Unlocking the Secrets of Asteroid Ryugu: How a Surprising Mineral Discovery Could Rewrite Its History

A surprising find has emerged from the asteroid Ryugu, which was explored by the Japanese Hayabusa2 mission in 2020. Researchers discovered a mineral called djerfisherite in a dust grain from this carbon-rich asteroid. This discovery challenges our long-held ideas about how certain asteroids formed.

Djerfisherite, an iron-nickel sulfide combined with potassium, is typically found in rare meteorites known as enstatite chondrites. These meteorites formed in the inner solar system around 4.6 billion years ago, under extreme heat, over 662°F (350°C). So, it’s quite a shock to find this mineral in Ryugu, which is thought to have formed in much cooler conditions in the outer solar system.

Masaaki Miyahara, a planetary scientist from Hiroshima University, compared this find to “a tropical seed in Arctic ice,” suggesting either an unexpected local condition or long-distance transport of materials during the solar system’s early days.

Ryugu’s history suggests it was once part of a larger protoplanet that got blasted apart by an impact. This parent body was rich in water and carbon dioxide ice. As it formed, heat from radioactive decay would have melted this ice, allowing chemical changes in Ryugu. However, temperatures wouldn’t have reached high enough for djerfisherite to form naturally—at least, not under known conditions.

The discovery raises questions. Could the djerfisherite be from an enstatite chondrite impact? Or could it have formed locally in conditions we don’t yet understand—possibly requiring potassium-rich fluids and higher temperatures than previously thought?

To address these questions, isotopic data will be crucial, but researchers don’t have enough yet to clarify the origins of djerfisherite. Miyahara’s team leans towards the idea that it formed on Ryugu itself, but how this happened is still a mystery.

This finding could change how scientists view the chemical landscape of primitive asteroids. It may indicate that materials with different histories mixed during the early solar system’s formation, or that localized conditions on Ryugu created unexpected chemistry.

As a result, scientists are re-examining Ryugu samples to uncover if more evidence supports this intriguing discovery. They aim to better understand how minerals formed and mixed in the early solar system, tracing the chemical evolution that eventually led to the formation of planets and asteroids.

Research like this sheds light on the complexities of our solar system’s history and could provide insights into how different environments shape mineral formation. Djerfisherite’s discovery was reported in the journal Meteoritics & Planetary Science on May 28, 2023.



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