases, whereas hydrothermal synthesis experiments show that the mineral can also arise from reactions involving potassium-rich fluids and iron-nickel sulfides at temperatures exceeding 350°C.
This raises two plausible hypotheses regarding the occurrence of djerfisherite in the Ryugu grain: either it was introduced from an external source during the formation of Ryugu’s parent body, or it formed as the temperature of Ryugu itself elevated beyond 350°C. Preliminary evidence leans toward the latter hypothesis, suggesting that intrinsic formation within Ryugu may be more probable. Upcoming isotopic studies of Ryugu grains are essential and will help clarify their origins, contributing to a broader understanding of early solar system conditions.
The implications extend far beyond the mineral itself. The findings prompt reconsideration of the early solar system’s dynamics, particularly concerning how materials with divergent formation histories might have mixed during planetary evolution. This new perspective emphasizes the need to investigate the geological past of primitive celestial bodies critically. The complexity unearthed by this discovery necessitates a reevaluation of long-held beliefs about the homogeneity of Ryugu and, by extension, other similar celestial bodies.
Ultimately, the goal of this ongoing research is to reconstruct the complexities of early mixing processes and thermal histories that shaped not only Ryugu but also other small bodies in the Solar System. Such endeavors could illuminate the pathways leading to planetary formation and the transport of materials in our cosmic neighborhood.
As research progresses, the insights gained from the analysis of Ryugu samples could shed light on the formative processes of the Solar System and advance our understanding of astrobiology as we look for potential life-sustaining materials in other celestial environments. The prospect of discovering similar minerals in other celestial bodies could radically redefine our understanding of planetary formation and the distribution of diverse materials across the solar system.
This groundbreaking discovery not only challenges existing frameworks about Ryugu’s nature but also opens up a multitude of questions about the environmental conditions present in the early Solar System. As scientists continue to analyze the Ryugu samples, the answers may reshape our understanding of planetary history and the conditions under which life could arise elsewhere in the universe.
In an era increasingly captivated by the quest to uncover extraterrestrial life, the findings from Ryugu remind us of the inherent complexity of asteroids and the vital clues they hold regarding the early framework of our Solar System.
Subject of Research: Discovery of djerfisherite in Ryugu grain
Article Title: Djerfisherite in a Ryugu grain: A clue to localized heterogeneous conditions or material mixing in the early solar system
News Publication Date: 28-May-2025
Web References: DOI
References: None
Image Credits: Hiroshima University/Masaaki Miyahara
Keywords
Primitive asteroids, Ryugu, Djerfisherite, Hayabusa2 mission, CI chondrites, Solar System formation, extraterrestrial materials, geological history, planetary science, mineral discovery.
